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Published online by Cambridge University Press: 16 January 2025
Ongoing policy negotiations, such as the negotiations for a future global plastics treaty, include calls for increased recycling of plastics. However, before recycling of plastics can be considered a safe practice, the flaws in today’s systems must be addressed. Plastics contain a vast range of chemicals, including monomers, polymers, processing agents, fillers, antioxidants, plasticizers, pigments, microbiocides and stabilizers. The amounts and types of chemicals in plastics products vary, and there are little requirements for transparency and reporting. Additionally, they are inherently contaminated with reaction by-products and other nonintentionally added substances (NIASs). As the chemical composition of plastics wastes is largely unknown, and many plastics chemicals are hazardous, they therefore hinder safe recycling since recyclers are not able to exclude materials that contain hazardous chemicals. To address this problem, we suggest the following policy strategies: 1) improved reporting, transparency and traceability of chemicals in plastics throughout their full life cycle; 2) chemical simplification and group-based approaches to regulating hazardous chemicals; 3) chemical monitoring, testing and quality control; 4) economic incentives that follow the waste hierarchy; and 5) support for a just transition to protect people, including waste pickers, impacted throughout the plastics life cycle.
Dear editors,
We are hereby submitting a perspectives article entitled “Addressing the hazardous chemicals problem in plastics recycling”. As the nations of the world struggle to grapple with the plastics pollution threats, recycling has been put forth as one of several solutions. However, hazardous chemicals in plastics, including both additives and non-intentionally added substances render these options less that optimal. In cases of mechanical recycling, hundreds of toxic contaminants have been identified in recycled pellets in the Global South, as we documented here: A dataset of organic pollutants identified and quantified in recycled polyethylene pellets - ScienceDirect. https://www.sciencedirect.com/science/article/pii/S2352340923008090
In this article we identify possible means of how to move towards safer and more circular uses of plastics by addressing hazardous chemicals that often hinder safe and sustainable use, reuse, recycling and repurposing. We discuss five key steps includes transparency, reporting and traceability; chemical simplification; monitoring, testing and quality controls; economic incentives and a just transition.
None of the authors have any conflicts of interest to declare.
Thank you for your time and attention,
Bethanie Carney Almroth, on behalf of all the authors
This perspective is of great environmental and practical significance, and the strategies presented are innovative, but there are some issues to consider, as follows.
1. What harmful substances can be released by plastics, and what type of plastic, at what concentration, will cause what harm to which biological or environmental media? Such specific content needs to be involved.
2. The chemicals in plastics can only be released under certain conditions, such as high temperature, and are not so easy to release and cause harm.
3. What are the external and internal conditions for plastics to release harmful chemicals?
4. Plastic in the recycling process, long time duration, many links, it is difficult to effectively recycle. Not only are large sizes difficult to recycle, small sizes are even more difficult to recycle. The most important issue is how to improve the efficiency of plastic recycling, which is the key to solving plastic pollution.
5. Plastics are distributed in various environmental media, with a wide distribution range, uneven concentration and different types, resulting in recycling difficulties. The challenge of plastic recycling is the low recycling rate, the lack of recycling equipment, and the lack of effective methods and strategies for recycling different plastics. Standard recycling methods and processes should be developed.
6. The author puts forward five strategies for controlling harmful chemicals contained in plastics, but does not put forward corresponding methodology. For example, what is the system of each strategy? What are the specific links and steps? What are the types of people involved? Is there a feedback mechanism?
7. Whether it is plastic recycling or plastic harmful chemical substances control, appropriate information platforms should be established based on environmental data to achieve dynamic monitoring of plastic recycling effects, so as to reduce plastic pollution.
While I think the focus and content of the manuscript is highly topical and relevant for publication in this journal, I am left with the feeling that the manuscript needed a couple more rounds of quality assurance and integration of different sections of text before submission. There is no clear flow or story to the introduction section of the manuscript, and it lacks a clear structure, jumping around topics without providing sufficient detail or information for the reader. The authors are trying to pack in a lot of information, some of which is not in keeping with the main title of the manuscript, while at other times insufficient detail is given about highly relevant aspects. This makes it difficult for all readers to fully understand the information being communicated, while a lot of inherent knowledge and understanding is assumed by the authors from the readers. Importantly, the introduction fails to coherently present the current state of the art and to highlight the primary challenges associated with the presence of (toxic) chemicals when recycling plastics. In fact, I found it hard to identify any clearly defined challenges specifically linking chemicals and plastic recycling. As such, the introduction does not set up the manuscript for the recommended policy actions. Each policy recommendation should address a clearly defined issue in the introduction, but this is not the case. Furthermore, several of the policy recommendations do not even mention the word recycling, so it is not clear how they will improve the situation with respect to toxic chemicals and recycling. Overall, the manuscript does not actually reflect the title in a strong way, and I am left unsure about what it is the authors really what to communicate. Perhaps the recycling aspect is not needed and maybe the manuscript should just focus on trying to reduce the number and levels of additives and NIAS in plastic consumer products.
I do think somewhere in here is a perspective topic and text that is suitable for publication, but the manuscript needs some major revisions to address the issues outlined above and the specific comments I have listed below. Importantly, the authors need to decide exactly what they are presenting a perspective on and then write that manuscript.
