research paper on plastic waste

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• 12 July 2023

Plastic waste is everywhere — and countries must be held accountable for reducing it

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Plastic waste is damaging ecosystems around the world. Credit: Mark Rightmire/MediaNews Group/Orange County Register/Getty

Globally, some 400 million tonnes of plastic waste are produced each year 1 . Plastics have infiltrated some of the planet’s most remote and pristine areas, as two papers published in Nature show to dramatic effect 2 , 3 .

Veronica Nava and her colleagues systematically assess the extent of plastic contamination in diverse freshwater lakes and reservoirs across 23 countries , and find them to be widely contaminated with plastic 2 . Meanwhile, Hudson Pinheiro and his colleagues show that larger pieces of plastic litter, known as macroplastics, represent the largest share of anthropogenic debris found in shallow and deep coral reefs at 25 locations across the Pacific, Atlantic and Indian ocean basins. Even the deeper reefs, lying at depths of 30–150 metres, were found to be polluted; until now, the impact of plastics on these reefs has been little studied 3 .

Both studies will be important to talks, now under way at the United Nations, on a treaty to eliminate plastic pollution. This is an ambitious goal that will require a radical rethink of plastics production, recycling, remediation and disposal. Experience gained from decades of UN environmental treaties shows that trusted and effective measurement and compliance mechanisms are as important as the agreements themselves. So far, however, the negotiations do not include a specific plan to hold countries accountable for the pledges and promises they make on behalf of their plastics producers, exporters and recyclers. It is clear that this must change — and fast.

Multi-level problem

The research published this week highlights the multi-level problem that negotiators face. Pinheiro and his colleagues found debris in 77 of the 84 coral reef sites they surveyed globally. Larger pieces of debris, bigger than 5 centimetres across — mainly discarded or broken fishing equipment — were more prevalent in deeper reefs. This highlights complex trade-offs that treaty negotiators will have to grapple with to deliver a comprehensive solution to the plastics problem. Simply banning plastic nets and other fishing gear could harm livelihoods. Subsidies or incentives might be needed to enable communities that rely on fishing to switch from using gear that causes damage to deep reefs.

Large-scale collaborations uncover global extent of plastic pollution

The study by Nava and her colleagues highlights another facet of any meaningful treaty: getting measurements right. Countries will need to discuss and agree a standard or system for how they measure plastic pollution. Nava et al. developed a protocol for categorizing and measuring plastic pollution in freshwater samples and applied it to samples collected at the surface of 38 lakes and reservoirs, most of them in the Northern Hemisphere. The authors also collected data on the size of the population near each lake, the lake’s depth and how much of the land supplying inflow water is urban. Plastics in the samples were classified by shape, colour and size, and a subset were analysed using spectroscopic methods to identify the chemical composition of their polymers. This and other knowledge needs to feed into treaty talks.

The plastics treaty is on a supercharged schedule. Talks began in March 2022 and are due to conclude with a final text in 2024. If that happens, countries are expected to incorporate the treaty into national laws in 2025.

Environmental treaties often take between 5 and 15 years to complete, and accelerating the process could compel nations to focus on the essentials. However, at the most recent negotiating session, which concluded last month in Paris, countries spent most of the week discussing (and struggling to agree on) how they would make decisions. To adhere to the rapid timetable, subsequent sessions will need to get down to detail more quickly. But a downside of a fast-track approach is that there is less time for researchers and campaigners to influence the process.

Protecting the ocean requires better progress metrics

The talks are being organized by the UN Environment Programme (UNEP), based in Nairobi. It is inviting observers, including researchers, to make written submissions by 15 August, ahead of the publication of the treaty’s first draft text, or ‘zero draft’. Researchers should take this opportunity to urge negotiators to establish an expert group on measurement and compliance as part of the talks.

UNEP told Nature that there is no dedicated expert group looking at measurement or accountability. However, a representative said that negotiators will “consider how other multilateral agreements provide for monitoring and suggest best practice”. Studying how other agreements manage monitoring is important, but monitoring is not the same thing as compliance. There is a risk that, in a rush to meet the timetable, negotiators will settle for a treaty that demands little or nothing in the way of compliance.

For the treaty negotiations to be successful, countries must commit to being held accountable. Not having a group within the negotiations charged with ensuring measurement and compliance could be a costly error. The time between now and the next session, due to be held in Nairobi in November, offers a valuable and urgent opportunity for researchers to get their voices heard — so that we can finally start to reduce the stark toll of plastic pollution on the global environment.

Nature 619 , 222 (2023)

doi: https://doi.org/10.1038/d41586-023-02252-x

Lampitt, R. S. et al. Nature Commun. 14 , 2849 (2023).

Article   PubMed   Google Scholar  

Nava, V. et al. Nature 619 , 317–322 (2023).

Article   Google Scholar  

Pinheiro, H. T. et al. Nature 619 , 311–316 (2023).

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Plastic waste management: a review of existing life cycle assessment studies.

1. Introduction

1.1. plastics, 1.2. recycling of plastic, 1.3. waste management, 1.4. legal requirements for waste recycling.

• Establish a waste reduction research and development program;
• Direct several federal agencies in developing strategies to reduce waste;
• Develop standards for plastic recycling technologies.

1.5. Life Cycle Assessment

• Goal and scope definition;
• Life Cycle Inventory Analysis (LCI);
• Life Cycle Impact Assessment (LCIA);
• Interpretation.

1.6. Aims and Objectives

2. materials and methods, 2.1. selection criteria.

• An original research article focusing on environmental impacts associated with at least one plastic recycling technology.
• Contains a well-described methodology with a clearly defined functional unit, goal and scope, and system boundary.
• Results are quantified and tabulated as defined impact potentials covering at least two different categories.

2.2. Assessment Process

2.2.1. goal and scope.

• Types of plastics included some studies focus on a broad range of plastics, while others were restricted to just one polymer (for example, PET) or product type (example, plastic films).
• Study extent: Some studies cover the entire lifespan of the plastics; others are more focused on specific aspects of the process.

2.2.2. Functional Unit (FU)

• Type of waste (general waste, plastic waste, or specified waste type);
• Quantifier of waste amount (specific mass, volume).

2.2.3. Impact Category

• Different studies may choose to investigate and assess different categories;
• The result for an impact category may not be comparable across studies if the system boundaries, functional units or other factors are different.

2.2.4. System Boundary

• Study scope (included/excluded processes);
• Geographical area (the environmental impact may vary in different locations due to varying processes, environments, infrastructures, and ecosystem sensitivities);
• Time horizon (what timeframe is considered for pollutant degradation pathways and technologies);
• Boundaries with other life cycles (how does the process interact with other processes such as plastic production, consumer use, recycling technologies).

2.2.5. Sensitivity and Uncertainty Analysis

3.1. comparison of lca goals and scopes, 3.2. comparison of functional units, 3.3. comparison of impact assessment categories, 3.4. comparison of system boundaries, 3.5. comparison of geographical context, 3.6. sensitivity and uncertainty analysis, 4. discussion, 4.1. comparable studies, 4.2. other studies, 4.3. summary, 5. conclusions, author contributions, institutional review board statement, informed consent statement, data availability statement, conflicts of interest.

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Alhazmi, H.; Almansour, F.H.; Aldhafeeri, Z. Plastic Waste Management: A Review of Existing Life Cycle Assessment Studies. Sustainability 2021 , 13 , 5340. https://doi.org/10.3390/su13105340

Alhazmi H, Almansour FH, Aldhafeeri Z. Plastic Waste Management: A Review of Existing Life Cycle Assessment Studies. Sustainability . 2021; 13(10):5340. https://doi.org/10.3390/su13105340

Alhazmi, Hatem, Faris H. Almansour, and Zaid Aldhafeeri. 2021. "Plastic Waste Management: A Review of Existing Life Cycle Assessment Studies" Sustainability 13, no. 10: 5340. https://doi.org/10.3390/su13105340

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• Philos Trans R Soc Lond B Biol Sci
• v.364(1526); 2009 Jul 27

Plastics, the environment and human health: current consensus and future trends

Richard c. thompson.

1 Marine Biology and Ecology Research Centre, Marine Institute, University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK

Charles J. Moore

2 Algalita Marine Research Foundation, Long Beach, CA 90803, USA

Frederick S. vom Saal

3 Division of Biological Sciences, University of Missouri, Columbia, MO 65201, USA

Shanna H. Swan

4 Department of Obstetrics and Gynecology, University of Rochester, Rochester, NY 14642, USA

Plastics have transformed everyday life; usage is increasing and annual production is likely to exceed 300 million tonnes by 2010. In this concluding paper to the Theme Issue on Plastics, the Environment and Human Health, we synthesize current understanding of the benefits and concerns surrounding the use of plastics and look to future priorities, challenges and opportunities. It is evident that plastics bring many societal benefits and offer future technological and medical advances. However, concerns about usage and disposal are diverse and include accumulation of waste in landfills and in natural habitats, physical problems for wildlife resulting from ingestion or entanglement in plastic, the leaching of chemicals from plastic products and the potential for plastics to transfer chemicals to wildlife and humans. However, perhaps the most important overriding concern, which is implicit throughout this volume, is that our current usage is not sustainable. Around 4 per cent of world oil production is used as a feedstock to make plastics and a similar amount is used as energy in the process. Yet over a third of current production is used to make items of packaging, which are then rapidly discarded. Given our declining reserves of fossil fuels, and finite capacity for disposal of waste to landfill, this linear use of hydrocarbons, via packaging and other short-lived applications of plastic, is simply not sustainable. There are solutions, including material reduction, design for end-of-life recyclability, increased recycling capacity, development of bio-based feedstocks, strategies to reduce littering, the application of green chemistry life-cycle analyses and revised risk assessment approaches. Such measures will be most effective through the combined actions of the public, industry, scientists and policymakers. There is some urgency, as the quantity of plastics produced in the first 10 years of the current century is likely to approach the quantity produced in the entire century that preceded.

1. Introduction

Many of the current applications and the predicted benefits of plastic follow those outlined by Yarsley and Couzens in the 1940s. Their account of the benefits that plastics would bring to a person born nearly 70 years ago, at the beginning of this ‘ plastic age ’, was told with much optimism:

It is a world free from moth and rust and full of colour, a world largely built up of synthetic materials made from the most universally distributed substances, a world in which nations are more and more independent of localised naturalised resources, a world in which man, like a magician, makes what he wants for almost every need out of what is beneath and around him ( Yarsley & Couzens 1945 , p. 152).

The durability of plastics and their potential for diverse applications, including widespread use as disposable items, were anticipated, but the problems associated with waste management and plastic debris were not. In fact the predictions were ‘ how much brighter and cleaner a world [it would be] than that which preceded this plastic age ’ ( Yarsley & Couzens 1945 , p. 152).

This paper synthesizes current understanding of the benefits and concerns surrounding the use of plastics and looks to challenges, opportunities and priorities for the future. The content draws upon papers submitted to this Theme Issue on Plastics, the Environment and Human Health together with other sources. While selected citations are given to original sources of information, we primarily refer the reader to the discussion of a particular topic, and the associated references, in the Theme Issue papers. Here, we consider the subject from seven perspectives: plastics as materials; accumulation of plastic waste in the natural environment; effects of plastic debris in the environment and on wildlife; effects on humans; production, usage, disposal and waste management solutions; biopolymers, degradable and biodegradable polymer solutions; and policy measures.

2. Plastics as materials: an overview

Plastics are inexpensive, lightweight, strong, durable, corrosion-resistant materials, with high thermal and electrical insulation properties. The diversity of polymers and the versatility of their properties are used to make a vast array of products that bring medical and technological advances, energy savings and numerous other societal benefits ( Andrady & Neal 2009 ). As a consequence, the production of plastics has increased substantially over the last 60 years from around 0.5 million tonnes in 1950 to over 260 million tonnes today. In Europe alone the plastics industry has a turnover in excess of 300 million euros and employs 1.6 million people ( Plastics Europe 2008 ). Almost all aspects of daily life involve plastics, in transport, telecommunications, clothing, footwear and as packaging materials that facilitate the transport of a wide range of food, drink and other goods. There is considerable potential for new applications of plastics that will bring benefits in the future, for example as novel medical applications, in the generation of renewable energy and by reducing energy used in transport ( Andrady & Neal 2009 ).

Virgin plastic polymers are rarely used by themselves and typically the polymer resins are mixed with various additives to improve performance. These additives include inorganic fillers such as carbon and silica that reinforce the material, plasticizers to render the material pliable, thermal and ultraviolet stabilizers, flame retardants and colourings. Many such additives are used in substantial quantities and in a wide range of products ( Meeker et al. 2009 ). Some additive chemicals are potentially toxic (for example lead and tributyl tin in polyvinyl chloride, PVC), but there is considerable controversy about the extent to which additives released from plastic products (such as phthalates and bisphenol A, BPA) have adverse effects in animal or human populations. The central issue here is relating the types and quantities of additives present in plastics to uptake and accumulation by living organisms ( Andrady & Neal 2009 ; Koch & Calafat 2009 ; Meeker et al. 2009 ; Oehlmann et al. 2009 ; Talsness et al. 2009 ; Wagner & Oehlmann 2009 ). Additives of particular concern are phthalate plasticizers, BPA, brominated flame retardants and anti-microbial agents. BPA and phthalates are found in many mass produced products including medical devices, food packaging, perfumes, cosmetics, toys, flooring materials, computers and CDs and can represent a significant content of the plastic. For instance, phthalates can constitute a substantial proportion, by weight, of PVC ( Oehlmann et al. 2009 ), while BPA is the monomer used for production of polycarbonate plastics as well as an additive used for production of PVC. Phthalates can leach out of products because they are not chemically bound to the plastic matrix, and they have attracted particular attention because of their high production volumes and wide usage ( Wagner & Oehlmann 2009 ; Talsness et al. 2009 ). Phthalates and BPA are detectable in aquatic environments, in dust and, because of their volatility, in air ( Rudel et al. 2001 , 2003 ). There is considerable concern about the adverse effects of these chemicals on wildlife and humans ( Meeker et al. 2009 ; Oehlmann et al. 2009 ). In addition to the reliance on finite resources for plastic production, and concerns about additive effects of different chemicals, current patterns of usage are generating global waste management problems. Barnes et al. (2009) show that plastic wastes, including packaging, electrical equipment and plastics from end-of-life vehicles, are major components of both household and industrial wastes; our capacity for disposal of waste to landfill is finite and in some locations landfills are at, or are rapidly approaching, capacity ( Defra et al. 2006 ). So from several perspectives it would seem that our current use and disposal of plastics is the cause for concern ( Barnes et al. 2009 ; Hopewell et al. 2009 ).

3. Accumulation of plastic waste in the natural environment

Substantial quantities of plastic have accumulated in the natural environment and in landfills. Around 10 per cent by weight of the municipal waste stream is plastic ( Barnes et al. 2009 ) and this will be considered later in §6 . Discarded plastic also contaminates a wide range of natural terrestrial, freshwater and marine habitats, with newspaper accounts of plastic debris on even some of the highest mountains. There are also some data on littering in the urban environment (for example compiled by EnCams in the UK; http://www.encams.org/home ); however, by comparison with the marine environment, there is a distinct lack of data on the accumulation of plastic debris in natural terrestrial and freshwater habitats. There are accounts of inadvertent contamination of soils with small plastic fragments as a consequence of spreading sewage sludge ( Zubris & Richards 2005 ), of fragments of plastic and glass contaminating compost prepared from municipal solid waste ( Brinton 2005 ) and of plastic being carried into streams, rivers and ultimately the sea with rain water and flood events ( Thompson et al. 2005 ). However, there is a clear need for more research on the quantities and effects of plastic debris in natural terrestrial habitats, on agricultural land and in freshwaters. Inevitably, therefore, much of the evidence presented here is from the marine environment. From the first accounts of plastic in the environment, which were reported from the carcasses of seabirds collected from shorelines in the early 1960s ( Harper & Fowler 1987 ), the extent of the problem soon became unmistakable with plastic debris contaminating oceans from the poles to the Equator and from shorelines to the deep sea. Most polymers are buoyant in water, and since items of plastic debris such as cartons and bottles often trap air, substantial quantities of plastic debris accumulate on the sea surface and may also be washed ashore. As a consequence, plastics represent a considerable proportion (50–80%) of shoreline debris ( Barnes et al. 2009 ). Quantities are highly variable in time and space, but there are reports of more than 100 000 items m –2 on some shorelines ( Gregory 1978 ) and up to 3 520 000 items km –2 at the ocean surface ( Yamashita & Tanimura 2007 ). Gyres and oceanic convergences appear to be particularly contaminated, as do enclosed seas such as the Mediterranean ( Barnes et al. 2009 ; Ryan et al. 2009 ). Despite their buoyant nature, plastics can become fouled with marine life and sediment causing items to sink to the seabed. For example, shallow seabeds in Brazil were more heavily contaminated than the neighbouring shorelines ( Oigman-Pszczol & Creed 2007 ), indicating that the seabed may be an ultimate sink even for initially buoyant marine debris ( Barnes et al. 2009 ). In some locations around Europe, it has been suggested that quantities on the seabed may exceed 10 000 items ha –1 , and debris has even been reported more than a 1000 m below the ocean surface, including accounts of inverted plastic bags passing a deep-sea submersible like an assembly of ghosts ( Gregory 2009 ). Quantitative data on the abundance of debris on the seabed are still very limited, but there are concerns that degradation rates in the deep sea will be especially slow because of darkness and cold ( Barnes et al. 2009 ; Ryan et al. 2009 ).

Monitoring the abundance of debris is important to establish rates of accumulation and the effectiveness of any remediation measures. Most studies assess the abundance of all types of anthropogenic debris including data on plastics and/or plastic items as a category. In general, the abundance of debris on shorelines has been extensively monitored, in comparison to surveys from the open oceans or the seabed. In addition to recording debris, there is a need to collect data on sources; for plastic debris this should include discharges from rivers and sewers together with littering behaviour. Here, the limited data we have suggest that storm water pulses provide a major pathway for debris from the land to the sea, with 81 g m –3 of plastic debris during high-flow events in the USA ( Ryan et al. 2009 ). Methods to monitor the abundance of anthropogenic debris (including plastics) often vary considerably between countries and organizations, adding to difficulties in interpreting trends. As a consequence, the United Nations Environment Programme and the OSPAR Commission are currently taking steps to introduce standardized protocols ( OSPAR 2007 ; Cheshire et al. 2009 ). Some trends are evident, however, typically with an increase in the abundance of debris and fragments between the 1960s and the 1990s ( Barnes et al. 2009 ). More recently, abundance at the sea surface in some regions and on some shorelines appears to be stabilizing, while in other areas such as the Pacific Gyre there are reports of considerable increases. On shorelines the quantities of debris, predominantly plastic, are greater in the Northern than in the Southern Hemisphere ( Barnes 2005 ). The abundance of debris is greater adjacent to urban centres and on more frequented beaches and there is evidence that plastics are accumulating and becoming buried in sediments ( Barnes et al. 2009 ; Ryan et al. 2009 ). Barnes et al. (2009) consider that contamination of remote habitats, such as the deep sea and the polar regions, is likely to increase as debris is carried there from more densely populated areas. Allowing for variability between habitats and locations, it seems inevitable, however, that the quantity of debris in the environment as a whole will continue to increase—unless we all change our practices. Even with such changes, plastic debris that is already in the environment will persist for a considerable time to come. The persistence of plastic debris and the associated environmental hazards are illustrated poignantly by Barnes et al. (2009) who describe debris that had originated from an aeroplane being ingested by an albatross some 60 years after the plane had crashed.

4. Effects of plastic debris in the environment and on wildlife

There are some accounts of effects of debris from terrestrial habitats, for example ingestion by the endangered California condor, Gymnogyps californianus ( Mee et al. 2007 ). However, the vast majority of work describing environmental consequences of plastic debris is from marine settings and more work on terrestrial and freshwater habitats is needed. Plastic debris causes aesthetic problems, and it also presents a hazard to maritime activities including fishing and tourism ( Moore 2008 ; Gregory 2009 ). Discarded fishing nets result in ghost fishing that may result in losses to commercial fisheries ( Moore 2008 ; Brown & Macfadyen 2007 ). Floating plastic debris can rapidly become colonized by marine organisms and since it can persist at the sea surface for substantial periods, it may subsequently facilitate the transport of non-native or ‘alien’ species ( Barnes 2002 ; Barnes et al. 2009 ; Gregory 2009 ). However, the problems attracting most public and media attention are those resulting in ingestion and entanglement by wildlife. Over 260 species, including invertebrates, turtles, fish, seabirds and mammals, have been reported to ingest or become entangled in plastic debris, resulting in impaired movement and feeding, reduced reproductive output, lacerations, ulcers and death ( Laist 1997 ; Derraik 2002 ; Gregory 2009 ). The limited monitoring data we have suggest rates of entanglement have increased over time ( Ryan et al. 2009 ). A wide range of species with different modes of feeding including filter feeders, deposit feeders and detritivores are known to ingest plastics. However, ingestion is likely to be particularly problematic for species that specifically select plastic items because they mistake them for their food. As a consequence, the incidence of ingestion can be extremely high in some populations. For example, 95 per cent of fulmars washed ashore dead in the North Sea have plastic in their guts, with substantial quantities of plastic being reported in the guts of other birds, including albatross and prions ( Gregory 2009 ). There are some very good data on the quantity of debris ingested by seabirds recorded from the carcasses of dead birds. This approach has been used to monitor temporal and spatial patterns in the abundance of sea-surface plastic debris on regional scales around Europe ( Van Franeker et al. 2005 ; Ryan et al. 2009 ).

