Mapping the chemical complexity of plastics

Abstract

Plastic pollution is a pervasive and growing global problem^1–4. Chemicals in plastics are often not sufficiently considered in the overall strategy to prevent and mitigate the impacts of plastics on human health, the environment and circular economy^5–7. Here we present an inventory of 16,325 known plastic chemicals with a focus on their properties, presence in plastic and hazards. We find that diverse chemical structures serve a small set of functions, including 5,776 additives, 3,498 processing aids, 1,975 starting substances and 1,788 non-intentionally added substances. Using a hazard-based approach, we identify more than 4,200 chemicals of concern, which are persistent, bioaccumulative, mobile or toxic. We also determine 15 priority groups of chemicals, for which more than 40% of their members are of concern. Finally, we examine data gaps regarding the basic properties, hazards, uses and exposure potential of plastic chemicals. Our work maps the chemical landscape of plastics and contributes to setting the baseline for a transition towards safer and more sustainable materials and products. We propose that removing known chemicals of concern, disclosing the chemical composition and simplifying the formulation of plastics can provide pathways towards this goal.

An inventory of 16,325 known plastic chemicals, including >4,200 hazardous compounds, supports the development of safer plastics.

Main

Plastic pollution is a pervasive and growing global problem affecting all dimensions of the triple planetary crisis^8–10. Awareness of this issue has grown in recent years, and all United Nations member states committed to creating an international legally binding instrument to end plastic pollution in 2022 (ref. ⁵). Achieving this ambitious goal not only requires a holistic approach that addresses the entire life cycle of plastics but also encapsulates a vision to make plastics safer and more sustainable. Indeed, chemical safety is key to both, yet it is often neglected in these transition processes, creating a critical gap in the overall strategy to prevent and mitigate the impacts of plastics on human health and the environment globally.

Plastics contain complex mixtures of chemicals, including the polymer backbone and additives as well as unreacted starting substances, residual processing aids and non-intentionally added substances (NIASs), such as impurities and reaction by-products^11–13. These chemicals can be released throughout the entire plastic life cycle, from feedstock extraction and production to use and waste^7,14–19. Specific end-of-life treatments, such as uncontrolled landfilling or incineration, can further exacerbate chemical releases^20,21. This leads to widespread human and environmental exposures that can result in health impacts, with strong epidemiological evidence linking certain plastic chemicals to reproductive, neurodevelopmental, immune and metabolic disorders³.

Plastic chemicals may also impede the transition to a circular economy, including technological solutions to plastic pollution⁶. For instance, increasing the reuse of plastic products can increase the release of chemicals^22,23, and uncontrolled recycling can further perpetuate the spread of hazardous chemicals in products with high exposure potential, such as food packaging and toys^24,25. Chemicals in plastics can also hinder sorting and recycling and thereby impede the production of high-quality secondary materials^6,26,27. Transitioning to safer plastics and a sustainable plastics economy, therefore, requires a better understanding of the chemicals involved, including their properties, functions, hazards, prevalence and releases.

At present, crucial information on plastic chemicals remains scattered across the public domain or restricted within the private sector. Previous efforts to compile an overview of the chemical diversity of plastics^26–29 have jointly identified more than 13,000 known plastic chemicals³⁰. However, these studies are domain specific (for example, food contact plastics and plastic toys), lack a comprehensive assessment of hazards and other relevant properties, or focus on intentionally added chemicals. To address these gaps and equip the scientific community with the evidence needed to design safer plastics, we provide a comprehensive and consistent global inventory of known plastic chemicals, including relevant information on their properties, presence in plastics and regulation.

Taking this one step further, we identify chemicals of concern in plastics. We develop a hazard-based approach to classify chemicals as of concern if they are persistent, bioaccumulative, mobile or toxic. We also introduce a new approach to identify groups of chemicals of concern on the basis of their structure. The combination of these components creates a robust framework that addresses existing challenges in making plastics safer (Methods, Extended Data Fig. 1 and Supplementary Text 1) and can be translated to other domains, such as industrial sectors and materials. Finally, we outline pathways towards creating safer plastics by removing chemicals of concern, improving transparency and chemical simplification.

Extended Data Fig. 1. Workflow of compiling the PlastChem inventory.

The core inventory compiles and harmonizes data on plastic chemicals from six peer-reviewed and one regulatory source. Hazard information from 15 authoritative sources is scored using a consistent methodology. Additional data on function, use, occurrence, and release of plastic chemicals derive from the peer-reviewed literature. Regulatory data originate from four Multilateral Environmental Agreements and five regional or national legislative frameworks. Over 10,000 chemicals are grouped based on their structure, and 15 are priority groups identified.