Specific Comments
Line 45-48 – I think imbued is a strange word to choose here and not one that is commonly known internationally. Suggest replacing it with something clearer. Also, I think the opening statement needs a little more balance. Some plastic products do indeed contain a wide range of chemicals and certainly across all plastic consumer products the range is vast. However, some products contain very few chemicals and at low concentrations. The first two sentences also need a clearer separation. The first appears mainly to focus on additives, so monomers and (to some extent polymers) are not correct to mention there, while stating they are intentionally added (and why) is lacking. This then distinguishes more clearly from the residual chemicals and NIAS in the subsequent sentence.
Line 50-52 – you should specifically mention the main flaws, one of which is clearly the presence of additive chemicals and NIAS. I think the abstract currently lacks sufficient justification for why it is necessary to recommend the policy strategies outlined.
Line 52-57 – I appreciate this is the abstract and space is limited, but this reads like an idealized wish list without any clear consideration for what is feasible practically. For example, point one sounds great but how would that work practically? At this point, I have not read the main manuscript, so such information is possibly presented there. If not, this is something that needs reflecting upon in the manuscript, including who would have responsibility for establishing such a global/regional/national system.
Keywords – These are additional search terms for the manuscript to be found by people conducting literature searches. Therefore, you should avoid repeating words and terms already used in the manuscript title.
General comment – paragraph 1 needs to lead into paragraph 2 more smoothly. I think it would be Ok to add to paragraph 1 some text about the other proposed mitigations actions that would contribute to reducing plastic pollution and increasing plastic circularity.
General comment – I understand why you have used the word toxic in the manuscript title, but I think this is only part of the picture when it comes to plastic recycling. The presence of non-toxic chemicals and other materials can also complicate or prevent materials from being recycled. Clearly, the presence of chemicals that are known to be toxic prevents certain consumer products from being recycled into different consumer products (e.g. food contact materials and children’s toys are obvious examples). However, the presence of certain chemicals means the resulting plastic recyclate might have other properties that make it difficult to make wide use of the resulting recyclate (e.g. colorants, antimicrobials etc). I think a more general review of the issue of plastic chemicals and the implications for recycling is more valuable.
Line 78 - ….plastic that is sent…..
Line 81 - landfill
Line 82 - ….plastic waste that is …….
Line 82 – ….likely to be significantly…..
Line 84 - those scenarios call for true
Line 83-87 – This is a long sentence, and it is not clear why you have both 60% recycling rate and 15-68% recycling rate mentioned int e same sentence. Needs reformulating and clarifying.
Line 89 – Identified
Line 89-93 – This short paragraph seems to be ‘floating’ in between the other paragraphs and does not sit well here. Can it be located somewhere else in the manuscript, perhaps as part of another paragraph?
Line 95-101 – You need to include more info in this paragraph about the other technologies. What are they and why do they not work at scale? How do some of them lead to high emissions of toxic chemicals (give concrete examples of the toxic chemicals and numbers regarding the emissions). I think also you need to define what mechanical recycling is and describe more clearly what you mean about decreasing quality and increasing chemical contamination. Not all readers will have this knowledge already.
Line 103-110 – Similarly in this paragraph there is a lot of terminology that certain readers are likely to find confusing without clear descriptions and examples. For example, why exactly is material complexity and polymer degradation a drawback for plastic recycling? Perhaps most importantly, chemical contamination should be expanded a little here owing to this being a central theme to the manuscript. Similarly, why do you get increasing toxicity during the recycling process? Is this the case for all plastics recycling methods? I suspect it is the opposite for chemical recycling (despite its many other drawbacks and limitations).
Line 112-114 – Clunky sentence with the use of the word hierarchy twice. This could be simplified to something like: Regulatory documents, such as the European Waste Framework
113 Directive 2008/98/EC (EU, 2018), often place recycling in a low position on the plastic waste hierarchy, after prevention and reuse.
Line 114: It is grammatically incorrect to start a sentence with ‘However, although…..’. Just use the word ‘While’.
Line 112-124 – This paragraph seems to contradict itself. It starts out saying recycling is low on the waste hierarchy, then highlights bans on single use plastic products, then states that recycling is a common legislative initiative, then it suddenly brings in chemicals. Yet you still have not defined the main issues with the presence of chemicals in plastic and their impact on recycling. Again, I am left feeling that the flow and story that you are trying to communicate is getting lost due to a lack of structure to the whole document.
Line 126 – What is the limited efficacy? You have not described this yet. You have also not presented/described any other recycling technology than mechanical recycling.
Line 127 – While exposure to plastic chemicals during the use phase is very important, it is off topic for this manuscript. Keep the focus on recycling. You also need to describe how waste pickers are part of the recycling process if you want to use them as part of your perspective.
Line 129-136 – This is very important information, and I think it should be presented much earlier in the manuscript given that the focus is about toxic plastic chemicals. Again, it does not flow well to have this information here.
Line 135-136 – Important point and as you allude to in this sentence some materials and products are required to report the presence or absence of certain chemicals in the material formulation. You should expand a little on this here and give examples of such cases as this is one of your key recommendations. It would seem both balanced and appropriate to cite clear examples of such practices/requirements and discuss how they can be expanded to cover more products and scenarios.
Line 138-140 – Again, this is a little unbalanced. Recycling streams are like models: crap in, crap out. Recycling streams that handle specific feedstock materials that contain very few plastic chemicals can yield recyclates with a high value and low contamination. Of course what you state is also true when you have uncontrolled feedstock composition. Importantly, mixing plastic waste with high chemical content with plastic waste items with low chemical contents contaminates all of the resulting recyclate.
Line 141 – BDEs and PFAS are examples of POPs. Either use the term POPs or (preferably) just use examples of known plastic chemical groups like BDEs and PFAS.