An area of particular concern is the abundance of small plastic fragments or microplastics. Fragments as small as 1.6 µm have been identified in some marine habitats, and it seems likely there will be even smaller pieces below current levels of detection. A recent workshop convened in the USA by the National Oceanic and Atmospheric Administration concluded that microplastics be defined as pieces <5 mm with a suggested lower size boundary of 333 µm so as to focus on microplastics that will be captured using conventional sampling approaches ( Arthur et al. 2009 ). However, we consider it important that the abundance of even smaller fragments is not neglected. Plastic fragments appear to form by the mechanical and chemical deterioration of larger items. Alternative routes for microplastics to enter the environment include the direct release of small pieces of plastics that are used as abrasives in industrial and domestic cleaning applications (e.g. shot blasting or scrubbers used in proprietary hand cleansers) and spillage of plastic pellets and powders that are used as a feedstock for the manufacture of most plastic products. Data from shorelines, from the open ocean and from debris ingested by seabirds, all indicate that quantities of plastic fragments are increasing in the environment, and quantities on some shores are substantial (>10% by weight of strandline material; Barnes et al. 2009 ). Laboratory experiments have shown that small pieces such as these can be ingested by small marine invertebrates including filter feeders, deposit feeders and detritivores ( Thompson et al. 2004 ), while mussels were shown to retain plastic for over 48 days ( Browne et al. 2008 ). However, the extent and consequences of ingestion of microplastics by natural populations are not known.

In addition to the physical problems associated with plastic debris, there has been much speculation that, if ingested, plastic has the potential to transfer toxic substances to the food chain (see Teuten et al. 2009 ). In the marine environment, plastic debris such as pellets, fragments and microplastics have been shown to contain organic contaminants including polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons, petroleum hydrocarbons, organochlorine pesticides (2,2′-bis( p -chlorophenyl)-1,1,1 trichloroethane (DDT) and its metabolites; together with hexachlorinated hexane (HCH)), polybrominated diphenylethers (PBDEs), alkylphenols and BPA at concentrations ranging from ng g –1 to µg g –1 . Some of these compounds are added to plastics during manufacture while others adsorb to plastic debris from the environment. Work in Japan has shown that plastics can accumulate and concentrate persistent organic pollutants that have arisen in the environment from other sources. These contaminants can become orders of magnitude more concentrated on the surface of plastic debris than in the surrounding sea water ( Mato et al. 2001 ). Teuten et al. (2009) describe experiments to examine the transfer of these contaminants from plastics to seabirds and other animals. The potential for transport varies among contaminants, polymers and possibly also according to the state of environmental weathering of the debris. Recent mathematical modelling studies have shown that even very small quantities of plastics could facilitate transport of contaminants from plastic to organisms upon ingestion. This could present a direct and important route for the transport of chemicals to higher animals such as seabirds ( Teuten et al. 2007 , 2009 ), but will depend upon the nature of the habitat and the amount and type of plastics present. For instance, the extent to which the presence of plastic particles might contribute to the total burden of contaminants transferred from the environment to organisms will depend upon competitive sorption and transport by other particulates ( Arthur et al. 2009 ). The abundance of fragments of plastic is increasing in the environment; these particles, especially truly microscopic fragments less than the 333 µm proposed by NOAA (see earlier), have a relatively large surface area to volume ratio that is likely to facilitate the transport of contaminants, and because of their size such fragments can be ingested by a wide range of organisms. Hence, the potential for plastics to transport and release chemicals to wildlife is an emerging area of concern.

More work will be needed to establish the full environmental relevance of plastics in the transport of contaminants to organisms living in the natural environment, and the extent to which these chemicals could then be transported along food chains. However, there is already clear evidence that chemicals associated with plastic are potentially harmful to wildlife. Data that have principally been collected using laboratory exposures are summarized by Oehlmann et al. (2009) . These show that phthalates and BPA affect reproduction in all studied animal groups and impair development in crustaceans and amphibians. Molluscs and amphibians appear to be particularly sensitive to these compounds and biological effects have been observed in the low ng l –1 to µg l –1 range. In contrast, most effects in fish tend to occur at higher concentrations. Most plasticizers appear to act by interfering with hormone function, although they can do this by several mechanisms ( Hu et al. 2009 ). Effects observed in the laboratory coincide with measured environmental concentrations, thus there is a very real probability that these chemicals are affecting natural populations ( Oehlmann et al. 2009 ). BPA concentrations in aquatic environments vary considerably, but can reach 21 µg l –1 in freshwater systems and concentrations in sediments are generally several orders of magnitude higher than in the water column. For example, in the River Elbe, Germany, BPA was measured at 0.77 µg l –1 in water compared with 343 µg kg –1 in sediment (dry weight). These findings are in stark contrast with the European Union environmental risk assessment predicted environmental concentrations of 0.12 µg l –1 for water and 1.6 µg kg –1 (dry weight) for sediments.

Phthalates and BPA can bioaccumulate in organisms, but there is much variability between species and individuals according to the type of plasticizer and experimental protocol. However, concentration factors are generally higher for invertebrates than vertebrates, and can be especially high in some species of molluscs and crustaceans. While there is clear evidence that these chemicals have adverse effects at environmentally relevant concentrations in laboratory studies, there is a need for further research to establish population-level effects in the natural environment (see discussion in Oehlmann et al. 2009 ), to establish the long-term effects of exposures (particularly due to exposure of embryos), to determine effects of exposure to contaminant mixtures and to establish the role of plastics as sources (albeit not exclusive sources) of these contaminants (see Meeker et al. (2009) for discussion of sources and routes of exposure).

5. Effects on humans: epidemiological and experimental evidence

Turning to adverse effects of plastic on the human population, there is a growing body of literature on potential health risks. A range of chemicals that are used in the manufacture of plastics are known to be toxic. Biomonitoring (e.g. measuring concentration of environmental contaminants in human tissue) provides an integrated measure of an organism's exposure to contaminants from multiple sources. This approach has shown that chemicals used in the manufacture of plastics are present in the human population, and studies using laboratory animals as model organisms indicate potential adverse health effects of these chemicals ( Talsness et al. 2009 ). Body burdens of chemicals that are used in plastic manufacture have also been correlated with adverse effects in the human population, including reproductive abnormalities (e.g. Swan et al. 2005 ; Swan 2008 ; Lang et al. 2008 ).

Interpreting biomonitoring data is complex, and a key task is to set information into perspective with dose levels that are considered toxic on the basis of experimental studies in laboratory animals. The concept of ‘toxicity’ and thus the experimental methods for studying the health impacts of the chemicals in plastic, and other chemicals classified as endocrine disruptors, is currently undergoing a transformation (a paradigm inversion) since the disruption of endocrine regulatory systems requires approaches very different from the study of acute toxicants or poisons. There is thus extensive evidence that traditional toxicological approaches are inadequate for revealing outcomes such as ‘reprogramming’ of the molecular systems in cells as a result of exposure to very low doses during critical periods in development (e.g. Myers et al. 2009 ). Research on experimental animals informs epidemiologists about the potential for adverse effects in humans and thus plays a critical role in chemical risk assessments. A key conclusion from the paper by Talsness et al. (2009) is the need to modify our approach to chemical testing for risk assessment. As noted by these authors and others, there is a need to integrate concepts of endocrinology in the assumptions underlying chemical risk assessment. In particular, the assumptions that dose–response curves are monotonic and that there are threshold doses (safe levels) are not true for either endogenous hormones or for chemicals with hormonal activity (which includes many chemicals used in plastics) ( Talsness et al. 2009) .

The biomonitoring approach has demonstrated phthalates and BPA, as well as other additives in plastics and their metabolites, are present in the human population. It has also demonstrated that the most common human exposure scenario is to a large number of these chemicals simultaneously. These data indicate differences according to geographical location and age, with greater concentrations of some of these chemicals in young children. While exposure via house dust is extensive ( Rudel et al. 2008 ), it would appear that at least for some phthalates (e.g. diethylhexyl phthalate, DEHP), foodstuffs and to a lesser extent use of oral drugs probably present major uptake pathways ( Wormuth et al. 2006 ). Exposure data for BPA are similar but less extensive. While average concentrations of phthalates in selected populations worldwide appear quite similar, there is evidence of considerable variability in daily intake rates among individuals, and even within individuals ( Peck et al. 2009 ). Exposures through ingestion, inhalation and dermal contact are all considered important routes of exposure for the general population ( Adibi et al. 2003 ; Rudel et al. 2003 ). Koch & Calafat (2009 ) show that while mean/median exposures for the general population were below levels determined to be safe for daily exposure (USA, EPA reference dose, RfD; and European Union tolerable daily intake, TDI), the upper percentiles of di-butyl phthalate and DEHP urinary metabolite concentrations show that for some people daily intake might be substantially higher than previously assumed and could exceed estimated safe daily exposure levels. Current ‘safe’ exposure levels are typically based on the application of traditional toxicological assumptions regarding acute toxicants to calculate daily exposures for chemicals in a range of widely used plastic items. The toxicological consequences of such exposures, especially for susceptible subpopulations such as children and pregnant women, remain unclear and warrant further investigation. However, there is evidence of associations between urinary concentrations of some phthalate metabolites and biological outcomes ( Swan et al. 2005 ; Swan 2008 ). For example, an inverse relationship has been reported between the concentrations of DEHP metabolites in the mother's urine and anogenital distance, penile width and testicular decent in male offspring ( Swan et al. 2005 ; Swan 2008 ). In adults, there is some evidence of a negative association between phthalate metabolites and semen quality (Meeker & Sathyanarayana) and between high exposures to phthalates (workers producing PVC flooring) and free testosterone levels. Moreover, recent work ( Lang et al. 2008 ) has shown a significant relationship between urine levels of BPA and cardiovascular disease, type 2 diabetes and abnormalities in liver enzymes, and Stahlhut et al. (2009) have reported that exposure of adults in the USA to BPA is likely to occur from multiple sources and that the half-life of BPA is longer than previously estimated, and the very high exposure of premature infants in neonatal intensive-care units to both BPA and phthalates is of great concern ( Calafat et al. 2009 ). These data indicate detrimental effects in the general population may be caused by chronic low-dose exposures (separately or in combination) and acute exposure to higher doses, but the full extent to which chemicals are transported to the human population by plastics is yet to be confirmed.

Much has been learned about toxicological effects on humans from experiments using laboratory animals. This approach has been used to examine component chemicals used in plastic production. A summary of work on phthalates, BPA and tetrabromobisphenol A (TBBPA) is presented by Talsness et al. (2009) . The male reproductive tract is particularly sensitive to phthalate exposure. However, most reproductive effects are not exerted by phthalate diesters themselves, but by their monoester metabolites, which are formed in the liver. The majority of these studies have been done using rats as a model organism, with doses at least an order of magnitude higher than those to which humans are commonly exposed, but they have resulted in rapid, severe changes in the rat testis. Reproductive effects have also been described in mice and guinea pigs. Effects on pre- and early post-natal development are of particular concern, and recent animal studies have shown exposures to certain phthalates can result in severe disorders of the developing male reproductive system. It should be noted that most work on animals has used phthalate exposures much higher than estimated daily human exposures (see above), and researchers have only recently started to investigate possible biological effects within the range of median human phthalate exposure ( Talsness et al. 2009 ). This is of critical importance because epidemiological studies have reported associations between phthalate levels and a number of adverse health effects in humans ( Swan et al. 2005 ), suggesting that either humans are more sensitive to phthalates than experimental animals or that the testing paradigm used in traditional toxicological studies, which examines one phthalate at a time, has not served to accurately predict adverse effects from the mixture of phthalates to which humans are exposed ( Andrade et al. 2006 ; NAS 2008 ).

For BPA, there is an extensive published literature showing adverse effects of exposure at very low doses, based on administration during development and to adult experimental animals. In particular, unlike the case for experimental animal research on phthalates, there are now hundreds of experiments on laboratory animals using doses within the range of human exposures ( Vandenberg et al. 2007 ). The rate and extent to which BPA is metabolized affect the interpretation of these findings, but even very low doses of BPA have been shown to cause significant stimulation of insulin secretion followed by insulin resistance in mice, a significant decrease in sperm production by rats, a decrease in maternal behaviour in mice and disruption of hippocampal synapses, leading to the appearance of a brain typical of that seen in senility in both rats and monkeys. The greatest concerns with exposure to BPA are during development; BPA appears to affect brain development leading to loss of sex differentiation in brain structures and behaviour ( Talsness et al. 2009 ). A further important observation regarding adverse responses to developmental exposures of animals to very low doses of BPA is that many relate to disease trends in humans. Less has been published on effects of the flame retardant TBBPA, but there is evidence of effects on thyroid hormones, pituitary function and reproductive success in animals ( Talsness et al. 2009 ).

Despite the environmental concerns about some of the chemicals used in plastic manufacture, it is important to emphasize that evidence for effects in humans is still limited and there is a need for further research and in particular, for longitudinal studies to examine temporal relationships with chemicals that leach out of plastics ( Adibi et al. 2008 ). In addition, the traditional approach to studying the toxicity of chemicals has been to focus only on exposure to individual chemicals in relation to disease or abnormalities. However, because of the complex integrated nature of the endocrine system, it is critical that future studies involving endocrine-disrupting chemicals that leach from plastic products focus on mixtures of chemicals to which people are exposed when they use common household products. For example, in a study conducted in the USA, 80 per cent of babies were exposed to measurable levels of at least nine different phthalate metabolites ( Sathyanarayana et al. 2008 ), and the health impacts of the cumulative exposure to these chemicals need to be determined. An initial attempt at examining more than one phthalate as a contributor to abnormal genital development in babies has shown the importance of this approach ( Swan 2008 ). Studies of mixtures of chemicals therefore also need to extend beyond mixtures of the same class of chemical, such as mixtures of different phthalates or of different PCBs. For example, PVC (used in a wide range of products in the home including water pipes) may contain phthalates, BPA, flame retardants such as PBDEs or TBBPA, cadmium, lead and organotins, all of which have been shown in animal studies to result in obesity ( Heindel & vom Saal 2009 ). In addition, the monomer used to manufacture PVC plastic, vinyl chloride, is a known carcinogen and exposure can cause angiosarcoma of the liver among factory workers ( Bolt 2005 ; Gennaro et al. 2008 ). PVC in medical tubing has also been shown to be a source of high DEHP exposure among infants in neonatal intensive-care nurseries ( Green et al. 2005 ) and probably contributes to the high levels of BPA found in these babies since BPA is an additive in PVC plastic ( Calafat et al. 2009 ).

Examining the relationship between plastic additives and adverse human effects presents a number of challenges. In particular, the changing patterns of production and use of both plastics, and the additives they contain, as well as the confidential nature of industrial specifications makes exposure assessment particularly difficult. Evolving technology, methodology and statistical approaches should help disentangle the relationships between these chemicals and health effects. However, with most of the statistically significant hormone alternations that have been attributed to environmental and occupational exposures, the actual degree of hormone alteration has been considered subclinical. Hence, more information is required on the biological mechanisms that may be affected by plastic additives and in particular, low-dose chronic exposures. Meanwhile we should consider strategies to reduce the use of these chemicals in plastic manufacture and/or develop and test alternatives (for example citrates are being developed as substitute plasticizers). This is the goal of the new field of green chemistry, which is based on the premise that development of chemicals for use in commerce should involve an interaction between biologists and chemists. Had this approach been in place 50 years ago it would probably have prevented the development of chemicals that are recognized as likely endocrine disruptors ( Anastas & Beach 2007 ). There is also a need for industry and independent scientists to work more closely with, rather than against, each other in order to focus effectively on the best ways forward. For example, contrast comments on BPA by Bird (2005 ) with those of vom Saal (2005 ), and contrast comments in this volume on the safety of plastic additives by Andrady & Neal (2009 ) with those by Koch & Calafat (2009 ), Meeker et al. (2009 ), Oehlmann et al. (2009) and Talsness et al. (2009) .

6. Production, usage, disposal and waste management solutions

Accumulation of plastic debris in the environment and the associated consequences are largely avoidable. Considerable immediate reductions in the quantity of waste entering natural environments, as opposed to landfill, could be achieved by better waste disposal and material handling. Littering is a behavioural issue and some have suggested that it has increased in parallel with our use of disposable products and packaging. Perhaps increasing the capacity to recycle will help to reverse this trend such that we start to regard end-of-life materials as valuable feedstocks for new production rather than waste. To achieve this will require better education, engagement, enforcement and recycling capacity ( figure 1 a – f ). Unfortunately, we were unable to source a contribution on education and public engagement, but it is evident that social research on littering behaviour could be very informative. A recent report by EnCams in the UK examined attitudes towards littering in 2001 and then again in 2006. This indicated that despite greater awareness among the general public about the problems of littering, the propensity to litter had actually increased; five key attitudes and behaviours were noted and these offer valuable insight for future research ( EnCams 2006 ). There is evidence that appropriate education can influence behaviour. For example, pre-production plastic pellets (a feedstock for production of plastic products, also described as nurdles or mermaids tears) account for around 10 per cent, by number, of the plastic debris recorded on shorelines in Hawaii ( McDermid & McMullen 2004 ) and substantial quantities have been recorded on shorelines in New Zealand ( Gregory 1978 ). These pellets have entered the environment through spillage during transportation, handling and as cargo lost from ships. In the USA guidelines (Operation Clean-Sweep, figure 1 e ) on handling of resin pellets are reported to have reduced spillage during trials ( Moore et al . 2005 ). Conservation organizations such as the UK Marine Conservation Society play an important role in education, and the annual beach cleans they organize can be a good way to raise public awareness and to collect data on trends in the abundance of debris on shorelines (see www.mcsuk.org and Ocean Conservancy, International Coastal Cleanup www.oceanconservancy.org ). However, there is a pressing need for education to reduce littering at source ( figure 1 d and e ). This is especially important in urban settings where increased consumption of on-the-go/fast food coupled, in some locations, with a reduction in the availability of bins as a consequence of concerns about terrorism is likely to result in increased littering. Where plastic debris enters watercourses as a consequence of dumping or littering a range of strategies including catch basin inserts, booms and separators can be used to facilitate removal ( figure 1 f ).

Solutions include: ( a ) measures to reduce the production of new plastics from oil, here an example showing how small changes in product packing reduced the weight of packaging required by 70%, while ( b ) re-useable plastic packing crates have reduced the packaging consumption of the same retailer by an estimated 30,000 tonnes per annum; and ( c ) recycling; here, bales of used plastic bottles have been sorted prior to recycling into new items, such as plastic packaging or textiles. Measures to reduce the quantity of plastic debris in the natural environment include: ( d ) educational signage to reduce contamination via storm drains and ( e ) via industrial spillage, together with ( f ) booms to intercept and facilitate the removal of riverine debris. (Photographs ( a ) and ( b ), and associated usage statistics, courtesy of Marks and Spencer PLC; ( c ) courtesy of P. Davidson, WRAP; ( d , e , f ) courtesy of C. Moore, Algalita Marine Research Foundation.)

Substantial quantities of end-of-life plastics are disposed of to landfill. Waste generation statistics vary among countries and according to the rationale for data collection. For instance, plastics are a small component of waste by weight but a large component by volume. Temporal and spatial comparisons can thus be confounded, and data on quantities of waste recycled can be skewed according to categorization of various wastes. However, in many locations space in landfill is running out (e.g. Defra et al. 2006 ). It has also been suggested that because of the longevity of plastics, disposal to landfill may simply be storing problems for the future ( Barnes et al. 2009 ; Hopewell et al. 2009 ). For example, plasticizers and other additive chemicals have been shown to leach from landfills ( Teuten et al. (2009) and references therein). The extent of this varies according to conditions, particularly pH and organic content. There is evidence, however, that landfills can present a significant source of contaminants, such as BPA, to aquatic environments. Efficient treatment approaches are available and are in use in some countries ( Teuten et al. 2009 ).

From a waste management perspective, the three R's— reduce, reuse and recycle are widely advocated to reduce the quantities of plastic and especially plastics packaging the waste we generate ( figure 1 a – c ). Hopewell et al. (2009) outline the benefits and limitations of these strategies. They show that to be effective we need to consider the three R's in combination with each other and together with a fourth ‘R’, energy recovery . Indeed we also need to consider a 5th ‘R’, molecular redesign, as an emerging and potentially very important strategy. Hence, the three R's become five: ‘reduce, reuse, recycle, recover and redesign’. There are opportunities to ‘reduce’ usage of raw material by down gauging ( figure 1 a ) and there are also some opportunities to ‘reuse’ plastics, for example, in the transport of goods on an industrial (pallets, crates; figure 1 b ) and a domestic (carrier bags) scale. However, there is limited potential for wide-scale reuse of retail packaging because of the substantial back-haul distances and logistics involved in returning empty cartons to suppliers. Some of the energy content of plastics can be ‘recovered’ by incineration, and through approaches such as co-fuelling of kilns, reasonable energy efficiency can be achieved. These approaches have benefits compared with disposal to landfill since some of the energy content of plastics is recovered. However, energy recovery does not reduce the demand for raw material used in plastic production, hence it is considered less energy efficient than product recovery via recycling ( WRAP 2006 ; Defra 2007 ). In addition, concerns about emissions from incinerators ( Katami et al. 2002 ) can reduce the appeal of this waste disposal option. There is now strong evidence to indicate significant potential lies in increasing our ability to effectively recycle end-of-life plastic products ( WRAP 2006 , 2008 ; Defra 2007 ; fig 1 c ). Although thermoplastics have been recycled since the 1970s, the proportion of material recycled has increased substantially in recent years and represents one of the most dynamic areas of the plastic industry today ( WRAP 2006 , 2008 ).

