The 2022 world health organization reevaluation of human and mammalian toxic equivalency factors for polychlorinated dioxins, dibenzofurans and biphenyls

Regulation of in vitro human hematopoietic differentiation by dioxin-like compounds

Certain dioxin-like compounds (DLCs) pose health concerns. However, their impact on human hematopoiesis has not been explored. Role of 2,3,4,7,8-pentachlorodibenzofuran (PeCDF), 3,4,4',5-tetrachlorobiphenyl (PCB81), and 3,3',4,4',5-pentachlorobiphenyl (PCB126) in lineage specification from human cord-blood derived CD34+ hematopoietic stem and progenitor cells (HSPCs) was investigated. We compared these DLCs in relation to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Over a 28-day period, HSPCs were cultured in vitro in the presence of TCDD and DLCs at concentrations ranging from 0.1 to 50 nM. Cells were collected every 7 days for analysis. TCDD, PeCDF, PCB-126, and PCB-81 reduced percentage of CD10+ lymphoid progenitors and CD10 protein expression in a concentration-dependent manner. PeCDF was more potent than TCDD, and PCB81 had higher potency than PCB126. TCDD and PeCDF also induced reduction in CD34 expressing cells and CD1c+ dendritic cells, and an increase in promyelocytes at multiple time-points. These changes were mediated through the aryl hydrocarbon receptor (AHR). With increasing concentrations of TCDD and PeCDF, there was a trend towards decreases in CD41+ megakaryocyte progenitors and increases in CD14+ monocytes. This study demonstrated that these DLCs altered human HSPC differentiation process towards specific myeloid hematopoietic lineages at the expense of lymphoid progenitors, similar to TCDD, which may lead to reduced immune competence. Lineages that were most sensitive to developmental modulation by DLCs were identified. Interestingly, the relative potency of these DLCs in eliciting these effects in humans was different from the compounds' relative toxicological profiles as reported in murine studies, with important implications for human risk assessment for these compounds.

PCDD/Fs in human tissues: A review of global biomonitoring data

This review investigates the concentrations of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in internal human organs and tissues - excluding blood - with a particular focus on adipose tissue studies conducted worldwide up to January 2025. A thorough analysis of published literature highlights significant geographical and temporal trends in human PCDD/F exposure, including potential associations between PCDD/F levels and various health conditions. Several research gaps are identified, and proposals for future studies are given. Studies from Europe, Asia, and North America demonstrated a general decline in tissue PCDD/F concentrations over recent decades, particularly from the 1970s to early 2000s, attributed to successful emission control measures. Adipose tissue PCDD/F levels were typically higher in industrialized regions, with occupational exposure studies showing significantly elevated concentrations compared to the general population. Notable regional variations were observed, with some Asian countries continuing to show relatively high PCDD/F levels despite the overall declining trend. The review also highlighted potential associations between PCDD/F exposure and various health conditions, including endometriosis and cryptorchidism, though causal relationships remain unclear. Physiologically Based Pharmacokinetic (PBPK) modeling studies estimate valuable insights into the distribution and accumulation of these compounds in human tissues. Research gaps identified include limited data from developing countries and other underrepresented regions. It is also important to acknowledge the variability in analytical methods and reporting units across the reviewed studies, which may complicate direct comparisons of results. This review emphasizes the importance of continued biomonitoring efforts, particularly in underrepresented regions, to track exposure trends and protect vulnerable populations.

Contributions of the joint FAO/WHO expert committee on food additives to international food safety: celebrating the 100th meeting of the committee

The Joint FAO/WHO Expert Committee on Food Additives (JECFA) is an international scientific committee that carries out safety and risk assessments on substances that are intended to be added to food or may be present in food. It advises the Codex Alimentarius Commission and the member countries of the Food and Agricultural Organization and the World Health Organization. In 2025, JECFA has its 100th meeting. This paper reviews the work of JECFA since its inception in 1956. The Committee has evaluated over 660 food additives, 105 enzymes, 2500 flavourings, 11 groups of natural toxicants, 12 metals, 25 groups of synthetic chemical contaminants, and residues of 115 veterinary drugs. The Committee has made major contributions internationally on risk assessment methodology for food safety, including the setting of health-based guidance values for chemicals in food, the evaluation of genotoxic and carcinogenic contaminants in food, benchmark dose analysis, use of body burden comparisons, and global approaches to dietary exposure assessment. JECFA advice is independent and based on objective, state-of-the-science assessment of the evidence. Its advice and evaluations are a freely available online resource and play a pivotal role in ensuring the protection of consumer health and enabling the international trade of safe food.