Global inventory of plastic chemicals

We identify 16,325 unique chemicals that can be intentionally used or are unintentionally present in plastics by collating and harmonizing information from seven sources^{17,25–29,31} (Methods, Extended Data Fig. 2, Supplementary Text 2 and Supplementary Table 1), forming the core of the PlastChem inventory. We use their active Chemical Abstracts Service Registry Numbers (CAS RNs) as the unique identifiers to annotate additional information. We also incorporate structural information as Simplified Molecular Input Line Entry System (SMILES) or International Chemical Identifier (InChI) strings for a subset of 12,658 chemicals (Fig. 1a). The inventory contains another 1,607 substances for which we could not retrieve valid CAS RNs, resulting in a total of 17,932 entries. However, we exclude chemicals without valid CAS RN from further analysis as these cannot be traced across sources or de-duplicated. By including new information on chemicals detected in plastics, this inventory expands the known universe of plastic chemicals by >3,000 substances compared to previous work³⁰.

Extended Data Fig. 2. Overlap between the sources used to assemble the PlastChem inventory.

The seven sources used to compile the inventory show considerable intersection in the plastic chemicals (numbers) they report. However, the presence of many unique plastic chemicals highlights the importance of consolidating the available information into one consistent inventory. Overlaps of <100 are not shown.

Source data

Fig. 1. Overview of plastic chemicals in the inventory, and their basic chemistry and functions.

a, Overview of the chemicals in the PlastChem inventory, showing the original sources, the duplicates, the chemicals with CAS RNs and their basic chemistry. b, Example of major chemistries of the organic compounds in the inventory. c, Functions of plastic chemicals organized by top-level classes. Coloured lines show connections between chemicals used for multiple functions within the same class; grey lines indicate that functions spread across multiple classes. Only functions with >10 chemicals are shown. ‘Others’ in additives include anti-fog additives, pigments, ultraviolet-absorbing agents and other unspecified additives, and ‘others’ in processing aids include polymerization aids and surfactants. For details, see Supplementary Text 3.

Source Data

We take a deep dive into the chemical and functional space of these plastic chemicals. Most chemicals (12,658) are discrete compounds with known structures (Fig. 1a), covering inorganic, organic and organometallic chemistries, and spanning a wide space of physicochemical properties (Fig. 1b and Extended Data Fig. 3). For 3,667 substances (23% of the inventory), defined chemical structures and properties are lacking in the public domain. These include substances of unknown or variable composition, complex reaction products or biological materials (UVCBs), mixtures and polymers. For around 1,500 of them, the available structural information refers only to a minor part of the compounds they contain³². Owing to their ambiguous chemical compositions, these 3,667 substances cannot be assessed with confidence.

Extended Data Fig. 3. Chemical coverage of the chemicals included in the PlastChem inventory.

Red dots indicate chemicals of concern, orange dots indicate the less hazardous substances. Log Kow predictions were performed using the OPERA QSAR suite (v2.9.1, LogP module v2.6, QMRF: Q17-16-0016)⁵⁵. After OPERA’s standardization process from the 12,114 unique canonical SMILES of the PlastChem inventory, 783 structures were discarded, leaving 11,331 chemical structures for prediction. The molecular weights of these standardized structures were used for visualization. Resulting predictions were quality-assessed using OPERA’s applicability domains (ADs) and the guidelines in⁵⁵. Results within the global AD (global AD = 1) and local AD > 0.6, even outside the global AD (i.e., global AD = 0) were considered, resulting in 6,393 reliable Kow values for visualization. Structures without reliable predictions were assigned a value of -Inf to allow for molecular weight visualization without affecting log Kow histograms.

Source Data

Plastic chemicals serve diverse functions (Fig. 1c). Consolidating the different terminologies used previously^26–28 (Methods, Supplementary Text 3 and Supplementary Tables 2 and 3), we identify four top-level classes; that is, 5,776 plastic additives, 3,498 processing aids, 1,975 starting substances and 1,788 NIASs (Fig. 1c; see Supplementary Text 1 for definitions). Additives are the most diverse class covering 16 major functions, the most prevalent being colourants (3,674 chemicals), fillers (1,836), biozides (1,552) and plasticizers (883). Many different chemistries can serve the same function, and at least 4,054 substances have multiple functions at different stages of the plastic life cycle. For example, bisphenol A (CAS RN 80-05-7) functions as a co-monomer for polycarbonates and epoxy resins, a crosslinking agent in fluoroelastomers, an intermediate for producing the flame-retardant tetrabromobisphenol A (CAS RN 79-94-7), an antioxidant and a light stabilizer. These findings reveal the structural and functional diversity of plastic chemicals, as well as a substantial overlap in their roles.

