The United Nations have agreed to negotiate a legally binding instrument to eliminate plastic pollution which includes provisions to reduce environmental emissions of plastic through improved waste management. However, there is a paucity of scientific evidence to prioritize the actions which will have the greatest impact on plastic pollution mitigation and many of the specific emission and transmission pathways are highly challenging to observe and measure. To this, we apply an expert elicitation study to provide a systematic evidence base on which parts of the solid waste management (SWM) system have the highest potential for plastic emission as well as the effectiveness of specific interventions to reduce them. We found that SWM processes closer to the waste generator, such as the waste storage and collection stage, have the greatest potential for plastic emission, with the most effective mitigations often simple solutions, such as provision of rigid containers or ensuring waste is disposed of in bags. Our results contribute to a much-needed evidence base and demonstrate significant reduction in plastic debris emissions is achievable by deploying tangible and effective local SWM infrastructure and service interventions.

Ongoing negotiations for a ‘Legally Binding Instrument on Plastic Pollution’ recognise the substantial contribution made by the informal recycling sector (IRS - waste pickers) to plastic pollution mitigation as part of just transition. Negotiating parties will require baseline evidence of the sector’s activities to inform the development of local and national actions plans. To this, we carried out a review of IRS prevalence and productivity following the Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) method followed by extensive (statistical) data analytics. Waste pickers represent median 0.2% (interquartile range – IQR: 0.1-0.5%) of the urban population worldwide, collecting between 20 kg and 80 kg of engineered materials for recycling each day, of which 30% (mean wt. ar) are plastics. We identify substantial shortcomings in most methodologies used to gather data on the IRS, introducing epistemic uncertainty into some previous estimates of the sector’s activity. We recommend development of a standardised resource-efficient method of sampling and data gathering, suitable for implementation at municipal/local scale. Our work offers verifiable quantitative knowledge on the sector’s activities to date, suitable for use in plastic pollution quantification models and local/national action plans required to baseline and monitor progress towards multilateral targets.

Negotiations for a global treaty on plastic pollution(1) will shape future policies on plastics production, use and waste management. Its parties will benefit from a high-resolution baseline of waste flows and plastic emission sources to enable identification of pollution hotspots and their causes(2). Nationally aggregated waste management data can be distributed to smaller scales to identify generalized points of plastic accumulation and source phenomena(3-11). However, it is challenging to use this type of spatial allocation to assess the conditions under which emissions take place(12,13). Here we develop a global macroplastic pollution emissions inventory by combining conceptual modelling of emission mechanisms with measurable activity data. We define emissions as materials that have moved from the managed or mismanaged system (controlled or contained state) to the unmanaged system (uncontrolled or uncontained state-the environment). Using machine learning and probabilistic material flow analysis, we identify emission hotspots across 50,702 municipalities worldwide from five land-based plastic waste emission sources. We estimate global plastic waste emissions at 52.1[48.3-56.3]million metric tonnes (Mt) per year, with approximately 57%wt. and 43%wt. open burned and unburned debris, respectively. Littering is the largest emission source in the Global North, whereas uncollected waste is the dominant emissions source across the Global South. We suggest that our findings can help inform treaty negotiations and develop national and sub-national waste management action plans and source inventories.

