Per- and Polyfluoroalkyl Substances in Food Packaging: Migration, Toxicity, and Management Strategies.

PFASs are linked to serious health and environmental concerns. Among their widespread applications, PFASs are known to be used in food packaging and directly contribute to human exposure. However, information about PFASs in food packaging is scattered. Therefore, we systematically map the evidence on PFASs detected in migrates and extracts of food contact materials and provide an overview of available hazard and biomonitoring data. Based on the FCCmigex database, 68 PFASs have been identified in various food contact materials, including paper, plastic, and coated metal, by targeted and untargeted analyses. 87% of these PFASs belong to the perfluorocarboxylic acids and fluorotelomer-based compounds. Trends in chain length demonstrate that long-chain perfluoroalkyl acids continue to be found, despite years of global efforts to reduce the use of these substances. We utilized ToxPi to illustrate that hazard data are available for only 57% of the PFASs that have been detected in food packaging. For those PFASs for which toxicity testing has been performed, many adverse outcomes have been reported. The data and knowledge gaps presented here support international proposals to restrict PFASs as a group, including their use in food contact materials, to protect human and environmental health.

A vision for safer food contact materials: Public health concerns as drivers for improved testing.

Food contact materials (FCMs) and food contact articles are ubiquitous in today's globalized food system. Chemicals migrate from FCMs into foodstuffs, so called food contact chemicals (FCCs), but current regulatory requirements do not sufficiently protect public health from hazardous FCCs because only individual substances used to make FCMs are tested and mostly only for genotoxicity while endocrine disruption and other hazard properties are disregarded. Indeed, FCMs are a known source of a wide range of hazardous chemicals, and they likely contribute to highly prevalent non-communicable diseases. FCMs can also include non-intentionally added substances (NIAS), which often are unknown and therefore not subject to risk assessment. To address these important shortcomings, we outline how the safety of FCMs may be improved by (1) testing the overall migrate, including (unknown) NIAS, of finished food contact articles, and (2) expanding toxicological testing beyond genotoxicity to multiple endpoints associated with non-communicable diseases relevant to human health. To identify mechanistic endpoints for testing, we group chronic health outcomes associated with chemical exposure into Six Clusters of Disease (SCOD) and we propose that finished food contact articles should be tested for their impacts on these SCOD. Research should focus on developing robust, relevant, and sensitive in-vitro assays based on mechanistic information linked to the SCOD, e.g., through Adverse Outcome Pathways (AOPs) or Key Characteristics of Toxicants. Implementing this vision will improve prevention of chronic diseases that are associated with hazardous chemical exposures, including from FCMs.

Evaluating the food safety and risk assessment evidence-base of polyethylene terephthalate oligomers: A systematic evidence map.

BACKGROUND: The presence of polyethylene terephthalate (PET) oligomers in food contact materials (FCMs) is well-documented. Consumers are exposed through their migration into foods and beverages; however, there is no specific guidance for their safety evaluation. OBJECTIVES: This systematic evidence map (SEM) aims to identify and organize existing knowledge and associated gaps in hazard and exposure information on 34 PET oligomers to support regulatory decision-making. METHODS: The methodology for this SEM was recently registered. A systematic search in bibliographic and gray literature sources was conducted and studies evaluated for inclusion according to the Populations, Exposures, Comparators, Outcomes, and Study type (PECOS) framework. Inclusion criteria were designed to record hazard and exposure information for all 34 PET oligomers and coded into the following evidence streams: human, animal, organism (non-animal), ex vivo, in vitro, in silico, migration, hydrolysis, and absorption, distribution, metabolism, excretion/toxicokinetics/pharmacokinetics (ADME/TK/PK) studies. Relevant information was extracted from eligible studies and synthesized according to the protocol. RESULTS: Literature searches yielded 7445 unique records, of which 96 were included. Data comprised migration (560 entries), ADME/TK/PK-related (253 entries), health/bioactivity (98 entries) and very few hydrolysis studies (7 entries). Cyclic oligomers were studied more frequently than linear PET oligomers. In vitro results indicated that hydrolysis of cyclic oligomers generated a mixture of linear oligomers, but not monomers, potentially allowing their absorption in the gastrointestinal tract. Cyclic dimers, linear trimers and the respective smaller oligomers exhibit physico-chemical properties making oral absorption more likely. Information on health/bioactivity effects of oligomers was almost non-existent, except for limited data on mutagenicity. CONCLUSIONS: This SEM revealed substantial deficiencies in the available evidence on ADME/TK/PK, hydrolysis, and health/bioactivity effects of PET oligomers, currently preventing appropriate risk assessment. It is essential to develop more systematic and tiered approaches to address the identified research needs and assess the risks of PET oligomers.