Phototransformation behavior of octachlorodibenzofuran (OCDF) on the surface of river suspended particulate matter: Kinetics and products formation mechanism

Octachlorodibenzofuran (OCDF) readily adheres to particulate matters in the aqueous environment owing to its strong hydrophobicity. Phototransformation is a key abiotic transformation process for organic pollutants. Here, we systematically investigated the phototransformation behavior of OCDF on the surface of suspended particulate matter (SPM) from the tributary of the Yangtze River. It was found that acidic conditions and the presence of NO3-, Ca2+, and Mg2+ had inhibitory effect on OCDF photodegradation. Through quenching experiments, we discovered that hydroxyl radical (HO•), superoxide anion (O2•-) and singlet oxygen (1O2) all contributed to the removal of OCDF, with HO• and O2•- being the main reactive oxygen species (ROS). A total of ten intermediates were identified using mass spectrometry, and three possible pathways were proposed. Theoretical calculations revealed that 1O2 dominated the dechlorination reaction, HO• was responsible for the generation of ring cleavage products, and both HO• and O2•- participated in the formation of hydroxylated products. Toxicity predictions by the T.E.S.T software showed that the toxicity and bioconcentration factors of intermediates in the photochemical process were reduced, thus decreasing the environmental risk. This research deepened the understanding of the phototransformation behavior of OCDF on the SPM surface, providing a scientific basis for assessing its environmental fate.

Congener-specific transfer modelling of dioxins and dioxin-like PCBs in free-ranging cattle grazing in the Dutch floodplains

Cattle grazing in the Dutch floodplains are exposed to polychlorinated dibenzo-p-dioxins and dibenzofurans (dioxins) and dioxin-like PCBs (dl-PCBs) through the consumption of grass and adhering soil. This can lead to elevated dioxin and dl-PCB levels in meat fat. To manage this contamination issue, the kinetics of these compounds in cattle need to be better understood. This study describes the development and application of a physiologically based kinetic (PBK) model to predict dioxin and dl-PCB levels in muscle fat of 'Rode Geus' cattle based on measured levels in grass and soil. Calibration of the model was performed separately for each congener, using measured dioxin and dl-PCB levels in various tissues of 14 animals. Model validation performed using dioxin and dl-PCB samples of 14 other cattle, showed that PBK model predictions were on average a factor 2.4 higher than the measured dioxin and dl-PCB TEQ levels in fat. Despite this difference, the model may still be particularly useful to better understand the relation between environmental dioxin and dl-PCB levels and those in cattle. The model is publicly available with a user-friendly interface on www.feedfoodtransfer.nl and may provide relevant insights for risk assessment and risk management.

Dioxin-like polychlorinated biphenyls (dl-PCB) in hydrochars and biochars: Review of recent evidence, pollution levels, critical gaps, formation mechanisms and regulations

Contamination of chars with dioxin-like polychlorinated biphenyls (dl-PCB) significantly limits their use and hinders their deployment in the circular bioeconomy, specifically in applications that may lead to dietary exposure. Here, for the first time, we review the levels of contamination of chars produced from pyrolysis and hydrothermal carbonisation (HTC) with dl-PCB congeners. We conduct a detailed and critical examination of the role played by the processing parameters, such as temperature and residence time, and the reaction mechanisms, to detoxify the biomass under an oxygen-free atmosphere during its valorisation. The PCB-based toxicity of biomass depends mostly on the abundance of dl-PCB in the raw material, and on the dechlorination and other transformation processes that operate during the treatment. The key dechlorination steps make the toxicity of hydrochars pass through a maximum with increasing treatment time, whereas the toxicity of biochars in pyrolysis decreases monotonically. Pyrolysis displays more complex mechanistic pathways of volatilisation, dechlorination, degradation of PCB rings, minor de novo formation of dl-PCB in case of air leaks, and concentrating persistent organic pollutants (POP) in char matrices. In contrast, the mechanisms responsible for the evolution of toxicity in HTC processes comprise the dechlorination, possible chlorine position shift, and biomass densification. The kinetic model developed in this review affords insight into the evolution of the hydrochar toxicity that depends on process temperature and treatment time. The dl-PCB concentrations in treated biomass generally range from 1.06 ng WHO2005-TEQ (kg DM)-1 to 11.7 ng WHO2005-TEQ (kg DM)-1, whereas for biochars produced from contaminated sediments the toxicity varies from 0.00662 ng WHO1998-TEQ (kg DM)-1 to 1.42 ng WHO1998-TEQ (kg DM)-1. DM stands for dry matter, TEQ for toxic equivalency, and WHO1998 means the application of the toxic equivalency factors (TEF) set by the World Health Organization (WHO) in 1998 to calculate the TEQ. Finally, we identify the crucial gaps in the literature, review the regulations governing the use of biomass in feed and in the environment, and provide suggestions for future research. The findings in this article provide both the technical understanding of how to minimise the formation of dl-PCB in the production of chars and suggest modifications to the current guidelines. The latter will increase the consumer's trust in valorised biomass, leading to its wider acceptance in the circular bioeconomy as feed supplements and soil additives.