Increasing aspirations to develop a circular economy for waste plastics will result in an expansion of the global plastics reprocessing sector over the coming decades. Here we focus on two critical challenges within the value chain that as a result of such increased circularity may exacerbate existing issues for occupational and public health (1): Legacy contamination in secondary plastics, addressing the risk of materials and substances being inherited from the previous use and carried through into new products when the material enters its subsequent use phase; and challenge (2): Extrusion of secondary plastics in reprocessing, an end process of conventional mechanical recycling of plastics, involving heating secondary plastics under pressure until they melt and can be formed into new products. Via a systematic review (PRISMA guidelines, adapted), we considered over 4,000 sources of information, refined and consolidated into 20 relevant sources, which were critically assessed. We also derive prevalent risk scenarios of hazard-pathway-receptor combinations, subsequently being ranked. Our critical analysis highlights that despite stringent regulation, industrial diligence and enforcement, occasionally small amounts of potentially hazardous substances are able to pass through these safeguards and re-enter in the new product cycle. Although many are present at concentrations unlikely to pose a serious and imminent threat, their existence may be an indication of a wider or possibly increasing challenge of pollution dispersion, as the plastics reprocessing sector proliferates. But, in the Global South context, such controls may not be in place. Several studies showed emission control by passive ventilation, through open doors and windows followed by dilution and dispersion in the atmosphere, resulting in increased occupational exposure. It is recommended that further investigations are undertaken to establish the scale and magnitude of such phenomena, especially given the limited evidence base, with results informing improved future risk management protocols of a circular economy for plastics.

Systems to safely store, handle, treat and dispose of medical (healthcare) waste are well developed in the 21st century. Yet across many parts of the Global South (low- and middle-income countries) such systems, resources and know-how are lacking; to the extent that medical waste could be posing a serious threat to the health, safety and lives of millions of healthcare workers and waste handlers who regularly interact with this material. We present here a novel scope and dimension to investigating the risks and hazards to people who come into contact with medical waste, focusing on activity types and established medical practice. Based on a systematic review of the evidence (PRISMA approach, adapted), we critically analyzed and comparatively summarized data, and identified prevalent combinations of hazards, exposure and risk with a global scope. Subsequently, we assigned indicative comparative risk scores for such combinations. Our critical analysis unveils extensive mismanagement of medical waste globally, including the co-disposal with municipal solid waste (MSW), burning in open pits, and dumping even on public streets. Alarmingly, a small but non-negligible trade in reused medical equipment is proliferated by a cohort of waste reclamation specialists (sub-group of waste pickers): they collect hypodermic needles, and other single use medial items for resale to substance abusers and back into the healthcare system. We also highlight the dilemma faced by medical waste handlers in many parts of the world where a difficult choice is made between creating hazardous emissions from burning waste in the open or discarding it on land (e.g. in dumpsites) from where it risks accidentally infecting people with pathogens.

Over the coming decades, a large additional mass of plastic waste will become available for recycling, as efforts increase to reduce plastic pollution and facilitate a circular economy. New infrastructure will need to be developed, yet the processes and systems chosen should not result in adverse effects on human health and the environment. Here, we present a rapid review and critical semi-quantitative assessment of the potential risks posed by eight approaches to recovering value during the resource recovery phase from post-consumer plastic packaging waste collected and separated with the purported intention of recycling. The focus is on the Global South, where there are more chances that high risk processes could be run below standards of safe operation. Results indicate that under non-idealised operational conditions, mechanical reprocessing is the least impactful on the environment and therefore most appropriate for implementation in developing countries. Processes known as 'chemical recycling' are hard to assess due to lack of real-world process data. Given their lack of maturity and potential for risk to human health and the environment (handling of potentially hazardous substances under pressure and heat), it is unlikely they will make a useful addition to the circular economy in the Global South in the near future. Inevitably, increasing circular economy activity will require expansion towards targeting flexible, multi-material and multilayer products, for which mechanical recycling has well-established limitations. Our comparative risk overview indicates major barriers to changing resource recovery mode from the already dominant mechanical recycling mode towards other nascent or energetic recovery approaches.