Line 142 – Interesting example. Toys are one of the more regulated consumer products (along with food contact materials). So, you should explain here how we can end up in a situation where toys are being made from poor quality recyclate materials. Clearly something is wrong with the system if this is happening.
Line 143-149 – This should be combined with the text in lines 129-136 and moved much further towards the start of the manuscript. Define your problem there.
Line 151 – I read the opening statement to this paragraph, and I disagree. You have not actually outlined the challenges with plastics recycling. So much is missing, and a proportion of the preceding text is not really relevant (especially compared to what is not presented).
Line 164 – 204 – The current state of the art relating to this policy recommendation is missing in the introduction. Almost none of this section relates to recycling, but rather uses a lot of text explaining what the problem is. Here you should have already defined the problem in the introduction and instead be discussing how the implementation of your policy recommendation will positively impact recycling. Overall, this section feels long and not very well structured.
Line 206-228 – Here you are repeating information already presented in the introduction about the number of plastic chemicals and the toxicity. You should start this section from line 211 (While there are….). The rest of this section is well written and succinctly presented. That said, I don’t think the example you give is an example of what you are saying in line 211-212. If I understand correctly, a more accurate example would be that many thousands of plastic chemicals are or have been used as antioxidants and why would we need so many? This is a valid point, but important to remember that the efficacy of the different chemicals will vary. I do not disagree with your argument that it is likely some of the variety reflects competitiveness in the market and that this complicates risk assessment. However, I think it is important to give some space to the development of new, lower toxicity chemicals for a specific function or those that require less chemical to be added to achieve the same effect. Could you perhaps argue that any new chemical coming onto the market to serve a particular function for which chemicals already exist should meet the requirements of proven lower toxicity and lower environmental persistence? Is it not important to make sure we leave the door open for improvement from the current status quo? Importantly, this section does not mention recycling once…….so how does your policy recommendation relate to recycling in appositive way?
Line 230-243 – The concept here is sound in principle, but what the authors are proposing will require some quite significant analytical technology development to make the proposed analyses sufficiently fast to assess all individual items of plastic waste in a waste stream. Similarly, implementation will be costly, the processing will be quite slow, and the authors do not discuss what will happen to plastic waste items that ‘fail’ the assessment. I also strongly suspect that such a policy will significantly drive up the cost of the resulting recyclates, especially compared to production of virgin materials from fossil fuel feedstocks. It could be important to state in this section that the feasibility of implementing this policy is dependent upon the implementation of other policies ensuring consumer products contain a minimum level of recycled plastic. While the suggestion to develop and implement new safety assessments for mixtures is a nice concept, is this really feasible considering the almost infinite number of chemical mixtures present in a recycling stream and that the mixtures in a stream will be dynamic? How do you quickly identify a specific chemical mixture and assess its toxicity? The authors should at least propose some ideas for how this might be achieved. Again, this section does not mention link strongly enough to the title and recycling.
Line 245-274 – This is a topic that I do not really have much competence in, but I think you need to link in the chemical aspects a little more strongly. The section ventures into general plastic pollution and who should pay for that. Instead, you should keep the focus on chemicals and recycling. For example, how can taxes, caps, fees, bans etc be applied to chemicals and NIAS so that recycling can be improved. Similarly, how can incentives be provided to facilitate change upstream so that plastic consumer products entering the market are more suited for recycling and can yield higher value recyclates. I do think that you raise a good point about driving and incentivizing innovation, but some of your other policy recommendations above go against that concept (at least in part). I am also confused about the final statement in this section. I fully agree about the reduction in production and consumption, but this manuscript is about toxic chemicals and plastic recycling. Here you are arguing for making recycling a lower priority. This could be entirely correct when looking at the bigger picture, but when the title of the paper is about recycling and toxic chemicals, it seems like a strange policy recommendation in this context.
Line 276-297 – Without a stronger description of the role of waste pickers in plastic recycling streams in the introduction section, this policy recommendation seems to come from nowhere. Again, I am not doubting the proposed policy itself and I fully agree that there should be better protections for waste pickers. So again, this breaks up the story and flow of the manuscript. Some of the text present in this section could be moved to the introduction to outline the problem/challenge so that a clearly defined policy recommendation can be presented in this section.
Line 299-313 – Again, I still do not really see what message you are trying to promote with this perspective. Are you for recycling and see it at least as part of the solution to plastic consumption and pollution, or are you arguing that recycling is simply too challenging to develop and implement and therefore attentions should be focused on other mitigation measures? Throughout the manuscript I see evidence of both perspectives, but not a clear message one way or the other. The conclusion does start to link chemicals and recycling a little more clearly compared to the rest of the manuscript, but is essentially a repetition of everything stated already and is not really a generalized conclusion. Here I would like to see some concluding comments about how the authors would see a scenario where all or some of their proposed polices are implemented. What about stating that the time is now for action, especially given that we are in the late stages of the global plastic treaty process. How is that currently reflecting the polices proposed here?
Thank you for submitting your perspective manuscript to our journal. We believe this submission is a timely and important contribution to the field. After carefully considering the reviewers‘ feedback, we would like to request a revision of your manuscript before we can accept it for publication. The reviewers have suggested to improve the flow and clarity of your work, as well as to include additional details and supporting information. We encourage you to carefully address the reviewers’ comments and submit a revised version of your manuscript. We look forward to receiving your revised work on or before 28 October 2024.
No accompanying comment.