Chemicals of concern in plastics

Building on the inventory, we identify 4,219 chemicals of concern, representing one-quarter of all known plastic chemicals. We classify a chemical as of concern according to four broad hazard criteria, namely its persistence (P), bioaccumulation (B), mobility (M) and toxicity (T; Fig. 2a, Methods and Supplementary Text 4). The identification of chemicals of concern is based on information originating from 15 regulatory sources with high reliability (Methods and Supplementary Tables 4 and 5), either through robust assessments by government authorities, or through industry self-reporting, which tends towards under-reporting³³. More than half of the chemicals of concern (2,388) are classified as hazardous by at least two sources (Supplementary Table 6). The approach can be considered conservative as we do not include hazard information from the scientific literature. Considering that 10,726 plastic chemicals (66%) lack official hazard classifications by regulatory agencies or industry, it stands to reason that there could be more chemicals of concern in plastics than the ones identified here.

Fig. 2. Chemicals of concern in plastics, and their hazard classes and traits.

a, Number of the chemicals identified as of concern, less hazardous, not hazardous, and those without data or under development. The outer circle represents chemicals that are globally regulated. b, Number of chemicals of concern fulfilling the hazard criteria (P, persistence; B, bioaccumulation; M, mobility; and T, toxicity) and specific hazard traits (Aq. tox., aquatic toxicity; STOT, specific target organ toxicity; CMR, carcinogenic, mutagenic or toxic for reproduction; POP, persistent organic pollutant; PMT, persistent, mobile and toxic; PBT, persistent, bioaccumulative and toxic; EDC, endocrine-disrupting chemical; vPvM, very persistent and very mobile; vPvB, very persistent and very bioaccumulative). For details, see Supplementary Text 4.

Source data

Although the chemical identities of most of the 3,667 UVCBs, mixtures and polymers are incompletely understood or unknown, regulatory information supports the identification of 619 of them as chemicals of concern. Furthermore, the fact that >10% of polymers are hazardous challenges views that they do not pose any serious hazard owing to their large molecular weight³⁴. Therefore, it is critical to improve our understanding of the chemical identities and hazards of UVCBs, mixtures and polymers^32,34,35.

We also find that hazard classification distributes unevenly across chemicals of concern, with most being classified as toxic. One chemical (1,2,3-trichlorobenzene; CAS RN 87-61-6) fulfils all hazard criteria, 340 chemicals meet 3 criteria (that is, they are persistent, bioaccumulative and toxic (PBT) or persistent, mobile and toxic (PMT) chemicals) and 3,844 chemicals have been classified only as toxic to the aquatic environment (2,760) and/or to human health (2,421; Fig. 2b). Regarding the toxicity criterion, 1,774 chemicals are toxic for specific organs (STOT, for example, liver), 1,489 are carcinogenic, mutagenic or toxic for reproduction (CMR), and 47 are endocrine-disrupting chemicals (EDC, Extended Data Fig. 4). One reason for few plastic chemicals being classified as persistent, bioaccumulative or mobile is that we consider only chemicals that have undergone assessments for PBT, PMT, very persistent and very bioaccumulative (vPvB) or very persistent and very mobile (vPvM) properties (<4% of all chemicals), excluding those whose P, B or M properties have been assessed separately.

Extended Data Fig. 4. Overlap of the hazard criteria (left) and traits (right) of chemicals of concern.

Out of all chemicals of concern, 4,184 are classified as toxic, 225 as persistent, bioaccumulative and toxic, and 116 as persistent, mobile and toxic. Twelve and 23 are very persistent and bioaccumulative, and very persistent and very mobile without having been classified as toxic, respectively. The hazard traits for toxicity are dominated by chemicals being toxic to the aquatic environment (2,760), to specific organs (1,774), and being carcinogenic, mutagenic or reprotoxic (1,489).

Source Data

An additional 1,191 chemicals are less hazardous, as they have lower hazard levels according to the European Union’s Regulation on Classification, Labelling and Packaging of Substances and Mixtures (for example, class 2 for reproductive toxicity or mutagenicity)³⁶. Only 161 chemicals have evidence suggesting that they are not hazardous, although such classification may not necessarily be conclusive as none of these chemicals has been evaluated for all four hazard criteria. Indeed, all 161 compounds are classified as non-toxic, but only 12 of them are not persistent and bioaccumulative, properties considered concerning on their own. Given the lack of relevant hazard information, caution needs to be taken to not confuse this absence of evidence with evidence for absence of harm.