Despite the relatively benign characteristics of construction and demolition waste, its mismanagement can result in considerable harm to human health for 200 million workers and those who live and work in proximity to construction and demolition activities. The high number of workers classified as informal, results in a large unregulated and vulnerable workforce at a high risk of exposure to hazards. We focused a systematic scoping review (PRISMA-ScR) on evidence associating construction and demolition waste with hazards and risks in low- and middle-income countries. We reviewed more than 3,000 publications, narrowed to 49 key sources. Hazard-pathway-receptor scenarios/combinations were formulated, enabling indicative ranking and comparison of the relative harm caused to different groups. Though the evidential basis is sparse, there is a strong indication that the combustible fraction of construction and demolition waste is disposed of by open burning in many low- and middle-income countries, including increasing quantities of high chloride-content PVC; risking exposure to dioxins and related compounds. A long-standing and well-known hazard, asbestos, continues to represent a health threat throughout the world, claiming 250,000 lives per annum despite being banned in most countries. In the coming decades, it is anticipated that more than half of all deaths from asbestos will take place in India, where it is still sold. Comparatively, the highest risks from construction and demolition waste exist in low- and middle-income countries where attention to risk mitigation and control is needed.

‘Waste plastic moves around the world causing havoc’ could easily be the title of a news item these days – or a punch line of an environmental preservation non-governmental organisation (NGO). In fact, much stronger expressions are floating around in the heated public debate. But how informed is the overall discussion? Here, we outline some of the areas that are partially evading attention, and highlight some misconceptions that seem to have been established in the collective imagination over the last few years.

Large quantities of mismanaged plastic waste threaten the health and wellbeing of billions worldwide, particularly in low- and middle-income countries where waste management capacity is being outstripped by increasing levels of consumption and plastic waste generation. One of the main self-management strategies adopted by 2 billion people who have no waste collection service, is to burn their discarded plastic in open, uncontrolled fires. While this strategy provides many benefits, including mass and volume reduction, it is a form of plastic pollution that results in the release of chemical substances and particles that may pose serious risks to public health and the environment. We followed adapted PRISMA guidelines to select and review 20 publications that provide evidence on potential harm to human health from open burning plastic waste, arranging evidence into eight groups of substance emissions: brominated flame retardants; phthalates; potentially toxic elements; dioxins and related compounds; bisphenol A; particulate matter; and polycyclic aromatic hydrocarbons. We semiquantitatively assessed 18 hazard-pathway-receptor combination scenarios to provide an indication of the relative harm of these emissions so that they could be ranked, compared and considered in future research agenda. This assessment overwhelmingly indicated a high risk of harm to waste pickers, a large group of 11 million informal entrepreneurs who work closely with waste, delivering a circular economy but often without protective equipment or a structured, safe system of work. Though the risk to human health from open burning emissions is high, this remains a substantially under-researched topic.

Over the coming decades, a large additional mass of plastic waste will become available for recycling, as the world’s largest fast moving consumer goods companies step up efforts to reduce plastic pollution and facilitate a circular economy. Finding ways to recover value from this material is a substantial challenge that has prompted exploration of novel processes, such as ‘chemical recycling’, as well as more established ones, such as incineration with energy recovery. Many of these efforts will take place in the Global South, where plastic pollution and due to mismanagement of waste are most acute. New infrastructure will need to be developed, and it is important that the processes and systems chosen do not result in adverse effects on human health and the environment. This concern is particularly acute in countries that lack effective, well-resourced and independent systems for environmental regulation and the protection of occupational and public health. Here, we present a rapid review and critical semi-quantitative assessment of the potential risks posed by eight approaches to recovering value (resource recovery, circular economy) from post-consumer plastic packaging waste that has been collected and separated with the purported intention of recycling. The focus is on the Global South, where there are more chances that high risk processes could be run below standards of safe operation (though much of the evidence reviewed is inevitably based on research outcomes obtained in the Global North context). Our assessment indicates that under realistic, i.e. non-idealised operational conditions, mechanical reprocessing is the least impactful on the environment and is the most appropriate and effective method for implementation in the Global South. We find little difference in potential risks between so called ‘bottle-to-fibre’ and ‘bottle-to-bottle’ processes as they involve similar processing and both result in substantial avoided burdens from virgin production. The lack of real-world process data for the groups of processes known as ‘chemical recycling’ make them hard to assess. At present, there is no strong evidence that any of them have reached commercial stability when applied to processing post-consumer plastic packaging waste. Given this lack of maturity and potential for risk to human health and the environment (inferred through the handling of potentially hazardous substances under pressure and heat), it is hard to see how they will make a useful addition to the circular economy in the Global South in the near future. Incineration of waste plastics that have been collected for recycling is comparable with other forms of fossil fuel combustion used to generate energy and, despite the lack of process data, the same is likely for co-processing in cement kilns: notably, neither of these processes can be described as ‘recycling’ and, in general, are deemed as only the last resort in circular cascading systems. Though contemporary air pollution control technology is capable of comprehensively mitigating harmful emissions from combustion, there is a high risk that costly maintenance and management will not be carried out in the absence of strong regulation and enforcement. Inevitably, increasing circular economy activity will require expansion towards targeting flexible, multi-material and multi-layer products, for which mechanical recycling has well-established limitations; which has prompted exploration of alternative approaches. Yet, our comparative risk overview indicates major barriers to changing resource recovery mode from the already dominant mechanical recycling mode towards other nascent or energetic recovery approaches.