Dear editors,
Thank you for the opportunity to revise our manuscript. The reviewers provided helpful critical feedback which we have incorporated into the revised submission. We are also grateful for the kind extension of the deadline and expanded word count.
Best, Bethanie, on behalf of all authors
The response to reviewers document submitted to the journal appears incomplete. Not all of the comments I had previously provided have received responses and some of them appear to be allocated to co-authors that have not yetr provided a response. Either the incorrect document was submitted by the corresponding author or this process has been rushed. SO I am returning this to the authors so that they can complete the first review round fully before I make an assessment.
For comment 2, the conditions under which microplastics release toxic chemicals should be given.
For comment 6, if these five strategies are taken as the innovation point of this study, then the authors need to provide corresponding methodologies for each strategy as much as possible.
As agreed by both reviewers, the revised version of the manuscript has shown significant improvements in quality. However, there are still a few minor issues that need to be addressed before publication. Therefore, I recommend a minor revision prior to final acceptance.
No accompanying comment.
Dear all,
I have resubmitted the files as indicated and included the (correct) response to reviewers file (listed as a main document, I wasn’t sure how to upload it).
Warm regards, Bethanie
I have no further questions.
The authors have made a really impressive attempt to take onboard a lot of the comments and suggestions provided in my review of the original manuscript submisison. Importantly, I feel they have now more clearly defined the problem in the early part of the manuscript and have developed a much better flow to the overall document. The revisions also help to keep the content more clearly focused on the manuscript title, which is importnat. I fully understand they had constraints regarding the length of the document and agree with where they have chosen to to make more extensive edits/additions and where there has been a need to keep the length appropriate for the journal. The manuscript is no suitable for publication in my opinion.
No accompanying comment.
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Impact statement
Plastics pollution is recognized as a major threat to the environment, with impacts on human health and well-being. While plastics recycling is often presented as the solution, this narrative is currently challenged by major issues, one of which is the presence of toxic chemicals in plastics. This includes substances intentionally added at various stages of the life cycle of a plastics item as well as nonintentionally added substances (NIASs). If we are to include recycling in the battery of solutions needed to address the plastics pollution crisis, several steps would first be needed in order to improve safety and sustainability of these practices. Global, regional and national policy changes are needed to support improvements throughout the plastics life cycle and will need to address chemicals at each of these stages. This article identifies five policy strategies to support this transition to safer, more sustainable plastics: 1) improved reporting, transparency and traceability of chemicals in plastics throughout their full life cycle; 2) chemical simplification and group-based approaches to regulating hazardous chemicals; 3) chemical monitoring, testing and quality control; 4) economic incentives that follow the waste hierarchy; and 5) support for a just transition to protect people, including waste pickers, impacted throughout the plastics life cycle. Adoption and implementation of these strategies will require ambitious action from various societal actors before recycling can contribute in a meaningful way to abating plastic pollution.
Introduction
Plastics production has already reached levels that are threatening the stability of Earth system functions, and current production levels exceed the safe operating space for humanity (Persson et al., Reference Persson, Carney Almroth, Collins, Cornell, de Wit, Diamond, Fantke, Hassellöv, MacLeod, Ryberg, Søgaard Jørgensen, Villarrubia-Gómez, Wang and Hauschild2022). The consequences of the plastics crisis in the environment and on human health are acknowledged as the nations of the world negotiate an international legally binding instrument (ILBI) building on the UNEA 5/14 resolution to govern plastics globally (UNEA, 2022).
Assuming a business-as-usual scenario, estimates suggests that the production of plastics may triple by 2060 (OECD, 2023a). This projected increase would have direct consequences for people and the planet and scientific evidence and modeling reports all indicate that primary plastics production reduction will be essential (Baztan et al., Reference Baztan, Jorgensen, Carney Almroth, Bergmann, Farrelly, Muncke, Syberg, Thompson, Boucher, Olsen, Álava, Aragaw, Bailly, Jain, Bartolotta, Castillo Aragi, Collins, Cordier, De-Falco, Deeney, Fernandez, Gall, Gammage, Ghiglione, Gündoğdu, Hansen, Issifu, Knoblauch, Wang, Kvale, Monsaingeon, Sangcheol, Morales-Caselles, Reynaud, Rodrígues-Seijo, Stoett, Varea, Velis, Villarrubia-Gómez and Wagner2024; OECD, 2024). Controls on production volumes would also be in line with the waste hierarchy as it would focus on the prevention and reduction of future wastes (European Waste Framework Directive 2008/98/EC (EU, 2018)).
However, to date, most policy focuses more downstream regulations. A recent inventory of the global plastics policy landscape identified 291 subnational, national and regional regulations addressing plastics (Diana et al., Reference Diana, Vegh, Karasik, Bering, Llano Caldas, Pickle, Rittschof, Lau and Virdin2022). Several of these policies target recycling, for example, via regulating labeling practices or mandating take back systems for specific products. In the European Union (EU), for example, several legislative initiatives of the EU support a circular economy and aim to increase recycling, but the EU currently has no regulations that call for reduction in primary plastics production at the top of the waste hierarchy and start of the plastics life cycle. Similarly, the EU Packaging and Waste Directive (94/62/EC; European Parliament, 2018 ; COM/2023/304; EC, 2023) calls for increased masses of recycled materials. The European Strategy for Plastics in a Circular Economy (COM/2018/028; European Commission, 2018) addresses design standards and production of plastics and products, highlighting reuse, repair and recycling and the need for more sustainable materials.