Exposome Burden Scores to Summarize Environmental Chemical Mixtures: Creating a Fair and Common Scale for Cross-study Harmonization, Report-back and Precision Environmental Health

PURPOSE OF REVIEW

Environmental health researchers are increasingly concerned about characterizing exposure to environmental chemical mixtures (co-exposure to multiple chemicals simultaneously). We discuss approaches for quantifying an overall summary score or index that reflects an individual's total exposure burden to components of the mixture. We focus on unsupervised methods, in which the summary score is not computed in relation to a pre-specified health outcome.

RECENT FINDINGS

Sum-scores and principal components analysis (PCA) are common approaches for quantifying a total exposure burden metric but have several limitations: 1) they require imputation when using exposure biomarkers with high frequency of non-detection, 2) they do not account for exposure heterogeneity, 3) sum-scores assume the same measurement error for all people, while there is no error term inherent to the PCA model as its primary purpose is dimension reduction, and 4) in pooled analyses, both approaches are limited to analyzing the set of exposure variables that are in common across all studies, potentially discarding valuable information. Meanwhile, item response theory (IRT) is a novel and promising alternative to calculate an exposure burden score that addresses the above limitations. It allows for the inclusion of exposure analytes with high frequency of non-detects without the need for imputation. It can account for exposure heterogeneity to calculate fair metrics for all people, through assessment of differential item functioning and mixture IRT. IRT also quantifies measurement errors of the exposure burden score that are individual-specific, such that it appropriately assigns a larger standard error to an individual who has missing data on one or more exposure variables. Lastly, IRT enhances cross-study harmonization by enabling the creation of exposure burden calculators to set a common scale across studies, and allows for the inclusion of all exposure variables within a chemical class, even if they were only measured in a subset of participants. Summarizing total exposure burden, through the creation of fair and informative index scores, is a promising tool for environmental health research as environmental exposures are increasingly used for biomonitoring and clinical recommendations.

Polychlorinated dibenzo-dioxin/furan and polychlorinated biphenyl concentrations in the human milk of individuals living near municipal waste incinerators in the UK: Findings from the Breast milk, Environment, Early-life, and development (BEED) human biomonitoring study

The objective of this study is to report recent PCDD/F and PCB human milk concentrations in the United Kingdom (UK) and relate these to two proxies for exposure to municipal waste incinerator (MWI) emissions. As part of the Breast milk, Environment, Early-life, and Development (BEED) study, primiparous individuals were recruited from within 20 km of English MWIs between 2013 and 2015 and asked to provide human milk samples. The samples were analysed for quantitative concentrations of 17 PCDD/F and 12 PCB congeners. Linear regression models were used to investigate the association between two proxy measurements for exposure to MWI emissions: (i) log average modelled daily ground-level PM10 from MWIs (modelled PM10) and (ii) residential proximity to nearest MWI and the toxic equivalents (TEQs), ∑TEQ2005-PCDD, ∑TEQ2005-PCB and ∑TEQ2005-PCDD/F + PCB. Samples from 194 participants were analysed for PCDD/Fs and 150 for PCBs. Overall ∑TEQ2005-PCDD/F + PCBs ranged from 1.76 to 25.1 pg/g lipid with a geometric mean of 5.81 (Geometric standard deviation: 1.64). A doubling in modelled PM10 was significantly associated with an average increase of 9.71% (95% CI: 2.91%-16.5%) in ∑TEQ2005-PCDD/Fs + PCB, 9.14% (95% CI: 1.79%-16.5%) in ∑TEQ2005-PCDD/Fs and 9.02% (CI:1.57%-16.5%) in ∑TEQ2005-PCBs. MWI proximity was not associated with an increase of ∑TEQ2005-PCDD/Fs, ∑TEQ2005-PCBs, or ∑TEQ2005-PCDD/Fs + PCBs. The results from this study suggest that MWI emissions may make a small contribution to the body burden of toxic PCDD/F and PCB mixtures. Enhanced environmental monitoring and human biomonitoring of PCDD/Fs and PCBs near MWIs would be needed to investigate this further.

Environmental contamination with dioxins: experience of ecotoxicity survey and assessment using wild mammalian model (bank vole C. glareolus) inhabiting forests outside sanitary zones of municipal waste landfills

Dioxins are known to be toxic for biota at every dose and their long-term effects are reported for almost 50 years of investigations. Our researches of dioxin accumulation by bank voles living in the vicinity of several landfills near Moscow (landfills "Lesnaya" and "Kouchino") demonstrated the similarity of dioxin profiles in soil and animal samples, and an increase of highly toxic congeners' concentrations in the bank voles' bodies. We investigated also the probable public cancer risk resulting from the comparable lifetime exposure of the voles' population with dioxins' low doses, and our evaluation verified the hazard of cancer development supported by alterations in the ahr gene expression in the liver cells. The results of this study determined the usefulness of calculating the probability of cancer development in hypothetical residents of the area around both landfills. For the landfill "Lesnaya," the values corresponded to the level acceptable for professional groups (3.72E-04), but unacceptable for the population, whereas for residents of the area in the vicinity of the landfill "Kouchino," the level was considered to be unacceptable (1.91E-03) neither for the population nor for the professional groups. The revealed ecotoxicological situation may be quite hazardous for the population living in the area contaminated with dioxins, and the human health risks should be assessed. Thus, the prospects of the initial public health screening should consider our set of techniques used, as the effects described permit taking into account the mechanisms of interaction between the environmental factors and those determined by the characteristics of population real exposure.

