Toxic equivalency factors (TEFs) for PCBs, PCDDs, PCDFs for humans and wildlife

Characterization of medaka (Oryzias latipes) AHRs and the comparison of two model fishes-Medaka vs. zebrafish: The subform-specific sensitivity to dioxin

Dioxins and the emerging dioxin-like compounds (DLCs) have recruited increasing concerns about their environmental contamination, toxicity, health impacts, and mechanisms. Based on the structural similarity of dioxins and many DLCs, their toxicity was predominantly mediated by the dioxin receptor (aryl hydrocarbon receptor, AHR) in animals (including human), which can be different in expression and function among species and then possibly produce the species-specific risk or toxicity. To date, characterizing the AHR of additional species other than human and rodents can increase the accuracy of toxicity/risk evaluation and increase knowledge about AHR biology. As a key model, the medaka AHR has not been clearly characterized. Through genome survey and phylogenetic analysis, we identified four AHRs (olaAHR1a, olaAHR1b, olaAHR2a, and olaAHR2b) and two ARNTs (olaARNT1 and olaARNT2). The medaka AHR pathway was conserved in expression in nine tested tissues, of which olaAHR2a represented the predominant subform with greater abundance. Medaka AHRs and ARNTs were functional and could be efficiently transactivated by the classical dioxin congener 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), although olaAHR1a did not seem to cooperate with olaARNT2. In terms of function/sensitivity, the EC50 values of medaka olaAHR1a (9.01 ± 1.43 nM), olaAHR1b (4.00 ± 1.10 nM), olaAHR2a (8.75 ± 3.34 nM), and olaAHR2b (3.06 ± 0.81 nM) showed slight differences; however, they were all at the nM level. The sensitivity of four medaka AHRs to TCDD was similar to that of zebrafish dreAHR2 (the dominant form, EC50 = 3.14 ± 4.19 nM), but these medaka AHRs were more sensitive than zebrafish dreAHR1b (EC50 = 27.05 ± 18.51 nM). The additional comparison also indicated that the EC50 values in various species were usually within the nM range, but AHRs of certain subforms/species can vary by one or two orders of magnitude. In summary, the present study will enhance the understanding of AHR and help improve research on the ecotoxicity of dioxins/DLCs.

Global dioxin research trends and focal points: A century-long visual and bibliometric analysis (1923-2022)

Dioxin-like compounds, recognized by the World Health Organization (WHO) as among the most enduring toxic chemical substances in the environment, are linked to various occupational activities and industrial accidents worldwide. The aim of this study was to examine and present research publications on dioxins, pinpoint current research trends, identify research gaps, and highlight potential avenues for future exploration in the field. The study period for relevant research articles ranged from 1923 to December 31, 2022, and these articles were sourced from the Scopus database. The analysis involved the identification of key contributors to the field and the visualization of topics, themes, and international collaboration. VOSviewer software (version 1.6.20) was used for visualization analysis. A total of 11,620 publications on dioxins were documented in the Scopus database. The predominant category of these documents comprised 9780 original articles, which represents 84.17% of the total publications. The United States lead in the number of publications, with 3992 (34.35%), followed by Japan, with 1429 (12.3%), China, with 1005 (8.65%), and Germany, with 974 (8.38%). Before 2002, scholarly attention in this field focused primarily on the health effects, environmental fate, and mechanism of toxicity of tetrachlorodibenzo-p-dioxin (TCDD). However, a noticeable change in research focus has been observed since 2002, highlighting the emergence of a topic related to the health effects and environmental fate of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PFDFs). This study is the first to conduct a comprehensive quantitative bibliometric analysis of dioxins over time. These findings indicate a significant increase in the overall growth of the dioxin literature over the past 30 years. These findings may prove crucial in guiding and organizing subsequent investigations related to dioxins.

Neonatal Cannabidiol Exposure Impairs Spatial Memory and Disrupts Neuronal Dendritic Morphology in Young Adult Rats

Introduction: Early life is a sensitive period for brain development. Perinatal exposure to cannabis is increasingly linked to disruption of neurodevelopment; however, research on the effects of cannabidiol (CBD) on the developing brain is scarce. In this study, we aim to study the developmental effects of neonatal CBD exposure on behavior and dendritic architecture in young adult rats. Materials and Methods: Male and female neonatal Sprague Dawley rats were treated with CBD (50 mg/kg) intraperitoneally on postnatal day (PND) 1, 3, and 5 and evaluated for behavioral and neuronal morphological changes during early adulthood. Rats were subjected to a series of behavioral tasks to evaluate long-term effects of neonatal CBD exposure, including the Barnes maze, open field, and elevated plus maze paradigms to assess spatial memory and anxiety-like behavior. Following behavioral evaluation, animals were sacrificed, and neuronal morphology of the cortex and hippocampus was assessed using Golgi-Cox (GC) staining. Results: Rats treated with CBD displayed a sexually dimorphic response in spatial memory, with CBD-treated females developing a deficit but not males. CBD did not elicit alterations in anxiety-like behavior in either sex. Neonatal CBD caused an overall decrease in dendritic length and spine density (apical and basal) in cortical and hippocampal neurons in both sexes. Sholl analysis also revealed a decrease in dendritic intersections in the cortex and hippocampus, indicating reduced dendritic arborization. Conclusions: This study provides evidence that neonatal CBD exposure perturbs normal brain development and leads to lasting alterations in spatial memory and neuronal dendrite morphology in early adulthood, with sex-dependent sensitivity.

Dioxins vs. PFAS: Science and Policy Challenges

BACKGROUND

Dioxin-like chemicals are a group of ubiquitous environmental toxicants that received intense attention in the last two decades of the 20th century. Through extensive mechanistic research and validation, the global community has agreed upon a regulatory strategy for these chemicals that centers on their common additive activation of a single receptor. Applying these regulations has led to decreased exposure in most populations studied. As dioxin-like chemicals moved out of the limelight, research and media attention has turned to other concerning contaminants, including per- and polyfluoroalkyl substances (PFAS). During the 20th century, PFAS were also being quietly emitted into the environment, but only in the last 20 years have we realized the serious threat they pose to health. There is active debate about how to appropriately classify and regulate the thousands of known PFAS and finding a solution for these "forever chemicals" is of the utmost urgency.

OBJECTIVES

Here, we compare important features of dioxin-like chemicals and PFAS, including the history, mechanism of action, and effective upstream regulatory strategies, with the objective of gleaning insight from the past to improve strategies for addressing PFAS.

DISCUSSION

The differences between these two chemical classes means that regulatory strategies for dioxin-like chemicals will not be appropriate for PFAS. PFAS exert toxicity by both receptor-based and nonreceptor-based mechanisms, which complicates mixtures evaluation and stymies efforts to develop inexpensive assays that accurately capture toxicity. Furthermore, dioxin-like chemicals were unwanted byproducts, but PFAS are useful and valuable, which has led to intense resistance against efforts to restrict their production. Nonetheless, useful lessons can be drawn from dioxin-like chemicals and applied to PFAS, including eliminating nonessential production of new PFAS and proactive investment in environmental remediation to address their extraordinarily long environmental persistence. https://doi.org/10.1289/EHP14449.