Presence in and release from plastics

In addition to identifying chemicals of concern, we compile additional evidence for 6,278 chemicals showing that these are marketed for use in plastic production (2,899), detected in plastics in scientific studies (3,178) or shown to be released from plastics in migration experiments (1,572)^17,25,26 (Methods and Supplementary Text 5). Almost 30% of these compounds (1,875) are chemicals of concern. These include 850 chemicals with empirical evidence for presence in plastics and 508 with evidence for release (for example, into foodstuffs). This indicates that exposure to those chemicals is probable, although the prevalence and extent remains unknown. Notably, 1,322 known chemicals of concern are marketed for use in plastics manufacturing. This sheds light on the fact that many chemicals of concern are intentionally used or unintentionally present in plastics and can be released. Although our analysis is only qualitative, we argue that the exposure potential of these chemicals is high, especially considering that some have additional sources of exposure unrelated to plastics.

We next explore whether plastics made of certain polymer types may be particularly prone to contain chemicals of concern. Although information on the use of chemicals in specific polymer types is incomplete, we find that at least 400 chemicals of concern are associated with each major polymer type (Fig. 3a). For example, out of the 472 chemicals of concern detected in polyethylene terephthalate (PET), 143 have evidence for being released, including into foodstuffs. PET shares 163 of these 472 chemicals of concern with polyvinyl chloride (PVC; Fig. 3b), a polymer type often considered problematic for environment and health³⁷. This suggests that chemicals of concern are associated with all major polymer types (Fig. 3c).

Fig. 3. Use and detection of plastic chemicals in major polymer types.

a, Number of chemicals and chemicals of concern commercially used or detected in major polymer types. Polymer types with highest data availability are shown and details on the remaining polymer types are provided in Extended Data Fig. 5. PA, polyamide; PE, polyethylene; ABS, acrylonitrile butadiene styrene; PS, polystyrene. b, Comparison of chemicals used or detected in PET and PVC. Chemicals of concern are shown in red. c, Overlap of chemicals used and detected in major polymer types.

Source data

Data availability varies with polymer type, with most information being available for PET and polypropylene (PP; Extended Data Fig. 5). The fraction of chemicals of concern that are associated with a specific polymer type ranges from 31% in PET to 62% in polyurethane (PUR), with the highest prevalence in PUR, PVC (48%) and PP (45%). Notably, much less information is available for other polymer types, in particular for bio-based and/or biodegradable plastics. For example, we find very limited information on which chemicals are marketed for use in polylactic acid, and empirical evidence is scarce. Nevertheless, out of the 35 chemicals that have been detected in polylactic acid, 22 are of concern, a similar proportion of chemicals of concern as in fossil-based plastics. This highlights that the use of chemicals of concern extends to so-called bioplastics as well.

Extended Data Fig. 5. Use and detection of plastic chemicals across polymer types.

Number of chemicals and chemicals of concern commercially used or detected in all polymer types investigated in PlastChem. Note that the detected chemicals (right) may also have information on their commercial use (not shown here) and that the chemicals with information on use (left) have not been analysed or detected in plastics. LDPE = Low-density polyethylene, PA = Polyamide, HDPE = High-density polyethylene, PE = Polyethylene, PET = Polyethylene terephthalate, PVC = Polyvinyl chloride, PUR = Polyurethane, PP = Polypropylene, PS = Polystyrene, EPS = Expanded polystyrene, HIPS = High impact polystyrene, ABS = Acrylonitrile butadiene styrene, PC = Polycarbonate, EVA = Ethylene-vinyl acetate, PMMA = poly(methyl methacrylate), PVA = polyvinyl alcohol, SAN = Styrene-acrylonitrile resin, PLA = Polylactic acid, PHA = polyhydroxyalkanoates, PBS = Polybutylene succinate, PBAT = Polybutylene adipate terephthalate.

Source Data

State of governance of plastic chemicals

To better understand the state of play of the global governance, we assess which plastic chemicals are covered by Multilateral Environmental Agreements (Methods, Supplementary Text 6 and Supplementary Table 7). We find that only 6% of all plastic chemicals (980) are regulated under the Basel, Stockholm and Minamata Conventions, and the Montreal Protocol. These regulations address specific chemical classes (for example, persistent organic pollutants and mercury-containing substances), and some of them regulate chemicals only in certain stages of the life cycle (that is, waste in the Basel Convention). Of the 4,219 chemicals of concern identified, 568 are regulated under these Multilateral Environmental Agreements (Fig. 2a). However, most chemicals of concern (3,651) remain unregulated globally, despite plastic chemicals, materials, products and waste being globally traded. National regulations cover an additional 1,021 chemicals, although implementation and oversight vary widely across regions. This implies that a substantial governance gap exists regarding chemicals of concern in plastics.

Grouping to address chemicals of concern

Given the vast number and diversity of plastic chemicals, along with the many unknowns and data gaps, managing them individually is both challenging and inefficient. As a pragmatic solution, we group chemicals on the basis of structural similarities. Grouping also helps prevent regrettable substitutions, specifically in cases of ‘drop-in’ substitution, in which a known chemical of concern is replaced by a structurally similar chemical with similar hazard properties^38,39. Grouping of chemicals also has regulatory precedent, for instance, in the Montreal Protocol, Stockholm Convention and European REACH regulation³⁸.