Historically Polluted Area Increases Human Exposure Risks to Polychlorinated Naphthalenes through Waterfowl Egg Consumption

Polychlorinated naphthalenes (PCNs), which are ubiquitous in the environment, are listed as persistent organic pollutants under the Stockholm Convention. Poultry can be exposed to PCNs via feed and breeding environments, leading to PCNs accumulation in eggs. However, information on PCNs in eggs from waterfowl raised in contaminated regions is scarce. In this study, waterfowl and chicken eggs were collected from a historically polluted area in Hunan Province, China. In addition, waterfowl eggs were collected from Guangxi Province as a control. The mean concentrations of Σ75PCNs in waterfowl (30.8 pg/g wet weight [ww]) and chicken eggs (26.1 pg/g ww) from Hunan were significantly higher than in waterfowl eggs (15.6 pg/g ww) from Guangxi. The PCN homologue profiles in poultry eggs from the two regions varied, but both were dominated by lower chlorinated CNs. Correlation analysis showed that breeding environment made a greater contribution to PCNs in waterfowl eggs. Interestingly, PCNs and polychlorinated biphenyls (PCBs) showed a significant positive correlation in samples from Hunan, but not in those from Guangxi. Human exposure to PCNs and PCBs was higher through consumption of poultry eggs from historically contaminated areas.

Sources of polychlorinated dibenzo-p-dioxins and -furans to sediment in the Newtown Creek Superfund Site

Polychlorinated dibenzo-p-dioxins and -furans (PCDD/Fs) are contaminants of concern in the New York/New Jersey Harbor and in the organisms of the Newtown Creek Superfund site, which lies within the harbor. Because PCDD/Fs are never intentionally produced, identifying their sources can be challenging. In this work, sources of PCDD/Fs to the sediment of Newtown Creek were investigated using Positive Matrix Factorization (PMF) to analyze two data sets containing data on concentrations of (1) PCDD/Fs and (2) PCDD/Fs plus polychlorinated biphenyls (PCBs). The PCDD/F data set generated eight factors, but they were not particularly helpful in identifying PCDD/F sources. The combined PCDD/F plus PCB data set generated eleven factors, many of which represented Aroclors. Based on its spatial distribution, the primary source of PCDD/F-related Toxic Equivalency Quotient (TEQ) in the sediment (accounting for 53 % of total TEQ) may be related to a facility that performed smelting and refining of metals (primarily copper). Aroclors appear to be responsible for about 20 % of the total TEQ. This analysis revealed two additional secondary sources of PCDD/Fs to Newtown Creek sediment: the East River (3 % of TEQ) and Combined Sewer Outfalls (CSOs; 0.5 % of TEQ). The East River was responsible for most of the mass of 2,3,7,8-tetrachloro dibenzo-p-dioxin (TCDD) in the sediment, presumably because it transports TCDD-laden sediment from the Passaic River into Newtown Creek. CSOs were proportionately more important in surface sediments. Adding PCBs to the data matrix appears to increase ability of the PMF analysis to identify both primary (Aroclors) and secondary (CSOs, East River) PCDD/F sources, but it is unclear whether it may overstate the fraction of PCDD/Fs arising from Aroclors.

Spatial patterns, source apportionment, and risk assessment of polychlorinated biphenyls (PCBs) in the surface sediments of eastern China lakes along a latitudinal gradient: Insights guided by full-congener analysis

Understanding the occurrence, sources, and ecological risks of polychlorinated biphenyls (PCBs), which are universal persistent organic pollutants, is critical for improving the sustainability and ecological safety of lake systems. Herein, to determine PCB contamination levels and formulate control strategies in lake sediments, 210 sediment samples were collected from 21 lakes along a latitudinal gradient (18-45°N, ∼3000 km) across eastern China and were analyzed for all 209 PCB congeners. The results showed that the total PCB concentration varied greatly from 0.26 to 163.82 ng/g dry weight and exhibited a latitudinal trend of central > north/south. Spatial variations were affected mainly by the organic carbon fraction and local population density. Most lakes had similar PCB profiles, with lower chlorinated PCBs dominating. Notably, non-Aroclor PCB 11 was the most abundant congener. Moreover, unintentionally produced PCBs (UP-PCBs) accounted for ∼31 % of all PCBs. These findings highlight that the significance of UP-PCBs has been overlooked in past studies and that full-congener analysis is necessary for future monitoring. According to the ecological risk assessment of PCBs, zero to moderate risk existed in lake sediments. Therefore, effective strategies are needed to mitigate the impact of PCBs (especially UP-PCBs) from multiple sources on lakes.