Data show that plastics recycling has repeatedly failed to operate in a safe and circular manner (Allen et al., Reference Allen, Spoelman, Linsley and Johl2024; Carroll, Reference Carroll2023). Estimates indicate that only 9% of plastics have been recycled (Geyer et el. 2017). This leaves a massive gap to the scenarios that highlight recycling as a means to curb plastics pollution, since those scenarios call for true recycling rates of 60% by 2060 according to the OECD (2023a). Another study shows that a seven-fold increase compared to 2019 baselines, with an increase to 95% collection rates and 15–68% recycling rates, would be required (Shiran et al., Reference Shiran, de la Fuente, Ragot, von Boetticher, Fuchs, Mauth, Lingeswaran, Hahn and Stein2023).
There are several challenges with plastics recycling. These include material complexity (e.g., materials containing multiple layers of different polymers and chemicals) and polymer degradation (e.g., degradation of polymer backbones; Ragaert et al., Reference Ragaert, Delva and Van Geem2017), lack of economic incentives (Larrain et al., Reference Larrain, Van Passel, Thomassen, Van Gorp, Nhu, Huysveld, Van Geem, De Meester and Billen2021), chemical contamination (Carmona et al., Reference Carmona, Rojo-Nieto, Rummel, Krauss, Syberg, Ramos, Brosche, Backhaus and Almroth2023), spread of microplastics (Stapleton et al., Reference Stapleton, Ansari, Ahmed and Hai2023) and energy inefficiency (Vogt et al., Reference Vogt, Stokes and Kumar2021). Scientists have therefore warned that policy initiatives focused on recycling technologies risk creating infrastructure “lock-in” and increased waste production (Syberg, Reference Syberg2022).
Mechanical recycling, the most commonly applied technology, is plagued by problems associated with decreasing material quality and increasing chemical contamination of the resulting materials (Gerassimidou et al., Reference Gerassimidou, Lanska, Hahladakis, Lovat, Vanzetto, Geueke, Groh, Muncke, Maffini, Martin and Iacovidou2022; Horodytska et al., Reference Horodytska, Cabanes and Fullana2020; Leslie et al., Reference Leslie, Leonards, Brandsma, de Boer and Jonkers2016). The technology entails collection of plastics wastes, sorting and separation into desired fractions (e.g., polyethylene, polypropylene or mixed plastics fraction), cleaning, grinding/chipping or fragmentation, heating and melting and then extrusion. This process normally involves mixing of different products and therefore, different cocktails of chemicals (Hahladakis et al., Reference Hahladakis, Velis, Weber, Iacovidou and Purnell2018). This mixing has, for example, been demonstrated in food-grade plastics, including polyethylene terephthalate (PET). Even though PET is often collected in separated waste streams, recycled PET can still contain >800 different food contact chemicals (Geueke et al., Reference Geueke, Phelps, Parkinson and Muncke2023). Other technologies than mechanical recycling exist, including so-called chemical recycling technologies, but currently do not work at scale, in part due to risks associated with chemical impurities in feedstocks, and these technologies have also been shown to cause high emissions of toxic chemicals (Al-Salem et al., Reference Al-Salem, Antelava, Constantinou, Manos and Dutta2017; Bell et al., Reference Bell, Gitlitz, Congdon and Rollinson2023; Quicker, Reference Quicker2024; Rollinson and Oladejo, Reference Rollinson and Oladejo2019; Uekert et al., Reference Uekert, Singh, DesVeaux, Ghosh, Bhatt, Yadav, Afzal, Walzberg, Knauer, Nicholson, Beckham and Carpenter2023).
Additionally, the regulatory initiatives that focus on increasing recycling rarely take chemicals in the plastics feed stock of recycled materials into account and may therefore risk causing further harm to human health and the environment. More than 16,000 chemicals are used in plastics production and products, and more than 4,200 of these were recently identified as having hazardous properties (Wagner et al., Reference Wagner, Monclús, Arp, Groh, Løseth, Muncke, Wang and Wolf2024).These include, for example, phthalates, bisphenols, brominated diphenyl ether (BDEs) and per- and polyfluoroalkyl substances (PFAS). The chemicals used in plastics products pose significant risks for human health (Trasande et al., Reference Trasande, Krithivasan, Park, Obsekov and Belliveau2024), and many of the chemicals have shown to leach during realistic use scenarios (Zimmermann et al., Reference Zimmermann, Bartosova, Braun, Oehlmann, Völker and Wagner2021). Still, less than 1% of plastic-associated chemicals are regulated internationally throughout their full life cycle (BRS, 2023).This regulatory gap is a significant challenge in managing chemicals in recycled plastics, especially since it is coupled with almost nonexistent transparency and traceability of chemicals.
The consequence is that it is rarely possible for downstream users, producers or recyclers to know anything about the chemicals used in the plastics that they encounter. In addition to chemicals that were in the original primary plastics materials, recent work shows that recycled plastics materials contain numerous other contaminants that likely sorbed to the materials during use, handling, processing or while the materials were out in the environment (if the plastics were collected from dump sites or the open environment; Carmona et al., Reference Carmona, Rojo-Nieto, Rummel, Krauss, Syberg, Ramos, Brosche, Backhaus and Almroth2023). These chemicals include various pesticides, pharmaceuticals and biocides, which renders the recycled plastics unfit for use in many products, especially in children’s toys and food contact materials. The complexities of the plastics life cycle, value chains, international trade and waste flows are plagued by a lack of transparency and reporting on the production of plastics and the use and presence of chemicals, resulting in complex materials containing complex mixtures of chemicals.