The recycling message is simple; both industry and society need to regard end-of-life items, including plastics, as raw materials rather than waste. At present our consumption of fossil fuels for plastic production is linear, from oil to waste via plastics. It is essential to take a more cyclical approach to material usage, but achieving this goal is complex ( Hopewell et al. 2009 ). Greatest energy efficiency is achieved where recycling diverts the need for use of fossil fuels as raw materials ( figure 1 c ); good examples being the recycling of old polyethylene terephthalate (PET) bottles into new ones (closed-loop recycling) or where low-density polyethylene bottles are converted into waste bins (semi-closed loop). In addition to benefits as a consequence of more sustainable material usage, a recent life cycle analysis calculated that use of 100 per cent recycled PET rather than virgin PET to produce plastic bottles could give a 27 per cent reduction on CO 2 emissions ( WRAP 2008 ; Hopewell et al. 2009 ).

There are some very encouraging trends, with growth in mechanical recycling increasing at 7 per cent per annum in western Europe. However, there is considerable regional variation in recycling rates and globally only a small proportion of plastic waste is recycled (see Barnes et al. (2009) for US data; see Hopewell et al. (2009) for European data). Items made of a single polymer are easier and more efficient to recycle than composite items, films and mixed wastes. As a consequence, it is currently not possible to recycle a substantial proportion of the packaging in a typical shopping basket ( Hopewell et al. 2009 ). On reading the account by Hopewell et al. (2009) , the ingenuity of the separation procedures for recycling is evident (Fourier-transform near-infrared spectroscopy, optical colour separation, X-ray detection), but one cannot help but wonder why similar ingenuity has not been focused on designing products for better end-of-life recyclability. Historically, the main considerations for the design of plastic packaging have been getting goods safely to market and product marketing. There is an increasing urgency to also design products, especially packaging, in order to achieve material reduction and greater end-of-life recyclability. Public support for recycling is high in some countries (57% in the UK and 80% in Australia; Hopewell et al. 2009 ), and consumers are keen to recycle, but the small size and the diversity of different symbols to describe a product's potential recyclability, together with uncertainties as to whether a product will actually be recycled if it is offered for collection, can hinder engagement. In our opinion, what is needed is a simplification and streamlining of everyday packaging, to facilitate recyclability, together with clearer labelling to inform users. One option could be a traffic light system so that consumers can easily distinguish from printed product labelling between packages that use recycled content and have high end-of-life recyclability (marked with a green spot), those that have low end-of-life recyclability and are predominantly made of virgin polymer (red spot), and those which lie between these extremes (amber spot). With combined actions including waste reduction, design for end-of-life, better labelling for consumers, increased options for on-the-go disposal to recycling and improved recycling capability, Hopewell et al. (2009) consider it could be possible to divert the majority of plastic from landfill over the next few decades ( figure 1 a – c ). This will require consistency of policy measures and facilities among regions and will also require the cooperation of industry since ultimately there needs to be an acceptance of reduced usage and hence reduced income associated with the production of plastics from virgin polymer.

Molecular redesign of plastics (the 5th R) has become an emerging issue in green chemistry ( Anastas & Warner 1998 ; Anastas et al. 2000 ; Anastas & Crabtree 2009 ) that should be incorporated within the design and life cycle analysis of plastics. In this context, green chemists aspire to design chemical products that are fully effective, yet have little or no toxicity or endocrine-disrupting activity; that break down into innocuous substances if released into the environment after use; and/or that are based upon renewable feedstocks, such as agricultural wastes. One of the fundamental factors limiting progress on all other R's is that the design criteria used to develop new monomers have rarely included specifications to enhance reusability, recyclability or recovery of plastic once it has been used. Typically, such assessments have only been made after a product entered the marketplace and problems involving waste and/or adverse health effects have begun to appear. Had the guiding principles of Green Chemistry ( Anastas & Warner 1998 ) been available to inform the syntheses of polymers over the past century, perhaps some of the environmental and health concerns described in this Theme Issue would be more manageable. To date, the application of these design criteria to polymers has remained largely in the laboratory. Polylactic acid (PLA) ( Drumright et al. 2000 ), a biodegradable polymer sourced from corn and potatoes, has entered the marketplace and has the potential to make a valuable contribution among other strategies for waste management. However, life cycle analyses are required to help establish the most appropriate usage, disposal (e.g. Song et al. 2009 illustrate relatively slow degradability of PLA in home composting) and hence labelling, of biopolymers such as this ( WRAP 2009 ).

7. Biopolymers, degradable and biodegradable polymer solutions

Degradable polymers have been advocated as an alternative to conventional oil-based plastics and their production has increased considerably in recent decades. Materials with functionality comparable to conventional plastics can now be produced on an industrial scale; they are more expensive than conventional polymers and account for less than 1 per cent of plastics production ( Song et al. 2009 ). Biopolymers differ from conventional polymers in that their feedstock is from renewable biomass rather than being oil-based. They may be natural polymers (e.g. cellulose), or synthetic polymers made from biomass monomers (e.g. PLA) or synthetic polymers made from synthetic monomers derived from biomass (e.g. polythene derived from bioethanol) ( WRAP 2009 ). They are often described as renewable polymers since the original biomass, for example corn grown in agriculture, can be reproduced. The net carbon dioxide emission may be less than that with conventional polymers, but it is not zero since farming and pesticide production have carbon dioxide outputs ( WRAP 2009 ). In addition, as a consequence of our rapidly increasing human population, it seems unlikely that there will be sufficient land to grow crops for food, let alone for substantial quantities of packaging in which to wrap it. One solution is to recycle waste food into biopolymers; this has merit, but will ultimately be limited by the amount of waste food available.

Biopolymers that are designed to breakdown in an industrial composter are described as ‘biodegradables’ while those that are intended to degrade in a domestic composter are known as ‘compostable’. There are benefits of these biodegradable materials in specific applications, for example, with packaging of highly perishable goods where, regrettably, it can be necessary to dispose of perished unopened and unused product together with its wrapper. Song et al. (2009) show experimentally that degradation of biodegradable, as opposed to compostable, polymers can be very slow in home composters (typically less than 5% loss of biomass in 90 days). Degradation of these polymers in landfills is also likely to be slow and may create unwanted methane emissions. Hence, the benefits of biopolymers are only realized if they are disposed of to an appropriate waste management system that uses their biodegradable features. Typically, this is achieved via industrial composting at 50°C for around 12 weeks to produce compost as a useful product.

Some biopolymers, such as PLA, are biodegradable, but others such as polythene derived from bioethanol are not. A further complication is that degradable, as opposed to biodegradable, polymers (also called ‘oxo-biodegradable’, ‘oxy-degradable’ or ‘UV-degradable’) can also be made from oil-based sources but as a consequence are not biopolymers. These degradable materials are typically polyethylene together with additives to accelerate the degradation. They are used in a range of applications and are designed to break down under UV exposure and/or dry heat and mechanical stress, leaving small particles of plastic. They do not degrade effectively in landfills and little is known about the timescale, extent or consequences of their degradation in natural environments ( Barnes et al. 2009 ; Teuten et al. 2009 ). Degradable polymers could also compromise the quality of recycled plastics if they enter the recycling stream. As a consequence, use of degradable polymers is not advocated for primary retail packaging ( WRAP 2009 ).

There is a popular misconception that degradable and biodegradable polymers offer solutions to the problems of plastic debris and the associated environmental hazards that result from littering. However, most of these materials are unlikely to degrade quickly in natural habitats, and there is concern that degradable, oil-based polymers could merely disintegrate into small pieces that are not in themselves any more degradable than conventional plastic ( Barnes et al. 2009 ). So while biodegradable polymers offer some waste management solutions, there are limitations and considerable misunderstanding among the general public about their application ( WRAP 2007 ). To gain the maximum benefit from degradable, biodegradable and compostable materials, it is, therefore, essential to identify specific uses that offer clear advantages and to refine national and international standards (e.g. EN 13432, ASTM D6400-99) and associated product labelling to indicate appropriate usage and appropriate disposal.

8. Policy measures

Our intention when preparing this Theme Issue was to focus on the science surrounding all aspects pertinent to plastics, the environment and human health. There are some omissions from the volume, such as input from social scientists on how best to convey relevant information to influence littering behaviour, consumer choice and engagement with recycling. These omissions aside, to be of greatest value the science herein needs to be communicated beyond a purely scientific audience (see recommendations in table 1 ). This is in part the role of a Theme Issue such as this, and the final invited contribution to the volume examines the science–policy interface with particular reference to policy relating to plastics. Shaxson (2009) considers this interface from the perspectives of industry, the scientist and the policymaker. She emphasizes the need for policy relating to plastic to weigh societal and economic benefits against environmental and health concerns. This is a diverse subject area that will require a range of policies to focus at specific issues, including polymer safety, material reduction, reuse, recycling, biopolymers, biodegradable and compostable polymers, littering, dumping and industrial spillage. There are a range of appropriate measures ( National Research Council 2008 ) including information and recommendations (e.g. WRAP 2009 ), regulations (such as the Canadian Government restrictions on BPA in baby bottles), taxes (such as land fill tax, which incentivizes the diversion of waste from landfill to recycling), standards (such as EN 13432 covering compostable plastics) and allocation of funds for research, innovation and capacity building. However, the diversity of issues leads to an equally complex policy environment. In the UK, for example, there is not one, but many relevant policy interfaces and numerous policies. These activities are shared among several government departments, driven by national pressures, international obligations and European directives. In such a complex environment, even robust and clearly delivered information from the scientific community does not always have the most appropriate effects on the policy process.

Table 1.

Synthesis of current knowledge, uncertainty and recommended actions relevant to environmental and human health concerns arising from current production, use and disposal of plastics.

Shaxson presents evidence from case studies on policies relating to plastic litter in the marine environment and land-based plastic waste. She indicates that many plastic-related policy issues fall into what are defined as unstructured or badly structured problems—in essence, problems that lack consensus and clarity in the relevant policy question and in some cases lack clarity in the relevant knowledge base to inform any decision. Shaxson suggests such circumstances will require a reflexive approach to brokering knowledge between industry, scientists and policymakers, and that scientists will need to be prepared to make and facilitate value judgements on the basis of best evidence. From a UK perspective, she advocates using the science within this volume to help develop a ‘Plastics Road Map’, similar to the recently completed Milk and Dairy Road Map ( Defra 2008 ) to structure policy around plastics, the environment and human health and suggests that this be facilitated by appropriate and broad debate among relevant parties.

9. Plastics and the future

Looking ahead, we do not appear to be approaching the end of the ‘plastic age’ described by Yarsley and Couzens in the 1940s, and there is much that plastics can contribute to society. Andrady & Neal (2009) consider that the speed of technological change is increasing exponentially such that life in 2030 will be unrecognizable compared with life today; plastics will play a significant role in this change. Plastic materials have the potential to bring scientific and medical advances, to alleviate suffering and help reduce mankind's environmental footprint on the planet ( Andrady & Neal 2009 ). For instance, plastics are likely to play an increasing role in medical applications, including tissue and organ transplants; lightweight components, such as those in the new Boeing 787, will reduce fuel usage in transportation; components for generation of renewable energy and insulation will help reduce carbon emissions and smart plastic packaging will no doubt be able to monitor and indicate the quality of perishable goods.

In conclusion, plastics offer considerable benefits for the future, but it is evident that our current approaches to production, use and disposal are not sustainable and present concerns for wildlife and human health. We have considerable knowledge about many of the environmental hazards, and information on human health effects is growing, but many concerns and uncertainties remain. There are solutions, but these can only be achieved by combined actions (see summary table 1 ). There is a role for individuals, via appropriate use and disposal, particularly recycling; for industry by adopting green chemistry, material reduction and by designing products for reuse and/or end-of-life recyclability and for governments and policymakers by setting standards and targets, by defining appropriate product labelling to inform and incentivize change and by funding relevant academic research and technological developments. These measures must be considered within a framework of lifecycle analysis and this should incorporate all of the key stages in plastic production, including synthesis of the chemicals that are used in production, together with usage and disposal. Relevant examples of lifecycle analysis are provided by Thornton (2002) and WRAP (2006) and this topic is discussed, and advocated, in more detail in Shaxson (2009) . In our opinion, these actions are overdue and are now required with urgent effect; there are diverse environmental hazards associated with the accumulation of plastic waste and there are growing concerns about effects on human health, yet plastic production continues to grow at approximately 9 per cent per annum ( PlasticsEurope 2008 ). As a consequence, the quantity of plastics produced in the first 10 years of the current century will approach the total that was produced in the entire century that preceded.

Acknowledgements

We are indebted to James Joseph and Claire Rawlinson in the editorial office and Jessica Mnatzaganian in the journals production office at the Royal Society. Without their guidance and patience this volume would not have been possible. We also thank Dr J. P. Myers, Environmental Health Sciences, for his help in preparing text for the section on Green Chemistry.

One contribution of 15 to a Theme Issue ‘Plastics, the environment and human health’ .

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Recycling/reuse of plastic waste as construction material for sustainable development: a review

• Research on Sustainable Developments for Environment Management
• Published: 16 October 2021
• Volume 29 , pages 86156–86179, ( 2022 )

Cite this article

• Pooja Lamba 1 ,
• Dilraj Preet Kaur   ORCID: orcid.org/0000-0002-9032-0088 1 ,
• Seema Raj 1 &
• Jyoti Sorout 1  

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The exponential rise in the production of plastic and the consequential surge in plastic waste have led the scientists and researchers look out for innovative and sustainable means to reuse/recycle the plastic waste in order to reduce its negative impact on environment. Construction material, converting waste plastic into fuel, household goods, fabric and clothing are some of the sectors where waste plastic is emerging as a viable option. Out of these, construction material modified with plastic waste has garnered lot of attention. Modification of construction material with plastic waste serves a dual purpose. It reduces the amount of plastic waste going to landfills or litter and secondly lessens the use of mined construction materials, thereby mitigating the negative impact of construction industry on environment. This paper summarizes the developments with regard to the use of plastic waste as a constituent of construction material. Inclusion of plastic waste as a binder, aggregate, fine aggregate, modifier or substitute of cement and sand in the manufacturing of bricks, tiles, concrete and roads has been comprehensively reviewed. Also, the influence of addition of plastic waste on strength properties, water absorption, durability, etc. has been thoroughly discussed. The research studies considered for this review have been categorized based on whether they dealt with the use of plastic waste for bricks and tiles or in concrete for road construction.

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Introduction

Accumulation of plastic waste over the years and the lack of suitable disposal techniques have given rise to a crucial and unparalleled crisis where plastic waste is clogging our water resources and waterways, overflowing the landfills, leaching into soil and transferring through air, thus polluting every natural resource in our environment. Longevity; which is one of the most beneficial features of plastic, is also a detrimental factor in its safe disposal. In reality, plastic materials never degrade completely but disintegrate into smaller pieces over hundreds of years. According to a report by the United Nations Environment Programme, around 300 million tonnes of plastic waste is generated every year globally, whereas plastic waste ever recycled merely counts to 9%. A statement by UNEP executive director Inger Andersen:

‘By 2050, we will have about a billion metric tons of plastic in our landfills. We need to make a shift’.

presents a grim reality of the current scenario ( https://www.unep.org/news-and-stories/story/plastic-recycling-underperforming-sector-ripe-remake . Accessed 28 May 2021). The COVID-19 pandemic has further thrashed the efforts for reducing plastic pollution, where the disposal of used PPE kits, gloves, masks, sanitizer dispensers, etc. has created a scenario of ‘pandemic of plastic pollution’.

In the past few years, the plastic production has increased manifold and so does the plastic waste, but the problematic issue is that most of the plastic waste is going to the landfills or clogging our water bodies. Figure  1 shows the worldwide production of plastic in the recent past, and Fig.  2 depicts the scenario of plastic waste management.

Worldwide production of plastic

Scenario of plastic waste management

Owing to the beneficial properties such as longevity, lightweight, water resistant, high elasticity, strength, durability, resistant to corrosion, easy to transport and economical, plastics are otherwise highly useful materials. However, it is the overconsumption of plastic which is creating havoc. Plastics have become an indispensable part of our lives, so the only sustainable solution in sight to reduce plastic pollution is to maximize its recycling and reuse. There are many sectors where we can use the waste plastic or recycle it for further application vis-à-vis construction material, converting waste plastic into fuel, household goods, fabric and clothing, shoe soles, etc. The aim of the present study is to review comprehensively the utilization of plastic waste as a construction material. This paper analyses different research approaches that employ plastic waste as binder, aggregate, fine aggregate, modifier or substitute of cement and sand in the manufacturing of bricks, tiles and concrete.

Past reviews and gap

Recently, many reviews have been reported based on investigating the use of diverse types of waste materials in construction. In 2016, Tiwari et al. presented a review assessing different industrial waste products such as bottom ash, waste foundry sand, copper slag, plastic waste, recycled rubber waste and crushed glass aggregate as a replacement of fine aggregates in concrete (Tiwari et al. 2016 ). Guand Ozbakkaloglu summarized the studies on recycling techniques of plastic waste and the effect of its addition on the characteristics and morphology of concrete (Gu and Ozbakkaloglu 2016 ). In 2018, Toghroli et al. reviewed the usage of recycled waste materials in pavement concrete. The reviewed waste materials include recycled crushed glass, steel slag, steel fibre, tyres, plastics and recycled asphalt (Toghroli et al. 2018 ). Babafemi et al. presented a review on the properties of concrete incorporated with waste recycled plastic. It has shown the effect of recycled waste plastic on the mechanical properties and durability (Babafemi et al. 2018 ). There was also a detailed review of the properties of mortar and concrete composites containing recycled plastic (Mercante et al. 2018 ). Singh et al. critically reviewed the use of polyethylene terephthalate (PET) and marble dust in composites for construction (Singh et al. 2021 ). Another review reported PET plastic bricks used for Rohingya refugee camp (Haque 2019 ). Salih et al. reviewed the progress on bricks reinforced with fibres derived from waste materials (Salih et al. 2020 ). Bejan et al. presented the review on lightweight concrete using various waste materials, such as fly ash, blast furnace slag, fumed silica, tyre waste, plastics and agro waste (Bejan et al. 2020 ). Awoyera and Adesina presented a detailed review of the use of plastic waste as a constituent in cement composites. They also discussed the limitations and future prospects of using plastic waste (Awoyera and Adesina 2020 ). Li. et al. studied in detail about the effect of addition of rubber and plastic waste as an aggregate to the concrete (Li et al. 2020 ). Another review on the utilization of plastic waste as an aggregate in construction material and the effect on mechanical and durability properties was recently presented (Zulkernain et al. 2021 ). Vishnu and Singh presented a review on suitability of various waste materials for bituminous pavements (Vishnu and Singh 2020 ). Ogundairo et al. reviewed the use of plastic in bitumen modification and stabilization of soil and as reinforcement material in bricks (Ogundairo et al. 2021 ). From the above discussion, it is evident that some researchers have covered plastic waste as a scope of their study whereas others have covered it partially. Though there are many reviews, however, a detailed study on the incorporation of plastic waste in different aspects of construction material is missing. There is much scope in the analysis of different types of plastic waste that has been used across various sectors of construction material vis-à-vis in bricks, tiles, blocks, concrete and road construction. Realising this, we are presenting an exhaustive review on the range of plastic waste materials such as polythene, polypropylene (PP), polyethylene terephthalate (PET), high-density polythene (HDPE), low-density polythene (LDPE) and polyvinyl chloride (PVC) and their suitability for inclusion in the manufacturing of bricks, tiles, construction blocks and concrete for road construction. This review paper also presents the influence of plastic waste on the strength and durability of the end products.

Types of plastic

A variety of plastics are available in the market for diverse applications. However, only some plastics can be recycled, which falls under the category of thermoplastics, e.g. PET (polyethylene terephthalate), HDPE (high-density polyethylene), LDPE (low-density polyethylene), PVC (polyvinyl chloride), PP (polypropylene) and PS (polystyrene). The non-recyclable plastic is under the category of thermosetting plastics and synthetic fibres, e.g. multilayer and laminated plastic, Teflon, PUF (polyurethane foam), Bakelite, polycarbonate, melamine and nylon. Figure  3 shows the classification of different plastics and their suitable applications.

Classification of different types of plastics and suitable applications

Based on particle size, plastics are classified as:

Nanoplastics: particle size < 0.0001 mm

Small microplastics: particle size 0.00001–1 mm

Large microplastics: particle size 1–4.75 mm

Mesoplastics: particle size 4.76–200 mm

Macroplastics: particle size > 200 mm

Utilization of plastic waste in construction bricks, tiles and blocks

This section reviews the modification of masonry bricks/tiles/blocks with plastic waste. We have done a detailed study to accommodate all perspectives of plastic waste utilization in construction bricks, tiles and blocks, along with quantitative analysis.

In a study, polyethylene terephthalate (PET) scrap plastic wastes (SPW) and foundry sand (FS) were used in the construction of green productive bricks. They mixed FS and SPW in percentages of 80:20, 70:30 and 60:40 of the dry mass. The bricks were soaked in acid and water to check the toughness, and compressive and tensile strength tests examined the strength. Bricks with (SF: SPW = 70:30) showed the maximum compressive strengths of 38.14 MPa and tensile strength of 9.51 MPa (Aneke and Shabangu 2021 ). Another report suggested that the use of recycled crushed glass (RCG) along with PET plastic waste (PPW) in varying percentages of 80:20, 70:30 and 60:40 of RCG and PPW enhanced the tensile strength and compressive strength by 70.15% and 54.85%, respectively, compared to the strength of conventional clay bricks. The average compressive strength and tensile strength obtained were 42.01 MPa and 9.89 MPa, respectively, and the average water absorption value was only 2.7%. Because of high hydrophobic properties, both types of masonry bricks made from foundry sand and crushed glass do not need water for construction, were more resistant to chemical attack and were less deformable under strain stress as compared to burnt clay bricks (Ikechukwu and Shabangu 2021 ).