First assessment of persistent organic pollutants and halogenated natural compounds in an omnivorous resident coral-reef fish species, black triggerfish, Melichthys niger, from an Atlantic oceanic island, Brazil

Studies on the occurrence of POPs and other persistent compounds in pristine areas are extremely valuable, as they offer insights on the long-range transportation of POPs and the occurrence of natural compound producers' areas. In this regard, this study aimed to report data of both anthropogenic (polychlorinated biphenyls, PCBs, and polybrominated diphenyl ethers, PBDEs) and natural (methoxylated PBDEs, MeO-BDEs) compounds in tissues of the black triggerfish, Melichthys niger (Tetraodontiformes, Balistidae), specimens (n = 30) sampled in 2018 during a scientific expedition conducted at Trindade Island. Concentrations of ∑28PCBs ranged from 73 to 1052 ng g-1 lw in liver, 334 to 1981 ng g-1 lw in gonads, and 20 to 257 ng g-1 lw in muscle, with the predominance of PCB-180 in liver and PCB-52 in gonad and muscle. Concentrations of ∑7PBDEs ranged from Collapse

Key Words

• Brazilian island
• MeO-BDEs
• Omnivorous fish
• PBDEs
• Polychlorinated biphenyls
• Trindade Island

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Affiliation(s)

Dhoone Menezes-Sousa Universidade Federal do Rio de Janeiro, Instituto de Biofísica Carlos Chagas Filho, Laboratório de Micropoluentes Jan Japenga, Av. Carlos Chagas Filho, 373 CCS - Bl. G, Rio de Janeiro, RJ 21941-541, Brazil; Universidade Federal do Rio de Janeiro, Instituto de Biofísica Carlos Chagas Filho, Laboratório de Radioisótopos Eduardo Penna Franca, Av. Carlos Chagas Filho, 373 CCS - Bl. G, Rio de Janeiro, RJ 21941-541, Brazil.
Marcelo Vianna Universidade Federal do Rio de Janeiro, Instituto de Biologia. Laboratório de Biologia e Tecnologia Pesqueira, Departamento de Biologia Marinha, Av. Carlos Chagas Filho, 373, CCS, Bl. A., Rio de Janeiro, Rio de Janeiro 21941-541, Brazil; IMAM - AquaRio, Rio de Janeiro Aquarium Research Center, Rio de Janeiro, Brazil.
Olaf Malm Universidade Federal do Rio de Janeiro, Instituto de Biofísica Carlos Chagas Filho, Laboratório de Radioisótopos Eduardo Penna Franca, Av. Carlos Chagas Filho, 373 CCS - Bl. G, Rio de Janeiro, RJ 21941-541, Brazil
João Paulo Machado Torres Universidade Federal do Rio de Janeiro, Instituto de Biofísica Carlos Chagas Filho, Laboratório de Micropoluentes Jan Japenga, Av. Carlos Chagas Filho, 373 CCS - Bl. G, Rio de Janeiro, RJ 21941-541, Brazil
Mariana Batha Alonso Universidade Federal do Rio de Janeiro, Instituto de Biofísica Carlos Chagas Filho, Laboratório de Micropoluentes Jan Japenga, Av. Carlos Chagas Filho, 373 CCS - Bl. G, Rio de Janeiro, RJ 21941-541, Brazil

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Spatial distribution characteristics of carbazole and polyhalogenated carbazoles in water column and sediments in the open Western Pacific Ocean

Polyhalogenated carbazoles (PHCZs), an emerging persistent halogenated organic pollutant, have been detected in the environment. However, our understanding of PHCZs in the ocean remains limited. In this study, 47 seawater samples (covering 50 - 4000 m) and sediment samples (49 surface and 3 cores) were collected to investigate the occurrence and spatial distribution patterns of carbazole and its halogenated derivants (CZDs) in the Western Pacific Ocean. In seawater, the detection frequencies of CZ (97.87%) and 3-CCZ (57.45%) were relatively high. In addition, the average concentration of ΣPHCZs in the upper water (< 150 m, 0.23 ± 0.21 ng/L) was significantly lower than that in the deep ocean (1000 - 4000 m, 0.65 ± 0.56 ng/L, P < 0.05), which may indicate the vertical transport of PHCZs in the marine environment. The concentration of ΣCZDs in surface sediment ranges from 0.46 to 6.48 ng/g (mean 1.54 ng/g), among which CZ and 36-CCZ were the predominant components. Results from sediment cores demonstrate a noteworthy negative correlation between the concentration of CZDs and depth, indicating the ongoing natural degradation process occurring in sediment cores over a long period. This study offers distinctive insights into the occurrence, composition, and vertical features of CZDs in oceanic environments.

Systematic investigation of organochlorine pesticides and polychlorinated biphenyls blood levels in Greek children from the Rhea birth cohort suggests historical exposure to DDT and through diet to DDE

The blood levels of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) have been thoroughly investigated in Greek children from the Rhea birth cohort study. This investigation aimed to assess exposure levels, explore their possible relationship with children's age and sex, and indicate potential sources of exposure. Exposure patterns and common sources of PCBs and OCPs were analyzed using bivariate and multivariate statistics. A total of 947 blood samples from study participants were analyzed for OCP and PCB exposure, with 375 samples collected at 4 years old, 239 at 6.5 years old, and 333 at 11 years old. Elevated levels of DDE were observed in 6.5-year-old children compared to corresponding levels in other European countries. Higher levels of DDE were found in 4-year-old children, with the lowest concentrations in the 11-year-old group. The DDT/DDE ratio was consistently less than 1 among all the examined subjects. These results indicate exposure to DDT and DDE both in utero and through breastfeeding and dietary intake. For the entire cohort population, the highest concentration was determined for PCB 28, followed by PCBs 138, 153, and 180. The sum of the six indicator PCBs implied low exposure levels for the majority of the cohort population. Spearman correlations revealed strong associations between PCBs and OCPs, while principal component analysis identified two different groupings of exposure. DDE exhibited a correlation with a series of PCBs (153, 156, 163, 180), indicating a combined OCP-PCB source, and an anticorrelation with others (52, 28, 101), implying a separate and competing source.

Modeled Pathways and Fluxes of PCB Dechlorination by Redox Potentials

Dechlorination is one of the main processes for the natural degradation of polychlorinated biphenyls (PCBs) in an anaerobic environment. However, PCB dechlorination pathways and products vary with PCB congeners, types of functional dechlorinating bacteria, and environmental conditions. The present study develops a novel model for determining dechlorination pathways and fluxes by tracking redox potential variability, transforming the complex dechlorination process into a stepwise sequence. The redox potential is calculated via the Gibbs free energy of formation, PCB concentrations in reactants and products, and environmental conditions. Thus, the continuous change in the PCB congener composition can be tracked during dechlorination processes. The new model is assessed against four measurements from several published studies on PCB dechlorination. The simulation errors in all four measurements are calculated between 2.67 and 35.1% under minimum (n = 0) and maximum (n = 34) numbers of co-eluters, respectively. The dechlorination fluxes for para-dechlorination pathways dominate PCB dechlorination in all measurements. Furthermore, the model also considers multiple-step dechlorination pathways containing intermediate PCB congeners absent in both the reactants and the products. The present study indicates that redox potential might be an appropriate indicator for predicting PCB dechlorination pathways and fluxes even without prior knowledge of the functional dechlorinating bacteria.