We group more than 10,000 plastic chemicals (Methods, Supplementary Text 7 and Supplementary Table 8), resulting in 28 groups with clear structural similarities and containing at least 10 members each. The largest groups are alkenes (802 chemicals), silanes, siloxanes and silicones (443) and per- and polyfluoroalkyl substances (PFASs; 440), and parabens (10) is the smallest group. We prioritize 15 groups of chemicals of concern, with each group consisting of at least 40% of known chemicals of concern or having strong evidence for the entire group to be hazardous (for example, PFASs^40,41, chlorinated paraffins⁴²; Fig. 4 and Supplementary Tables 9 and 10). Among these 15 groups, aromatic amines, aralkyl aldehydes and alkylphenols are made up of more than 75% of chemicals of concern. Grouping plastic chemicals can support an efficient management and redesign of plastics by eliminating the need to fill data gaps and preventing regrettable substitutions. However, the grouping process also has some technical challenges, primarily due to the lack of a single automated tool for categorizing a large number of substances. Instead, various techniques are necessary. For instance, an algorithm helped identify homologue series covering more than 2,000 chemicals, but further expert evaluation is needed to refine these groups (see Methods for further details). To address these issues, better structural identifiers and automated grouping tools are needed.

Fig. 4. Proportion of chemicals of concern in major groups of plastic chemicals.

Major groups of chemicals based on their structure and the proportion of chemicals of concern in each group, the group size and the availability of hazard data for the chemicals. The grey shading indicates priority groups of chemicals. ^aRegulated globally; ^borganometallics containing lead, chromium, antimony, tin, cadmium, and nickel; ^cnot regulated globally. The hazard data availability shows the percentage of chemicals within each group that have hazard data in the consulted sources. For details, see Supplementary Text 7. PAHs, polycyclic aromatic hydrocarbons; PCBs, polychlorinated biphenyls.

Source data

Pathways towards safer plastics

Our study shows that the universe of chemicals in plastics is vast, with more than 16,000 known plastic chemicals, including in excess of 4,200 chemicals of concern. This poses two major challenges for the safety, sustainability and circularity of plastics. First, the sheer number of plastic chemicals exceeds the capacity of manufacturers and governments to ensure their safety, with more than 10,000 chemicals remaining to be tested and assessed. Second, we present robust evidence for the presence of numerous, well-established chemicals of concern, based on regulatory data and including their commercial use and detection in plastics. This suggests that plastic products on the global market can contain and release substances known to harm human health or the environment, across all major polymer types. Collectively, this raises the question of how the safety of plastics can be improved.

Removing known chemicals of concern, whether voluntarily or through regulatory measures, is a crucial first step in making plastics safer. This can be guided by the essential use concept, which involves three key considerations^43–45. First, chemicals of concern that are not necessary for the performance of a material, product or service can be removed. Second, chemicals of concern essential for health, safety or critical societal functions should be replaced with safer alternatives. Our results point towards the availability of alternatives as we find that many substances serve the same technical function (Fig. 1b). Finally, if one or more uses of a chemical of concern cannot be removed or replaced for the moment, innovative solutions, including new product design, should be fostered to substitute such uses. However, the major challenge in this process is the lack of suitable alternatives as indicated by the few non-hazardous chemicals we identify (Fig. 2a) and the high proportion of chemicals of concern in certain functions (for example, heat and light stabilizers; Extended Data Fig. 6). This emphasizes the need to develop safer plastic chemicals and create incentives for their adoption. Achieving this goal relies on suitable frameworks to guide chemical design, such as the ‘safe and sustainable by design’ framework⁴⁶ as well as robust tools to evaluate the safety of alternatives.

Extended Data Fig. 6. Proportion of chemicals of concern across major functions of plastic chemicals (left) and hazard data availability for these chemicals.

The percentage of hazard data availability shows the percentage of chemicals within each function group that have hazard data available in the consulted sources. For details see Supplementary Information Text S2.

Source Data

We also identify many data gaps that prevent understanding the complete scope of plastic chemicals and their impacts on human health and the environment. For instance, 9% of chemicals in the inventory lack basic structural information, 25% lack chemical property data, more than 50% miss details on their functions or presence in plastics, and 66% have no hazard information (Extended Data Fig. 7). By logic, the safety of these chemicals cannot be ascertained, and our assessment of chemicals of concern remains incomplete. This has multiple reasons, including the limitations of using CAS RNs for tracking information (for example, use of multiple CAS RNs per chemical, or the same CAS RN for multiple chemicals^32,47). However, major uncertainties in our work originate from the lack of transparency, as manufacturers do not publicly disclose the chemical composition of their materials and products²³. Accordingly, the PlastChem inventory may not reflect the dynamic changes in the plastics and chemical market. Removing existing barriers to information and creating more transparency within supply chains and the public domain⁴⁸ is key for resolving these issues.