Unpacking the complexity of the polyethylene food contact articles value chain: A chemicals perspective.

Polyethylene (PE) is the most widely used type of plastic food packaging, in which chemicals can potentially migrate into packaged foods. The implications of using and recycling PE from a chemical perspective remain underexplored. This study is a systematic evidence map of 116 studies looking at the migration of food contact chemicals (FCCs) across the lifecycle of PE food packaging. It identified a total of 377 FCCs, of which 211 were detected to migrate from PE articles into food or food simulants at least once. These 211 FCCs were checked against the inventory FCCs databases and EU regulatory lists. Only 25% of the detected FCCs are authorized by EU regulation for the manufacture of food contact materials. Furthermore, a quarter of authorized FCCs exceeded the specific migration limit (SML) at least once, while one-third (53) of non-authorised FCCs exceeded the threshold value of 10 µg/kg. Overall, evidence on FCCs migration across the PE food packaging lifecycle is incomplete, especially at the reprocessing stage. Considering the EU's commitment to increase packaging recycling, a better understanding and monitoring of PE food packaging quality from a chemical perspective across the entire lifecycle will enable the transition towards a sustainable plastics value chain.

Systematic evidence on migrating and extractable food contact chemicals: Most chemicals detected in food contact materials are not listed for use.

Food packaging is important for today's globalized food system, but food contact materials (FCMs) can also be a source of hazardous chemicals migrating into foodstuffs. Assessing the impacts of FCMs on human health requires a comprehensive identification of the chemicals they contain, the food contact chemicals (FCCs). We systematically compiled the "database on migrating and extractable food contact chemicals" (FCCmigex) using information from 1210 studies. We found that to date 2881 FCCs have been detected, in a total of six FCM groups (Plastics, Paper & Board, Metal, Multi-materials, Glass & Ceramic, and Other FCMs). 65% of these detected FCCs were previously not known to be used in FCMs. Conversely, of the more than 12'000 FCCs known to be used, only 1013 are included in the FCCmigex database. Plastic is the most studied FCM with 1975 FCCs detected. Our findings expand the universe of known FCCs to 14,153 chemicals. This knowledge contributes to developing non-hazardous FCMs that lead to safer food and support a circular economy.

The NORMAN Suspect List Exchange (NORMAN-SLE): facilitating European and worldwide collaboration on suspect screening in high resolution mass spectrometry.