Across the Global South, electrical and electronic waste (e-waste) is recovered using rudimentary and often dangerous methods in informal and unregulated facilities. Although these activities provide a valuable contribution to the global circular economy, their uncontrolled nature results in a risk of potentially hazardous substance emission into the environment from where they may pose considerable risk to both occupational and public health. Here, we focus a systematic PRISMA review on two distinct groups of activities undertaken in e-waste management in low- and middle-income countries (LIMICs): (i) Physical deconstruction and reclamation, involving dismantling assemblies of items and materials to recover value; and, (ii) hydrometallurgical treatment, involving the dissolution and suspension of precious metals using solvents (cyanide) and acids (aqua regia). For comparison purposes, we consolidate information on (i) and (ii) according to the types of substances evidenced; and identify, critically assess and rank most prevalent hazard-pathway-receptor (H-P-R) risk combinations experienced by people working across the Global South. Despite the proliferation of publications, evidence to assess risk is comparatively limited. Still, we are confident to highlight the extremely hazardous nature of work undertaken, often by children, handling highly hazardous substances without protective equipment to reclaim gold and other precious metals using hydrometallurgical processes. Emissions of hazardous substances, particularly potentially toxic elements (PTEs) from physical dismantling also represent a serious risk to health. Numerous sources speculatively link concentrations in the environment (a significant risk to children who have a tendency to eat soil) to e-waste dismantling processed. However, many of the sources that identify elevated substance concentrations in environmental media face difficulties in unambiguously and convincingly linking emissions from specific activities to the environmental concentrations, i.e. establishing causality. This key limitation presents us with a challenge for designing and implementing interventions to target, control and replace such highly risky resource recovery methods. Yet, such insufficient information cannot be used as an excuse for inaction, especially as our generalized H-P-R inferences here provide for sufficient interlinkages.

The critical functionality provided by the informal e-waste recycling sector to the global circular economy is marred by the hazardous emissions from this practice when it is carried out under informal and unregulated conditions in the Global South. Here, we focus a systematic review (PRISMA) of evidence specifically on rudimentary thermal processing activities that are carried out to disassemble and recover metals bonded into the complex assemblies and composites of electrical and electronic products and items. We identified main combinations of hazard-pathway-receptor (H-P-R) associated with exposure to risk and ranked them to indicate severity and prioritise research needs and interventions. Two practices, open burning and heating/melting/roasting are highly efficient in comparison to mechanical disassembly of many components and materials, presenting a challenge for actors who want to discourage them. Yet, these activities result in significant and very serious potential health effects as evidenced by 48 references screened and critically assessed. Though a large body of research exists that report observations of potentially hazardous substances in environmental media and human bodies, there is an abject paucity of reliable or even indicative data to indicate the scale of the e-waste processing activity. Moreover, the concentrations measured in almost all studies suffer from a multiplicity of confounding activities, creating challenges regarding identifying the activity source. System level interventions should be designed to effectively mitigate the risk, whilst rapidly transitioning to low-risk processing with effective pollution abatement in place and safe systems of work.