Extended Data Fig. 7. Overview of the data availability in the PlastChem inventory.

The figure presents the number of chemicals of the PlastChem inventory with data on use, presence and release, hazards, and functions, and their overlaps.

Redesigning plastic materials and products towards safety and sustainability is essential to enable a transition towards a non-toxic circular economy⁴⁶. Removing known chemicals of concern and improving transparency are necessary but not sufficient to address the chemical complexity of plastics. It is improbable that regulators and scientists can determine the impacts of 16,000 plastic chemicals on human health and the environment in a timely manner, particularly as new ones continue to proliferate. Therefore, a simplification of plastics is needed⁴⁹. This includes minimizing the number and molecular complexity of chemicals intentionally used in plastics as well as optimizing production processes to mitigate the introduction and generation of NIASs (for instance, by using additives with higher purity). The aforementioned redesign should start with critically assessing the true needs for specific chemical functionalities in specific plastic applications. This requires engaging with all relevant stakeholders, in particular plastic manufacturers⁴⁸.

Our work sets the baseline for the transition to a safer, more sustainable and circular plastics economy by mapping the chemical complexity of plastics consistently and comprehensively. It also provides scientists and other stakeholders working towards such transition with consolidated information on plastic chemicals, their hazards and regulation, their uses and functions, and their detection in polymer types. A dedicated list of chemicals of concern and the associated chemical groups will further help to avoid problematic chemistries in the design and manufacture of plastics.

Methods

Rationale and conceptual considerations

We built a comprehensive and globally applicable inventory of all known plastics chemicals and developed an innovative framework combining hazard and grouping components with the aim to facilitate a transition towards safer plastics. We define plastic chemicals as all chemicals that can be present in plastic materials and products, including the polymer backbone, intentionally added substances (that is, starting substances, processing aids and additives) and NIASs (for example, impurities, unreacted intermediates, reaction by-products and degradation products). The fact that some plastic chemicals may have additional uses in non-plastic applications has no bearing on their inclusion. Contaminants sorbing to plastics during use or end-of-life are not considered plastic chemicals. See complete definitions in Supplementary Text 1.

To identify chemicals of concern in plastics, we developed and applied a hazard-based approach. In brief, we classified a plastic chemical as of concern on the basis of the criteria of persistence, bioaccumulation, mobility and toxicity. The rationale for taking this approach is threefold. First, we argue that plastics should not contain hazardous chemicals, to protect human health and the environment. Although this approach might be considered conservative, it enables scientists and businesses to improve the safety of plastics and proactively prevent potential harm in a timely and efficient manner. Second, we posit that exposure to most plastic chemicals is probable given that most are not covalently bound to the polymer. This is backed by empirical evidence showing that 83% of the 1,788 chemicals tested for release from plastic food contact materials indeed migrate into foodstuff^17,25. Third, we reason that an alternative risk-based approach is neither efficient nor effective—and often infeasible—to identify chemicals of concern owing to numerous practical challenges, blind spots and high implementation costs that would unduly delay a transition to safer plastics.

Apart from the identification of chemicals of concern, we collected additional evidence on the use, presence and release of plastic chemicals. We use this information to link chemicals to specific polymer types, shed light on which compounds are intentionally added to plastics (commercial use) and infer their exposure potential. Although the last of these is only qualitative, it suggests that human and environmental exposures to these chemicals are probable, given that scientific studies demonstrate their migration or volatilization into foodstuff or environmental media.

We grouped plastic chemicals on the basis of their structure to efficiently address chemicals of concern as well as regrettable ‘drop-in’ substitutions (that is, replacing a chemical of concern with a structurally very similar compound). We assumed a chemical without hazard data is ‘guilty by association’ if it is part of a group that consists of many known chemicals of concern. This is supported by ample evidence available for certain groups, such as bisphenols⁵⁰, as well as the fact that the structure of a chemical determines its hazards. In combination with the hazard-based approach, such chemical grouping offers a robust framework to improve the chemical safety of plastics in a timely and efficient manner.

Building the PlastChem inventory

We built the PlastChem inventory by: compiling and harmonizing information from seven prior databases; retrieving additional and updated information on hazard classifications and regulatory status from 15 authoritative sources (latest update August 2023) to identify chemicals of concern; integrating data on the use, detection and release of chemicals in and from plastics; and grouping the chemicals on the basis of their structure (Extended Data Fig. 1). All data engineering work was performed using R (R Consortium, 2023) and Microsoft Excel (see Data and Code availability).