Feed materials - Levels and characteristic profiles of dioxins and PCBs

Dioxins (PCDD/PCDF) are toxic compounds that are ubiquitous in the environment; although present in low concentrations, they are persistent and highly toxic and they bioaccumulate in food chains. Therefore, it is very important that feed is free of these types of contaminants, because otherwise they can become a source that can negatively affect animal health and the safety of food of animal origin. The aim of the study was to comprehensively assess the concentrations of dioxins and polychlorinated biphenyls (PCBs) in a variety of feed materials available on the Polish market. In addition, characteristic profiles of congeners for given categories of feeds were investigated and defined. Approximately 95 % of the 523 samples of various feed materials tested over seven years (2013-2018 and 2022) met the requirements of European Union feed law (Commission Regulation 277/2012/EU). The highest average PCDD/PCDF/dl-PCB concentrations were found in fish oils and meal and were respectively 1.17 ± 0.78 and 5.51 ± 4.51 ng WHO-TEQ/kg of feed at 12 % moisture. Median and background level concentrations of PCDD/PCDFs, dl-PCBs, PCDD/PCDF/dl-PCBs, and ndl-PCBs were significantly lower than their average concentrations for each individual feed material category. The WHO-TEQ profiles enabled the identification of three different characteristic profiles in feed materials.

Legacy contaminant trends in the Great Lakes uncovered by the wildlife environmental quality index

Since the 1970s, wildlife managers have prioritized the recovery of Great Lakes ecosystems from contamination by Persistent Organic Pollutants (POPs). Monitoring and quantifying the region's recovery is challenged by the diversity of legacy contaminants in the environment and the lack of benchmarks for their potential biological effects. We address this gap by introducing the Wildlife Environmental Quality Index (WEQI) based on prior water and sediment quality indices. The tool summarizes, in a single score, the exposure of wildlife to harmful levels of multiple contaminants - with harmful levels set by published guidelines for protecting piscivorous wildlife from biological impacts. We applied the new index to a combined Canadian and American dataset of Herring Gull (Larus argentatus) egg data to elucidate trends in wildlife for eight legacy industrial pollutants and insecticides in the Great Lakes. Environmental quality of the Great Lakes region (as indexed by WEQI) improved by 18% between 2002 and 2017. Improvement came from reductions in both the scope of contamination (the number of guideline-exceeding contaminants) and its amplitude (the average size of guideline exceedances) at bird colonies. But recovery was unequal among lakes, with Lake Erie showing no improvement at one extreme. Weakly- or non-recovering lakes (Erie, Ontario, Huron) were marked by inconsistent improvement in scope and amplitude, likely due to ongoing loading, sediment resuspension and other stressors reported elsewhere. Fast-recovering lakes (Superior and Michigan), meanwhile, improved in both scope and amplitude. Contrasting trends and contaminant profiles (e.g., exceedances of PCBs versus DDTs) highlight the importance of lake-specific management for equalizing recoveries. Lower environmental quality at American than Canadian colonies, particularly in Lake Huron, further suggest uneven success in - and opportunities for - the binational management of wildlife exposure to legacy contaminants.

Gene-Environment Interactions: My Unique Journey

I am deeply honored to be invited to write this scientific autobiography. As a physician-scientist, pediatrician, molecular biologist, and geneticist, I have authored/coauthored more than 600 publications in the fields of clinical medicine, biochemistry, biophysics, pharmacology, drug metabolism, toxicology, molecular biology, cancer, standardized gene nomenclature, developmental toxicology and teratogenesis, mouse genetics, human genetics, and evolutionary genomics. Looking back, I think my career can be divided into four distinct research areas, which I summarize mostly chronologically in this article: (a) discovery and characterization of the AHR/CYP1 axis, (b) pharmacogenomics and genetic prediction of response to drugs and other environmental toxicants, (c) standardized drug-metabolizing gene nomenclature based on evolutionary divergence, and (d) discovery and characterization of the SLC39A8 gene encoding the ZIP8 metal cation influx transporter. Collectively, all four topics embrace gene-environment interactions, hence the title of my autobiography.

Levels and species-specific organochlorine accumulation in three shark species from the western Gulf of California with different life history traits

Organochlorine compounds (OCs), such as organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs), remain ubiquitous in marine ecosystems despite their prohibition or restriction, posing a risk to marine wildlife and humans. Their accumulation in liver tissue and potential toxicity in three exploited shark species (the scalloped hammerhead, Sphyrna lewini; the Pacific sharpnose shark, Rhizoprionodon longurio; and the Pacific angel shark, Squatina californica) with different physiological and ecological features from the western Gulf of California (GC) were investigated. Forty of the 47 OCs analyzed were identified, evidencing a greater agricultural than industrial influence considering the high DDTs/PCBs ratios. The DDT group was the main contributor to ∑OCs in the three species, while hexa- and hepta-CBs dominated the PCB profiles. S. lewini (juveniles) and R. longurio (juveniles and adults) had similar and significantly (p < 0.05) higher ∑OCP concentrations than S. californica (juveniles and adults), which is attributed to their migration to other polluted regions of the gulf. The three species' ∑PCB levels (lipid weight) were comparable and considered low in comparison to those documented in prior studies conducted worldwide. No intraspecific differences were observed when comparing by sex, but OC concentrations were higher in larger individuals. S. lewini and R. longurio showed different OC bioaccumulation trends against size, while no relationship between size and ∑OC concentrations was observed in S. californica. All shark species' toxic equivalents (TEQs) were calculated from dioxin-like PCB concentrations and were far below the established TEQ fish thresholds. However, future research is needed regarding the possible PCB and OCP effects in elasmobranchs. This study provides the basis for monitoring organic contaminants in predatory sharks from the western GC. It also highlights the importance of further research on unintentionally produced organochlorine environmental levels and sources.