Comprehensive model for predicting toxic equivalents (TEQ) reduction due to dechlorination of polychlorinated dibenzo-p-dioxin and dibenzofurans (PCDD/F congeners)

Remediation-focused predictive tools for polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) rely on transformation models to evaluate the reduction in total contaminant load and toxic equivalency (TEQ). In this study, a comprehensive model predicting the profiles of PCDD/F congeners and the associated TEQs was developed. The model employs first-order kinetics to describe the transformation of 256 reactions for 75 PCDD congeners and 421 reactions for 135 PCDF congeners. It integrates the growth of anaerobic microbial guilds using Monod kinetics on hydrogen release compounds and stoichiometric growth for Dehalococcoides sp. The effects of temperature, salinity, pH, and availability of vitamin B12 (a cofactor) were also integrated. The PCDD/F congeners model was used to extract the first-order dechlorination rate constants from a number of pure culture and mixed microbial microcosm studies. Simulations for the transformation of PCDD/F congeners at concentrations representative of the Tittabawassee or Saginaw Rivers and watershed in MI, USA were carried out. For a starting TEQ of 5000 ng per kg dry sediment (ppt), the model predicted a decrease in the overall TEQ to below 2000 ppt after 2.6 years and below 250 ppt after ∼21 years. The developed model may be used for extracting rates from microcosm studies and to evaluate the effect of engineering interventions on TEQ reduction.

Multi-media environmental fate of polychlorinated dibenzo-p-dioxins and dibenzofurans in China: A systematic review of emissions, presence, transport modeling and health risks

Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) are notorious persistent organic pollutants (POPs) with proven toxicity to human and ecosystems. This review critically evaluates existing research, emphasizing knowledge gaps regarding PCDD/F emissions, environmental behavior, human exposure, and associated risks in China. The current emission inventory of PCDD/Fs in China remains highly uncertain, both in terms of total emissions and emission trends. Moreover, existing monitoring data primarily focus on areas near pollution sources, limiting comprehensive understanding of the overall spatiotemporal characteristics of PCDD/F pollution. To address this, we propose a novel approach that integrates the Multi-media Urban Mode (MUM) model with an atmospheric chemical transport model that includes a dual adsorption model to capture gas-particle partitioning of PCDD/Fs in the atmosphere. This coupled model can simulate the transport and fate of PCDD/Fs in multi-media environments with high spatiotemporal resolution, facilitating a nuanced understanding of the impacts of emissions, climate, urbanization and other factors on PCDD/F pollution. Additionally, dietary ingestion, particularly from animal-derived foods, is identified as the predominant source (up to 98%) of human exposure to PCDD/Fs. While the changes in dietary structure, population distribution, and age structure can influence human exposure to PCDD/Fs, their impacts have not yet been quantified. The proposed model lays the foundation for a systematic assessment of health risks from PCDD/F exposure through various pathways by further incorporating a food chain model. Overall, this review offers a comprehensive strategy for assessing PCDD/F pollution, encompassing the entire continuum from emissions to environmental impacts.

Investigation of the effect of chlorine in different additives on dioxin formation during high temperature processing of iron ore

Ironmaking can have an important role in the circular economy by utilising alternative carbon bearing materials, which are otherwise of low value in use or landfilled. Biomass and plastic wastes have been proposed as alternatives for coke and coal in sintering, blast furnace ironmaking and direct iron ore reduction processes. However, introduction of the alternative carbon sources with higher chlorine contents may influence the formation of some pollutants, most notably, dioxins. This study investigated the effects of carbon bearing materials, i.e., coke, biomass and polyvinyl chloride (PVC), on formation of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs) during high temperature processing of iron ore. The effect of copper (Cu) as a known dioxin synthesis catalyst, on formation of the dioxins was also investigated. The study found an exponential increasing relationship between the chlorine content in the fuel source and the dioxin emissions. The addition of both biomass and PVC materials contributed to significantly increased dioxin formation, especially for the case of plastics. PCBs had higher concentrations than PCDD/Fs in all cases except when CuCl2 was added due to its catalytic properties to synthesise PCDD/Fs. PCDF concentrations far outweighed the PCDDs, suggesting that de novo reaction mechanism, where carbon particles are oxidised by a transition metal in presence of chlorine, dominated the formation of the dioxins in the process.

Emission characteristics and process distributions of multiple brominated persistent organic pollutants during co-disposal of hexabromocyclododecane-containing waste in a municipal solid waste incinerator