Background: The NORMAN Association (https://www.norman-network.com/) initiated the NORMAN Suspect List Exchange (NORMAN-SLE; https://www.norman-network.com/nds/SLE/) in 2015, following the NORMAN collaborative trial on non-target screening of environmental water samples by mass spectrometry. Since then, this exchange of information on chemicals that are expected to occur in the environment, along with the accompanying expert knowledge and references, has become a valuable knowledge base for "suspect screening" lists. The NORMAN-SLE now serves as a FAIR (Findable, Accessible, Interoperable, Reusable) chemical information resource worldwide. Results: The NORMAN-SLE contains 99 separate suspect list collections (as of May 2022) from over 70 contributors around the world, totalling over 100,000 unique substances. The substance classes include per- and polyfluoroalkyl substances (PFAS), pharmaceuticals, pesticides, natural toxins, high production volume substances covered under the European REACH regulation (EC: 1272/2008), priority contaminants of emerging concern (CECs) and regulatory lists from NORMAN partners. Several lists focus on transformation products (TPs) and complex features detected in the environment with various levels of provenance and structural information. Each list is available for separate download. The merged, curated collection is also available as the NORMAN Substance Database (NORMAN SusDat). Both the NORMAN-SLE and NORMAN SusDat are integrated within the NORMAN Database System (NDS). The individual NORMAN-SLE lists receive digital object identifiers (DOIs) and traceable versioning via a Zenodo community (https://zenodo.org/communities/norman-sle), with a total of > 40,000 unique views, > 50,000 unique downloads and 40 citations (May 2022). NORMAN-SLE content is progressively integrated into large open chemical databases such as PubChem (https://pubchem.ncbi.nlm.nih.gov/) and the US EPA's CompTox Chemicals Dashboard (https://comptox.epa.gov/dashboard/), enabling further access to these lists, along with the additional functionality and calculated properties these resources offer. PubChem has also integrated significant annotation content from the NORMAN-SLE, including a classification browser (https://pubchem.ncbi.nlm.nih.gov/classification/#hid=101). Conclusions: The NORMAN-SLE offers a specialized service for hosting suspect screening lists of relevance for the environmental community in an open, FAIR manner that allows integration with other major chemical resources. These efforts foster the exchange of information between scientists and regulators, supporting the paradigm shift to the "one substance, one assessment" approach. New submissions are welcome via the contacts provided on the NORMAN-SLE website (https://www.norman-network.com/nds/SLE/). Supplementary Information: The online version contains supplementary material available at 10.1186/s12302-022-00680-6.

Implementing the EU Chemicals Strategy for Sustainability: The case of food contact chemicals of concern.

The EU Chemicals Strategy for Sustainability (CSS) aims at removing the most harmful chemicals from consumer products, including from food contact materials (FCMs). If implemented as intended, the CSS has the potential to significantly improve the protection of public health by banning the use of chemicals of concern that are carcinogenic, mutagenic, or toxic to reproduction (CMRs), or persistent and bioaccumulative, or endocrine-disrupting chemicals (EDCs) in FCMs. However, until now an overview of such food contact chemicals of concern (FCCoCs) has not been available, because the CSS is fairly recent. Therefore, we here systematically analyze the food contact chemicals listed for intentional use in FCMs and identify known FCCoCs. We present a list of 388 FCCoCs that should be phased-out from use. Of these, 352 are CMRs, four are per- and polyfluoroalkyl substances (PFAS), and 127 have empirical evidence for presence in FCMs. Importantly, 30 FCCoCs with evidence for presence are monomers of which 22 have evidence for migration into foodstuff showing that monomers in FCMs indeed become relevant for human exposure. Our findings justify moving away from a risk- towards a hazard-based approach to regulation of chemicals in FCMs.

Evaluating the food safety and risk assessment evidence-base of polyethylene terephthalate oligomers: Protocol for a systematic evidence map.

BACKGROUND: Polyethylene terephthalate (PET) oligomers are ubiquitous in PET used in food contact applications. Consumer exposure by migration of PET oligomers into food and beverages is documented. However, no specific risk assessment framework or guidance for the safety evaluating of PET oligomers exist to date. AIM: The aim of this systematic evidence map (SEM) is to identify and organize existing knowledge clusters and associated gaps in hazard and exposure information of PET oligomers. Research needs will be identified as an input for chemical risk assessment, and to support future toxicity testing strategies of PET oligomers and regulatory decision-making. SEARCH STRATEGY AND ELIGIBILITY CRITERIA: Multiple bibliographic databases (incl. Embase, Medline, Scopus, and Web of Science Core Collection), chemistry databases (SciFinder-n, Reaxys), and gray literature sources will be searched, and the search results will be supplemented by backward and forward citation tracking on eligible records. The search will be based on a single-concept PET oligomer-focused strategy to ensure sensitive and unbiased coverage of all evidence related to hazard and exposure in a data-poor environment. A scoping exercise conducted during planning identified 34 relevant PET oligomers. Eligible work of any study type must include primary research data on at least one relevant PET oligomer with regard to exposure, health, or toxicological outcomes. STUDY SELECTION: For indexed scientific literature, title and abstract screening will be performed by one reviewer. Selected studies will be screened in full-text by two independent reviewers. Gray literature will be screened by two independent reviewers for inclusion and exclusion. STUDY QUALITY ASSESSMENT: Risk of bias analysis will not be conducted as part of this SEM. DATA EXTRACTION AND CODING: Will be performed by one reviewer and peer-checked by a second reviewer for indexed scientific literature or by two independent reviewers for gray literature. SYNTHESIS AND VISUALIZATION: The extracted and coded information will be synthesized in different formats, including narrative synthesis, tables, and heat maps. SYSTEMATIC MAP PROTOCOL REGISTRY AND REGISTRATION NUMBER: Zenodo: https://doi.org/10.5281/zenodo.6224302.