Assessing the Toxicity of Benzotriazole Ultraviolet Stabilizers to Fishes: Insights into Aryl Hydrocarbon Receptor-Mediated Effects

Benzotriazole ultraviolet stabilizers (BUVSs) are chemicals used to mitigate UV-induced damage to manufactured goods. Their presence in aquatic environments and biota raises concerns, as certain BUVSs activate the aryl hydrocarbon receptor (AhR), which is linked to adverse effects in fish. However, potencies of BUVSs as AhR agonists and species sensitivities to AhR activation are poorly understood. This study evaluated the toxicity of three BUVSs using embryotoxicity assays. Zebrafish (Danio rerio) embryos exposed to BUVSs by microinjection suffered dose-dependent increases in mortality, with LD50 values of 4772, 11 608, and 56 292 ng/g-egg for UV-P, UV-9, and UV-090, respectively. The potencies and species sensitivities to AhR2 activation by BUVSs were assessed using a luciferase reporter gene assay with COS-7 cells transfected with the AhR2 of zebrafish and eight other fishes. The rank order of potency for activation of the AhR2 from all nine species was UV-P > UV-9 > UV-090. However, AhR2s among species differed in sensitivities to activation by up to 100-fold. An approximate reversed rank order of species sensitivity was observed compared to the rank order of sensitivity to 2,3,7,8-tetrachlorodibenzo[p]dioxin, the prototypical AhR agonist. Despite this, a pre-existing quantitative adverse outcome pathway linking AhR activation to embryo lethality could predict embryotoxicities of BUVSs in zebrafish.

Risks of obstructive genitourinary birth defects in relation to trihalomethane and haloacetic acid exposures: expanding disinfection byproduct mixtures analyses using relative potency factors

BACKGROUND

Some disinfection byproducts (DBPs) are teratogens based on toxicological evidence. Conventional use of predominant DBPs as proxies for complex mixtures may result in decreased ability to detect associations in epidemiological studies.

OBJECTIVE

We assessed risks of obstructive genitourinary birth defects (OGDs) in relation to 12 DBP mixtures and 13 individual component DBPs.

METHODS

We designed a nested registry-based case-control study (210 OGD cases; 2100 controls) in Massachusetts towns with complete quarterly 1999-2004 data on four trihalomethanes (THMs) and five haloacetic acids (HAAs). We estimated temporally-weighted average DBP exposures for the first trimester of pregnancy. We estimated adjusted odds ratios (aORs) and 95% confidence intervals (CIs) for OGD in relation to individual DBPs, unweighted mixtures, and weighted mixtures based on THM/HAA relative potency factors (RPF) from animal toxicology data for full-litter resorption, eye defects, and neural tube defects.

RESULTS

We detected elevated aORs for OGDs for the highest of bromodichloromethane (aOR = 1.75; 95% CI: 1.15-2.65), dibromochloromethane (aOR = 1.71; 95% CI: 1.15-2.54), bromodichloroacetic acid (aOR = 1.56; 95%CI: 0.97-2.51), chlorodibromoacetic acid (aOR = 1.97, 95% CI: 1.23-3.15), and tribromoacetic acid (aOR = 1.90; 95%CI: 1.20-3.03). Across unweighted mixture sums, the highest aORs were for the sum of three brominated THMs (aOR = 1.74; 95% CI: 1.15-2.64), the sum of six brominated HAAs (aOR = 1.43; 95% CI: 0.89-2.31), and the sum of nine brominated DBPs (aOR = 1.80; 95% CI: 1.05-3.10). Comparing eight RPF-weighted to unweighted mixtures, the largest aOR differences were for two HAA metrics, which both were higher with RPF weighting; other metrics had reduced or minimally changed ORs in RPF-weighted models.

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

In October 2022, the World Health Organization (WHO) convened an expert panel in Lisbon, Portugal in which the 2005 WHO TEFs for chlorinated dioxin-like compounds were reevaluated. In contrast to earlier panels that employed expert judgement and consensus-based assignment of TEF values, the present effort employed an update to the 2006 REP database, a consensus-based weighting scheme, a Bayesian dose response modeling and meta-analysis to derive "Best-Estimate" TEFs. The updated database contains almost double the number of datasets from the earlier version and includes metadata that informs the weighting scheme. The Bayesian analysis of this dataset results in an unbiased quantitative assessment of the congener-specific potencies with uncertainty estimates. The "Best-Estimate" TEF derived from the model was used to assign 2022 WHO-TEFs for almost all congeners and these values were not rounded to half-logs as was done previously. The exception was for the mono-ortho PCBs, for which the panel agreed to retain their 2005 WHO-TEFs due to limited and heterogenous data available for these compounds. Applying these new TEFs to a limited set of dioxin-like chemical concentrations measured in human milk and seafood indicates that the total toxic equivalents will tend to be lower than when using the 2005 TEFs.

Development and application of a systematic and quantitative weighting framework to evaluate the quality and relevance of relative potency estimates for dioxin-like compounds (DLCs) for human health risk assessment

The toxic equivalency factors (TEFs) approach for dioxin-like chemicals (DLCs) is currently based on a qualitative assessment of a heterogeneous data set of relative estimates of potency (REPs) spanning several orders of magnitude with highly variable study quality and relevance. An effort was undertaken to develop a weighting framework to systematically evaluate and quantitatively integrate the quality and relevance for development of more robust TEFs. Six main-study characteristics were identified as most important in characterizing the quality and relevance of an individual REP for human health risk assessment: study type, study model, pharmacokinetics, REP derivation method, REP derivation quality, and endpoint. Subsequently, a computational approach for quantitatively integrating the weighting framework parameters was developed and applied to the REP2004 database. This was accomplished using a machine learning approach which infers a weighted TEF distribution for each congener. The resulting database, weighted for quality and relevance, provides REP distributions from >600 data sets (including in vivo and in vitro studies, a range of endpoints, etc.). This weighted database provides a flexible platform for systematically and objectively characterizing TEFs for use in risk assessment, as well as providing information to characterize uncertainty and variability. Collectively, this information provides risk managers with information for decision making.

Estimation of dietary intake of polychlorinated dibenzo-p-dioxins and dibenzofurans and dioxin-like polychlorinated biphenyls from the Thai total diet study in 2019

Dietary intakes of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (DL-PCBs) were assessed in the Thai Total Diet Study (TDS) in 2019. Food samples including portable water (n = 1048) were collected from four regions of Thailand to represent a whole diet of Thai population, prepared as consumed and analyzed. To estimate the dietary intakes of PCDD/Fs and DL-PCBs, the concentrations in 18 food groups were combined with the respective food consumption from the national consumption data of Thailand and with a mean body weight of 57.57 kg for Thai population aged ≥ 3 years. The dietary intakes of PCDD/Fs, DL-PCBs and ∑PCDD/Fs/DL-PCBs were estimated to be 8.09, 4.93 and 13.02 pg WHO2005-TEQ kg-1 body weight month-1, respectively (upper bound). The major contributors to the total dietary intake were marine animals, followed by milk and milk products, freshwater animals, pork and pork products, and eggs, corresponding to 26, 22, 21, 10 and 9%, respectively. In comparison to health-based guidance value (HBGV), the intake of ∑PCDD/Fs/DL-PCBs (upper bound) was equal to 19% of the provisional tolerable monthly intake set by JECFA in 2001. Moreover, a comparison with other HBGVs was additionally presented and discussed.