Co-disposal of hexabromocyclododecane (HBCD)-containing waste during municipal solid waste incineration (MSWI) was conducted, achieving a destruction efficiency exceeding 99.999%. Simultaneous determination of HBCD, polybrominated diphenyl ethers (PBDEs) and polybrominated dibenzo-p-dioxins and dibenzofurans (PBDD/Fs) at multiple stages of a MSWI plant was performed. This aimed to clarify their concentration and congener variations along the flue, with the goal of elucidating their formation mechanisms and control. This study confirmed that HBCD was present in daily MSW, and that PBDEs and PBDD/Fs can be unintentionally produced. The average mass emission factors of HBCD, PBDEs, and PBDD/Fs from stack gas were 6.4 ± 5.0, 98.8 ± 4.6, and 2.8 ± 1.7 μg t-1, respectively. HBCD and PBDEs were much higher in slag, raising concerns about the secondary release of brominated pollutants during the reprocessing or reuse of incinerator slag. The concentrations of PBDEs and PBDD/Fs increased after the air pollution control devices, largely due to the "memory effect", with regenerated PBDD/Fs being mainly high-brominated homologs. The disposal of HBCD increased PBDEs concentration and altered PBDD/F homolog distribution. Possible formation pathways of PBDEs and PBDD/Fs from HBCD were proposed. HBCD could degraded into brominated short-chain hydrocarbons and aromatic fragments, which may promote the formation of PBDEs and PBDD/Fs.

Polychlorinated dibenzo-p-dioxin and dibenzofuran contamination of free-range eggs: estimation of the laying hen's soil ingestion based on a toxicokinetic model, and human consumption recommendations

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) are ubiquitous in the environment. The main route of human exposure is through food consumption. Soil contamination can be problematic for sanitary safety depending on the usage of the soil, such as farming. In case of environmental soil contamination with PCDD/Fs, hen's eggs may be contaminated due to soil ingestion by hens. For this reason, it is important to understand the parameters that influence eggs' contamination when hens are raised in contaminated areas. After the discovery of a contaminated area in Lausanne (Switzerland), we collected hens' eggs from ten domestic-produced eggs and one farm. Based on PCDD/F measurements of eggs and soil, and a toxicokinetic model, we estimated individual hen's soil intake levels and highlighted appropriate parameters to predict the dose ingested. Recommended weekly consumption for home-produced eggs was calculated based on the tolerable weekly intake proposed by EFSA in 2018. The most important parameter to assess the soil ingestion does not seem to be the soil coverage by vegetation but rather the hen's pecking behaviour, the latter being difficult to estimate objectively. For this reason, we recommend using a realistic soil ingestion interval to assess the distribution of egg PCDD/F concentration from free-range hens reared on contaminated soil. The addition of soil contamination in the toxicokinetic model can then be used to recommend to the general population weekly consumption of eggs. The consumption by adults of free-range eggs produced on land with soil containing >90 ng toxic-equivalent (TEQ)/kg dry soil should be avoided. Even with a low level of soil contamination (1-5 ng TEQ/kg dry soil), we would recommend consuming not more than 5 eggs per week for adults and no more than 2 eggs for children below 4 years old.

Uptake, Elimination and Metabolism of Brominated Dibenzofurans in Mice

Polybrominated dibenzofurans (PBDFs) are major brominated dioxins in the environment, but information on their bioaccumulation potential and toxicokinetics is limited. This study conducted oral exposure experiments with C57BL/6J mice to investigate the uptake ratios, distribution in the liver, plasma and brain, metabolism, and elimination kinetics of four bromine/chlorine-substituted dibenzofurans (TrBDF: 2,3,8-tribromo, TeBDF: 2,3,7,8-tetrabromo, PeBDF: 1,2,3,7,8-pentabromo, TrBCDF: 2,3,7-tribromo-8-chloro) in comparison with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). The hepatic uptake ratios of 2,3,7,8-substituted dibenzofurans were lower than that of TCDD (up to 84% of the administered doses) and decreased with the number of Br substitutions (42%, 33%, and 29% for TrBCDF, TeBDF, and PeBDF, respectively). The brain uptake ratios of these dibenzofurans were less than 0.05%, and the plasma-to-brain transfer ratio also decreased with the Br number. All 2,3,7,8-substituted compounds were eliminated from the liver following first-order kinetics, with half-times in the order of TrBCDF (5.6 days) < TeBDF (8.8 days) ≈ TCDD (8.7 days) < PeBDF (13 days). The non-2,3,7,8-substituted TrBDF was poorly retained in the liver (<0.01% of the dose at 1 day) and rapidly eliminated following two-phase kinetics. All dibenzofurans were metabolised into monohydroxylated products in the liver, but the contribution of this metabolic pathway to hepatic elimination was only significant for TrBDF. As the toxic effects of dioxin-like compounds are influenced by their biological persistence, the slow elimination of TrBCDF, TeBDF, and PeBDF observed in this study suggests that exposure risk of brominated dibenzofurans may be underestimated using the toxic equivalency factors of the less persistent chlorinated analogues.