Disposal on land has persisted as the most predominant form of waste disposal for millennia and despite advances in modern engineered landfills, large quantities (405 Mt y-1) of collected municipal solid waste (MSW) are still deposited and concentrated in open, uncontrolled dumpsites throughout low- and middle-income countries (LIMICs) worldwide – a key form of waste mismanagement. These pose major threats to the health and safety of surrounding populations and mainly waste pickers who across the Global South target dumpsites to salvage and recycle under minimal protection measures. Here, we conducted an adapted PRISMA systematic review, distilling over 3,000 papers into 40 core sources from 22 countries, to critically assess the evidence on the associated risks. We identified prevalent hazard-pathway-receptor combinations and subsequently scored, compared and ranked the relative risk of exposure to harm experienced by various actors in land disposal sites. Our assessment indicates high risk levels experienced through interaction with medical waste, emissions from waste combustion, and critically through the fatal risk of waste slope failure, claiming the lives of at least (on average) of 34 people per year since 1992. Despite the strong anecdotal signals on the generic nature of the health and safety challenges at hand, many of the sources lack critical information with which to determine and link causality of health effects with the existence, or even exposure to emissions or other hazards. Yet, our critical analysis clearly demonstrates an unacceptable potential for damage to human health and safety; alerting us on the need to close, and immediately manage risks at dumpsites, preventing harm to some of the worlds’ poorest inhabitants. Our aspiration is that quantification and mitigation of risks from dumpsites attracts substantial and scientifically robust efforts.

Plastic pollution is a pervasive and growing problem. To estimate the effectiveness of interventions to reduce plastic pollution, we modeled stocks and flows of municipal solid waste and four sources of microplastics through the global plastic system for five scenarios between 2016 and 2040. Implementing all feasible interventions reduced plastic pollution by 40% from 2016 rates and 78% relative to "business as usual" in 2040. Even with immediate and concerted action, 710 million metric tons of plastic waste cumulatively entered aquatic and terrestrial ecosystems. To avoid a massive build-up of plastic in the environment, coordinated global action is urgently needed to reduce plastic consumption; increase rates of reuse, waste collection, and recycling; expand safe disposal systems; and accelerate innovation in the plastic value chain.

Mechanical-biological and biological-mechanical treatment (MBT/BMT) are effective methods for reducing biogenic additions to landfill, producing fuel products and recovering recyclate from residual waste. However, large amounts of contamination in the non-biological outputs reduce their market value. The aim of this study was therefore to identify the principal drivers and barriers to the marketability of ferrous metals (MBTFe) and heavy inert rejects (MBTr) recovered from four UK MBT/BMT plants. The plants were either using biodrying or anaerobic digestion (AD-MBT) for biological processing. Samples were collected at the different recovery stage processes and characterised for elemental composition and particle size distribution. Results showed that processes at the two biodrying plants produced MBTFe with 10% less contamination by non-target materials than the two AD-MBT plants. Further to this, approximately 10% of the MBTFe fraction sampled at all four facilities comprised non-target material which had become entrapped in the folds of metal food containers. A possible cause is waste comminution in the cutting gap of the low-speed high-torque cutting mills. Upgrading MBTFe outputs could save the UK MBT/BMT industry up to 4.4 pound million per annum which equates to 230,000 pound per annum for an average sized facility (i.e. capacity 108,000 tpa). Glass content in the MBTr samples ranged between 44% and 62%, however all plants showed approximately 85% combined content of glass, bricks, stones and ceramics. The biodegradable content in the MBTr samples indicated that only minimal upgrade would be required to achieve the Landfill Directive requirements for inert waste. Again valorisation of MBTr could save the UK MBT/BMT industry up to 1.9 pound million pa which equates to 160,000 pound per annum for an average sized facility. (C) 2015 Elsevier Ltd. All rights reserved.