Core of the PlastChem inventory

We compiled and harmonized information from prior databases that had identified chemicals in plastics, relying on six peer-reviewed and one regulatory source. As a first step, we retrieved lists of plastic chemicals from seven sources, including: the dataset of ref. ²⁷; the database of Chemicals associated with Plastic Packaging (CPPdb, version 1)²⁸; the European Union (EU) list of Authorized Substances Annex I, Plastic Food Regulation 10/2011/EU (PFCRdb)³¹; the Food Contact Chemicals database (FCCdb, version 5)²⁹; the PlasticMAP dataset²⁶; the dataset on Migrating and Extractable Food Contact Chemicals (FCCmigex, version February 2023)¹⁷; and the LitChemPlast dataset (version June 2023)²⁵. Given the scale of the results, we deemed verifying the original sources not feasible and accepted the entries in the seven databases as plastic chemicals.

To identify chemical structures, compile data from various sources and assemble the inventory, we used CAS RNs or chemical names (when CAS RNs were invalid or unavailable) with the automatic Application Programming Interface services of PubChem. The information retrieved included the PubChem Compound Identification (CID), molecular formula, molecular weight, canonical SMILES, isomeric SMILES, InChI, InChIKey, IUPAC name, predicted octanol/water partition coefficient (XLogP), exact mass, monoisotopic mass, topological polar surface area, complexity and charge. CAS RNs were validated according to CAS guidelines⁵¹. Further details are available in Supplementary Text 2.

Despite thorough quality assurance and control, some uncertainties may remain in the inventory (Supplementary Text 2). For example, 400 duplicates were identified, originating from the use of multiple names for the same chemical or from non-unique CAS RNs that correspond to multiple substances. These duplicates are shown in an additional file in the inventory. Of these, 188 chemicals were manually selected by expert judgement for inclusion in the main inventory, as they were deemed the most likely matches for the corresponding CAS RNs. Although we validated and curated the CAS RNs to reduce duplication, additional duplicates may still exist.

Information on functions and regulation

Additional information on the known functions of plastic chemicals and their regulatory status is also included in the PlastChem inventory. Briefly, the functions were gathered from ref. ²⁷, CPPdb²⁸ and PlasticMAP²⁶, aligned to a common terminology and assigned larger functional classes (starting substances, additives, processing aids and NIASs). See further details in Supplementary Text 3.

To integrate regulatory information, we compiled information from the Basel, Stockholm and Minamata Conventions, along with the Montreal Protocol, to identify the chemicals globally regulated under Multilateral Environmental Agreements at present. In addition, we also included regional and national lists of chemicals that were easily accessible, including chemicals regulated in the EU, Japan, the Republic of Korea and the USA, along with those substances regulated under the Rotterdam Convention. See further details in Supplementary Text 6.

Identification of chemicals of concern

Hazard information was collected from 15 regulatory sources, some of which aligned with the Globally Harmonized System of Classification and Labelling (Supplementary Table 4). This information is consistent with the principles outlined in the EU Chemicals Strategy for Sustainability⁵² and the updated Classification, Labelling and Packaging of Substances and Mixtures regulation³⁶. We did not include hazard information from the scientific literature because relevant studies are either already synthesized in the regulatory sources or would require individual quality assessment, data extraction and analysis. Accordingly, we consider the regulatory sources used as authoritative.

We applied a stepwise process to harmonize the compiled hazard information and translate it into a single hazard score per chemical. First, chemicals with hazard data for a specific trait (for example, carcinogenicity) were assigned a score ranging from 0 to 2, with 0 indicating non-hazardous, 0.5 indicating less hazardous, 1 indicating hazardous, and 2 indicating very hazardous (Supplementary Table 5). Chemicals with hazard evaluations under development, postponed or pending received a score of 0.25 to reflect that these are undergoing assessment but have not been classified yet. A blank indicates that no information is available. In cases of multiple classifications per source, we used the highest scores for each trait, with regulatory information taking precedence over industry data. As a second step, we aggregated the individual scores per trait into a single score for each hazard criterion (P, B, M and T) using the highest score whenever multiple traits within a criterion had information, retaining the 0–2 scoring system as described above. Finally, the maximum score across the P, B, M and T criteria resulted in a unique hazard score for each chemical that we used to identify chemicals of concern when the score was ≥1, indicating that a chemical of concern fulfils at least one hazard criterion. Additionally, we calculated the sum of hazard scores across the P, B, M and T criteria, ranging from 0 to 8, and provide an evidence score reflecting the number of sources that classify a chemical as hazardous for the same criterion, ranging from 0 to 31. Further details are available in Supplementary Text 4.