Unpacking the complexity of the PET drink bottles value chain: A chemicals perspective.

Chemicals can migrate from polyethylene terephthalate (PET) drink bottles to their content and recycling processes may concentrate or introduce new chemicals to the PET value chain. Therefore, even though recycling PET bottles is key in reducing plastic pollution, it may raise concerns about safety and quality. This study provides a systematic evidence map of the food contact chemicals (FCCs) that migrate from PET drink bottles aiming to identify challenges in closing the plastic packaging loop. The migration potential of 193 FCCs has been investigated across the PET drink bottles lifecycle, of which 150 have been detected to migrate from PET bottles into food simulants/food samples. The study reveals that much research has focused on the migration of antimony (Sb), acetaldehyde and some well-known endocrine-disrupting chemicals (EDCs). It indicates and discusses the key influential factors on FCCs migration, such as physical characteristics and geographical origin of PET bottles, storage conditions, and reprocessing efficiency . Although, safety and quality implications arising from the recycling of PET bottles remain underexplored, the higher migration of Sb and Bishphenol A has been reported in recycled (rPET) compared to virgin PET. This is attributed to multiple contamination sources and the variability in the collection, sorting, and decontamination efficiency. Better collaboration among stakeholders across the entire PET bottles lifecycle is needed to ensure sustainable resource management and food contact safety of rPET.

Role of epidemiology in risk assessment: a case study of five ortho-phthalates.

BACKGROUND: The association between environmental chemical exposures and chronic diseases is of increasing concern. Chemical risk assessment relies heavily on pre-market toxicity testing to identify safe levels of exposure, often known as reference doses (RfD), expected to be protective of human health. Although some RfDs have been reassessed in light of new hazard information, it is not a common practice. Continuous surveillance of animal and human data, both in terms of exposures and associated health outcomes, could provide valuable information to risk assessors and regulators. Using ortho-phthalates as case study, we asked whether RfDs deduced from male reproductive toxicity studies and set by traditional regulatory toxicology approaches sufficiently protect the population for other health outcomes. METHODS: We searched for epidemiological studies on benzyl butyl phthalate (BBP), diisobutyl phthalate (DIBP), dibutyl phthalate (DBP), dicyclohexyl phthalate (DCHP), and bis(2-ethylhexyl) phthalate (DEHP). Data were extracted from studies where any of the five chemicals or their metabolites were measured and showed a statistically significant association with a health outcome; 38 studies met the criteria. We estimated intake for each phthalate from urinary metabolite concentration and compared estimated intake ranges associated with health endpoints to each phthalate's RfD. RESULT: For DBP, DIBP, and BBP, the estimated intake ranges significantly associated with health endpoints were all below their individual RfDs. For DEHP, the intake range included associations at levels both below and above its RfD. For DCHP, no relevant studies could be identified. The significantly affected endpoints revealed by our analysis include metabolic, neurodevelopmental and behavioral disorders, obesity, and changes in hormone levels. Most of these conditions are not routinely evaluated in animal testing employed in regulatory toxicology. CONCLUSION: We conclude that for DBP, DIBP, BBP, and DEHP current RfDs estimated based on male reproductive toxicity may not be sufficiently protective of other health effects. Thus, a new approach is needed where post-market exposures, epidemiological and clinical data are systematically reviewed to ensure adequate health protection.

Overview of intentionally used food contact chemicals and their hazards.