The right to knowledge and information has recently been highlighted as a human right to science in the context of toxic substances (Orellana and Wastes, Reference Orellana2021) and indicates that chemicals in plastics should be transparently reported, and trackable and traceable throughout the value chain. The importance of access to information on toxic chemicals is also highlighted under Article 9 of the Stockholm Convention on Persistent Organic Pollutants (POPs) which states that “information on health and safety of humans and the environment shall not be regarded as confidential” (UNEP, 2004). Existing EU regulations support this principle – in theory. For instance, Article 5 of the REACH legislation (EC, 2006) introduces the “no data, no market” principle – “substances on their own, in preparations or in articles shall not be manufactured in the community or placed on the market unless they have been registered in accordance with the relevant provisions.” However, a substantial amount of the REACH data are confidential and are therefore of only limited use for communicating chemical hazards and risk along the supply chain.
Therefore, beyond the limited efficacy of different recycling methodologies and practices, there are several concerns about consumers exposed to chemicals during the use of products and materials made from recycled plastics (Gerassimidou et al., Reference Gerassimidou, Lanska, Hahladakis, Lovat, Vanzetto, Geueke, Groh, Muncke, Maffini, Martin and Iacovidou2022; Geueke et al., Reference Geueke, Phelps, Parkinson and Muncke2023; Hawkins et al., Reference Hawkins, Potter and Race2015; Yang et al., Reference Yang, Ma, Thompson and Flower2018) and about the safety of waste pickers and other people working with plastics wastes and recycling. For workers, it has, for example, been shown that heavy metals were present in recycled plastics at or above the US EPA levels and that there was a clear exposure-risk association between heavy metals and worker health (Huang et al., Reference Huang, Xie, Li and Zhang2021). Waste pickers in Africa are exposed to hazardous materials including toxic chemicals (Binion and Gutberlet, Reference Binion and Gutberlet2012; Uhunamure et al., Reference Uhunamure, Edokpayi and Shale2021). Studies on materials and products made from recycled plastics have also shown that chemicals contaminate recycled materials, including food packaging and toys made from recycled plastics (Brosché et al., Reference Brosché, Strakova, Bell and Karlsson2021; Chibwe et al., Reference Chibwe, De Silva, Spencer, Teixera, Williamson, Wang and Muir2023; Gerassimidou et al., Reference Gerassimidou, Lanska, Hahladakis, Lovat, Vanzetto, Geueke, Groh, Muncke, Maffini, Martin and Iacovidou2022; Horodytska et al., Reference Horodytska, Cabanes and Fullana2020). The chemicals include POPs such as brominated flame retardants, benzotriazole UV stabilizers and PFAS and endocrine disrupting chemicals such as bisphenols. Aside from the safety concerns associated with toxic chemicals, some of the chemicals also pose physical challenges for the recycling process, for example, carbon black which complicates identification of plastic type (Rozenstein et al., Reference Rozenstein, Puckrin and Adamowski2017).
Given the challenges with plastic chemicals and recycling of plastics as it is currently conducted, it would be ill-advised to rely on recycling as a main solution to the plastics crisis. Instead, work needs to focus upstream and center on managing and decreasing production volumes, since reduction is at the center of the waste hierarchy and since the current production volumes are unmanageable, while simultaneously phasing out and eliminating toxic chemicals to allow for safer circular approaches. To move toward a circular economy and a safer, more sustainable, use of plastics, we must address toxic chemicals. We have identified several important areas for policy development: 1) improved reporting, transparency and traceability of chemicals in plastics throughout their full life cycle; 2) chemical simplification and group-based approaches to regulating hazardous chemicals; 3) chemical monitoring, testing and quality control; 4) economic incentives that follow the waste hierarchy; and 5) support for a just transition to protect people, including waste pickers, impacted throughout the plastics life cycle. These are developed below.
Improved reporting, transparency and traceability of chemicals in plastics throughout their full life cycle
A compulsory, globally standardized mandate that ensures transparent reporting of information regarding the chemicals used in plastics, including monomers, polymers, additives and nonintentionally added substances (NIASs) is an essential cornerstone for facilitating a safer and more sustainable reuse, refill, repurpose and recycling market. The ongoing negotiations for a future plastics treaty presents an opportunity to improve transparency and traceability through the implementation of suitable control measures.
To facilitate informed decisions regarding restrictions, bans and elimination of hazardous chemicals, it is important that a globally standardized public database with curated data on production and use of processing aids, additives and monomers and polymers within materials, products and their chemical constituents becomes publicly available. This inventory should encompass details about production and trade quantities of polymers and materials, along with the complete array of chemicals present in plastics products and materials throughout their complex value chains.
Such an approach will foster transparency and accountability and put the economic burden of generating information on producers and manufacturers. A system that systematically collects relevant information and makes them publicly available would be significantly more efficient than the current piecemeal production and publication of the necessary information by only a few companies, academic research projects and public authorities. The introduction of a universally standardized central data management system would not only cut down costs for individual nations but also ensure equal access to data globally. It would also simplify reuse, refill, repurposing and recycling of plastics as data availability will support increased safety of use of materials or products in these more downstream applications.
It is important to note that recycling practices may need to be sectorial to ensure that chemicals used for a specific purpose in one sector, for example, flame retardants in electronics, do not contaminate plastic streams in another sector, for example, toys or food packaging. Transparency and traceability, through labeling and other means of identification of chemicals used in the various plastics materials, would facilitate such sectorial recycling efforts.