Polychlorinated biphenyls in the surface and deep waters of the Southern Indian Ocean and Coastal Antarctica

Polychlorinated biphenyl compounds (PCBs) are industrial chemicals whose production was discontinued in the early nineties in most countries. Sill, PCBs are detectable in pristine and remote locations. Occurrence in regions such as Southern Oceans and Antarctica are influenced by the global, and regional, cycling. Here, we studied the surface and deep ocean distribution of indicator- and dioxin-like PCB congeners in the Southern Indian Ocean (SIO), and the coast of Antarctica (COA) during the tenth Indian Southern Ocean Expedition (SOE-10), December 2017-February 2018. ∑21PCBs in SIO surface waters ranged from 3.8 to 167.1 pg L-1 (average ± standard deviation: 35.7 ± 48.4 pg L-1), and in COA from 1.0 to 41.8 pg L-1 (13.8 ± 12.7 pg L-1), respectively. A noticeable gradient was observed, with higher PCBs levels in northern latitudes than southern latitudes in the SIO, and higher levels in the eastern longitudes compared to western longitudes in the COA. Results suggest the influence of secondary sources, or re-emission, of PCBs in the Southern Oceans and Antarctica. Both regions showed notable PCB levels in surface and deep waters (up to 1000 m) due to ongoing surface sources and remineralization processes in deeper waters. Multimedia modeling with the global model (BETR-Global) suggests the SIO act as a net sink for PCBs in the ocean.

Guidance on risk-benefit assessment of foods

The EFSA Scientific Committee has updated its 2010 Guidance on risk-benefit assessment (RBA) of foods. The update addresses methodological developments and regulatory needs. While it retains the stepwise RBA approach, it provides additional methods for complex assessments, such as multiple chemical hazards and all relevant health effects impacting different population subgroups. The updated guidance includes approaches for systematic identification, prioritisation and selection of hazardous and beneficial food components. It also offers updates relevant to characterising adverse and beneficial effects, such as measures of effect size and dose-response modelling. The guidance expands options for characterising risks and benefits, incorporating variability, uncertainty, severity categorisation and ranking of different (beneficial or adverse) effects. The impact of different types of health effects is assessed qualitatively or quantitatively, depending on the problem formulation, scope of the RBA question and data availability. The integration of risks and benefits often involves value-based judgements and should ideally be performed with the risk-benefit manager. Metrics such as Disability-Adjusted Life Years (DALYs) and Quality-Adjusted Life Years (QALYs) can be used. Additional approaches are presented, such as probability of all relevant effects and/or effects of given severities and their integration using severity weight functions. The update includes practical guidance on reporting results, interpreting outcomes and communicating the outcome of an RBA, considering consumer perspectives and responses to advice.

Atmospheric Concentrations and Potential Sources of Dioxin-Like Contaminants to Acadia National Park

Acadia National Park (ANP) is located on Mt. Desert Island, ME on the U.S. Atlantic coast. ANP is routinely a top-ten most popular National Park with over four million visits in 2022. The overall contribution and negative effects of long-range atmospheric transport and local sources of dioxin-like contaminants endangering natural and wildlife resources is unknown. Dioxin-like (DL) contaminants polychlorinated dibenzo-p-dioxins (∑PCDD) and polychlorinated dibenzofurans (∑PCDF), non-ortho coplanar PCBs (∑CP4), and polychlorinated naphthalenes (∑PCNs) were measured at the McFarland Hill air monitoring station (44.37⁰N, 68.26⁰W). On a mass/volume basis, total PCNs averaged 90.9 % (788 fg/m3) of DL contaminants measured annually, with 92.9 % of the collected total in the vapor-phase. Alternatively, total dioxin/furans (∑PCDD/Fs) represented 71.6 % of the total toxic equivalence (∑TEQ) (1.018 fg-TEQ/m3), with 69.7 % in the particulate-phase. Maximum concentrations measured for individual sampling events for ∑PCDD/F, ∑CP4, and ∑PCN were 159 (winter), 139 (summer), and 2100 (autumn), fg/m3 respectively. Whereas the maximum ∑TEQ concentrations for individual sampling events for ∑PCDD/F, ∑CP4, and ∑PCN were 2.8 (autumn), 0.38 (summer), and 0.71 (autumn), fg-TEQ/m3 respectively. Pearson correlations were calculated for ∑PCDD/Fs and ∑PCN particulate/vapor-phase air concentrations and PM2.5 wood smoke "indicator" species. The most significant correlations were observed in autumn for particulate-phase ∑PCDD/Fs suggesting a relationship between visitation-generated combustion sources (campfires and/or waste burning) or climate-change mediated forest fires. Significant Clausius-Clapeyron (C-C) correlations observed for particulate-phase ∑PCDDs (r2=0.567) as ambient temperatures decreased suggests a connection between localized domestic heating sources or visitor-based burning of wood/trash resources. Alternatively, highly significant C-C vapor-phase ∑CP4-PCBs correlations (r2=0.815) implies that the majority of ∑CP4-PCB loading to ANP is from long-range atmospheric transport processes. Based on these findings, Acadia National Park should be classified as a remote site with minor depositional impacts from ∑PCDD/Fs, ∑CP4-PCBs, and ∑PCN atmospheric transport or local diffuse sources.