Compacted earth blocks (CEB) were made from clayey sand and PET waste in shredded form mixed in various percentages (0, 1, 3, and 7%). The mixture was tested for explicit gravity, molecule size dispersion, Atterberg limits and compaction to evaluate the properties of soil. The results showed that the compressive strength of CEB was poor, i.e. 0.45 MPa without any additive. The CEB containing 1% of plastic waste of size 6.3 mm showed the highest compressive strength with an increment of 244.4%. The disintegration rate was lowest in the test involving 1% plastic waste with size less than 6.3 mm. The findings of the Atterberg limits showed that the soil fines have a low pliancy. A binder such as cement, lime or any material with cementitious nature was mixed with the soil and shredded waste plastic during the CEB production process to improve the compressive strength and sturdiness (Akinwumi et al. 2019 ).

As an alternative to traditional bricks, authors suggested the use of construction and demolition waste and plastic bottles. They filled the used plastic bottles with compressed recycled aggregates (RA) with water content as 0, 2.5, 5, 7.5 and 10%. Bottles containing crushed RA of size less than 425 μm exhibited higher compressive strength (15.25 N/mm 2 ) than those containing RA of a size between 425 and 4.75 μm (9.84 N/mm 2 ) with a 5% water content. The compressive strength at 5% water content was comparable with the compressive strength of conventional red clay brick (17 N/mm 2 ) and fly ash brick (12 N/mm 2 ) (Lalzarliana Paihte et al. 2019 ). Another report suggested the manufacturing of construction units from plastic bottles (PET) filled with either dry sand, saturated sand or air, with cement mortar acting as a binder. The resulting solid masonry walls were having low thermal conductivity. Bottle blocks packed with dry sand showed a compressive strength of 623 kN/m 2 and a bulk unit weight of 17.67 kN/m 3 , whereas bottle blocks filled with saturated sand had a compressive strength of 609 kN/m 2 and a bulk unit weight of 19.59 kN/m 3 , and air-filled bottle blocks showed compressive strength of 670 kN/m 2 and a bulk unit weight of 11.02 kN/m 3 . Although the gross strength of these plastic bottle blocks (670 kN/m 2 ) was significantly lower than that of standard blocks (3670 kN/m 2 ), still the blocks of air-filled bottles could prove useful as partition walls or as bearing walls for a single roof slab. In terms of thermal insulation, air-filled bottles outperformed traditional construction blocks, which may serve as a thermal insulator (Mansour and Ali 2015 ). Another researcher placed waste plastic bags inside 500 mL PET bottles to make eco-bricks. After packaging, the weight of the eco-brick must not be less than 220 g. They compared these bricks to traditional bricks in terms of compression, sound isolation and light transmission. These eco-bricks exhibited a high sound reduction index and withstood a maximum compression force of 40.1kN, giving them a resistance of 2.96 MPa. The value of Poisson’s ratio was between 0.27 and 0.35 range (Taaffe et al. 2014 ). Plastic waste bottles were also used in the manufacturing of concrete blocks. For this purpose, authors compared the traditional hollow concrete blocks having dimensions 200 × 200 × 400 mm (purchased from market) and concrete blocks of same size embedded with plastic bottles. The standard hollow blocks had an average weight of 20.08 kg and a compressive strength of 6.38 MPa after 28 days, but the plastic bottle block had a weight of 24.85 kg and a compressive strength of 10.03 MPa. According to the findings, using waste plastic bottles in concrete block masonry not only helps to solve the problem of finding a new use for plastic waste, but it also improves the masonry’s weight and strength attributes (Safinia and Alkalbani 2016 ). Mokhtar et al. used plastic bottles as a wall structure for greenhouses to reduce CO 2 emissions into the atmosphere. Sand was filled in discarded plastic bottles and compressed with a tamping rod in the investigation. The plastic brick had a maximum compressive strength of 38.34 N/mm 2 , which was nearly 3–4 times higher than that of the normal clay brick (maximum of 8.58 N/mm 2 ). The comparison of the indoor and outdoor wall temperatures, air humidity and wind velocity of the plastic bottle greenhouse and the normal brick house showed that the plastic bottle had the highest outdoor wall temperature of 36 °C and the lowest outdoor humidity and wind velocity, respectively, of 78% and 0.8 m/s (Mokhtar et al. 2016 ).

Various studies reported the use of HDPE and PET polymeric waste to increase the efficiency of unfired clay bricks. Three separate grain size additives (between 1 and 3 mm and 3 and 6 mm) were examined at percentage of 0, 1, 3, 7, 15 and 20% by weight. The efficiency of the brick sample improved with the smallest polymeric grain additive of size 1 mm. The bulk density of the bricks was less than 1.75 g/cm 3 , which indicates that the bricks were lightweight. The water absorption coefficient increased by nearly 17%, and the compressive strength increased by 28% (Limami et al. 2020a , 2020b ).

Water sachets made of LDPE can make LDPE sand bricks. The water sachets were first melted and then mixed with sand. Density, compressive strength and water adsorption of the bricks were dependent on sand particle size and sand to plastic ratio. The flexural strength and thermal conductivity of the best samples were measured. When processed under ideal processing conditions, LDPE-bonded sand proved to be a solid, durable material with compressive strength up to 27 MPa. They found the thermal conductivity at about 1.72 W/mK. In the bricks, the thermal diffusivity and specific heat values were 0.86 mm 2 /s and 2.0 MJ/m 3 k, respectively (Kumi-Larbi et al. 2018 ).

According to a report, plastic waste and manufacturing sand were combined to make plastic-manufacturing sand (M sand) bricks. Based on trial and error, they used waste plastic and M sand in the ratio of 1:1 and 1:2. To ensure the performance, strength and durability, the authors checked bricks for compression, water absorption, soundness and hardness tests. Plastic-M sand (ratio 1:2) bricks had the maximum compressive strength of 55.91 MPa, which was higher than that of regular bricks by 88.59% and 18.7% higher than bricks made from (1:1) plastic-M sand. Water absorption percentages for plastic-M sand ratio (1:1), for plastic-M sand ratio (1:2) and for regular bricks were 0.452%, 4.16% and 19.8%, respectively (Leela Bharathi et al. 2020 ). Pavement bricks have also been reported by using polypropylene, manufacturing sand (M sand), river sand and ash. Three samples of bricks containing plastic and M sand (20% and 80%), plastic and river sand (25% and 75%) and plastic and ash (30% & 70%) were reported. Sample made up of waste plastic and fly ash had the highest compressive strength of 22.85 MPa and the highest hardness of 6.087 (BHN or Brinell hardness number). Up to 80 °C, the bricks didn’t degenerate. While checking efflorescence, a white patch was observed on the surface of the bricks. Results showed that plastic and ash-containing bricks were the most successful combination (Velmurugan 2019 ).

Polyethylene terephthalate (PET) and polyurethane (PU) binder was used to replace clay and cement in the production of interlocking bricks. The plastic bottles were finely chopped and grated to a size of 0.75 mm before combining with polyurethane (PU) and polymer. The mixer was placed in the interlocking brick machine mould and condensed. Using PET/PU in the ratio 60:40, the highest compressive strength achieved was 84.54% (lower than the control group), the highest tensile strength was 1.3 MPa, and maximum impact value was 23.343 J/m. The thermal conductivity was between 0.15 and 0.3 W/m K. These bricks were suggested for use as a partition wall and found to be suitable as non-load-bearing masonry bricks (Alaloul et al. 2020 ). A moulded composite material was created by combining used PET from a municipal solid waste (MSW) landfill with fly ash. The fly ash percentage ranged from 0 to 50% by weight. The end products were examined for compressive strength, water absorption and density. It was found that fly ash lowers the thermal decomposition of PET, accelerates melting and mixing of PET and hampers shrinkage of the material during the moulding process. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) studies were used to investigate the microstructure and bonding mechanism. According to XRD results, PET and fly ash bonded physically without any chemical reaction. The material’s microstructure, as seen in the SEM micrographs, showed that the fly ash particles were homogeneously encapsulated in PET mass, resulting in a smooth surface of the composite material. The compressive strength was found to increase from 61 to 93 MPa as with the increase in fly ash content from 0 to 50%. The ductility of the composite material also increased with the increase in fly ash content. Furthermore, raising the amount of fly ash from 0 to 50% decreased linear shrinkage by a factor of 7, from 3.9 to 0.54%. The addition of fly ash to PET enhanced melting and mixing, while inhibiting thermal decomposition of PET. The water absorption value of composite material was very small (Li et al. 1998 ). Polyethylene terephthalate (PET), polypropylene (PP) waste, soil quarry waste and bitumen were employed in the manufacturing of bricks. Plastic waste from 65 to 80% and bitumen from 2 to 5% were employed in the production method. Plastic has sensible resistant properties. It is resistant to ozone, UV radiations and acid–alkali attack. Bitumen enhanced the binding property of plastic. With 5% bitumen and 70% plastic content, the maximum compressive strength was 10 N/mm 2 . Maximum water absorption value was 1.8242% with 2% of bitumen and 45% plastic waste. Higher compressive strength was reported with PP as compared to PET (Puttaraj et al. 2018 ). PET waste in varied percentage of 0.5%,1%,1.5%, 2%, cement (7.5%), fly ash (30%) and quarry dirt (62.5%) were used for manufacturing bricks. Four different samples with varied percentage of PET waste were created and cured for 7, 14 and 28 days for performing tests. Compressive strength, water absorption, bulk density, modulus of rupture and impact tests were performed, and the results were compared with ash bricks and clay bricks. PET bricks were less porous, uniform in form having rough surface and lighter have higher compressive strength and higher water absorption capability than the fly ash and clay bricks. Sample with 1% PET content gave highest compressive strength of 18.56 N/mm 2 and lowest bulk density, whereas sample with 0.5% waste gave highest modulus of rupture of 5.57 N/mm after 28 days of curing. Sample with 2% waste has maximum impact value of 2.333 after 7 days of curing. Water absorption value was maximum, i.e. 11.5% for sample having 1.5% waste after 7 days of curing (Suganya 2015 ). PET bottles and sand were utilized in the manufacturing of bricks in the ratio 1:2, 1:3 and 1:4 which gives maximum water absorption value of 4.72% for 1:4 plastic-sand ratio and maximum compressive strength of 8.06 N/mm 2 for 1:3 plastic-sand ratio. Efflorescence test results were null. However, the sole drawback with these plastic sand bricks was that they ignite pronto (Selvamani et al. 2019 ). Polyethylene terephthalate (PET) mixed with lateritic clay at an increment of 5% up to 20% for making fired bricks results in maximum compressive strength of 5.15 N/mm 2 and maximum modulus of rupture value of 13.20 N/mm 2 with 0% plastic waste which showed that with addition of waste, both compressive strength and modulus of rupture decreased. Water absorption value bated from 10.29 to 6.57% on addition of plastic waste (Akinyele et al. 2020 ).

Waste thermoplastics, such as polycarbonates (PC), polystyrenes (PS), mixed plastic, as well as sand, ash and regular Portland cement in varying proportions, were used in the construction of bricks. The proportion of thermoplastic was 0–10% by weight, sand was 60–70% by weight, and the proportion of fly ash and Portland cement was 15%. Resulting bricks were porous, lightweight and thermal resistant and have compressive strength over 17 MPa and maximum water absorption value of 14.18%, and bulk density decreased from 2.06 to 1.60 g/cm 3 on addition of waste (Mondal et al. 2019 ). Rice husks and waste expanded polystyrene along with styrene as a binder in different mix proportions were used to prepare rice husks-plastic building composites using a hot press moulding process. These composites were tested for apparent density, water absorption, thickness expansion and dry and wet flexural forces. The apparent density of the composites was between 0.80 and 1.60 g/cm 3 . Regardless of the filler-binder ratio, the water absorption of the composites reduced with an increase in binder content. The dry and wet flexural strength of the composites improved with an improvement in the filler-binder ratio, reaching the maximum value at a binder content of 30% (Choi et al. 2006 ). However, bricks made from waste plastics like polyethylene, high-density compound (nylon 66) and polythene terephthalate along with red soil, river sand and stone crush in numerous compositions showed 0% water absorption value for plastic bricks and maximum compressive strength of 15.50kN when river sand was used with plastic waste. No sound was detected throughout the soundness test, and these bricks were hard and durable (Kognole et al. 2019 ).

Nowadays ash from thermal power plants is also used for bricks and other construction material. Taking the advantage of ash bricks, researches are examining its combination with waste plastic as well. In bricks, LDPE can be mixed with materials such as bottom ash, copper slag and ceramic in various quantities. In rough weather conditions, LDPE and bottom Ash mixed in ratio (3:1) yields the maximum compressive strength of around 16 MPa and 4.2% water absorption, satisfying all standard specifications except the ASTM average. LDPE mixed with ceramic aggregates in ratio (3:1) and 10% oil yields the maximum compressive strength of around 22 MPa and water absorption value of 4.9%, and any mix with ceramic aggregates had theoretically crossed 15 MPa and had satisfied all normal specifications except ASTM norm in hard weather condition. The highest compressive strength of around 21.4 MPa and water absorption value of 4.5% were obtained by mixing LDPE with copper slag in a 2:1 blend ratio in the presence of a coupling agent. Plastic and ceramic waste combined in a 3:1 ratio gave the best block (Monish et al. 2021 ). Also, various amounts of plastic trash (LDPE type) were mixed with granite dust, sand and clay to form paver blocks. The 50:50 mix ratio (plastic melt-granite dust) achieved the highest compressive strength of 15.0 N/mm 2 , according to the compression test. The 70:30 mix ratio (sand-plastic melt) had the highest flexural strength of 14.28 kN, according to the flexural test results (Wahab Folorunsho et al. 2020 ).

A study reported composite bricks made up of powdered polythene waste mixed with fly ash and tested for soundness, hardness, water absorption ability and compressive strength. Composite bricks made a much clearer tone and were much more resilient than red and ash bricks. Water absorption capacity reduced from 0.8206% with no waste to 0.40043% with 100% polythene waste. The maximum wet and dry compressive strength with 10% polyethylene composite bricks was 20.34 MPa and 21.017 MPa. Results showed that these bricks were cost-effective and environmentally friendly (Sonone and Devalkar 2017 ). Another paper reported fly ash combined with recycled polymers in percentage of 0%, 25%, 50% and 75% by weight of fly ash. The properties of ash mixed with recycled plastics obtained from computers, TV sets, mobile phones, AC, table, chairs and electronic chip waste had been checked. Direct shear test, triaxial shear test and X-ray light test were performed on ash alone and ash mixed with recycled plastic polymers. The maximum dry density (MDD) was 1330 kg/m 3 , and the maximum optimum moisture content (OMC) value was 30% with 50% recycled plastic (Salunkhe and Mandal 2014 ).

Bricks and paver blocks made from plastic waste (HDPE and PE) and sand taken in ratio 1:2, 1:3, 1:4, 1:5 and 1:6 were reported and evaluated for compressive strength, water absorption, efflorescence, hardness and fireplace resistance. A comparative study of ash bricks, plastic sand bricks, and traditional bricks showed that plastic sand bricks have highest compressive strength of 5.12 N/mm 2 out of these bricks and paver blocks have compressive strength 9.19 N/mm 2 . The water absorption capability of plastic sand bricks was 1.10%, and that of plastic paver blocks was 1.082%. Structural property of bricks and blocks didn’t show significant changes up to 180 °C. All these results showed that the plastic sand bricks and paver blocks were of better quality than ash bricks and traditional clay bricks (Sellakutty et al. 2016 ). Waste plastic obtained from potable bottles (PET), carry bags, bottles caps, household articles (HDPE), milk pouches, sacks, carry bags, bin linings, cosmetics and detergent bottles (LDPE), etc. can also be used for making bricks. All the plastic waste was pulverized, heated in a chamber, mixed with stone dirt and moulded to make bricks and tiles. Absorption test, form and size test, soundness test, hardness test, efflorescence test and compressive strength tests were performed on the plastic bricks. The authors found that the values for water absorption and efflorescence tests were nil. Plastic sand bricks were heavy with a scratch on the surface with a compressive strength of 5.6 N/mm 2 (Singhal and Omprakash Netula 2018 ). Apart from the mixture of waste plastic, the dust obtained from PVC pipes was employed in the manufacturing of bricks by using plastic extruder machine. These bricks were then compared with burnt clay bricks. Plastic dust bricks were lighter with compressive strength of 6.66 N/mm 2 which was more than that of clay bricks having compressive strength 3–5 N/mm 2 (Shah et al. 2017 ). High-density polyethylene (HDPE) in different percentages as 2.5%, 3.0% and 3.5% was used in construction bricks. Compressive strength and the initial water absorption tests were performed on the bricks on the 7th and 28th day. On the 28th day, samples containing 3.0% HDPE had the highest compressive strength of 15.9 N/mm 2 as compared to samples containing 2.5% and 3.5% HDPE. The initial water absorption rate was recorded as 2.35 kg/m 2 min for 3.5% HDPE replacement (Ali et al. 2017 ). In this study, earth clay was mixed with various amounts of high-density polyethylene (HDPE) and polyethylene terephthalate (PET) additives with three different grain sizes. Thermal conductivity, specific heat capacity, time lag and decrement factor properties were investigated on the prepared samples. In comparison to control samples having thermal conductivity 0.48 W/m K, the thermal conductivity for large polymeric additions reached 0.18 W/m K and 0.20 W/m K for PET- and HDPE-based samples, respectively, suggesting a 63% and 58% increase in thermal conductivity. When compared to control specimens, the gain percentage for specific heat capacity was in the range of 85% and 79% for PET and HDPE additive brick samples, respectively. In fact, the reported time lag and decrement factor for a 0.3-m-thick external wall made of PET-based samples were 13.50 h and 0.148, respectively, compared to 8.99 h and 0.346 for reference values (Limami et al. 2020a , 2020b ).

Besides bricks and paver blocks, plastic waste has also been employed for making different tiles. Roof tiles using recycled high-density polythene (HDPEr) and sand were reported. The percentage of HDPEr in the mixture varied from 30 to 80% by weight. Density test, flexural breaking load test and impermeability test were performed on the tiles. The results revealed that as the percentage of plastic waste increased, the density of tiles decreased from 1.8 to 1.379 kg/m 3 , impermeability decreased, but flexural strength increased (Seghiri et al. 2017 ). Usage of waste plastic and broken glass was also reported for roof tiles, hollow blocks and floor tiles. In these, plastic waste replaced cement and broken glass replaced river sand partially. For hollow blocks, the proportion of plastic waste, fine glass and fine sand was 33%, 11.2% and 44.6%, respectively. For roof tiles, 30% plastic waste and 70% glass were used, and for floor tiles, 32% plastic and 68% glass were used. The optimum compressive strength got was 27 MPa. For roof tiles, the average breaking strength was measured to be 2356 N (Behera 2018 ).

Polythene luggage and demolition waste in place of cement were used to produce paver blocks. They made three distinct samples using plastic and sand in the ratios of 1:2, 1:3 and 1:4. River sediment made up 0.75% of the sand mix, while demolition waste made up 0.25%. The investigators checked paver blocks for compressive strength, flexural strength, tensile strength, water absorption, efflorescence, toughness, fire resistance, free thaw resilience and SEM study. After extensive research, it was determined that paver blocks with a quantitative relationship of 1:3 have the best outcomes. Sample 2 had a maximum compressive strength of 7.74 N/mm 2 , a maximum flexural strength of 1.17 N/mm 2 and maximum tensile break strength of 5.21 N/mm 2 . Sample 2 showed the lowest water absorption ratio, 1.33%. Since the plastic content of sample 1 is high, the scratch is simply rendered on the paver block’s surface. Because of the weak bonding in sample 3, sand separates from the paver block’s base, making it less durable (Hemalatha 2019 ). Another report suggested the use of melted waste plastic bags as a cement substitute in the manufacturing of building bricks and concrete blocks. Thermal conductivity of the bricks reduced from 1.70 × 10 −3  W/m K to 1.43 × 10 −3  W/m K with the increment in plastic content from 33.33 to 66.67%. While increasing the plastic content in concrete blocks from 20 to 50%, the thermal conductivity fell from 1.61 × 10 −3  W/m K to 1.50 × 10 −3  W/m K. (7). The authors had observed that the variation of thermal conductivity with plastic content (50%) is similar in bricks and concrete blocks. The bending moment, hence the bending stress, increased with increase in plastic content for both the bricks and concrete. Increasing the brick’s plastic content from 33.33 to 66.67% resulted in an increase in the bending moment from 540.00 to 1711.25 N m and the bending stress from 3.24 to 10.26 N m 2 . Because of its lightweight, high adaptability and ability to be changed to fit specific technological needs, waste plastic can be made as construction materials such as bricks and concrete blocks (Abdel Tawab et al. 2020 ).

All the above-mentioned significant results are tabulated in Table 1 , to analyse the optimum mechanical properties of different compositions of waste plastics in the manufacturing of bricks, tiles and blocks.

Utilization of plastic waste in concrete/road construction

For road construction, the improvisation of concrete using plastic is already in practice in different parts of the world. Researchers have investigated different admixtures of plastics as a partial or total replacement of aggregate.