Chemical simplification and group-based approaches to regulating hazardous chemicals
While there are thousands of chemicals used in plastics, the number of functions fulfilled by those substances is actually quite low. For example, a recent publication investigating the production and use of phenolic antioxidants in plastics (Orndoff et al., Reference Orndoff, Lone, Beymer-Farris, Wood, Sadler, Ternes, Hester, Miller and Seay2023) found that the large number of different chemicals in this group comprise only a limited number of functional groups. The slight variations in the side chains of the molecules are likely simply a means for different companies to compete for a given market segment. However, the resulting chemical complexity hinders testing, monitoring and tracing of chemicals in complex value chains. Thus, it is important to move toward more limited numbers of chemical molecules with simple structures, as Kümmerer et al. (Reference Kümmerer, Clark and Zuin2020) and Fenner and Scheringer (Reference Fenner and Scheringer2021) suggested in a chemical simplification concept.
To facilitate this transition, it is important that chemicals associated with plastics are not allowed to be used without publicly available data on their toxicity (see above, on data transparency). It is also important that the most hazardous chemicals are phased out and eliminated globally to ensure that future waste streams contain safer materials. Any new chemical coming onto the market to serve a particular function for which chemicals already exist should meet the requirements of proven lower toxicity and lower environmental persistence. Given the large number of chemicals in circulation and the current data gaps, the most suitable approach would be to use a group-based approach, which is an approach that has been used for several listings under the Stockholm convention (UNEP, 2024). These control measures could be developed under the Plastics Treaty. It is important to note that the regulation of chemicals under the treaty need to cover the full life cycle, so that it also includes production and recycling processes.
If implemented, this would result in a smaller number of chemicals, more readily traceable throughout the plastics life cycle, which would result in better control of chemicals in waste streams and ultimately in plastics recyclate.
Chemical monitoring, testing and quality control
Chemical simplification, together with mandatory reporting and transparency, will address chemical monomers, polymers and additives in plastics and products, but these policies will not prevent contamination of plastics during their use and waste phases. Even if waste streams are separated and new collection systems are supported, contamination of plastics with NIASs will occur, in particular during the use phase of the various plastic items, see the discussion of Carmona et al. (Reference Carmona, Rojo-Nieto, Rummel, Krauss, Syberg, Ramos, Brosche, Backhaus and Almroth2023) above. Therefore, analytical chemistry technologies will need to be developed in order to measure and assure that recycled materials are safe for their intended uses. New testing paradigms for improved safety need to be developed and implemented to address not only single chemicals but also the chemical mixtures present in the recycled materials. These methodologies for toxicity testing could include endpoints associated with noncommunicable diseases associated with exposure to plastics chemicals, as described in recent publication by Muncke et al. (Reference Muncke, Andersson, Backhaus, Belcher, Boucher, Carney Almroth, Collins, Geueke, Groh, Heindel, von Hippel, Legler, Maffini, Martin, Peterson Myers, Nadal, Nerin, Soto, Trasande, Vandenberg, Wagner, Zimmermann, Thomas Zoeller and Scheringer2023). This includes several cancers, metabolic and cardiovascular diseases, and reproductive and immunological disorders.
Development of new technologies can be costly and will require investments and capacity building, both of which should be supported by the future Global Plastics Treaty. However, it is important to acknowledge the high societal and health care costs associated with plastics chemicals (Trasande et al., Reference Trasande, Krithivasan, Park, Obsekov and Belliveau2024) and the potential benefits of implementing such requirements. Moreover, by increasing the transparency of chemicals throughout the full life cycle of plastics, the overall needs and costs associated with testing are expected to decrease and more targeted screenings can be done for NIASs.
Economic incentives that follow the waste hierarchy
While acknowledging the costs of a shift from the current production and consumption patterns of plastics to a safer and more sustainable system we must also recognize the costs of inaction. A recent publication estimates the global costs of action toward zero plastic pollution versus inaction, finding that costs of inaction might be significantly higher, though there are large uncertainties in the calculations (Cordier et al., Reference Cordier, Uehara, Jorgensen and Baztan2024). Beyond the hazardous properties of many plastic-associated chemicals (Groh et al., Reference Groh, vom Berg, Schirmer and Tlili2022; Landrigan et al., Reference Landrigan, Raps, Cropper, Bald, Brunner, Canonizado, Charles, Chiles, Donohue, Enck, Fenichel, Fleming, Ferrier-Pages, Fordham, Gozt, Griffin, Hahn, Haryanto, Hixson, Ianelli, James, Kumar, Laborde, Law, Martin, Mu, Mulders, Mustapha, Niu, Pahl, Park, Pedrotti, Pitt, Ruchirawat, Seewoo, Spring, Stegeman, Suk, Symeonides, Takada, Thompson, Vicini, Wang, Whitman, Wirth, Wolff, Yousuf and Dunlop2023; Sigmund et al., Reference Sigmund, Ågerstrand, Antonelli, Backhaus, Brodin, Diamond, Erdelen, Evers, Hofmann, Hueffer, Lai, Torres, Mueller, Perrigo, Rillig, Schaeffer, Scheringer, Schirmer, Tlili, Soehl, Triebskorn, Vlahos, vom Berg, Wang and Groh2023), and potential loss of ecosystem services and costs resulting from plastics pollution (Beaumont et al., Reference Beaumont, Aanesen, Austen, Börger, Clark, Cole, Hooper, Lindeque, Pascoe and Wyles2019; Cordier et al., Reference Cordier, Uehara, Jorgensen and Baztan2024), there are significant costs in human populations associated with adverse health outcomes and health care (Trasande et al., Reference Trasande, Krithivasan, Park, Obsekov and Belliveau2024).