Identification and verification of PCDD/Fs indicators from four typical large-scale municipal solid waste incinerations with large sample size in China

Monitoring PCDD/Fs emissions from municipal solid waste incinerations (MSWIs) is of paramount importance, yet it can be time-consuming and labor-intensive. Predictive models offer an alternative approach for estimating their levels. However, robust models specific to PCDD/Fs were lacking. In this study, we collected 190 PCDD/Fs samples from 4 large-scale MSWIs in China, with the average PCDD/Fs levels and TEQ levels of 0.987 ng/m3 and 0.030 ng TEQ/m3, respectively. We developed and evaluated predictive models, including traditional statistical methods, e.g., linear regression (LR) as well as machine learning models such as back propagation-artificial neural networks (BP ANN) and random forest (RF). Correlation analysis identified 2,3,4,7,8-PeCDF, 1,2,3,6,7,8-HxCDF, 2,3,4,6,7,8-HxCDF were better indicator congeners for PCDD/Fs estimation (R2 > 0.9, p < 0.001). The predictive results favored the RF model, exhibiting a high R2 value and low root mean square error (RMSE) and mean absolute error (MAE). Additionally, the RF model showed excellent prediction ability during external validation, with low absolute relative error (ARE) of 10.9 %-12.6 % for the three indicator congeners in the normal PCDD/F TEQ levels group (<0.1 ng TEQ/m3) and slightly higher ARE values (13.8 %-17.9 %) for the high PCDD/F TEQ levels group (>0.1 ng TEQ/m3). In conclusion, our findings strongly support the RF model's effectiveness in predicting PCDD/Fs TEQ emission from MSWIs.

Transfer of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs) from oral exposure into cow's milk - Part I: state of knowledge and uncertainties

Polychlorinated dibenzo-para-dioxins (PCDDs) and dibenzofurans (PCDFs) (collectively and colloquially referred to as 'dioxins') as well as polychlorinated biphenyls (PCBs) are persistent and ubiquitous environmental contaminants that may unintentionally enter and accumulate along the food chain. Owing to their chronic toxic effects in humans and bioaccumulative properties, their presence in feed and food requires particular attention. One important exposure pathway for consumers is consumption of milk and dairy products. Their transfer from feed to milk has been studied for the past 50 years to quantify the uptake and elimination kinetics. We extracted transfer parameters (transfer rate, transfer factor, biotransfer factor and elimination half-lives) in a machine-readable format from seventy-six primary and twenty-nine secondary literature items. Kinetic data for some toxicologically relevant dioxin congeners and the elimination half-lives of dioxin-like PCBs are still not available. A well-defined selection of transfer parameters from literature was statistically analysed and shown to display high variability. To understand this variability, we discuss the data with an emphasis on influencing factors, such as experimental conditions, cow performance parameters and metabolic state. While no universal interpretation could be derived, a tendency for increased transfer into milk is apparently connected to an increase in milk yield and milk fat yield as well as during times of body fat mobilisation, for example during the negative energy balance after calving. Over the past decades, milk yield has increased to over 40 kg/d during high lactation, so more research is needed on how this impacts feed to food transfer for PCDD/Fs and PCBs.

A critical review on quantitative evaluation of aqueous toxicity in water quality assessment

Conventional chemical techniques have inherent limitations in detecting unknown chemical substances in water. As a result, effect-based methods have emerged as a viable alternative to overcome these limitations. These methods provide more accurate and intuitive evaluations of the toxic effects of water. While numerous studies have been conducted, only a few have been applied to national water quality monitoring. Therefore, it is crucial to develop toxicity evaluation methods and establish thresholds based on quantifying toxicity. This article provides an overview of the development and application of bioanalytical tools, including in vitro and in vivo bioassays. The available methods for quantifying toxicity are then summarized. These methods include aquatic life criteria for assessing the toxicity of a single compound, comprehensive wastewater toxicity testing for all contaminants in a water sample (toxicity units, whole effluent toxicity, the potential ecotoxic effects probe, the potential toxicology method, and the lowest ineffective dilution), methods based on mechanisms and relative toxicity ratios for substances with the same mode of action (the toxicity equivalency factors, toxic equivalents, bioanalytical equivalents), and effect-based trigger values for micropollutants. The article also highlights the advantages and disadvantages of each method. Finally, it proposes potential areas for applying toxicity quantification methods and offers insights into future research directions. This review emphasizes the significance of enhancing the evaluation methods for assessing aqueous toxicity in water quality assessment.

Insight into the formation of polychlorinated dibenzo-p-dioxins and dibenzofurans in hazardous waste incineration and incinerators: Formation process and reduction strategy

Incineration technology has been widely adopted to safely dispose of hazardous waste (HW). While the incineration process causes the formation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). Due to its extreme toxicity, many scholars have been committed to determining the PCDD/F formation process and reducing emissions in incinerators. Previous studies ignored the impact of incineration and fluctuation of feeding materials on PCDD/F formation in hazardous waste incinerators (HWIs). In this study, differences in PCDD/F formation between HWIs and municipal solid waste incinerators (MSWIs) were pointed out. The incineration section in HWIs should be carefully considered. Laboratory experiments, conventional analysis and thermogravimetry experiments were conducted. An obvious disparity of PCDD/F formation between 12 kinds of HWs was found. Distillation residue was found with remarkably higher PCDD/F concentrations (11.57 ng/g). Except for the Cl content, aromatic rings and C-O bond organics were also found with high correlation coefficients with PCDD/F concentrations (>0.92). And PCDD/Fs were formed through a chlorination process and structure formation process. All of these are helpful to further understand the PCDD/F formation process during HW incineration, optimize the operation conditions in HWIs and reduce the emission pressure of PCDD/Fs in the future.

Maternal serum dioxin-like activity and gestational age at birth and indices of foetal growth: The Aarhus birth cohort

Human exposure to lipophilic persistent organic pollutants (lipPOP) is ubiquitous and life-long, beginning during foetal development. Exposure to lipPOP elicits a number of species and tissue specific responses including dioxin-like activity which involve the activation of aryl hydrocarbon receptor (AhR). This study aims i) to describe the combined dioxin-like activity in serum from Danish pregnant women collected during 2011-2013; ii) to assess the association between maternal serum dioxin-like activity, gestational age at birth and foetal growth indices. The serum lipPOP fraction was extracted using Solid Phase Extraction and cleaned-up on Supelco multi-layer silica and florisil columns. The combined dioxin-like activity of the extract was determined using the AhR reporter gene bioassay, expressed as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) toxic equivalent (TEQ) [AhR-TEQ (pg/g lipid)]. The associations of AhR-TEQ and foetal growth indices (birth weight, birth length and head circumference) and gestational age were assessed by linear regression models. We detected AhR-TEQ in 93.9 % of maternal first trimester serum samples, with a median level of 185 pg/g lipid. Each ln-unit increase in AhR-TEQ was associated with an increase in birth weight of 36 g (95 % CI: 5; 68), birth length of 0.2 cm (95 % CI: 0.01; 0.3) and pregnancy duration of 1 day (95 % CI: 0; 1.5). In women who never smoked, higher AhR-TEQ values were associated with higher birth weight and longer duration of gestation, while in smokers the association was the opposite. Mediation analyses suggested that gestational age may mediate the association of AhR-TEQ with foetal growth indices. We conclude that AhR activating substances are present in the bloodstream of almost all pregnant women in Denmark and the AhR-TEQ level was around four times higher than previously reported. The AhR-TEQ was associated with slightly longer gestational duration and thereby higher birth weight and birth length.