Use, presence and release information

We compiled and harmonized data on the use, presence and release of chemicals in plastic polymers from FCCmigex¹⁷, PlasticMAP²⁶ and LitChemPlast²⁵. Presence data were derived from studies performing extraction experiments (for example, with solvents); release data came from studies performing migration experiments (for example, with food simulants). Chemicals with release data were assigned a score of 2, and those with only presence data received a score of 1. Data on the commercial use of plastic chemicals were sourced from PlasticMAP and given lower priority (score of 0.5 if no presence or release data are available). Chemicals with inconclusive information were scored 0.25, and substances that were analysed but not detected in experimental studies were scored 0. Finally, chemicals without data received a blank. See Supplementary Text 5 for further details.

Grouping and groups of concern

Plastic chemicals were grouped on the basis of their structures following two approaches (details in Supplementary Text 7). In brief, the first approach consisted of searching a predefined set of keys in the chemical names to identify inorganic compounds, organometallics and metalorganics, UVCBs, polymers and mixtures. This was followed by searching the name and chemical symbol of respective elements in the chemical names and SMILES to identify organohalogens, organophosphates, organosilicons and various chemicals containing certain metal(loid) elements. The second approach consisted of matching chemicals in the PlastChem inventory with existing lists of chemical groups (list in Supplementary Text 7). In addition, we applied expert judgement to identify PFASs from all organofluorine chemicals, as well as those PFASs and chlorinated paraffins regulated under the Stockholm Convention.

Groups of plastic chemicals were prioritized on the basis of the number of chemicals of concern they contain. As some groups of chemicals lack hazard data, our prioritization considers only groups with sufficient information. Starting with more than 100 initial groups, we isolated relevant groups by excluding groups that were too large and unspecific (for example, mixtures), groups that are regulated internationally, and groups with too few members. The final selection of prioritized groups was ranked on the basis of the proportion of known chemicals of concern they contain. This follows the rationale that groups consisting of many hazardous chemicals have more evidence for being concerning. Priority was assigned to groups for which ≥40% of the members are chemicals of concern or if additional scientific considerations pointed towards group-specific hazards (details in Supplementary Text 6 and Supplementary Table 9).

During the grouping, we also identified some technical challenges. Notably, no single automated tool is available to consistently group large numbers of chemicals. Instead, a combination of various techniques is required. For example, we used an algorithm⁵³ to identify homologue series containing repeating units of –CH₂–, –CF₂–, –CF₂O– or –CF₂CF₂O–, covering more than 2,000 substances. Additionally, it is possible to identify UVCBs, polymers and other mixtures using predefined keyword searches⁴⁷. However, in both cases, the subsequent assignment into more specific groups (for example, PFASs) requires manual inspection and expert judgement. This is due to a lack of machine-processable structural identifiers for these substances. Therefore, the manual curation of grouping and certain entries may have introduced some inconsistencies in our inventory. More work is needed to improve the availability of unique structural identifiers for chemicals on the global market, and to develop cheminformatics tools for grouping.

Online content

Any methods, additional references, Nature Portfolio reporting summaries, source data, extended data, supplementary information, acknowledgements, peer review information; details of author contributions and competing interests; and statements of data and code availability are available at 10.1038/s41586-025-09184-8.

Author contributions

L.M.: conceptualization; methodology; software; formal analysis; investigation; data curation; visualization; writing – original draft; writing – review and editing. H.P.H.A.: conceptualization; methodology; validation; writing – review and editing. K.J.G.: conceptualization; methodology; writing – review and editing. A.F.: software; visualization; writing – review and editing. M.E.L.: conceptualization; writing – review and editing. J.M.: conceptualization; writing – review and editing. Z.W.: conceptualization; methodology; formal analysis; validation; writing – review and editing. R.W.: methodology; software; data curation; visualization; writing – review and editing. L.Z.: conceptualization; writing – review and editing. M.W.: conceptualization; methodology; formal analysis; validation; investigation; data curation; writing – review and editing; resources; funding acquisition.

Peer review

Peer review information

Nature thanks Beate Escher, Margaret Sobkowicz, Costas Velis and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Peer reviewer reports are available.

Data availability

This study is based on the PlastChem report⁵⁴ (10.5281/zenodo.10701706), which also contains the PlastChem inventory. Supplementary Data are freely available as part of the Supplementary Information. Source data are provided with this paper.

Code availability

All code necessary to assemble the PlastChem inventory is publicly available at GitHub via https://github.com/PlastChem/DB.

Competing interests

M.W. and K.J.G. are unremunerated members of the Scientific Advisory Board of the Food Packaging Forum Foundation. The other authors declare no competing interests.

Extended data

is available for this paper at 10.1038/s41586-025-09184-8.

Supplementary information

The online version contains supplementary material available at 10.1038/s41586-025-09184-8.