A study reported recycled plastic-bounded concretes (RPBCs) made from 100% waste plastic and no asphalt binder or Portland cement. They investigated mechanical properties, crack recovery and thermal and moisture sensitivity of recycled plastic bounded concrete. Two types of recycled plastic waste, recycled high-density polyethylene (rHDPE) and recycled polypropylene (rPP), were used. The compressive strength of recycled polypropylene-bounded concrete was 30 MPa, which was almost three times that of asphalt binder concrete. Recycled PP had three times the bending strength of plain cement concrete (PCC) and five times the bending strength of asphalt concrete (ACs). The crack healing performance of RPBCs was approximately 92%. RPBC showed greater resistance to moisture exposure. The strength of recycled PP was reduced by 5%, while the strength of asphalt concrete was reduced by 17%. The bending power of ACs was just up to 10%, but the strength of recycled HDPE- and recycled PP-bounded concrete was 85 and 99%, respectively. Because of its failure to confine the aggregates in concrete, the authors inferred that recycled HDPE was not as effective as recycled PP. Since cement production releases an extensive amount of CO 2 and requires a sizeable amount of oil, substituting waste plastic for cement was environmentally friendly (Dalhat and Al-Abdul Wahhab 2016).

In some reports, PET derived from drinking water bottles was used as a replacement of sand in concrete formation. Different volumetric percentages of sand, such as 2%, 5%, 10%, 15%, 20%, 30%, 50%, 70% and 100%, were substituted by the same volumetric percentage of recycled PET aggregate. When the volume of aggregate was between 0 and 30%, the bulk density remains small. However, as the volume approaches 50%, the bulk density decreased and showed a minimum value of 1000 kg/m 3 . In addition, by increasing the amount of aggregate from 0 to 50%, the compressive power reduced by 15.7% as compared to the reference mortar. However, compressive strength greater than 3.5 MPa was observed when the volume of sand was fully replaced by PET. Up to a replacement stage of 50%, high compactness was found. Beyond 50% volume, the arrangement seems to be more spacious/broad (Marzouk et al. 2007). The mechanical properties of concrete with polyethylene terephthalate fibres (PET) of length 10, 15 and 20 mm and volume in percentages of 0%, 0.05%, 0.18% and 0.30% were investigated. With PET fibres, the slump value of concrete decreased from 100 to 50 mm. After 28 days, the maximum flexural intensity was 4.47 MPa, and after 150 days, it was 4.48 MPa with 0.30% fibre volume. With 0.30% fibre volume, the maximum compressive intensity was 29.52 MPa after 28 days and 29.69 MPa after 150 days. After 150 days of curing, the highest modulus of elasticity was 27.31 GPa (Pelisser et al. 2012 ). A report suggested concrete made from recycled PET flake aggregates. PET was used in percentages of 1, 3, 5, 7 and 10% by weight of Portland cement. The maximum compressive strength with 1% PET was 20.720 MPa, and the flexural strength increased to 23.11% and 25.59% in comparison to the concrete without waste. The density of concrete declined from 2.276 to 2.15 g/cm 3 as the percentage of PET increased from 1 to 10%. Splitting tensile strength improved, especially at 1% and 7% PET, with increment ratios of 130% and 102%, respectively, as compared to the reference concrete (Hameed and Fatah Ahmed 2019 ). Similarly, waste PET was used as a plastic aggregate in concrete. Waste plastic replaced conventional coarse aggregates in the quantity of 5%, 10% and 20% by volume. Concrete samples with plastic waste were then compared with concrete without plastic waste. Compressive strength, tensile strength, modulus of elasticity, flexural strength and shrinkage test were performed according to ASTM C39, ASTM C496, ASTM C469, ASTM C78 and IS:1199–1959 standards. Investigators observed that the density of concrete decreased on addition of plastic waste. Concrete specimen containing 10% of waste PET showed higher values of compressive strength and modulus of elasticity as compared to other specimens. The flexural strength of concrete declined on the addition of waste plastic. Water absorption was found maximum in concrete containing 20% plastic by volume (Hossain et al. 2016 ). To overcome the environmental effects of PET disposal, PET waste was investigated as a replacement of aggregate in asphalt concrete mixes (PlastiPhalt). Four different volume percentages of plastic (0%, 10%, 20%, 30%, 40%, 50%) were used to make total forty-eight specimens, and six beams and cylinders each for M20 grade of concrete were prepared.

Concrete containing synthetic aggregates (SA) was investigated for toughness properties. SA replaced natural pumice lightweight coarse aggregate or Lytag aggregate in 25%, 50%, 75% and 100% by volume of concrete. Split tensile strength decreased as the percentage of plastic waste increased. It was because of the weak bonding between plastic aggregate and cement paste, which reduces the resilience of the concrete mixture to loads. When compared to the control mixes, the synthetic aggregate concrete (SAC) was less consistent. The slump of SAC mixes was 11–23% lower than lightweight aggregate and 31% lower than Lytag aggregate. As the percentage of aggregate increased from 50 to 100%, the drying shrinkage of the SAC mixes increased by 19–54% after 182 days of curing. After 28 days of curing, the water absorption and chloride permeability of SAC mixes decreased by 5–20% and 9–17%, respectively, as the substitution amount of PA with SA increased from 25 to 100%. The reduction in water absorption and chloride permeability for SAC with 100% substitution of Lytag aggregate (LA) was 23% and 18%, respectively (Alqahtani et al. 2018 ). In another study on lightweight concrete, thermosetting plastic was used as an admixture in the blend design and tested for dry density and compressive strength. In this work, different proportions of plastic, sand, water-cement ratio, aluminium powder and lignite fly ash were used. The experimental findings showed that the use of plastic resulted in decreased dry density and less power. It was observed that the mix proportion of 1.0:0.8:0.3:0.9 of clay, sand, fly ash and plastic, respectively, was an acceptable mix proportion (Panyakapo and Panyakapo 2008). A study reported that devulcanized synthetic resin terephthalate would improve the performance and properties of modified asphalt binders. Penetration, softening point, storage stability and dynamic shear rheometer tests were performed to investigate the behaviour of four binder samples. As compared to base asphalt binder, the compound showed less penetration and enhanced softening point, viscosity and permanent deformation resistance of modified binders. Storage stability testing revealed that each compound alteration would not satisfy the Superpave binder standard limit and would not be a storage stable combination . The rutting parameter and high failure temperature values of all three polymers were increased (Ameri and Nasr 2016).

In M20 grade paver and solid blocks, waste plastic from 0 to 10% (in an increment of 2%) was used to replace the same amount of aggregate. Compressive strength analysis for 7, 14 and 28 days revealed that the maximum compressive strength was 26.4 N/mm 2 for paver blocks and 23 N/mm 2 for solid blocks with 2% waste plastic. The optimum modifier percentage was 4% for paver blocks and 2% for solid blocks (Vanitha et al. 2015 ).

Stabilized stone mastic asphalt (SMA) mixtures were compared to the conventional mix (without plastic). The mixtures underwent tests for Marshall stability, tensile strength, compressive strength and triaxial test. An addition of 10% plastic content resulted in an increase in the stability, split tensile strength and compressive strength of about 64%, 18% and 75%, respectively, compared to the conventional SMA mix. The Marshall stability value of stabilized SMA was 16.83 kN with a comparative increase of 64%. Compressive strength of stabilized mix increased by 14%. Triaxial test results exhibited an increase of 44% in cohesion. Angle of shearing resistance showed a decrease of 29% indicating an increase in the shear strength (Bindu and Beena 2010).

Researchers reported manufacturing of lightweight and ductile concrete by partial replacement of river sand with PVC pipe waste granules in percentages of 5%, 15%, 30% and 45% by volume. Resulting concrete showed higher Poisson’s ratio and decreased modulus of elasticity. It also possessed greater resistance to chloride ion penetration and less shrinkage on drying. The drying shrinkage further reduced with an increase in the quantity of waste plastic. However, high amounts of plastic waste also led to a reduction in workability, compressive strength and tensile splitting strength of the concretes (Kou et al. 2009). Another report on the utilization of PVC powder and granules in concrete showed normal to high strength concretes by using 10%, 20% and 30% replacement ratios of PVC powder and granules by volume of aggregate. Then, physical and mechanical properties of polyvinyl chloride (PVC)-containing concretes were observed. The compressive strength and capillary water absorption values of the modified concrete are lower than that of the reference mixtures. Limit of abrasion resistance decreased with the increase in percentage of PVC powder and granules (Bolat and Erkus 2016).

Haghighatnejad et al. studied the effect of curing condition on the compressive strength, splitting tensile strength, elastic modulus and initial and final absorption of concrete containing natural sand aggregate and concrete with recycled PVC (RPVC) aggregate. Results showed that irrespective of the curing condition, RPVC reduces the mechanical properties of concrete measured in terms of compressive strength, splitting tensile strength and modulus of elasticity. Curing condition affects the strength of both natural and RPVC aggregate concretes; however, the RPVC aggregate concrete is more sensitive to air storage curing. Splitting tensile strength and modulus of elasticity of mixtures decreased up to 23.4% with an increase in the RPVC aggregate content after 28 curing days. Use of RPVC aggregate reduced the slump value of normal concrete up to 48% due to its sharp edges (Haghighatnejad et al. 2016).

Dombe et al. prepared bituminous mixtures made of E-waste and plastic waste. Waste plastic substituted bitumen by 4.5 to 6% of the total amount of bitumen used. Shredded electronic waste partially substituted aggregates (7.5%, 10%, 12.5% and 15% by volume of the mould). Plastic raises the melting point of bitumen, allowing the asphalt to remain flexible throughout the winter, and shredded plastic waste helps to keep the road in good condition. The penetration value of bitumen declined by 6.68% after mixing 6.5% waste plastic in it, but the softening point of bitumen improved by 8.60% The other properties of bitumen remained the same. Upon coating 7% of waste plastic on aggregate, the specific gravity increased by 2.88%, while the crushing value, effect value and loss abrasion value decreased by 3 to 4% (Dombe et al. 2020 ). Similarly, electronic plastic waste was used in concrete by replacing aggregates from 0 to 20% on strength criteria of M20 grade. Optimum values of hardness and durability of concrete were obtained by addition of 10% E-plastic content in cement. Compressive strength decreased from 18.55 to 10.72 N/mm 2 on adding waste from 0 to 20% on 28 days of testing. Flexural strength decreased from 3.14 to 2.74 N/mm 2 , and split tensile strength decreased from 2.137 to 1.91 N/mm 2 . Authors suggested that utilization of E-plastic in concrete will reduce the requirement for conventional fine aggregates resulting in conservation of natural resources (Gavhane et al. 2016 ). It was also found that E-waste from 0 to 21.5% (i.e. 7.5%, 14% and 21.5%) on strength criteria of M30 concrete reduces the compressive strength by 52.98% when fine aggregates were replaced by 21.5% E-waste (Damal et al. 2015 ). Another paper reported that by using 30% of E-waste, the slump value of concrete decreased from 128 (control) to 75 mm (30% E-waste) and compressive strength decreased from 47.18 to 22.15 N/mm 2 after 28 days of curing. Split tensile strength decreased from 4.9 to 3.8 N/mm 2 , and flexural strength decreased from 4.35 to 2.5 N/mm 2 on addition of waste plastic after 28 days of curing (Manjunath 2016 ). Another researcher examined plastic waste as a replacement to natural aggregate in concrete. They casted 60 cubes, 60 cylinders and 40 prisms to identify the compressive strength, split tensile strength and flexural strength. Fine aggregates were replaced with plastic fine (PF) aggregate measured as 10%, 15% and 20% by weight, and coarse aggregates were replaced with corresponding 15%, 20% and 25% plastic coarse (PC) aggregate. In addition, 0.3% of steel fibre was added by weight of cement. The compressive strength of concrete decreased from 9 to 17% on adding waste plastic. It was attributed to poor bonding between concrete and plastic aggregates. Split tensile strength decreased from 10 to 24% and flexural strength reduced in the range 20 to 30% (Jaivignesh and Sofi 2017). In a report, researchers utilized processed tenuity polythene (LDPE) plastic in share from 1 to 5% for the preparation of bituminous mix. Use of polyethylene waste in bituminous mix reduces porousness; however, absorption of wetness increases the binding property. The Marshall stability test exhibited value of 17.7 kg on the addition of 4% plastic waste, and the Marshall flow value weakened from 2.31 to 2.18 mm on addition of waste from 0 to 5%. The results obtained on using 4% polyethylene waste showed higher performance than alternative mixes of waste (Soyal 2015 ). Concrete incorporated with quarry dust and plastic waste was examined for strength properties. Quarry dust and waste plastic (LDPE) in fibre form were added as 0%, 25%,50%, 75% and 100%, respectively, to replace natural sand. Particle size distribution was studied by X-ray diffractometry (XRD) and scanning electron microscopy (SEM) techniques. SEM results showed that quarry dust particles are fine in nature with average size of 2 to 3 µm, and LDPE images show that it is having lamellar, crystalline (fibre like) structure. It is not having porous structure but its lamellar structure increases the strength carrying capacity. Digital microscopy showed that conventional concrete mixes were more porous leading to matrix cracking, but the mixture of quarry dust-waste plastic substitution resulted in refined matrix densification (Bahoria et al. 2017 ).

Waste plastic like polyethylene and polystyrene in sliced form was coated over aggregates and mixed with hot bitumen. Various tests like crushing strength test, abrasion test, Los Angeles abrasion test, impact test, softening point test and surface test were performed on traditional aggregates and plastic-coated aggregates. Crushing value decreased from 23.22 to 14.22% on adding plastic waste. The softening point was 81.2 °C and penetration value was 67 mm. The loss angle abrasion value reduced from 5.6 to 4.2% of plastic-coated hydrocarbon (Manju R et al. 2017).Various varieties of plastics like thermosets, elastomers and thermoplastics reported to increase the temperature of the bitumen, hence improving the road life. Waste plastic coating over mixture enhanced the compressive strength to 320 MPa and bending strength to 390 MPa by exploitation of 40% waste plastic (Rokdey et al. 2015).

A recent communication reported high-strength lightweight concrete employing recycled high-impact polystyrene (HIPS) and low-density polyethylene (LDPE) plastic wastes. Plastic granules with particle sizes of about 2 mm were obtained by recycling HIPS and LDPE plastic wastes. These plastic wastes partially replaced sand at various percentage levels of 0, 10, 30 and 50% by weight in concrete mixes. Investigators casted 100 mm concrete cube samples and examined both the fresh and hardened states. As the quantity of recycled waste plastic granules increased, test results showed a reduction in workability, density and compressive strength. After 28 days of curing, the concrete mixtures having 10% recycled plastics were able to meet the goal strength of 30 N/mm 2 (Olofinnade et al. 2021 ).

Basha et al. reported recycled waste plastic as a substitute of natural aggregates. They prepared eighteen concrete compositions with varied recycled plastic aggregate (RPA) proportions (25, 50, 75 and 100%) and two cement contents (350, 370 kg/m 3 ) having water to cement ratios of 0.45 and 0.4 and assessed their mechanical and thermal properties. To create lightweight concrete with a unit weight of 1500 kg/m 3 and a compressive strength of 17 MPa, 100% recycled plastic aggregate (RPA) was used. The maximum compressive strength of 35 MPa was observed with 25% RPA. The control concrete had a thermal conductivity of 1.7 W/m K, while the RPA concrete had a thermal conductivity of 1.1–0.5 W/mK. The flexural strength of concrete with a water/cement ratio of 0.4 and 0.45 was 4.9 to 2.6 MPa and 4.5 to 2.6 MPa, respectively (Basha et al. 2020 ).

The waste plastic bottles, cups, caps, etc. were powdered or blended with crusher and coated over the aggregate and bitumen mixture by heating process for road construction. The aggregate of size 10–20 mm and 60/70 and 80/100 grade of bitumen was used. As the percentage of plastic increased, the softening point, flash point and fire point improved, whereas penetration value and ductility decreased. The polymer-coated aggregate and bitumen mixture showed higher strength, better binding property, stability, increase in wear resistance and better durability of roads (Chada Jithendra Sai Raja et al. 2020 ).

Recycled polypropylene (PP) plastic particles were used as a modifier in self-compacting lightweight concrete (SCLC). In the concrete, waste plastic replaced sand (10%, 15%, 20% and 30% by volume). This paper reported a different trend in slump value, where increase in percentage substitution resulted in enhanced slump flow value of concrete. With a replacement of up to 15%, passing ability improved, whereas the viscosity and elastic modulus of SCLC showed a reduction. The dry bulk density of concrete decreased up to 15% with 30% replacement level of sand. The compressive strength, splitting tensile strength and flexural tensile strength showed increase with the replacement level up to 15%. Up to 20% replacement level, the compressive strength of SCLC was improved, but with 15% sand, the maximum compressive strength was obtained. The measurement of splitting tensile strengths and flexural tensile strength after 7 days and 28 days showed maximum value when the replacement level was 15%. But beyond this percentage, the properties deteriorated due to the mismatch between the plastic and cement paste (Yang et al. 2015 ). Shredded plastic bags (SPB) in varying percentages (0, 0.5, 1, 2, 3 and 5%) by weight of concrete were used as concrete additive materials. The specimens were then examined for workability, density, compressive strength, flexural strength, water permeability, static and dynamic modulus of elasticity and abrasion resistance. The maximum compressive strength of 26.1 MPa and maximum flexural strength of 3.55 MPa were observed with 0.5% waste plastic bags after 28 days of curing. Water penetration and abrasion resistance against rubbing and scraping effect of SPB increased with increase in plastic waste. However, mechanical properties of concrete degraded with increase in percentage of waste plastic. Poor bonding was observed between concrete and plastic matrix (Jain et al. 2019 ).

Waste polythene in the range of 5 to 11%, when mixed with bitumen (60/70) grade, proved to be a good binding agent for the construction of road (Kazmi and Rao 2015). In a report, waste plastic collected from municipal solid waste was used as a coated mixture in bituminous construction. Marshall properties, impact values, abrasion, water absorption and soundness tests were performed on the plastic-coated aggregates. Maximum value of Marshall stability for plastic-coated mixture was found to be 2812.1 kg corresponding to 4.7% bitumen by weight. Plastic-coated mixture showed improved water absorption and soundness. Once used for construction, it will stand up to higher temperature (Dawale 2016 ). Waste plastic was also used as a modifier for quasi-dense bituminous concrete. Chopped plastic was mixed in hot mixture by using 6, 8, 10, 12 and 14% plastic by weight of hydrocarbon. Marshall stability value was maximum, i.e.13.0 kg for 12% plastic by weight of the bitumen; however, for this % of plastic, the soundness value has ablated. Maximum flow value was 4.0 mm, and voids filled with bitumen (VFB) was 75.9% by adding 14% waste plastic (Rajput and Yadav 2016).

Azhdarpour et al. reported that the addition of plastic particles to freshly formed concrete impacted both physical and strength-related characteristics. Precisely, as the plastic fragment ratios increased, physical attributes (like density and ultra sound velocity) dropped significantly. When 5–10% of the concrete fine particles were replaced with the same amount of polyethylene terephthalate (PET) fragments, the compressive, tensile and flexural strength of the samples increased. The study also indicated that substitution of more than 10% results in a significant decrease in all concrete strength-related measures. As a result, it was proposed that replacing fine particles with PET fragments may have a positive impact on the strength-related characteristics of concrete samples as long as the substitution ratio is less than 10%. The addition of plastic to the concrete mixture decreased both the fresh and dry densities of the concrete, according to the results of fresh and dry density measurements. The samples containing 30% plastic particles experienced the greatest loss of density, which was equal to 9% (Azhdarpour et al. 2016 ).