Reevaluation of 2,3,7,8-Tetrachlorodibenzo-p-Dioxin Equivalency Factors for Dioxin-Like Polychlorinated Dibenzo-p-Dioxins, Polychlorinated Dibenzofurans, and Polychlorinated Biphenyls for Fishes

An expert meeting was organized by the World Health Organization (WHO) in 1997 to streamline assessments of risk posed by mixtures of dioxin-like chemicals (DLCs) through development of 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) equivalency factors (TEFs) for mammals, birds, and fishes. No reevaluation has been performed for fish TEFs. Therefore, the objective of the present study was to reevaluate the TEFs for fishes based on an updated database of relative potencies (RePs) for DLCs. Selection criteria consistent with the WHO meeting resulted in 53 RePs across 14 species of fish ultimately being considered. Of these RePs, 70% were not available at the time of the WHO meeting. These RePs were used to develop updated TEFs for fishes based on a similar decision process as used at the WHO meeting. The updated TEF for 16 DLCs was greater than the WHO TEF, but only four differed by more than an order of magnitude. Measured concentrations of DLCs in four environmental samples were used to compare 2,3,7,8-TCDD equivalents (TEQs) calculated using the WHO TEFs relative to the updated TEFs. The TEQs for none of these environmental samples differed by more than an order of magnitude. Therefore, present knowledge supports that the WHO TEFs are suitable potency estimates for fishes. However, the updated TEFs pull from a larger database with a greater breadth of data and as a result offer greater confidence relative to the WHO TEFs. Risk assessors will have different criteria in the selection of TEFs, and the updated TEFs are not meant to immediately replace the formal WHO TEFs; but those who value a larger database and increased confidence in TEQs could consider using the updated TEFs. Environ Toxicol Chem 2023;42:2215-2228. © 2023 Wiley Periodicals LLC. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

AOP Report: Aryl Hydrocarbon Receptor Activation Leads to Early-Life Stage Mortality via Sox9 Repression-Induced Craniofacial and Cardiac Malformations

The aryl hydrocarbon receptors (Ahrs) are evolutionarily conserved ligand-dependent transcription factors that are activated by structurally diverse endogenous compounds as well as environmental chemicals such as polycyclic aromatic hydrocarbons and halogenated aromatic hydrocarbons. Activation of the Ahr leads to several transcriptional changes that can cause developmental toxicity resulting in mortality. Evidence was assembled and evaluated for two novel adverse outcome pathways (AOPs) which describe how Ahr activation (molecular initiating event) can lead to early-life stage mortality (adverse outcome), via either SOX9-mediated craniofacial malformations (AOP 455) or cardiovascular toxicity (AOP 456). Using a key event relationship (KER)-by-KER approach, we collected evidence using both a narrative search and a systematic review based on detailed search terms. Weight of evidence for each KER was assessed to inform overall confidence of the AOPs. The AOPs link to previous descriptions of Ahr activation and connect them to two novel key events (KEs), increase in slincR expression, a newly characterized long noncoding RNA with regulatory functions, and suppression of SOX9, a critical transcription factor implicated in chondrogenesis and cardiac development. In general, confidence levels for KERs ranged between medium and strong, with few inconsistencies, as well as several opportunities for future research identified. While the majority of KEs have only been demonstrated in zebrafish with 2,3,7,8-tetrachlorodibenzo-p-dioxin as an Ahr activator, evidence suggests that the two AOPs likely apply to most vertebrates and many Ahr-activating chemicals. Addition of the AOPs into the AOP-Wiki (https://aopwiki.org/) helps expand the growing Ahr-related AOP network to 19 individual AOPs, of which six are endorsed or in progress and the remaining 13 relatively underdeveloped. Environ Toxicol Chem 2023;42:2063-2077. © 2023 SETAC. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

Legacy persistent organic pollutants (POPs) in eggs of night herons and poultries from the upper Yangtze Basin, Southwest China

Black-crowned night heron (Nycticorax nycticorax) eggs have been identified as useful indicators for biomonitoring the environmental pollution in China. In this study, we investigated thirty eggs of black-crowned night heron collected from the upper Yangtze River (Changjiang) Basin, Southwest China, for the occurrence of legacy persistent organic pollutants (POPs), including polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs). Our results showed a general presence of POPs in night heron eggs with OCPs being the dominant contaminants, having a geometric mean concentration of 22.2 ng g-1 wet weight (ww), followed by PCBs (1.36 ng g-1 ww), PBDEs (0.215 ng g-1 ww), and PCDD/Fs (23.0 pg g-1 ww). The concentration levels were found to be significantly higher in night heron eggs than in poultry eggs by one or two magnitude orders. Among OCP congeners, p,p'-DDE was found to be predominant in night heron eggs, with a geometric mean concentration of 15.1 ng g-1 ww. Furthermore, species-specific congener patterns in eggs suggested similar or different sources for different POPs, possibly associated with contaminated soil and parental dietary sources. Additionally, estimated daily intakes (EDIs) were used to evaluate non-carcinogenic and carcinogenic risk associated with consumption of bird eggs. Our results revealed non-negligible non-cancer and cancer risk for humans who consume wild bird eggs as a regular diet instead of poultry eggs.

A multi-tiered hierarchical Bayesian approach to derive toxic equivalency factors for dioxin-like compounds

In 2005, the World Health Organization (WHO) re-evaluated Toxic Equivalency factors (TEFs) developed for dioxin-like compounds believed to act through the Ah receptor based on an updated database of relative estimated potency (REP)(REP2004 database). This re-evalution identified the need to develop a consistent approach for dose-response modeling. Further, the WHO Panel discussed the significant heterogeneity of experimental datasets and dataset quality underlying the REPs in the database. There is a critical need to develop a quantitative, and quality weighted approach to characterize the TEF for each congener. To address this, a multi-tiered approach that combines Bayesian dose-response fitting and meta-regression with a machine learning model to predict REPS' quality categorizations was developed to predict the most likely relationship between each congener and its reference and derive model-predicted TEF uncertainty distributions. As a proof of concept, this 'Best-Estimate TEF workflow' was applied to the REP2004 database to derive TEF point-estimates and characterizations of uncertainty for all congeners. Model-TEFs were similar to the 2005 WHO TEFs, with the data-poor congeners having larger levels of uncertainty. This transparent and reproducible computational workflow incorporates WHO expert panel recommendations and represents a substantial improvement in the TEF methodology.