Food contact materials (FCMs) are used to make food contact articles (FCAs) that come into contact with food and beverages during, e.g., processing, storing, packaging, or consumption. FCMs/FCAs can cause chemical contamination of food when migration of their chemical constituents (known as food contact chemicals, FCCs) occurs. Some FCCs are known to be hazardous. However, the total extent of exposure to FCCs, as well as their health and environmental effects, remain unknown, because information on chemical structures, use patterns, migration potential, and health effects of FCCs is often absent or scattered across multiple sources. Therefore, we initiated a research project to systematically collect, analyze, and publicly share information on FCCs. As a first step, we compiled a database of intentionally added food contact chemicals (FCCdb), presented here. The FCCdb lists 12'285 substances that could possibly be used worldwide to make FCMs/FCAs, identified based on 67 FCC lists from publicly available sources, such as regulatory lists and industry inventories. We further explored FCCdb chemicals' hazards using several authoritative sources of hazard information, including (i) classifications for health and environmental hazards under the globally harmonized system for classification and labeling of chemicals (GHS), (ii) the identification of chemicals of concern due to endocrine disruption or persistence related hazards, and (iii) the inclusion on selected EU- or US-relevant regulatory lists of hazardous chemicals. This analysis prioritized 608 hazardous FCCs for further assessment and substitution in FCMs/FCAs. Evaluation based on non-authoritative, predictive hazard data (e.g., by in silico modeling or literature analysis) highlighted an additional 1411 FCCdb substances that could thus present similar levels of concern, but have not been officially classified so far. Lastly, for over a quarter of all FCCdb chemicals no hazard information could be found in the sources consulted, revealing a significant data gap and research need.

Impacts of food contact chemicals on human health: a consensus statement.

Food packaging is of high societal value because it conserves and protects food, makes food transportable and conveys information to consumers. It is also relevant for marketing, which is of economic significance. Other types of food contact articles, such as storage containers, processing equipment and filling lines, are also important for food production and food supply. Food contact articles are made up of one or multiple different food contact materials and consist of food contact chemicals. However, food contact chemicals transfer from all types of food contact materials and articles into food and, consequently, are taken up by humans. Here we highlight topics of concern based on scientific findings showing that food contact materials and articles are a relevant exposure pathway for known hazardous substances as well as for a plethora of toxicologically uncharacterized chemicals, both intentionally and non-intentionally added. We describe areas of certainty, like the fact that chemicals migrate from food contact articles into food, and uncertainty, for example unidentified chemicals migrating into food. Current safety assessment of food contact chemicals is ineffective at protecting human health. In addition, society is striving for waste reduction with a focus on food packaging. As a result, solutions are being developed toward reuse, recycling or alternative (non-plastic) materials. However, the critical aspect of chemical safety is often ignored. Developing solutions for improving the safety of food contact chemicals and for tackling the circular economy must include current scientific knowledge. This cannot be done in isolation but must include all relevant experts and stakeholders. Therefore, we provide an overview of areas of concern and related activities that will improve the safety of food contact articles and support a circular economy. Our aim is to initiate a broader discussion involving scientists with relevant expertise but not currently working on food contact materials, and decision makers and influencers addressing single-use food packaging due to environmental concerns. Ultimately, we aim to support science-based decision making in the interest of improving public health. Notably, reducing exposure to hazardous food contact chemicals contributes to the prevention of associated chronic diseases in the human population.

Overview of known plastic packaging-associated chemicals and their hazards.