Another study reported the influence of plastic as an alternative coarse aggregate on various fresh and harden properties of concrete. The thermoplastic polymer polyethylene terephthalate (PET) was regarded an alternative aggregate and was replaced with natural coarse aggregate, such as brick chips. PET aggregation was made by shredding, melting and crushing the PET bottles that have been collected. The authors compared the compressive strength, unit weight and workability of PET aggregate concrete (PAC) to that of natural aggregate concrete (NAC). In comparison to NAC, PAC has lower unit weights and compressive strength as the PET replacement ratio and w/c ratio increase. At a 0.42 w/c ratio, the compressive strength of 20% PET-substituted PAC is 30.3 MPa, which is only 9% less than NAC. However, PAC has a strong workability, as seen by a 1.8 cm slump value when 20% PET was replaced with PAC at a 0.42 w/c ratio. As a result, structural concrete can be made from PET-replaced concrete with a low w/c ratio and great workability (Islam et al. 2016). Metalized plastic waste (MPW) such as polypropylene (PP) was used in concrete to check its workability and strength properties by evaluating slump, compressive and splitting tensile strength and flexure strength values. MPW fibres were shredded into 5-mm-, 10-mm- and 20-mm-long fibres and mixed in concrete from 0 to 2% by volume of mix. Addition of MSW fibres results an increase in splitting tensile strength and ductility of concrete. However, the workability, compressive strength and flexural strength showed a negligible reduction at 1% dosage of MPW fibres. Up to 1% addition of waste by volume, the reduction in compressive strength was negligible, but beyond 1%, addition reduction in compressive strength reaches to 9% and 11%. Splitting tensile strength was increased from 21 and 33% up to 1% addition. For all test conditions, higher MPW dosage lowered workability. At increasing volume fractions, a higher MPW fibre dose raises the viscosity of the matrix and lowers the consistency of the concrete (Bhogayata et al. 2017). The purpose of this study was to see how employing plastic trash as a partial replacement for fine aggregate affected the fresh properties of self-compacting concrete (SSC). Different self-compacting concrete mixes were created for this purpose, with a constant water-to-binder ratio of 0.32 and a binder content of 520 kg/m 3 . As a partial replacement for cement, class F fly ash was employed (30% by weight of cement). Experimental conditions included six distinct plastic waste contents of 0, 2.5, 5, 7.5, 10 and 12.5%, as well as three different sized plastic wastes (fine plastic wastes, coarse plastic wastes and mixed plastic waste). Slump flow diameter was used to test the workability qualities of self-compacting concrete mixtures. The compressive strength of concrete mixtures with plastic waste was lower than that of control mix without plastic waste. This could be due to the fact that plastic garbage is a softer substance than natural aggregate. 12.5% fine plastic waste, 12.5% coarse plastic waste and 12.5% mixed plastic waste all had compressive strengths of 47.0, 37.0 and 42 MPa, respectively (Hama et al. 2017). According to a review on use of various types of plastic on the fresh, mechanical and thermal properties of concrete, it was observed that workability, modulus of elasticity and compressive strength of concrete decrease but the tensile strength and flexural strength increase as the amount of plastic content increased (Sharma et al. 2016). The effects of size and shape of recycled plastic aggregates on workability were discovered in a review on the use of plastic waste aggregates in cement and concrete mortars. It was stated that the size and shape of aggregate used do not affect the strength of mortars but the strength of mortar decreases as the aggregate content increases. The flexure and splitting tensile strength improves to some level, as do the permeability and chemical resistance, according to the review (Yin et al. 2015 ). According to a research study on the use of plastic in concrete, the compressive, flexural and tensile strengths of concrete decrease as the proportion of plastic waste increases due to inadequate adhesive strength between the surface of the plastic aggregates (PA) and cement paste. The UPV (ultrasonic pulse velocity) of concrete, which represents its quality, falls as the plastic content increased. Plastic-containing concrete has a higher permeability than regular concrete. This concrete can be utilized in a variety of applications, including highway medians, highway pavement sub-bases and other constructions where strength is not a critical consideration. Several admixtures, such as super plasticizers, can be used to improve the workability of concrete containing plastic. As plastic does not mix well with natural aggregates, therefore water absorption, permeability and carbonation of concrete containing PA increase as the replacement ratio of fine aggregate (FA) increases, resulting in a porous matrix. Chloride penetration, on the other hand, is significantly reduced due to the impermeable plastic particles that prevent the chloride ion’s passage (Almeshal et al. 2020). The effect of incorporating polypropylene (PP) as a partial replacement of natural stone aggregate (SA) and burnt clay brick aggregate (BA) was examined on the properties of concrete. PP was used in different percentages of 0%, 10%, 20% and 30% with water-cement ratio of 0.45 and 0.55. Workability, hardened density, compressive and tensile strengths, modulus of rupture, modulus of elasticity (MoE), ultrasonic pulse velocity (UPV) and cost analysis were all examined. With raising the w/c ratio, the workability of stone aggregate concrete (SAC), brick aggregate concrete (BAC) and PP aggregate concrete (PAC) enhances. SAC has a density range of 2367 to 2096 kg/m 3 , while BAC has a density range of 2075 to 1879 kg/m 3 . When compared to normal concrete, concrete containing 10% PPA had stronger bonding between the aggregates and cement paste, resulting in a higher compressive strength. Compressive strength was found to be reduced with 20% and 30% PPA, respectively. The compressive strength of 50% of the specimens was over 20 MPa and 18 MPa for PP concrete with SA and BA, respectively, according to the cumulative distribution function (CDF) graph. The modulus of elasticity decreased by 1–47% for SAC and 5 –36% for BAC depending on the percentage of PPA and w/c ratios (Islam and Shahjalal 2021). Belmokaddem et al. examined the morphological, thermal, mechanical and acoustic properties of concrete made from three types of waste plastics (PP, HDPE and polyvinyl chloride (PVC)) and natural aggregate. Concrete with 75% plastic particles had a low dynamic modulus and thermal conductivity, according to the test results. At high replacement levels with PP, the maximum reduction in hardened density was achieved; the value was 46% lower than that of reference concrete, i.e. 1318 kg/m 3 . The compressive strength of concretes containing PVC, PP and PE ranged from 12 to 26.9 MPa, 5.2 to 25.4 MPa, and 4 to 19.5 MPa at 28 days, respectively. In comparison to the values of reference concrete, the reduction in UPV ranged from 9.3 to 34.4%, 10.5 to 47.6% and 11.9 to 48.7% for the PVC, PP and PE concrete mixes, respectively. Furthermore, the utilization of discarded plastic particles improved the acoustic qualities (Belmokaddem et al. 2020 ). The rheological, mechanical and durability properties of self-compacting concrete (SCC) were examined using waste polyethylene terephthalate (PET) particles and pozzolanic ingredients. The weight replacement ratios of fine aggregates with waste PET aggregates were used in the percentages of 5, 10 and 15%, respectively, for replacing the same weight of fine aggregate. The cement replacement ratio was 10 and 30% keeping the weight of silica fume and fly ash same. Slump flow, V-funnel and L-box tests were used to examine the workability of SCC containing waste PET particles. Mechanical (compressive, tensile, and flexural strengths and modulus of elasticity) and rheological (L-box, slump flow and V-funnel) qualities, as well as durability (water absorption and electrical resistance) properties, were evaluated. The research suggests that waste PET particles can be employed as aggregates in a wide range of applications. Compressive, tensile and flexural strengths are all reduced when waste PET was used in SCC. Pozzolanic ingredients (fly ash and silica fume) compensate for the strength loss induced by the addition of PET. Waste PET has no effect on electrical resistance and makes concrete more fragile. The modulus of elasticity value decreased, and water absorption value increases by addition of waste PET (Sadrmomtazi et al. 2015 ). Faraj et al. explored the hardened properties of high-strength self-consolidating concrete (SCC) made using recycled polypropylene plastic particles (RPPP) and silica fume (SF). The cement content was 550 kg/m 3 , with a maximum w/c ratio of 0.32. RPPP was used to replace up to 40% of the natural aggregate. The fracture and durability properties of the concrete appeared to significantly increase, and the addition of SF improved the hardened properties of the concrete. For combinations without SF, increasing RPPP percentage from 0 to 40% lowered splitting tensile strength from 6.08 to 4.33 MPa. In addition, when the RPPP content was increased from 0 to 40% containing 10% SF, the splitting tensile strength reduced from 6.41 to 4.48 MPa. The results further showed that with an RPPP content of up to 40% replacement level by total medium aggregate volume (MAV) and 10% SF, SCC with compressive strength more than 70 MPa at 90 days may be generated. The static elastic modulus was reduced by an average of 22% regardless of the SF content when the replacement amount of RPPP content was increased from 0 to 40%. A concrete including RPPP may be used as structural concrete with a 70% reduction in cement and a 40% substitution of natural particles with plastic aggregates, according to the researchers.

In Table 2 , optimum compressive strengths are reported with different compositions of plastic waste for concrete in road construction processes.

Utilization of biomedical plastic waste in road construction

Enormous amount of plastic wastes are generated in the medical field on a daily basis, for example, syringes, medicine wrappers, tubings, gloves, medicine bottles and bags. Therefore, there is a need to recycle such plastic waste as well. Few studies (Table 3 ) have reported the utilization of aldohexose bottles, syringes in bituminous mix construction. Bituminous mix prepared from drug plastic waste was then compared with ancient bituminous mix. Twelve plastic modified mix specimens were prepared with plastic proportion varied from 6, 8, 10 and 12% by weight of bitumen. Marshall methodology is adopted for mix designs. Various Marshall parameters like stability value, flow value and air voids were evaluated. The maximum flow value was observed to be 3.2 mm with 12% waste plastic. The optimum plastic content was found to be 9.33%. Maximum stability was observed to be 24.77 kN with 10% plastic content (Sunny 2018).

Utilization of waste plastic with waste rubber in concrete/road construction

Plastic waste in combination with rubber waste has been used to provide strength to rubber as well as the concrete. Table 4 presents the record of different compositions of plastic with rubber. It provides the detailed information and importance of plastic with rubber to enhance its applicability. To enhance the chemical properties of crumb rubber modified asphalt (CRMA), waste PET additives, derived through the associate degree aminolysis method, were used. It has been noted that the inclusion of these additives to CRMA increased the storage stability, rutting and fatigue resistance and inflated the rotational viscosity (RV) of the changed binders. The addition of bis(2-hydroxy ethylene) terephthalamide (BHETA) to the rubber binders reduces the penetration values. Up to 3 to 5% BHETA addition, the consistency was comparatively little however on using 7% of BHETA additive; the consistency considerably inflated. Crumb rubber changed with BHETA offered higher fatigue resistance. The addition of BHETA additives to CRMA inflated the stiffness and storage stability (Leng et al. 2018 ).

In a study, LDPE, HDPE and crumb rubber (CR) in percentages (2, 4, 8 and 10% by weight of bitumen) were mixed with base matrix of bitumen. The investigations on the viscous and elastic behaviour of binders at varied temperatures and frequencies revealed that the addition of plastic wastes, like LDPE, HDPE and CR, to binder improved the elastic behaviour of binder. It can extend the service life of pavements in terms of reduced susceptibility to rutting and cracking (Khan et al. 2016 ).

Admixtures of 2, 4, 6, 8 and 10% recycled plastic waste were used to modify 60/70 penetration grade asphalt binder by wet method, whereas 1, 2, 3, 4 and 5% crumb rubber was customized for mineral aggregates by dry method. It was observed that with the addition of 2% crumb rubber and 4% LDPE, the Marshall stability value was found to be 30% more than the standard asphalt concrete mix. The LDPE changed asphalt binder showed a rise in viscosity, softening point and stiffness of binder (Onyango et al. 2015 ).

In a research study, bituminous mix was modified with plastic and rubber waste to be used in road construction. The modified bituminous mix was way stronger (61%) than that of standard mix. Marshall quotient (MQ) was also enhanced by 52% as compared to the reference bituminous mix which indicated higher stiffness combined with an enhanced ability to bear the applied load and counter the deformation (Islam et al. 2016). Plastic waste like carry luggage, cups and tyres have been used for coating over aggregates. Polymer-coated aggregates have shown higher strength. Softening point exaggerated; however, the penetration value and malleability decrease with increase in amount of plastic waste. Polymer-coated aggregates show higher binding property and reduced air voids (Barad 2015 ). In another report, plastic waste and crumb rubber were used as a partial replacement of bitumen in the manufacturing of an amended binder for bituminous concrete mix. To replicate field conditions, Marshall stability analysis revealed that the bitumen modified with plastic waste and crumb rubber in certain proportion possess higher (Bansal et al. 2017 ).

Effect of percentage of waste plastic on the properties of concrete

In concrete materials, mechanical properties particularly the strength behaviour are the decisive parameter outlining its suitability for practical applications. This section aims to recapitulate the effect of addition of waste plastic on the compressive strength, flexural strength and workability.

As is evident from the discussion in previous sections, addition of waste plastics from low to moderate replacement level resulted in an increase in compressive strength; however, higher level of replacement deteriorates the strength. This is shown in Fig.  4 . Akinyele (2020) mixed PET with clay in fired bricks. Results show that with 0%, 5%, 10%, 15% and 20% of PET, the compressive strength increases up to 2.30 MPa with 5% PET, and afterwards, it declines till 0.85 MPa with 10% PET. Azhdarpour (2016) replaced concrete fine aggregate by equivalent waste fragments, and results were taken after 3 days, 14 days and 28 days of curing. Compressive strength increases till 5% of waste plastic addition (21 MPa) followed by a decline. PET flakes were also used by replacing Portland cement (Hameed 2019). Of PET flakes, 1%, 3%, 5%, 7% and 10% are mixed, but the compressive strength was highest with 1% (20.720 MPa) only. Ikechukwo (2021) used melted PET with recycled crushed glass in masonry bricks. At 20%, the compressive strength was 33.45 MPa, and at 30%, the compressive strength was 43.14 MPa. But at 40%, compressive strength decreased up to 38.25 MPa. When shredded plastic was mixed with soil for compressed earth bricks (CEB) (Akinwumi, 2019), the compressive strength increased with 1% composition (1.098 MPa) as compared to control (0.45 MPa). On the 28th day, the compressive strength was almost equal to 2.5%, 3.0% and 3.5% of HDPE (12.5 MPa/12.6 MPa) (Ali 2017). These results indicate that at first, the compressive strength exhibits an increase with the addition of waste plastic but after a certain percentage, it declines. Most of the researchers have reported similar behaviour. They have attributed this behaviour to the stress redistribution at low to moderate percentage replacement. As the percentage of plastic waste increases, non-uniformity of concrete, huge voids, less fluidity, etc. influence the compaction. Also the presence of huge voids results in increased stresses at the plastic concrete interface, leading to a decrease in strength. Though there is no definite pattern of increase or decline in strength corresponding to the percentage replacement, the acceptable range of addition of plastic waste is 5–30%, by weight corresponding to which maximum compressive strength of 43.14 MPa can be obtained. The strength behaviour also has a significant dependence on the pre-treatment of plastic waste. Another important property is the workability of concrete. Addition of waste plastics reduces the workability of concrete which is measured in terms of slump value. Bhogayata et al. (2017) detected up to 25% decline in workability for the 2% of polythene plastic pieces. However, at low percentage, the decline in workability suffices the acceptable range of slump values. Though many properties show a decline by the addition of waste plastic, the above reported studies show an increment in the flexural strength (Seghiri et al. 2017 , Hameed and Fatah Ahmed 2019 , Azhdarpour et al. 2016 ).

Effect of the percentage of waste plastic on the compressive strength of concrete

For road construction, combination of waste plastic and waste rubber is showing beneficial properties. Addition of plastic by 10% in conjunction with waste rubber has improved elastic properties and reduced susceptibility to rutting and cracking (Khan et al. 2016 ).

Future scope of work

Clearly, plastic waste can prove to be a sustainable additive and partial replacement of conventional construction materials thereby addressing the dual issue of management of plastic waste and helping in the reduction of footprints caused by construction industry on the environment. However, a long road is ahead before the commercial implementation of the idea can be realized. More research is required to fully understand the advantages and limitations of plastic waste-based construction material qualitatively and quantitatively. Several issues to be addressed for commercialization and for future research are:

Optimum proportions of plastic waste as a constituent of construction materials are required.

Safe methods of sanitization of plastic waste in order to eliminate the potential contaminants.

Analysis of carbon life cycle to reinforce the claim for sustainability.

Cost–benefit analysis for the commercial production of such construction material.

Dedicated standards to evaluate the quality of plastic waste-based construction material.

Public awareness drives to communicate about the environmental and economic advantages of waste-based construction material are required for its acceptance by consumers and public in general.

Growing amounts of plastic waste in our ecosystem can be strategically tackled by its recycling/reuse in an effective and beneficial manner. This review gave a focussed summary of the research work being carried out to exploit plastic waste as a constituent of construction material. It is a meticulous study of utilization of waste plastic in construction bricks, blocks, tiles and concrete for road construction. It also touches the usage of medical plastic waste and admixtures of plastic waste with waste rubber in construction materials. On the basis of such an extensive study, the following are the conclusions:

Plastic waste from PET, PVC, PU, LDPE, HDPE, nylon 66, etc. can be efficiently used in conjunction with fly ash, sand, cement and other materials for the production of bricks, blocks and tiles. However, PET waste is a favourable replacement.

Lightweight concrete containing 10% of HIPS and LDPE plastic wastes attained 30 N/mm 2 compressive strength after 28 days of curing.

Workability of the concrete decreases with increasing percentage of plastic; however, it can be maintained to some extent by increasing the water/cement ratio (w/c) ratio.

Workability of plastic waste-based concrete depends significantly on the size, shape and roughness of plastic aggregates and water-cement ratio.

Inclusion of waste plastic decreases the modulus of elasticity of concrete.

Plastic waste-based concrete possessed greater resistance to chloride ion penetration and less shrinkage on drying.

Recycled plastic aggregates can successfully be used in concrete bricks/pavement blocks non-structural panels.

Concrete containing waste plastic bottles is useful in making temporary shelters.

Plastic waste-based concrete can be highly useful for low load-bearing structures such as partitions and decorative tiles.

Mix of waste plastic with crumb rubber acts as modifier and binder in road construction.

Data availability

Not applicable.

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Lamba, P., Kaur, D.P., Raj, S. et al. Recycling/reuse of plastic waste as construction material for sustainable development: a review. Environ Sci Pollut Res 29 , 86156–86179 (2022). https://doi.org/10.1007/s11356-021-16980-y

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Solid health care waste management practice in Ethiopia, a convergent mixed method study

• Yeshanew Ayele Tiruneh 1 ,
• L. M. Modiba 2 &
• S. M. Zuma 2  

BMC Health Services Research volume  24 , Article number:  985 ( 2024 ) Cite this article

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Introduction

Healthcare waste is any waste generated by healthcare facilities that is considered potentially hazardous to health. Solid healthcare waste is categorized into infectious and non-infectious wastes. Infectious waste is material suspected of containing pathogens and potentially causing disease. Non-infectious waste includes wastes that have not been in contact with infectious agents, hazardous chemicals, or radioactive substances, similar to household waste, i.e. plastic, papers and leftover foods.

This study aimed to investigate solid healthcare waste management practices and develop guidelines to improve solid healthcare waste management practices in Ethiopia. The setting was all health facilities found in Hossaena town.

A mixed-method study design was used. For the qualitative phase of this study, eight FGDs were conducted from 4 government health facilities, one FGD from each private health facility (which is 37 in number), and forty-five FGDs were conducted. Four FGDs were executed with cleaners; another four were only health care providers because using homogeneous groups promotes discussion. The remaining 37 FGDs in private health facilities were mixed from health professionals and cleaners because of the number of workers in the private facilities. For the quantitative phase, all health facilities and health facility workers who have direct contact with healthcare waste management practice participated in this study. Both qualitative and quantitative study participants were taken from the health facilities found in Hossaena town.

Seventeen (3.1%) health facility workers have hand washing facilities. Three hundred ninety-two (72.6%) of the participants agree on the availability of one or more personal protective equipment (PPE) in the facility ‘‘ the reason for the absence of some of the PPEs, like boots and goggles, and the shortage of disposable gloves owes to cost inflation from time to time and sometimes absent from the market’’ . The observational finding shows that colour-coded waste bins are available in 23 (9.6%) rooms. 90% of the sharp containers were reusable, and 100% of the waste storage bins were plastic buckets that were easily cleanable. In 40 (97.56%) health facilities, infectious wastes were collected daily from the waste generation areas to the final disposal points. Two hundred seventy-one (50.2%) of the respondents were satisfied or agreed that satisfactory procedures are available in case of an accident. Only 220 (40.8%) respondents were vaccinated for the Hepatitis B virus.

Hand washing facilities, personal protective equipment and preventive vaccinations are not readily available for health workers. Solid waste segregation practices are poor and showed that solid waste management practices (SWMP) are below the acceptable level.

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Healthcare waste (HCW) encompasses all types of waste generated while providing health-related services, spanning activities such as diagnosis, immunization, treatment, and research. It constitutes a diverse array of materials, each presenting potential hazards to health and the environment. Within the realm of HCW, one finds secretions and excretions from humans, cultures, and waste containing a stock of infectious agents. Discarded plastic materials contaminated with blood or other bodily fluids, pathological wastes, and discarded medical equipment are classified as healthcare waste. Sharps, including needles, scalpels, and other waste materials generated during any healthcare service provision, are also considered potentially hazardous to health [ 1 ].

Healthcare waste in solid form (HCW) is commonly divided into two primary groups: infectious and non-infectious. The existence of pathogens in concentrations identifies infectious waste or amounts significant enough to induce diseases in vulnerable hosts [ 1 ] If healthcare facility waste is free from any combination with infectious agents, nearly 85% is categorized as non-hazardous waste, exhibiting characteristics similar to conventional solid waste found in households [ 2 ]. World Health Organization (WHO) recommends that appropriate colour-coded waste receptacles be available in all medical and other waste-producing areas [ 3 ].

Solid waste produced in the course of healthcare activities carries a higher potential for infection and injury than any other type of waste. Improper disposal of sharps waste increases the risk of disease transmission among health facility workers and general populations [ 1 ]. Inadequate and inappropriate handling of healthcare waste may have serious public health consequences and a significant environmental impact. The World Health Organization (2014) guidelines also include the following guidance for hand washing and the use of alcohol-based hand rubs: Wash hands before starting work, before entering an operating theatre, before eating, after touching contaminated objects, after using a toilet, and in all cases where hands are visibly soiled [ 4 ].

Among the infectious waste category, sharps waste is the most hazardous waste because of its ability to puncture the skin and cause infection [ 3 ]. Accidents or occurrences, such as near misses, spills, container damage, improper waste segregation, and incidents involving sharps, must be reported promptly to the waste management officer or an assigned representative [ 5 ].

Africa is facing a growing waste management crisis. While the volumes of waste generated in Africa are relatively small compared to developed regions, the mismanagement of waste in Africa already impacts human and environmental health. Infectious waste management has always remained a neglected public health problem in developing countries, resulting in a high burden of environmental pollution affecting the general masses. In Ethiopia, there is no updated separate regulation specific to healthcare waste management in the country to enforce the proper management of solid HCW [ 6 ].

In Ethiopia, like other developing countries, healthcare waste segregation practice was not given attention and did not meet the minimum HCWM standards, and it is still not jumped from paper. Previous study reveals that healthcare waste generation rates are significantly higher than the World Health Organization threshold, which ranges from 29.5–53.12% [ 7 , 8 ]. In Meneilk II Hospital, the proportion of infectious waste was 53.73%, and in the southern and northern parts of Ethiopia, it was 34.3 and 53%, respectively. Generally, this figure shows a value 3 to 4 times greater than the threshold value recommended by the World Health Organization [ 7 ].