PCB126 exposure during pregnancy alters maternal and fetal gene expression

Polychlorinated biphenyls (PCBs) are organic pollutants that can have lasting impacts on offspring health. Here, we sought to examine maternal and fetal gene expression differences of aryl hydrocarbon receptor (AHR)-regulated genes in a mouse model of prenatal PCB126 exposure. Female mice were bred and gavaged with 1 µmole/kg bodyweight PCB126 or vehicle control on embryonic days 0 and 14, and maternal and fetal tissues were collected on embryonic day 18.5. Total RNAs were isolated, and gene expression levels were analyzed in both maternal and fetal tissues using the NanoString nCounter system. Interestingly, we found that the expression levels of cytochrome P450 (Cyp)1a1 and Cyp1b1 were significantly increased in response to PCB exposure in the tested maternal and fetal tissues. Furthermore, PCB exposure altered the expression of several other genes related to energy balance, oxidative stress, and epigenetic regulation in a manner that was less consistent across tissue types. These results indicate that maternal PCB126 exposure significantly alters gene expression in both developing fetuses and pregnant dams, and such changes vary in intensity and expressivity depending on tissue type. The altered gene expression may provide insights into pathophysiological mechanisms by which in utero PCB exposures contribute to PCB-induced postnatal metabolic diseases.

Historical production and release inventory of PCDD/Fs in China and projections upon policy options by 2025

Using the source identification and classification methodology described in UNEP standardized toolkit for dioxin releases, combined with research data over the past decade, the production and release of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) from 6 major sectors in China were inventoried from 2003 to 2020, and were projected until 2025 based on current control measures and relevant industrial plans. The results showed that after ratification of the Stockholm Convention, China's production and release of PCDD/Fs began to decline after peaking in 2007, demonstrating the effectiveness of preliminary control measures. However, the continual expansion of manufacturing and energy sectors, along with the lack of compatible production control technology, reversed the declining trend of production after 2015. Meanwhile, the environmental release continued to decrease, but at a slower rate after 2015. If subject to current policies, production and release would remain elevated with an expanding gap in between. This study also established the congener inventories, revealing the significance of OCDF and OCDD in terms of both production and release, and that of PeCDF and TCDF in terms of environmental impacts. Lastly, through comparison with other developed countries and regions, it was concluded that room for further reduction exists, but can only be achieved through strengthened regulations and improved control measures.

Pre- and postnatal developmental exposure to the polychlorinated biphenyl mixture aroclor 1221 alters female rat pituitary gonadotropins and estrogen receptor alpha levels

Polychlorinated-biphenyls (PCBs) are industrial compounds, which were widely used in manufacturing of electrical parts and transformers. Despite being banned in 1979 due to human health concerns, they persist in the environment. In humans and experimental model systems, PCBs elicit toxicity in part by acting as endocrine-disrupting chemicals (EDCs). Aroclor 1221 (A1221) is a weakly estrogenic PCB mixture known to alter reproductive function in rodents. EDCs can impact hormone signaling at any level of the hypothalamic-pituitary-gonadal (HPG) axis, and we investigated the effects of A1221 exposure during the prenatal and postnatal developmental periods on pituitary hormone and steroid receptor expression in female rats. Examining offspring at 3 ages, postnatal day 8 (P8), P32 and P60, we found that prenatal exposure to A1221 increased P8 neonate pituitary luteinizing hormone beta (Lhb) mRNA and LHβ gonadotrope cell number while decreasing LH serum hormone concentration. No changes in pituitary hormone or hormone receptor gene expression were observed peri-puberty at P32. In reproductively mature rats at P60, we found pituitary follicle stimulating hormone beta (Fshb) mRNA levels increased by prenatal A1221 exposure with no corresponding alterations in FSH hormone or FSHβ expressing cell number. Estrogen receptor alpha (ERα) mRNA and protein levels were also increased at P60, but only following postnatal A1221 dosing. Together, these data illustrate that exposure to the PCB A1221, during critical developmental windows, alters pituitary gonadotropin hormone subunits and ERα levels in offspring at different phases of maturation, potentially impacting reproductive function in concert with other components of the HPG axis.

Dioxin-like POPs in national samples from global monitoring plan projects (2017-2019)

The global monitoring plan (GMP) established under the Stockholm Convention on Persistent Organic Pollutants (POPs) had defined ambient air, human milk or blood, and water as core matrices to be analyzed and assessed for spatial and temporal distribution. Within projects coordinated by the United Nations Environment Programme (UNEP), developing countries were offered to have other matrices analyzed for dioxin-like POPs (dl-POPs) in experienced laboratories. Subsequently, 185 samples from 27 countries located in Africa, Asia, and Latin America were collected during 2018-2019 and analyzed for polychlorinated dibenzodioxins (PCDD), dibenzofurans (PCDF), and biphenyls (PCB). Using the WHO₂₀₀₅ toxic equivalency approach (TEQ), the amounts of dl-POPs found were low (<1 pg TEQ/g); however, singular samples had higher values; e.g., egg from Morocco, fish from Argentina or Tunisia; soil and sediment samples. Results showed that the matrix, abiotic or biota, had more impact on the TEQ pattern than the geographic location. Independent of the location and across all samples, dl-PCB in (shell)fish and beef samples had a contribution of 75% to the total TEQ; milk (63%), chicken (52%), and butter (50.2%) more than 50%. Sediment (57% and 32%) and soil (40% and 36%)) samples were dominated by PCDD and PCDF, respectively; therein, dl-PCB had shares of 11% and 24%. Egg samples (N = 27) did not follow the general biota pattern and had 21% of the TEQ from the PCDD, 45% from PCDF, and 34% from dl-PCB; thus, indicating that abiotic matrices such as soil or other material may have an impact.

In Vitro Genotoxicity Evaluation of PAHs in Mixtures Using Experimental Design

Settled dusts are sinks for environmental pollutants, including Polycyclic Aromatic Hydrocarbons (PAHs) that are ubiquitous, persistent, and carcinogenic. To assess their toxicity in mixtures, Toxic Equivalent Factors (TEFs) are routinely used and based on the hypothesis of additive effects, although PAH interactions may occur and remain an open issue. This study investigated genotoxic binary interaction effects for six PAHs in mixtures using two in vitro assays and estimated Genotoxic Equivalent Factors (GEFs) to roughly predict the genotoxicity of PAH in mixtures. The Design of the Experiment approach was used with the micronucleus assay for cytostasis and micronuclei frequency and the alkaline comet assay for DNA damage. GEFs were determined for each PAH independently and in a mixture. For the cytostasis endpoint, no PAHs interaction was noted. BbF and BaP had a synergistic effect on DNA damage. All the PAH interacted between them regarding chromosomal damage. Although the calculated GEFs were similar to the TEFs, the latter may underestimate the genotoxic potential of a PAH mixture. GEFs calculated for PAH alone were lower than GEFs for PAHs in mixtures; thus, mixtures induce greater DNA/chromosomal damage than expected. This research helps to advance the challenging issue of contaminant mixtures' effects on human health.