Global plastics production has reached 380 million metric tons in 2015, with around 40% used for packaging. Plastic packaging is diverse and made of multiple polymers and numerous additives, along with other components, such as adhesives or coatings. Further, packaging can contain residues from substances used during manufacturing, such as solvents, along with non-intentionally added substances (NIAS), such as impurities, oligomers, or degradation products. To characterize risks from chemicals potentially released during manufacturing, use, disposal, and/or recycling of packaging, comprehensive information on all chemicals involved is needed. Here, we present a database of Chemicals associated with Plastic Packaging (CPPdb), which includes chemicals used during manufacturing and/or present in final packaging articles. The CPPdb lists 906 chemicals likely associated with plastic packaging and 3377 substances that are possibly associated. Of the 906 chemicals likely associated with plastic packaging, 63 rank highest for human health hazards and 68 for environmental hazards according to the harmonized hazard classifications assigned by the European Chemicals Agency within the Classification, Labeling and Packaging (CLP) regulation implementing the United Nations' Globally Harmonized System (GHS). Further, 7 of the 906 substances are classified in the European Union as persistent, bioaccumulative, and toxic (PBT), or very persistent, very bioaccumulative (vPvB), and 15 as endocrine disrupting chemicals (EDC). Thirty-four of the 906 chemicals are also recognized as EDC or potential EDC in the recent EDC report by the United Nations Environment Programme. The identified hazardous chemicals are used in plastics as monomers, intermediates, solvents, surfactants, plasticizers, stabilizers, biocides, flame retardants, accelerators, and colorants, among other functions. Our work was challenged by a lack of transparency and incompleteness of publicly available information on both the use and toxicity of numerous substances. The most hazardous chemicals identified here should be assessed in detail as potential candidates for substitution.

Kinetics and stereochemistry of LinB-catalyzed δ-HBCD transformation: Comparison of in vitro and in silico results.

LinB is a haloalkane dehalogenase found in Sphingobium indicum B90A, an aerobic bacterium isolated from contaminated soils of hexachlorocyclohexane (HCH) dumpsites. We showed that this enzyme also converts hexabromocyclododecanes (HBCDs). Here we give new insights in the kinetics and stereochemistry of the enzymatic transformation of δ-HBCD, which resulted in the formation of two pentabromocyclododecanols (PBCDols) as first- (P1δ, P2δ) and two tetrabromocyclododecadiols (TBCDdiols) as second-generation products (T1δ, T2δ). Enzymatic transformations of δ-HBCD, α1-PBCDol, one of the transformation products, and α2-PBCDol, its enantiomer, were studied and modeled with Michaelis-Menten (MM) kinetics. Respective MM-parameters KM, vmax, kcat/KM indicated that δ-HBCD is the best LinB substrate followed by α2- and α1-PBCDol. The stereochemistry of these transformations was modeled in silico, investigating respective enzyme-substrate (ES) and enzyme-product (EP) complexes. One of the four predicted ES-complexes led to the PBCDol product P1δ, identical to α2-PBCDol with the 1R,2R,5S,6R,9R,10S-configuration. An SN2-like substitution of bromine at C6 of δ-HBCD by Asp-108 of LinB and subsequent hydrolysis of the alkyl-enzyme led to α2-PBCDol. Modeling results further indicate that backside attacks at C1, C9 and C10 are reasonable too, selectively binding leaving bromide ions in a halide pocket found in LinB. Docking with α2-PBCDol, also allowed productive enzyme binding. A TBCD-1,5-diol with the 1S,2S,5R,6R,9S,10R-configuration is the predicted second-generation product T1δ. In conclusion, in vitro- and in silico findings now allow a detailed description of step-wise enzymatic dehalohydroxylation reactions of δ-HBCD to specific PBCDols and TBCDdiols at Å-resolution and predictions of their stereochemistry.

Scientific Challenges in the Risk Assessment of Food Contact Materials.

BACKGROUND: Food contact articles (FCAs) are manufactured from food contact materials (FCMs) that include plastics, paper, metal, glass, and printing inks. Chemicals can migrate from FCAs into food during storage, processing, and transportation. Food contact materials' safety is evaluated using chemical risk assessment (RA). Several challenges to the RA of FCAs exist. OBJECTIVES: We review regulatory requirements for RA of FCMs in the United States and Europe, identify gaps in RA, and highlight opportunities for improving the protection of public health. We intend to initiate a discussion in the wider scientific community to enhance the safety of food contact articles. DISCUSSION: Based on our evaluation of the evidence, we conclude that current regulations are insufficient for addressing chemical exposures from FCAs. RA currently focuses on monomers and additives used in the manufacture of products, but it does not cover all substances formed in the production processes. Several factors hamper effective RA for many FCMs, including a lack of information on chemical identity, inadequate assessment of hazardous properties, and missing exposure data. Companies make decisions about the safety of some food contact chemicals (FCCs) without review by public authorities. Some chemical migration limits cannot be enforced because analytical standards are unavailable. CONCLUSION: We think that exposures to hazardous substances migrating from FCAs require more attention. We recommend a) limiting the number and types of chemicals authorized for manufacture and b) developing novel approaches for assessing the safety of chemicals in FCAs, including unidentified chemicals that form during or after production. https://doi.org/10.1289/EHP644.