Except for sharp wastes, segregation practice was poor, and all solid wastes were collected without respecting the colour-coded waste disposal system [ 9 ]. The median waste generation rate was found to vary from 0.361- 0.669 kg/patient/day, comprising 58.69% non-hazardous and 41.31% hazardous wastes. The amount of waste generated increased as the number of patients flow increased. Public hospitals generated a high proportion of total healthcare waste (59.22%) in comparison with private hospitals (40.48) [ 10 ]. The primary SHCW treatment and disposal mechanism was incineration, open burning, burring into unprotected pits and open dumping on municipal dumping sites as well as in the hospital backyard. Carelessness, negligence of the health workers, patients and cleaners, and poor commitment of the facility leaders were among the major causes of poor HCWM practice in Ethiopia [ 9 ]. This study aimed to investigate solid healthcare waste management practices and develop guidelines to improve solid healthcare waste management practices in Ethiopia.

The setting for this study was all health facilities found in Hossaena town, which is situated 232 kms from the capital city of Ethiopia, Addis Ababa, and 165 kms from the regional municipality of Hawasa. The health facilities found in the town were one university hospital, one private surgical centre, three government health centres, 17 medium clinics, and 19 small clinics were available in the city and; health facility workers who have direct contact with generating and disposal of HCW and those who are responsible as a manager of health facilities found in Hossaena town are the study settings. All health facilities except drug stores and health facility workers who have direct contact with healthcare waste generation participated in this study.

A mixed-method study design was used. For the quantitative part of this study, all healthcare workers who have direct contact with healthcare waste management practice participated in this study, and one focus group discussion from each health facility was used. Both of the study participants were taken from the same population. All health facility workers who have a role in healthcare waste management practice were included in the quantitative part of this study. The qualitative data collection phase used open-ended interviews, focus group discussions, and visual material analysis like posters and written materials. All FGDs were conducted by the principal investigator, one moderator, and one note-taker, and it took 50 to 75 min. 4–6 participants participated in each FGD.

According to Elizabeth (2018: 5), cited by Creswell and Plano (2007: 147), the mixed method is one of the research designs with philosophical assumptions as well as methods of inquiry. As a method, it focuses on collecting, analyzing, and mixing both quantitative and qualitative data in a single study. As a methodology, it involves philosophical assumptions guiding the direction of the collection and analysis and combining qualitative and quantitative approaches in many phases of the research project. The central premise is that using qualitative and quantitative approaches together provides a better understanding of the research problems than either approach alone.

The critical assumption of the concurrent mixed methods approach in this study is that quantitative and qualitative data provide different types of information, often detailed views of participants’ solid waste management practice qualitatively and scores on instruments quantitatively, and together, they yield results that should be the same. In this approach, the researcher collected quantitative and qualitative data almost simultaneously and analyzed them separately to cross-validate or compare whether the findings were similar or different between the qualitative and quantitative information. Concurrent approaches to the data collection process are less time-consuming than other types of mixed methods studies because both data collection processes are conducted on time and at the same visit to the field [ 11 ].

Data collection

The data collection involves collecting both quantitative and qualitative data simultaneously. The quantitative phase of this study assessed three components. Health care waste segregation practice, the availability of waste segregation equipment for HCW segregation, temporary storage facilities, transportation for final disposal, and disposal facilities data were collected using a structured questionnaire and observation of HCW generation. Recycling or re-using practice, waste treatment, the availability of the HCWM committee, and training data were collected.

Qualitative data collection

The qualitative phase of the data collection for this study was employed by using focus group discussions and semi-structured interviews about SHCWMP. Two focus group discussions (FGD) from each health facility were conducted in the government health facilities, one at the administrative level and one at the technical worker level, and one FGD was conducted for all private health facilities because of the number of available health facility workers. Each focus group has 4–6 individuals.

In this study, the qualitative and the quantitative data provide different information, and it is suitable for this study to compare and contrast the findings of the two results to obtain the best understanding of this research problem.

Quantitative data collection

The quantitative data were entered into Epi data version 3.1 to minimize the data entry mistakes and exported to the statistical package for social science SPSS window version 27.0 for analysis. A numeric value was assigned to each response in a database, cleaning the data, recoding, establishing a codebook, and visually inspecting the trends to check whether the data were typically distributed.

Data analysis

Data were analyzed quantitatively by using relevant statistical tools, such as SPSS. Descriptive statistics and the Pearson correlation test were used for the bivariate associations and analysis of variance (ANOVA) to compare the HCW generation rate between private and government health facilities and between clinics, health centres and hospitals in the town. Normality tests were performed to determine whether the sample data were drawn from a normally distributed population.

The Shapiro–Wilk normality tests were used to calculate a test statistic based on the sample data and compare it to critical values. The Shapiro–Wilk test is a statistical test used to assess whether a given sample comes from a normally distributed population. The P value greater than the significance level of 0.05 fails to reject the null hypothesis. It concludes that there is not enough evidence to suggest that the data does not follow the normal distribution. Visual inspection of a histogram, Q-Q plot, and P-P plot (probability-probability plot) was assessed.

Bivariate (correlation) analysis assessed the relationships between independent and dependent variables. Then, multiple linear regression analysis was used to establish the simple correlation matrices between different variables for investigating the strength relationships of the study variables in the analysis. In most variables, percentages and means were used to report the findings with a 95% confidence interval. Open-ended responses and focused group findings were undertaken by quantifying and coding the data to provide a thematic narrative explanation.

Appropriate and scientific care was taken to maintain the data quality before, during, and after data collection by preparing the proper data collection tools, pretesting the data collection tools, providing training for data collectors, and proper data entry practice. Data were cleaned on a daily basis during data collection practice, during data entry, and before analysis of its completeness and consistency.

Data analysis in a concurrent design consists of three phases. First, analyze the quantitative database in terms of statistical results. Second, analyze the qualitative database by coding the data and collapsing the codes into broad themes. Third comes the mixed-method data analysis. This is the analysis that consists of integrating the two databases. This integration consists of merging the results from both the qualitative and the quantitative findings.

Descriptive analysis was conducted to describe and summarise the data obtained from the samples used for this study. Reliability statistics for constructs, means and modes of each item, frequencies and percentage distributions, chi-square test of association, and correlations (Spearman rho) were used to portray the respondents’ responses.

All patient care-providing health facilities were included in this study, and the generation rate of healthcare waste and composition assessed the practice of segregation, collection, transportation, and disposal system was observed quantitatively using adopted and adapted structured questionnaires. To ensure representativeness, various levels of health facilities like hospitals, health centres, medium clinics, small clinics and surgical centres were considered from the town. All levels of health facilities are diagnosing, providing first aid services and treating patients accordingly.

The hospital and surgical centre found in the town provide advanced surgical service, inpatient service and food for the patients that other health facilities do not. The HCW generation rate was proportional to the number of patients who visited the health facilities and the type of service provided. The highest number of patients who visited the health facilities was in NEMMCSH; the service provided was diverse, and the waste generation rate was higher than that of other health facilities. About 272, 18, 15, 17, and 20 average patients visited the health facilities daily in NEMMCSH: government health centres, medium clinics, small clinics, and surgical centres. Paper and cardboard (141.65 kg), leftover food (81.71 kg), and contaminated gloves (42.96 kg) are the leading HCWs generated per day.

A total of 556 individual respondents from sampled health facilities were interviewed to complete the questionnaire. The total number of filled questionnaires was 540 (97.1) from individuals representing these 41 health facilities.

The principal investigator observed the availability of handwashing facilities near SHCW generation sites. 17(3.1%) of health facility workers had hand washing facilities near the health care waste generation and disposal site. Furthermore,10 (3.87%), 2 (2.1%), 2 (2.53%), 2 (2.1%), 1 (6.6%) of health facility workers had the facility of hand washing near the health care waste generation site in Nigist Eleni Mohamed Memorial Comprehensive Specialized Hospital (NEMMCSH), government health centres, medium clinics, small clinics, and surgical centre respectively. This finding was nearly the same as the study findings conducted in Myanmar; the availability of hand washing facilities near the solid health care waste generation was absent in all service areas [ 12 ]. The observational result was convergent with the response of facility workers’ response regarding the availabilities of hand washing facilities near to the solid health care waste generation sites.

The observational result was concurrent with the response of facility workers regarding the availability of hand-washing facilities near the solid health care waste generation sites.

The availability of personal protective equipment (PPE) was checked in this study. Three hundred ninety-two (72.6%) of the respondents agree on the facility’s availability of one or more personal protective equipment (PPE). The availability of PPEs in different levels of health facilities shows 392 (72.6%), 212 (82.2%), 56 (58.9%), 52 (65.8%), 60 (65.2%), 12 (75%) health facility workers in NEMMCSH, government health centres, medium clinics, small clinics, and surgical centres respectively agree to the presence of personal protective equipment in their department. The analysis further shows that the availability of masks for healthcare workers was above the mean in NEMMCSH and surgical centres.

Focus group participants indicated that health facilities did not volunteer to supply Personal protective equipment (PPEs) for the cleaning staff.

“We cannot purchase PPE by ourselves because of the salary paid for the cleaning staff.”

Cost inflation and the high cost of purchasing PPEs like gloves and boots are complained about by all (41) health facility owners.

“the reason for the absence of some of the PPEs like boots, goggles, and shortage of disposable gloves are owing to cost inflation from time to time and sometimes absent from the market is the reason why we do not supply PPE to our workers.”

Using essential personal protective equipment (PPEs) based on the risk (if the risk is a splash of blood or body fluid, use a mask and goggles; if the risk is on foot, use appropriate shoes) is recommended by the World Health Organization [ 13 ]. The mean availability of gloves in health facilities was 343 (63.5% (95% CI: 59.3–67.4). Private health institutions are better at providing gloves for their workers, 67.1%, 72.8%, and 62.5% in medium clinics, small clinics, and surgical centres, respectively, which is above the mean.

Research participants agree that.

‘‘ there is a shortage of gloves to give service in Nigist Eleni Mohamed Memorial Comprehensive Specialized Hospital (NEMMCSH) and government health centres .’’

Masks are the most available personal protective equipment for health facility workers compared to others. 65.4%, 55.6%, and 38% of the staff are available with gloves, plastic aprons and boots, respectively.

The mean availability of masks, heavy-duty gloves, boots, and aprons was 71.1%, 65.4%, 38%, and 44.4% in the study health facilities. Health facility workers were asked about the availability of different personal protective equipment, and 38% of the respondents agreed with the presence of boots in the facility. Still, the qualitative observational findings of this study show that all health facility workers have no shoes or footwear during solid health care waste management practice.

SHCW segregation practice was checked by observing the availability of SHCW collection bins in each patient care room. Only 4 (1.7%) of the room’s SHCW bins are collected segregated (non-infectious wastes segregated in black bins and infectious wastes segregated in yellow bins) based on the World Health Organization standard. Colour-coded waste bins, black for non-infectious and yellow for infectious wastes, were available in 23 (9.6%) rooms. 90% of the sharp containers were reusable, and 100% of the waste storage bins were plastic buckets that were easily cleanable. Only 6.7% of the waste bins were pedal operated and adequately covered, and the rest were fully opened, or a tiny hole was prepared on the container’s cover. All of the healthcare waste disposal bins in each health facility and at all service areas were away from the arm’s reach distance of the waste generation places, and this is contrary to World Health Organization SHCWM guidelines [ 13 ]. The observation result reveals that the reason for the above result was that medication trolleys were not used during medication or while healthcare providers provided any health services to patients.

Most medical wastes are incinerated. Burning solid and regulated medical waste generated by health care creates many problems. Medical waste incinerators emit toxic air pollutants and ash residues that are the primary source of environmental dioxins. Public concerns about incinerator emissions and the creation of federal regulations for medical waste incinerators are causing many healthcare facilities to rethink their choices in medical waste treatment. Health Care Without Harm [ 14 ], states that non-incineration treatment technologies are a growing and developing field. The U.S. National Academy of Science 2000 argued that the emission of pollutants during incineration is a potential risk to human health, and living or working near an incineration facility can have social, economic, and psychological effects [ 15 ].

The incineration of solid healthcare waste technology has been accepted and adopted as an effective method in Ethiopia. Incineration of healthcare waste can produce secondary waste and pollutants if the treatment facilities are not appropriately constructed, designed, and operated. It can be one of the significant sources of toxic substances, such as polychlorinated dibenzo-dioxins/dibenzofurans (PCDD/ PCDF), polyvinyl chloride (PVC), hexachlorobenzenes and polychlorinated biphenyls, and dioxins and furans that are known as hazardous pollutants. These pollutants may have undesirable environmental impacts on human and animal health, such as liver failure and cancer [ 15 , 16 ].

All government health facilities (4 in number) used incineration to dispose of solid waste. 88.4% and 100% of the wastes are incinerated in WUNEMMCSH and government health centres. This finding contradicts the study findings in the United States of America and Malaysia, in which 49–60% and 59–60 were incinerated, respectively, and the rest were treated using other technologies [ 15 , 16 ].

World Health Organization (2014:45) highlighted those critical elements of the appropriate operation of incinerators include effective waste reduction and waste segregation, placing incinerators away from populated areas, satisfactory engineered design, construction following appropriate dimensional plans, proper operation, periodic maintenance, and staff training and management are mandatory.

Solid waste collection times should be fixed and appropriate to the quantity of waste produced in each area of the health care facility. General waste should not be collected simultaneously or in the same trolley as infectious or hazardous wastes. The collection should be done daily for most wastes, with collection timed to match the pattern of waste generation during the day [ 13 ].

SHCW segregation practices were observed for 240 rooms in 41 health facilities that provide health services in the town. In government health centres, medium clinics, small clinics, and surgical centres, SHCW segregation practice was not based on the World Health Organization standard. All types of solid waste were collected in a single container near the generation area, and there were no colour-coded SHCW storage dust bins. Still, in NEMMCSH, in most of the service areas, colour-coded waste bins are available, and the segregation practice was not based on the standard. Only 3 (10%) of the dust bins collected the appropriate wastes according to the World Health Organization standard, and the rest were mixed with infectious and non-infectious SHCW.

Table 1 below shows health facility managers were asked about healthcare waste segregation practices, and 9 (22%) of the facility leaders responded that there is an appropriate solid healthcare waste segregation practice in their health facilities. Still, during observation, only 4 (1.7%) of the rooms in two (4.87%) of the facilities, SHCW bins collected the segregated wastes (non-infectious wastes segregated at the black bin and infectious wastes segregated at yellow bin) based on the world health organization standard. The findings of this study show there is a poor segregation practice, and all kinds of solid wastes are collected together.

In 40 (97.56%) health facilities, infectious wastes were collected daily from the waste generation areas to the final disposal points. During observation in one of the study health facilities, infectious wastes were not collected daily and left for days. Utility gloves, boots, and aprons are not available for cleaning staff to collect and transport solid healthcare wastes in all study health facilities. 29.26% of the facilities’ cleaning staff have a face mask, and 36.5% of the facilities remove waste bins from the service area when 3/4 full, and the rest were not removed or replaced with new ones. There is a separate container only in 2 health facilities for infectious and non-infectious waste segregation practice, and the rest were segregated and collected using single and non-colour coded containers.

At all of the facilities in the study area, SHCW was transported from the service areas to the disposal site were transported manually by carrying the collection container and there is no trolley for transportation. This finding was contrary to the study findings conducted in India, which show segregated waste from the generation site was being transported through the chute to the carts placed at various points on the hospital premises by skilled sanitary workers [ 17 ].

Only 2 out of 41 health facilities have temporary solid waste storage points at the facility. One of the temporary storage places was clean, and the other needed to be properly cleaned and unsightly. Two (100%) of the temporary storage areas are not fenced and have no restriction to an authorized person. Temporary storage areas are available only in two health facilities that are away from the service provision areas.

Observational findings revealed that pre-treatment of SHCW before disposal was not practised at all study health facilities. 95% of the facilities have no water supply for hand washing during and after solid healthcare waste generation, collection, and disposal.

The United States Agency estimated sharp injuries from medical wastes to health professionals and sanitary service personnel for toxic substances and disease registry. Most of the injuries are caused during the recapping of hypodermic needles before disposal into sharps containers [ 13 ]. Nearly half of the respondents, 245 (51.5%), are recapping needles after providing an injection to the patient. Recapping was more practised in NEMMCSH and surgical centres, which is 57.5% and 57.5%, respectively. In government health centres, medium clinics, and surgical centres, the recapping of used needles was practised below the mean, which is 47.9%, 48, and 43.8%, respectively. This finding was reasonable compared to the study findings of Doylo et al. [ 18 ] in western Ethiopia, where 91% of the health workers are recapping needles after injection [ 18 ]. The research finding shows that there is no significant association P-value of 0.82 between the training and recapping of needles after injection.

Focus group participants ’ response for appropriate SHCWMP regarding patients ’ and visitors ’ lack of knowledge on SHCW segregation practice

“The personal responsibilities of patients and visitors on solid HCW disposal should be explained to help appropriate safe waste management practice and maintain good hygiene .” “Providing waste management training and creating awareness are the two aspects of improving SHCW segregation practice.” “Training upgrades and creates awareness on hygiene for all workers.”

Sharp waste collection practices were observed in 240 rooms in the study health facilities, and 9.2% of the rooms used disposable sharp containers.

Sixty per cent (60%), 13.3%, 8.24%, and 15.71% of the sharps containers in NEMMCSH, government health centres, medium clinics, and small clinics, respectively, were using disposable sharps containers; sharps were disposed together with the sharps container, and surgical centre was using reusable sharp collection container. All disposable sharps containers in medium and small clinics used non-puncture-resistant or simple packaging carton boxes. 60% and 13.3% of the disposable sharps containers in NEMMCSH and the government health centre use purposefully manufactured disposable safety boxes.

Needle sticks injury reporting and occurrence

A total of 70 injuries were reported to the health facility manager in the last one year, and 44 of the injuries were reported by health professionals. The rest of the injuries were reported by supportive staff. These injuries were reported from 35 health facilities, and the remaining six health facilities did not report any cases of injury related to work; see Tables 2 and 3 below.

Accidents or incidents, including near misses, spillages, damaged containers, inappropriate segregation, and any incidents involving sharps, should be reported to the waste-management officer. Accidental contamination must be notified using a standard-format document. The cause of the accident or incident should be investigated by the waste-management officer (in case of waste) or another responsible officer, who should also take action to prevent a recurrence [ 13 ]. Two hundred seventy-one (50.2% (CI: 45.7–54.6) of the respondents agree that satisfactory procedures are available in case of an accident, while the remaining 269 (49.8%( CI: 45.4–54.3) of respondents do not agree on the availability of satisfactory procedures in case of an accident, see Table  4 below. The availability of satisfactory procedures in case of an accident is above the mean in medium clinics, which is 60.8%. 132(24.4%) of the staff are pricked by needle stick injury while providing health services. Nearly half of the respondents, 269 (49.8%), who have been exposed to needle stick injury do not get satisfactory procedures after being pricked by a needle, and those who have not been stung by a needle stick injury for the last year. 204 (37.8%) disagree with the presence of satisfactory procedures in the case of a needle stick injury. In NEMMCSH, 30.2% of the research participants were pricked by needle stick injury within one year of period, and 48.8% of those who were stung by needle stick injuries did not agree upon the presence of satisfactory procedures in case of needle stick injuries in the study hospital. 17.9% and 49.5%, 24.1% and 60.8%, 7.6% and 50% of the respondents are pricked by needle sticks, and they disagree on the availability of satisfactory procedures in case of accidents, respectively, in government health centres, medium clinics, small clinics, and surgical centre respectively.

One hundred seventy-seven (32.7% (CI:29.1–37) respondents were exposed to needle stick injury while working in the current health facilities. One hundred three (58.1%) and 26 (32.9%) needle stick injuries were reported from WUNEMMCSH and medium clinics, which is above the mean. One hundred thirty-two(24.7% (95%CI:20.7–28.1) of the respondents are exposed to needle stick injury within one year of the period. Seventy-eight(30.2%), 17 (17.9%), 19 (24.1%), 15 (16.3%), 3 (18.8%) of the staff are injured by needle sticks from NEMMCSH, government health centres, medium clinics, small clinics, and surgical centre staffs respectively within one year of service.

The mean availabilities of satisfactory procedures in case of accidents were 321 (59.4% (CI:55.4–63.7). Out of this, 13.7% of the staff is injured by needle sticks within one year before the survey. Except in NEMMCSH, the mean availabilities of satisfactory procedures were above the mean, which is 50%, 60%, 77.2%, 66.3%, and 81.3% in NEMMCSH, government health centres, medium clinics, small clinics, and surgical centres respectively.

Table 5 below shows that Hepatitis B, COVID-19, and tetanus toxoid vaccinations are the responses of the research participants to an open-ended question on which vaccine they took. The finding shows that 220 (40.8%) of the respondents were vaccinated to prevent themselves from health facility-acquired infection. One hundred fifty-six (70.9%) of the respondents are vaccinated to avoid themselves from Hep B infection. Fifty-nine (26%0.8) of the respondents were vaccinated to protect themselves from two diseases that are Hep B and COVID-19.

Appropriate health care waste management practice was assessed by using 12 questions: availability of colour-coded waste bins, foot-operated dust bins, elbow or foot-operated hand washing basin, personal protective equipment, training, role and responsibility of the worker, the presence of satisfactory procedures in case of an accident, incinerator, vaccination, guideline, onsite treatment, and the availability of poster. The mean of appropriate healthcare waste management practice was 55.58%. The mean of solid health care waste management practice based on the level of health facilities was summed and divided into 12 variables to get each health facility’s level of waste management practice. 64.9%, 45.58%, 49%, 46.9%, and 51.8% are the mean appropriate health care waste management practices in NEMMCSH, government health centres, medium clinics, small clinics, and surgical centres, respectively. In NEMMCSH, the practice of solid healthcare waste management shows above the mean, and the rest was below the mean of solid healthcare waste management practice.