PCB169 exposure aggravated the development of non-alcoholic fatty liver in high-fat diet-induced male C57BL/6 mice

Polychlorinated biphenyls (PCBs) are lipophilic environmental toxicants. Epidemiological studies have established a link between PCBs and both metabolic syndrome and nonalcoholic fatty liver disease (NAFLD). Multiple studies have reported that exposure to both PCB156 and PCB126 among the 12 dioxin-like PCBs leads to the development of NAFLD. However, studies to elucidate whether PCB169 induces the development of NAFLD by constructing in vivo models have not been reported. Therefore, we evaluated the effects of exposure to PCB169 (5 mg/kg-bw) on hepatic lipid metabolism in C57BL/6 mice from control diet and high-fat diet cohorts. The results showed that PCB169 exposure reduced body weight and intraperitoneal fat mass in mice on the control diet, but the liver lipid levels were significantly increased, exacerbating NAFLD in mice on a high-fat diet. Through transcriptomics studies, it was found that PCB169 exposure induced significant up-regulation of Pparγ, Fasn, and Aacs genes involved in hepatic lipogenesis, as well as remarkable up-regulation of Hmgcr, Lss, and Sqle genes involved in cholesterol synthesis. Additionally, there was notable down-regulation of Pparα and Cpt1 genes involved in lipid β-oxidation, leading to abnormal lipid accumulation in the liver. In addition, we found that PCB169 exposure significantly activated the Arachidonic acid metabolism, PPAR signaling pathway, Metabolism of xenobiotics by cytochrome P450, and Retinol metabolism pathways, and so on. Our study suggests that PCB169 can modify gene expression related to lipid metabolism, augument lipid accumulation in the liver, and further contribute to the development of NAFLD, thereby revealing the detrimental effects associated with PCB exposure on animal growth and metabolism.

Species differences in specific ligand-binding affinity and activation of AHR: The biological basis for calculation of relative effective potencies and toxic equivalence factors

In 2022 the World Health Organization (WHO) published updated 'Toxic Equivalence Factors' (TEFs) for a wide variety of chlorinated dioxins, dibenzofurans and PCBs [collectively referred to as 'dioxin-like chemicals'; DLCs) that interact with the aryl hydrocarbon receptor (AHR)]. Their update used sophisticated statistical analysis of hundreds of published studies that reported estimation of 'Relative Effective Potency' (REP) values for individual DLC congeners. The weighting scheme used in their assessment of each study favored in vivo over in vitro studies and was based largely on rodent studies. In this Commentary, we highlight the large body of published studies that demonstrate large species differences in AHR-ligand activation and provide supporting evidence for our position that the WHO 2022 TEF values intended for use in human risk assessment of DLC mixtures will provide highly misleading overestimates of 'Toxic Equivalent Quotients' (TEQs), because of well-recognized striking differences in AHR ligand affinities between rodent (rat, mouse) and human. The data reviewed in our Commentary support the position that human tissue-derived estimates of REP/TEF values for individual DLC congeners, although uncertain, will provide much better, more realistic estimates of potential activation of the human AHR, when exposure to complex DLC mixtures occurs.

Persistent Organic Pollutants in Austrian Human Breast Milk Collected between 2013 and 2016

Breast milk holds an immense nutritional value as it contains health-promoting substances in a unique, optimal form. Additionally, breast milk's significance extends to health and environmental protection, as it serves as an indicator of both maternal and infant exposure. In this study, breast milk samples collected in 2013 and in 2014-2016 from mothers in Vienna (Austria) were analysed for polybrominated diphenyl ethers (PBDE) and per- and polyfluoroalkyl substances (PFAS), as well as further substances which have been listed under the Stockholm Convention on Persistent Organic Pollutants (POPs) due to their persistent, bioaccumulative and toxic properties. The total concentration of the PBDE congeners in the samples (n = 18, sampled 2013) ranged from 0.055 to 52 ng/g lipid, and from 0.002 to 2.5 ng/g breast milk. In the pooled sample, the sum of PBDEs was detected at a level of 4.4 ng/g lipid. Based on the 2014-2016 study population, certain PFAS were detected in all samples (n = 40). Exposure to the sum of four specific PFAS including perfluorooctanesulphonate (PFOS), perfluorooctanoic acid (PFOA), perfluoro-n-nonanoic acid (PFNA) and perfluoro-1-hexanesulfonate (PFHxS) ranged between 0.014 and 0.12 ng/L breast milk. In the pooled sample, PFOS and PFOA were found in concentrations of 0.025 ng/g and of 0.045 ng/g, respectively. In addition, the first generation of POPs, mainly organochlorine compounds, was measured in a pooled sample of breast milk from participants sampled in 2014-2016 as part of the WHO/UNEP breast milk monitoring program and compared to the POPs measured in pooled samples collected in 1987/1988 and 1992/1993, respectively. Therefore, this paper demonstrates the effectiveness of the Stockholm Convention on POPs by comparing the Austrian results from the WHO/UNEP global breast milk study from 1987 to 2016. However, the data also show that, despite these reductions, health-relevant levels are still being reached, particularly in terms of children's health when the presence of the new generation of POPs, such as PBDEs and PFAS, in human breast milk is taken into account.