Food contact materials and gut health: Implications for toxicity assessment and relevance of high molecular weight migrants.

Gut health is determined by an intact epithelial barrier and balanced gut microbiota, both involved in the regulation of immune responses in the gut. Disruption of this system contributes to the etiology of various non-communicable diseases, including intestinal, metabolic, and autoimmune disorders. Studies suggest that some direct food additives, but also some food contaminants, such as pesticide residues and substances migrating from food contact materials (FCMs), may adversely affect the gut barrier or gut microbiota. Here, we focus on gut-related effects of FCM-relevant substances (e.g. surfactants, N-ring containing substances, nanoparticles, and antimicrobials) and show that gut health is an underappreciated target in the toxicity assessment of FCMs. Understanding FCMs' impact on gut health requires more attention to ensure safety and prevent gut-related chronic diseases. Our review further points to the existence of large population subgroups with an increased intestinal permeability; this may lead to higher uptake of compounds of not only low (<1000 Da) but also high (>1000 Da) molecular weight. We discuss the potential toxicological relevance of high molecular weight compounds in the gut and suggest that the scientific justification for the application of a molecular weight-based cut-off in risk assessment of FCMs should be reevaluated.

Biotransformation of hexabromocyclododecanes with hexachlorocyclohexane-transforming Sphingobium chinhatense strain IP26.

Bacterial evolution has resulted in the appearance of several Sphingomonadacea strains that gained the ability to metabolize hexachlorocyclohexanes (HCHs). HCHs have been widely used as pesticides but were banned under the Stockholm Convention on persistent organic pollutants (POPs) in 2009. Here we present evidence for bacterial transformation reactions of hexabromocyclododecanes (HBCDs), which are structurally related to HCHs. HBCDs were used as flame retardants. They are now also considered as POPs and their production and use is restricted since 2013. Racemic α-, ß-, and γ-HBCDs and their mixture were exposed to Sphingobium chinhatense IP26 in resting cell assays in parallel to ß-HCH. All HBCD stereoisomers were converted with (-)ß-HBCD being the best and both α-HBCD enantiomers the poorest substrates. HBCD conversion rates were 27-430 times slower than that of ß-HCH. Three generations of hydroxylated transformation products were observed, 7 pentabromocyclododecanol isomers (PeBCD-ols), 11 tetrabromocyclododecadiols (TeBCD-diols) and 3 tribromocyclododecatriols (TrBCD-triols). The conversion of (+)α-, (-)ß- and (-)γ-HBCD was faster than those of their enantiomers. Therefore the respective enantiomeric excess increased to 3 ± 1%, 36 ± 1% and 6 ± 2% during 48 h of bacterial exposure. PeBCD-ols appeared first, followed by TeBCD-diols and TrBCD-triols indicating stepwise hydrolytic dehalogenation reactions. In conclusion, severe HCH pollution at geographically distinct dumpsites triggered bacterial evolution to express enzymes transforming such compounds. We used S. chinhatense IP26 bacteria to transform structurally related HBCDs, also regulated under the Stockholm Convention. Such bacteria might be useful for bioremediation but the toxicity of the numerous transformation products observed must be assessed in advance.

Laboratory and field scale bioremediation of hexachlorocyclohexane (HCH) contaminated soils by means of bioaugmentation and biostimulation.