There is a need for policy instruments that ensures that producers and other economic actors pay for the externalities caused by hazardous chemicals in plastics. Taxes, caps, fees, bans and extended producer responsibility regulations are examples of such instruments which, depending on the context, can be implemented to internalize the full costs of hazardous chemicals during the production, use and disposal of plastics (OECD, 2023b). When economic actors need to pay the full cost of pollution, this creates incentives for innovation and substitution to safer alternatives. However, improved transparency and access to information about hazardous chemicals in plastic products is a crucial prerequisite for the effective use of such instruments. The revised European eco-design regulation, mandating the use of digital product passports to track substances of concern throughout the life cycle of products and make this information available to consumers and waste management operators, is a positive development in this regard (European Parliament and Council of the European Union, 2024). The significant health, environmental and economic risks associated with plastic pollution are increasingly impacting insurance and investment portfolios. These risks – ranging from human health hazards to potential liability claims related to marine litter and plastic pollution – are expected to become increasingly relevant for insurers in the coming years (UNEPFI, 2019). Such policy changes will also affect private sector investments, which currently are primarily focused on downstream actions to reduce plastic pollution. Recovery and recycling receive 88% of investment capital, while only 4% is invested in reuse systems (Mah, Reference Mah2021; TCI, 2023). Public and private investments in reduce, reuse and redesign are essential to meet goals to prevent plastics pollution. Redesign could include redesigning for safer recycling, including phasing out hazardous chemicals and applying the concept of essential use (Cousins et al., Reference Cousins, Goldenman, Herzke, Lohmann, Miller, Ng, Patton, Scheringer, Trier, Vierke, Wang and DeWitt2019) to both chemicals and plastics, all of which would drive innovation and the potential for new marketable products. It is essential that funding is also invested in upstream mechanisms including product design at the polymer and chemical stage in order to facilitate circular initiatives in plastics production and consumption, including shifts to refill/reuse systems, and as a lower priority, recycling.
Support a just transition to support people throughout the plastics life cycle
A just transition should address environmental injustices throughout the plastics life cycle, including those caused by toxic chemicals, and should protect communities and Indigenous Peoples. Designing plastics that are safer, more durable and more sustainable would protect communities, including fence line and frontline communities, consumers and workers, including those in the informal waste sector.
Waste pickers account for 50–80% of recovery and recycling in the Global South, helping to uphold these systems while experiencing socioeconomic precarity alongside unhealthy working conditions and chemicals exposures (Dey, Reference Dey2020; Gidwani, Reference Gidwani2015; Gutberlet, Reference Gutberlet2023). While informal waste pickers are widespread in developing countries, they also exist in developed countries, and these individuals also suffer from social stigma, poverty and health and safety risks (Morais et al., Reference Morais, Corder, Golev, Lawson and Ali2022). Any circular transition must ensure safe working conditions and secure working contracts with rights and sufficient financial benefits to ensure sustainable livelihoods. Moreover, informal actors in waste-picking and recycling hold valuable practical and technical insights on the actual material complexities of plastic wastes (Dey, Reference Dey2022; Gill, Reference Gill2009). Many of these workers have previously recycled other materials, like glass, metals, paper, which can substitute plastics in many applications. As such, the practical expertise of material recovery agents and mechanical recyclers needs to be taken seriously, with provisions to include and reward their labor, enterprise, tacit knowledge and skills. By integrating the knowledge and skills of informal waste pickers alongside formal recycling systems, we can promote a more inclusive and sustainable approach to plastics management.
Conclusion
Plastics recycling is challenged by major issues, leading us to conclude that we cannot rely on recycling to end the plastics pollution crisis as things are done today. One of the major underlying reasons is the presence of toxic chemicals in plastics, either intentionally added or sorbed at various stages of the life cycle of a plastic item. The global Plastics Treaty negotiations should address these challenges with new policy obligations to support a future where recycling is safer and more sustainable. Improvements both upstream, midstream and downstream in the plastics life cycle are needed. A substantial reduction in the multitude of chemicals used in plastics manufacturing should be mandated in upstream interventions, in line with a “chemical simplification.” This effort should prioritize bans of chemicals known to be detrimental to both human health and the environment. Transparent reporting, tracking and monitoring of chemicals throughout the full life cycle will allow for safer and more sustainable systems, supporting reuse, repurposing and sectorial recycling. Downstream improvements in waste management infrastructure and strict regulations governing the discretionary use of recycled plastics must be enforced. The methodologies for implementing the strategies described here would be several and would require that changes in policy and best practices be adopted and implemented by several actors throughout the plastics value chain, including law makers, plastics producers, manufacturers, agencies responsible for monitoring and compliance, among others. Further development via multistakeholder dialogues and agreements together with education and support for implementation would support these efforts. Implementing these changes, together with appropriate economic investments would increase the safety of plastics, contributing to the transformation urgently needed.
Open peer review
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Author contribution
BCA and TK conceptualized the article; all authors contributed to the writing, reviewing and editing of the article. All authors have read and agreed to the published version of the manuscript.
Financial support
The authors thank the Swedish Research Council for Sustainable Development FORMAS (grant number 2021-00913) for financial support.
Competing interest
BCA is a non-remunerated steering committee member of the Scientists Coalition for an Effective Plastics Treaty. TB is an unpaid member of the board of the Food Packaging Foundation, a Swiss foundation working on the issue of plastics food packaging and plastics in general. The rest of the authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.