Healthcare waste treatment and disposal practice

Solid waste treatment before disposal was not practised at all study health facilities. There is an incineration practice at all of the study health facilities, and the World Health Organization 2014 recommended three types of incineration practice for solid health care waste management: dual-chamber starved-air incinerators, multiple chamber incinerators, and rotary kilns incinerators. Single-chamber, drum, and brick incinerators do not meet the best available technique requirements of the Stockholm Convention guidelines [ 13 ]. The findings of this study show that none of the incinerators found in the study health facilities meet the minimum standards of solid healthcare waste incineration practice, and they need an air inlet to facilitate combustion. Eleven (26.82%) of the health facilities have an ash pit to dispose of burned SHCW; the majority, 30 (73.17%), dispose of the incinerated ash and burned needles in the municipal waste disposal site. In one out of 11 health facilities with an ash pit, one of the incinerators was built on the ash pit, and the incinerated ashes were disposed of in the ash pit directly. Pre-treatment of SHCW before disposal was not practised at all health facilities; see Table  6 below.

All government health facilities use incineration to dispose of solid waste. 88.4% and 100% of the solid wastes are incinerated in WUNEMMCS Hospital and government health centres, respectively. This finding was not similar to the other studies because other technologies like autoclave microwave and incineration were used for 59–60% of the waste [ 15 ]. Forty-one (100%) of the study facilities were using incinerators, and only 5 (12.19%) of the incinerators were constructed by using brick and more or less promising than others for incinerating the generated solid wastes without considering the emitting gases into the atmosphere and the residue chemicals and minerals in the ashes.

Research participants’ understanding of the environmental friendliness of health care waste management practice was assessed, and the result shows that more than half, 312(57%) of the research participants do not agree on the environmental friendliness of the waste disposal practices in the health facilities. The most disagreement regarding environmental friendliness was observed in NEMMCSH; 100 (38.8%) of the participants only agreed the practice was environmentally friendly of the service. Forty-four (46.3%), 37 (46.8%), 40 (43.5%), and 7 (43.8%) of the participants agree on the environmental friendliness of healthcare waste management practice in government health centres, medium clinics, small clinics, and surgical centres, respectively.

One hundred twenty-five (48.4%) and 39(42.4%) staff are trained in solid health care waste management practice in NEMMCSH and small clinic staff, respectively; this result shows above the mean. Twenty-seven (28.4%), 30 (38%), and 4 (25%) of the staff are trained in health care waste management practice in Government health centres, medium clinics, and surgical centres, respectively. The training has been significantly associated with needle stick injury, and the more trained staff are, the less exposed to needle stick injury. One hundred ninety-six (36.4%) of the participants answered yes to the question about the availability of trainers in the institution. 43.8% of the NEMMCSH staff agreed on the availability of trainers on solid health care waste management, which is above the mean, and 26.3%, 31.6%, 31.5%, and 25% for the government health centres, medium clinics, small clinics, and surgical centre respectively, which is below the mean.

Trained health professionals are more compliant with SHCWM standards, and the self-reported study findings of this study show that 41.7% (95%CI:37.7–46) of the research participants are trained in health care waste management practice. This finding was higher compared to the study findings of Sahiledengle in 2019 in the southeast of Ethiopia, shows 13.0% of healthcare workers received training related to HCWM in the past one year preceding the study period and significantly lower when compared to the study findings in Egypt which is 71% of the study participants were trained on SHCWM [ 8 , 19 , 20 ].

Three out of four government health facility leaders, 17 (45.94%) of private health facility leaders/owners of the clinic and 141 FGD participants complain about the absence of some PPEs like boots and aprons to protect themselves from infectious agents.

‘ ‘Masks, disposable gloves, and changing gowns are a critical shortage at all health facilities.’’

Cleaners in private health facilities are more exposed to infectious agents because of the absence of personal protective equipment. Except for the cleaning staff working in the private surgical centre, all cleaning staff 40 (97.56) of the health facilities complain about the absence of changing gowns and the fact that there are no boots in the facilities.

Cost inflation and the high cost of purchasing PPEs like gloves and boots are complained by all of (41) the health facility owners and the reason for the absence of some of the PPEs like boots, goggles, and shortage of disposable gloves. Sometimes, absence from the market is the reason why we do not supply PPE to our workers.

Thirty-four (82.92%) of the facility leaders are forwarded, and there is a high expense and even unavailability of some of the PPEs, which are the reasons for not providing PPEs for the workers.

‘‘Medical equipment and consumables importers and whole sellers are selective for importing health supplies, and because of a small number of importers in the country and specifically, in the locality, we can’t get materials used for health care waste management practice even disposable gloves. ’’

One of the facility leaders from a private clinic forwarded that before the advent of COVID-19 -19) personal protective equipment was more or less chip-and-get without difficulty. Still, after the advent of the first Japanese COVID-19 patient in Ethiopia, people outside the health facilities collect PPEs like gloves and masks and storing privately in their homes.

‘‘PPEs were getting expensive and unavailable in the market. Incinerator construction materials cost inflation, and the ownership of the facility building are other problems for private health facilities to construct standard incinerators.’’

For all of the focus group discussion participants except in NEMMCSH and two private health facilities, covered and foot-operated dust bins were absent or in a critical shortage compared to the needed ones.

‘‘ Waste bins are open and not colour-coded. The practice attracts flies and other insects. Empty waste bins are replaced without cleaning and disinfecting by using chlorine solution.’’ “HCW containers are not colour-coded, but we are trying to label infectious and non-infectious in Amharic languages.”

Another issue raised during focus group discussions is incineration is not the final disposal method. It needs additional disposal sites, lacks technology, is costly to construct a brick incinerator, lacks knowledge for health facility workers, shortage of man powers /cleaners, absence of environmental health professionals in health centres and all private clinics, and continues exposure to the staff for needle stick injury, foully smell, human scavengers, unsightly, fire hazard, and lack of water supply in the town are the major teams that FGD participants raise and forwarded the above issue as a problem to improve SHCWMP.

Focus group participants, during the discussion, raised issues that could be more comfortable managing SHCWs properly in their institution. Two of the 37 private health facilities are working in their own compound, and the remaining 35 are rented; because of this, they have difficulty constructing incinerators and ash removal pits and are not confident about investing in SHCWM systems. Staff negligence and involuntary abiding by the rules of the facilities were raised by four of the government health facilities, and it was difficult to punish those who violated the healthcare waste management rules because the health facility leaders were not giving appropriate attention to the problem.

Focus group participants forwarded recommendations on which interventions can improve the management of SHCW, and recommendations are summarised as follows:

“PPE should be available in quality and quantity for all health facility workers who have direct contact with SHCW.” “Scientific-based waste management technologies should be availed for health facilities.” “Continuous induction HCW management training should be provided to the workers. Law enforcement should be strengthened.” “Communal HCW management sites should be availed, especially for private health facilities.” “HCWM committee should be strengthened.” “Non-infectious wastes should be collected communally and transported to the municipal SHCW disposal places.” “Leaders should be knowledgeable on the SHCWM system and supervise the practice continuously.” “Patient and client should be oriented daily about HCW segregation practice.” “Regulatory bodies should supervise the health facilities before commencing and periodically between services .”

The above are the themes that FGD participants discussed and forwarded for the future improvements of SHAWMP in the study areas.

Lack of water supply in the town

Other issues raised during FGDs were health facilities’ lack of water supply. World Health Organization (2014: 89) highlights that water supply for the appropriate waste management system should be mandatory at any time in all health service delivery points.

Thirty-nine (95.12%) of the health facilities complain about the absence of water supply to improve HCW management practices and infection prevention and control practices in the facilities.

“We get water once per week, and most of the time, the water is available at night, and if we are not fetching as scheduled, we can’t get water the whole week”.

In this research, only those who have direct contact have participated in this study, and 434 (80.4%) of the respondents agree they have roles and responsibilities for appropriate solid health care waste management practice. The rest, 19.6%, do not agree with their commitment to manage health care wastes properly, even though they are responsible. Health facility workers in NEMMCSH and medium clinics know their responsibilities better than others, and their results show above the mean. 84.5%, 74.5%, 81%, 73.9% and 75% in NEMMCSH, Government health centres, medium clinics, small clinics, and surgical centres, respectively.

Establishing a policy and a legal framework, training personnel, and raising public awareness are essential elements of successful healthcare waste management. A policy can be viewed as a blueprint that drives decision-making at a political level and should mobilize government effort and resources to create the conditions to make changes in healthcare facilities. Three hundred and seventy-four (69.3%) of the respondents agree with the presence of any solid healthcare waste management policy in Ethiopia. The more knowledge above the mean (72.9%) on the presence of the policy is reported from NEMMCSH.

Self-reported level of knowledge on what to do in case of an accident revealed that 438 (81.1% CI: 77.6–84.3%) of the respondents knew what to do in case of an accident. Government health centre staff and medium clinic staff’s knowledge about what to do in case of an accident was above the mean (88.4% and 82.3%), respectively, and the rest were below the mean. The action performed after an occupational accident revealed that 56 (35.7%) of the respondents did nothing after any exposure to an accident. Out of 56 respondents who have done nothing after exposure, 47 (83.92%) of the respondents answered yes to their knowledge about what to do in case of an accident. Out of 157 respondents who have been exposed to occupational accidents, only 59 (37.6%) of the respondents performed the appropriate measures, 18 (11.5%), 9 (5.7%), 26 (16.6%), 6 (3.8%) of the respondents are taking prophylaxis, linked to the incident officer, consult the available doctors near to the department, and test the status of the patient (source of infection) respectively and the rest were not performing the scientific measures, that is only practising one of the following practices washing the affected part, squeezing the affected part to remove blood, cleaning the affected part with alcohol.

Health facility workers’ understanding of solid health care waste management practices was assessed by asking whether the current SHCWM practice needs improvement. Four hundred forty-nine (83.1%) health facility workers are unsatisfied with the current solid waste management practice at the different health facility levels, and they recommend changing it to a scientific one. 82.6%, 87.4%, 89.9%, 75%, and 81.3% of the respondents are uncomfortable or need to improve solid health care waste management practices in NEMMCSH, government health centres, medium clinics, small clinics, and surgical centres, respectively.

Lack of safety box, lack of colour-coded waste bins, lack of training, and no problems are the responses to the question problems encountered in managing SHCWMP. Two Hundred and Fifty (46.92%) and 232 (42.96%) of the respondents recommend the availability of safety boxes and training, respectively.

Four or 9.8% of the facilities have infection prevention and control (IPC) teams in the study health facilities. This finding differed from the study in Pakistan, where thirty per cent (30%) of the study hospitals had HCWM or infection control teams [ 21 ]. This study’s findings were similar to those conducted in Pakistan by Khan et al. [ 21 ], which confirmed that the teams were almost absent at the secondary and primary healthcare levels [ 20 ].

The availability of health care waste management policy report reveals that 69.3% (95% CI: 65.4–73) of the staff are aware of the presence of solid health care waste management policy in the institution. Availability of health care waste management policy was 188 (72.9%), 66 (69.5%), 53 (677.1%), 57 (62%), 10 (62.5%) in NEMMCSH, Government health centres, medium clinics, small clinics, and surgical centre respectively. Healthcare waste management policy availability was above the mean in NEMMCSH and government health centres; see Table  6 below.

Open-ended responses on the SHCWM practice of health facility workers were collected using the prepared interview guide, and the responses were analyzed using thematic analysis. All the answered questions were tallied on the paper and exported to Excel software for thematic analysis.

The study participants recommend.

“appropriate segregation practice at the point of generation” "health facility must avail all the necessary supplies that used for SHCWMP, punishment for those violating the rule of SHCWMP",

“waste management technologies should be included in solid waste management guidelines, and enforcement should be strengthened.”

The availability of written national or adopted/adapted SHCWM policies was observed at all study health facilities. Twenty eight (11.66%) of the rooms have either a poster or a written document of the national policy document. However, all staff working in the observed rooms have yet to see the inside content of the policy. The presence of the policy alone cannot bring change to SHCWMP. This finding shows that the presence of policy in the institution was reasonable compared to the study findings in Menelik II hospital in Addis Ababa, showing that HCWM regulations and any applicable facility-based policy and strategy were not found [ 22 ]. The findings of this study were less compared to the study findings in Pakistan; 41% of the health facilities had the policy document or internal rules for the HCWM [ 21 ].

Focus group participants have forwarded recommendations on which interventions can improve the management of SHCW, and recommendations are summarised as follows.

‘‘Supplies should be available in quality and quantity for all health facility workers with direct contact with SHCW. Scientific-based waste management technologies should be available for health facilities. Continues and induction health care waste management training should be provided to the workers. Law enforcement should be strengthened. Community healthcare waste management sites should be available, especially for private health facilities. HCWM committee should be strengthened. Non-infectious wastes should be collected communally and transported to the municipal SHCW disposal places. Leaders should be knowledgeable about the SHCWM system and supervise the practice continuously. Patients and clients should be oriented daily about health care waste segregation practices. Regulatory bodies should supervise the health facilities before commencing and periodically in between the service are the themes those FGD participants discussed and forward for the future improvements of SHCWMP in the study areas.’’

The availability of PPEs in different levels of health facilities shows 392 (72.6%), 212 (82.2%), 56 (58.9%), 52 (65.8%), 60 (65.2%), 12 (75%) health facility workers in NEMMCSH, government health centres, medium clinics, small clinics, and surgical centres respectively agree to the presence of personal protective equipment in their department. The availability of PPEs in this study was nearly two-fold when compared to the study findings in Myanmar, where 37.6% of the staff have PPEs [ 12 ].

The mean availability of masks, heavy-duty gloves, boots, and aprons was 71.1%, 65.4%, 38%, and 44.4% in the study health facilities. This finding shows masks are less available in the study health facilities compared to other studies. The availability of utility gloves, boots, and plastic aprons is good in this study compared to the study conducted by Banstola, D in Pokhara Sub-Metropolitan City [ 23 ].

The findings of this study show there is a poor segregation practice, and all kinds of solid wastes were collected together. This finding was similar to the study findings conducted in Addis Ababa, Ethiopia, by Debere et al. [ 24 ] and contrary to the study findings conducted in Nepal and India, which shows 50% and 65–75% of the surveyed health facilities were practising proper waste segregation systems at the point of generation without mixing general wastes with hazardous wastes respectively [ 9 , 17 ].

Ninety percent of private health facilities collect and transport SHCW generated in every service area and transport it to the disposal place by the collection container (no separate container to collect and transport the waste to the final disposal site). This finding was similar to the study findings of Debre Markos’s town [ 25 ]. At all of the facilities in the study area, SHCW was transported from the service areas to the disposal site manually by carrying the collection container, and there was no trolley for transportation. This finding was contrary to the study findings conducted in India, which show segregated waste from the generation site was being transported through the chute to the carts placed at various points on the hospital premises by skilled sanitary workers [ 17 ].

Observational findings revealed that pre-treatment of SHCW before disposal was not practised at all study health facilities. This study was contrary to the findings of Pullishery et al. [ 26 ], conducted in Mangalore, India, which depicted pre-treatment of the waste in 46% of the hospitals [ 26 ]. 95% of the facilities have no water supply for handwashing during and after solid healthcare waste generation, collection, and disposal. This finding was contrary to the study findings in Pakistan hospitals, which show all health facilities have an adequate water supply near the health care waste management sites [ 27 ].

Questionnaire data collection tools show that 129 (23.8%) of the staff needle stick injuries have occurred on health facility workers within one year of the period before the data collection. This finding was slightly smaller than the study findings of Deress et al. [ 25 ] in Debre Markos town, North East Ethiopia, where 30.9% of the workers had been exposed to needle stick injury one year prior to the study [ 25 ]. Reported and registered needle stick injuries in health facilities are less reported, and only 70 (54.2%) of the injuries are reported to the health facilities. This finding shows an underestimation of the risk and the problem, which was supported by the study conducted in Menilik II hospitals in Addis Ababa [ 22 ]. 50%, 33.4%, 48%, 52%, and 62.5% of needle stick injuries were not reported in NEMMCSH, Government health centres, medium clinics, small clinics, and surgical centres, respectively, to the health facility manager.

Nearly 1/3 (177 or 32.7%) of the staff are exposed to needle stick injuries. Needle stick injuries in health facilities are less reported, and only 73 (41.24%) of the injuries are reported to the health facilities within 12 months of the data collection. This finding is slightly higher than the study finding of Deress et al. [ 25 ] in Debere Markos, Ethiopia, in which 23.3% of the study participants had encountered needle stick/sharps injuries preceding 12 months of the data collection period [ 25 ].

Seventy-three injuries were reported to the health facility manager in the last one year, 44 of the injuries were reported by health professionals, and the rest were reported by supportive staff. These injuries were reported from 35(85.3%) health facilities; the remaining six have no report. These study findings were better than the findings of Khan et al. [ 21 ], in which one-third of the facilities had a reporting system for an incident, and almost the same percentage of the facilities had post-exposure procedures in both public and private sectors [ 21 ].

Within one year of the study period, 129 (23.88%) needle stick injuries occurred. However, needle stick injuries in health facilities are less reported, and only 70 (39.5%) of the injuries are reported to the health facilities. These findings were reasonable compared to the study findings of the southwest region of Cameroon, in which 50.9% (110/216) of all participants had at least one occupational exposure [ 28 , 29 ]. This result report shows a very high exposure to needle stick injury compared to the study findings in Brazil, which shows 6.1% of the research participants were injured [ 27 ].

The finding shows that 220 (40.8%) of the respondents were vaccinated to prevent themselves from health facility-acquired infection. One Hundred Fifty-six (70.9%) of the respondents are vaccinated in order to avoid themselves from Hep B infection. Fifty-nine (26%0.8) of the respondents were vaccinated to protect themselves from two diseases that are Hep B and COVID-19. This finding was nearly the same as the study findings of Deress et al. [ 7 ],in Ethiopia, 30.7% were vaccinated, and very low compared to the study findings of Qadir et al. [ 30 ] in Pakistan and Saha & Bhattacharjya India which is 66.67% and 66.17% respectively [ 25 , 30 , 31 ].

The incineration of solid healthcare waste technology has been accepted and adopted as an effective method in Ethiopia. These pollutants may have undesirable environmental impacts on human and animal health, such as liver failure and cancer [ 15 , 16 ]. All government health facilities use incineration to dispose of solid waste. 88.4% and 100% of the wastes are incinerated in WUNEMMCSH and government health centres, respectively. This finding contradicts the study findings in the United States of America and Malaysia, which are 49–60% and 59–60 are incinerated, respectively, and the rest are treated using other technologies [ 15 , 16 ].

All study health facilities used a brick or barrel type of incinerator. The incinerators found in the study health facilities need to meet the minimum standards of solid health care waste incineration practice. These findings were similar to the study findings of Nepal and Pakistan [ 32 ]. The health care waste treatment system in health facilities was found to be very unsystematic and unscientific, which cannot guarantee that there is no risk to the environment and public health, as well as safety for personnel involved in health care waste treatment. Most incinerators are not properly operated and maintained, resulting in poor performance.

All government health facilities use incineration to dispose of solid waste. All the generated sharp wastes are incinerated using brick or barrel incinerators, as shown in Fig.  1 above. This finding was consistent with the findings of Veilla and Samwel [ 33 ], who depicted that sharp waste generation is the same as sharps waste incinerated [ 33 ]. All brick incinerators were constructed without appropriate air inlets to facilitate combustion except in NEMMCSH, which is built at a 4-m height. These findings were similar to the findings of Tadese and Kumie at Addis Ababa [ 34 ].

Barrel and brick incinerators used in private clinic

Strengths and limitations

This is a mixed-method study; both qualitative and quantitative study design, data collection and analysis techniques were used to understand the problem better. The setting for this study was one town, which is found in the southern part of the country. It only represents some of the country’s health facilities, and it is difficult to generalize the findings to other hospitals and health centres. Another limitation of this study was that private drug stores and private pharmacies were not incorporated.

Conclusions

In the study, health facilities’ foot-operated solid waste dust bins are not available for healthcare workers and patients to dispose of the generated wastes. Health facility managers in government and private health institutions should pay more attention to the availability of colour-coded dust bins. Most containers are opened, and insects and rodents can access them anytime. Some of them are even closed (not foot-operated), leading to contamination of hands when trying to open them.

Healthcare waste management training is mandatory for appropriate healthcare waste disposal. Healthcare-associated exposure should be appropriately managed, and infection prevention and control training should be provided to all staff working in the health facilities.

Availability of data and materials

The authors declare that data for this work are available upon request to the first author.

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Acknowledgements

The authors are grateful to the health facility leaders and ethical committees of the hospitals for their permission. The authors acknowledge the cooperation of the health facility workers who participated in this study.

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

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Wachemo University College of Medicine and public health, Hossana, Ethiopia

Yeshanew Ayele Tiruneh

Department of Public Health, University of South Africa, College of Human Science, Pretoria, South Africa

L. M. Modiba & S. M. Zuma

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Dr. Yeshanew Ayele Tiruneh is a researcher of this study; the principal investigator does all the proposal preparation, methodology, data collection, result and discussion, and manuscript writing. Professor LM Modiba and Dr. SM Zuma are supervisors for this study. They participated in the topic selection and modification to the final manuscript preparation by commenting on and correcting the study. Finally, the three authors read and approved the final version of the manuscript and agreed to submit the manuscript for publication.

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Correspondence to Yeshanew Ayele Tiruneh .

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Tiruneh, Y.A., Modiba, L.M. & Zuma, S.M. Solid health care waste management practice in Ethiopia, a convergent mixed method study. BMC Health Serv Res 24 , 985 (2024). https://doi.org/10.1186/s12913-024-11444-8

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Received : 05 March 2023

Accepted : 14 August 2024

Published : 26 August 2024

DOI : https://doi.org/10.1186/s12913-024-11444-8

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