Hexachlorocyclohexane (HCH) contaminated soils were treated for a period of up to 64 days in situ (HCH dumpsite, Lucknow) and ex situ (University of Delhi) in line with three bioremediation approaches. The first approach, biostimulation, involved addition of ammonium phosphate and molasses, while the second approach, bioaugmentation, involved addition of a microbial consortium consisting of a group of HCH-degrading sphingomonads that were isolated from HCH contaminated sites. The third approach involved a combination of biostimulation and bioaugmentation. The efficiency of the consortium was investigated in laboratory scale experiments, in a pot scale study, and in a full-scale field trial. It turned out that the approach of combining biostimulation and bioaugmentation was most effective in achieving reduction in the levels of α- and ß-HCH and that the application of a bacterial consortium as compared to the action of a single HCH-degrading bacterial strain was more successful. Although further degradation of ß- and δ-tetrachlorocyclohexane-1,4-diol, the terminal metabolites of ß- and δ-HCH, respectively, did not occur by the strains comprising the consortium, these metabolites turned out to be less toxic than the parental HCH isomers.

Stereochemistry of enzymatic transformations of (+)ß- and (-)ß-HBCD with LinA2--a HCH-degrading bacterial enzyme of Sphingobium indicum B90A.

LinA2, a bacterial enzyme expressed in various Sphingomonadaceae, catalyzes the elimination of HCl from hexachlorocyclohexanes (HCHs) and, as discussed here, the release of HBr from certain hexabromocyclododecanes (HBCDs). Both classes of compounds are persistent organic pollutants now regulated under the Stockholm Convention. LinA2 selectively catalyzes the transformation of ß-HBCDs; other stereoisomers like α-, γ-, and δ-HBCDs are not converted. The transformation of (-)ß-HBCD is considerably faster than that of its enantiomer. Here, we present the XRD crystal structure of 1E,5S,6S,9R,10S-pentabromocyclododecene (PBCDE) and demonstrate that its enantiomer with the 1E,5R,6R,9S,10R-configuration is the only metabolite formed during LinA2-catalyzed dehydrobromination of (-)ß-HBCD. Formation of this product can be rationalized by HBr elimination at C5 and C6. A reasonable enzyme-substrate complex with the catalytic dyad His-73 and Asp-25 approaching the hydrogen at C6 and a cationic pocket of Lys-20, Try-42 and Arg-129 binding the leaving bromine at C5 was found from in silico docking experiments. A second PBCDE of yet unknown configuration was obtained from (+)ß-HBCD. We predicted its stereochemistry to be 1E,5S,6S,9S,10R-PBCDE from docking experiments. The enzyme-substrate complex obtained from LinA2 and an activated conformation of (+)ß-HBCD allows the HBr elimination at C9 and C10 leading to the predicted product. Both modeled enzyme-substrate complexes are in line with 1,2-diaxial HBr eliminations. In conclusion, LinA2, a bacterial enzyme of the HCH-degrading strain Sphingobium indicum B90A was able to stereoselectively convert ß-HBCDs. Configurations of both PBCDE metabolites were predicted by molecular docking experiments and confirmed in one case by XRD data.

Food contact substances and chemicals of concern: a comparison of inventories.

Food contact materials (FCMs) are intended to be in contact with food during production, handling or storage. They are one possible source of food contamination, because chemicals may migrate from the material into the food. More than 6000 FCM substances appear on regulatory or non-regulatory lists. Some of these substances have been linked to chronic diseases, whilst many others lack (sufficient) toxicological evaluation. The aim of this study was the identification of known FCM substances that are also considered to be chemicals of concern (COCs). The investigation was based on the following three FCM lists: (1) the 2013 Pew Charitable Trusts database of direct and indirect food additives legally used in the United States (or Pew for short), (2) the current European Union-wide positive list for plastic FCMs (or Union for short), and (3) the 2011 non-plastics FCM substances database published by EFSA (or ESCO for short). These three lists of food contact substances (Pew, Union, ESCO lists) were compared with the Substitute It Now! (SIN) list 2.1, which includes chemicals fulfilling the criteria listed in article 57 of Regulation (EC) No. 1907/2006 (REACH), and the TEDX database on endocrine-disrupting chemicals. A total of 175 chemicals used in FCMs were identified as COCs. Fifty-four substances present on the SIN list 2.1 were also found on the Union and/or ESCO lists. Twenty-one of those 54 substances are candidates for Substances of Very High Concern (SVHC), and six of these 21 are listed on Annex XIV and intended for phase-out under REACH. In conclusion, COCs used in FCMs were identified and information about their applications, regulatory status and potential hazards was included.