Polychlorinated dibenzo-p-dioxins and dibenzofurans and dioxin-like polychlorinated biphenyls in human milk from national human breast milk monitoring in 2016-2019 in China

Human breast milk monitoring programs were recommended to be carried out to assess human body burden to persistent organic pollutants and their temporal trends. Thus, we conducted a national survey during the period of 2016-2019 to determine PCDD/Fs and dl-PCBs in human breast milk from China. The total TEQ amounts in the upper bound (UB) was in the range of 1.97 to 15.1 pg TEQ g^-1 fat with a geometric mean (GM) of 4.50 pg TEQ g^-1 fat. 2,3,4,7,8-PeCDF, 1,2,3,7,8-PeCDD, and PCB-126 were more predominant contributors with the percentage contribution of 34.2 %, 17.9 %, and 17.4 %, respectively. By comparison with our previous monitoring results, the total TEQ in breast milk sample of the present study is statistically lower than that in 2011 with a reduction of 16.9 % in the average (p < 0.05), and comparable to that in 2007. The estimated GM of dietary intake of total TEQ for the breastfed was 25.4 pg TEQ kg^-1 body weight day^-1 that was higher than that of the adult. It is therefore worthy to make more efforts to reduce amounts of PCDD/Fs and dl-PCBs in breast milk and to continue monitoring to further observe if the amount of these chemicals continue to decrease.

Occurrence, distribution, and risk assessment of halogenated organic pollutants (HOPs) in marine fish muscle: The case study of Vietnam

Halogenated organic pollutants (HOPs), including polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), and chlorophenols (CPs), were identified in three marine fish species in Vietnam. Total PCBs, OCPs, and CPs concentrations ranged from 4.5 to 711.6 ng g^-1 lipid weight (lw), 69.9-2360 ng g^-1 lw, and 208.1-3941.2 ng g^-1 lw, respectively. CPs were the most frequently detected pollutants in the marine environment of Vietnam of the three HOPs studied, followed by OCPs and PCBs. There are significant differences in HOPs between three types of seafood in Vietnam, including yellowstripe scad, Indian mackerel, and silver pomfret in this study. Notably, the types and amounts of HOPs found in the fish were differently influenced by the economic and industrial activities of the sampled areas. Despite these findings, the consumption of HOP-contaminated fish from the study areas was found not to pose any significant health risks to Vietnam's coastal population.

Effects of Hudson River Stressors on Atlantic Tomcod: Contaminants and a Warming Environment

The Hudson River (HR) Estuary has a long history of pollution with a variety of contaminants including PCBs, and dioxins. In fact, 200 miles of the mainstem HR is designated a U.S. federal Superfund site, the largest in the nation, because of PCB contamination. The tidal HR hosts the southernmost spawning population of Atlantic tomcod, and studies revealed a correlation between exposure of juveniles to warm water temperature during summer to abundance of spawning adults of the same cohort in the following winter. Further, a battery of mechanistically linked biomarkers, ranging from the molecular to the population levels, were significantly impacted from contaminant exposures of the HR tomcod population. In response to xenobiotic insult, the HR tomcod population developed resistance to PCB sand TCDD toxicity resulting from a deletion in the aryl hydrocarbon receptor2 (AHR2) gene. Furthermore, RNA-Seq analysis of global gene expression demonstrated that effects of the AHR2 polymorphism were far more pervasive than anticipated. The most highly PCB-contaminated sediments in the upper HR were dredged between 2009 and 2015 with the objective of lowering PCB concentrations in fishes in the lower HR. Success of the remediation project has been controversial. These observations suggest that tomcod provides an informative model to evaluate the efficacy of HR PCB remediation efforts on downriver fish populations and possible interactive effects between contaminant exposure and a warming environment.

First insight into accumulation of characteristics and tissue distribution of PCBs, PBDEs, and other BFRs in the living Indonesian coelacanth (Latimeria menadoensis)

Persistent organic pollutants, including polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and other brominated flame retardants, were detected in the liver, muscle, and ovary tissues of the Indonesian coelacanth (Latimeria menadoensis) incidentally caught around Gangga Island, North Sulawesi Province, Indonesia, on November 5, 2014. Concentrations of total PCBs (209 congeners, 300-2600 ng g^-1 lipid weight) in all tissues showed higher than those of PBDEs (41 congeners, 3.9-6.3 ng g^-1 lw) and BTBPE (1.1-3.6 ng g^-1 lw). The tissue-specific PCB and PBDE profiles were likely due to differences in the lipid composition. Toxic equivalent (TEQ) values of dioxin-like PCBs in coelacanth tissues were lower than the benchmark values for early-life fish. However, compared with the data reported for deep-sea fishes in the Pacific and Indian Oceans, the relatively high concentrations of PCBs detected in this study raise concerns regarding Indonesian coelacanth conservation and habitat conditions.

Residential proximity to dioxin emissions and risk of breast cancer in the sister study cohort

Some dioxins are carcinogenic, but few studies have investigated the relationship between ambient polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) and risk of breast cancer. We evaluated associations between proximity-based residential exposure to industrial emissions of PCDD/F and breast cancer risk in a large U.S. cohort. Sister Study participants at enrollment (2003-2009) were followed for incident breast cancer through September 2018. After restricting to participants with ≥10 years of residential history prior to enrollment (n = 35,908), we generated 10-year distance- and toxic equivalency quotient (TEQ)-weighted average emissions indices (AEI [g TEQ/km2]) within 3, 5, or 10 km of participants' residences, overall and by facility type. Multivariable Cox regression models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for the association between AEI quartiles (vs. zero AEI) and risk of breast cancer [invasive or ductal carcinoma in situ]. There were 2670 incident breast cancer cases over 11 years (median) of follow-up. Breast cancer risk was increased for those in the highest quartile [Q] of AEI exposure within 3 km (HRQ4:1.18, 95% CI: 0.99,1.40, Ptrend = 0.03). The HR was higher for the 10-year AEI at 3 km from municipal solid waste facilities (HR ≥ median.vs.0:1.50, 95% CI: 0.98, 2.29; Ptrend = 0.07). Risk was higher among ever smokers (vs. never smokers) in the top quartile of the 3 km AEI (HRQ4:1.41, 95% CI:1.12,1.77, Ptrend = 0.003; Pinteraction = 0.03) and higher risk for ER negative tumors was suggested (HRQ4:1.47, 95% CI: 0.95, 2.28, Ptrend = 0.07, Pheterogeneity = 0.17). Our findings suggest that residential exposure to PCDD/F emissions may confer an increased risk of breast cancer.

Verification of In Vivo Estrogenic Activity for Four Per- and Polyfluoroalkyl Substances (PFAS) Identified as Estrogen Receptor Agonists via New Approach Methodologies

Given concerns about potential toxicological hazards of the thousands of data-poor per- and polyfluorinated alkyl substances (PFAS) currently in commerce and detected in the environment, tiered testing strategies that employ high-throughput in vitro screening as an initial testing tier have been implemented. The present study evaluated the effectiveness of previous in vitro screening for identifying PFAS capable, or incapable, of inducing estrogenic responses in fish exposed in vivo. Fathead minnows (Pimephales promelas) were exposed for 96 h to five PFAS (perfluorooctanoic acid [PFOA]; 1H,1H,8H,8H-perfluorooctane-1,8-diol [FC8-diol]; 1H,1H,10H,10H-perfluorodecane-1,10-diol [FC10-diol]; 1H,1H,8H,8H-perfluoro-3,6-dioxaoctane-1,8-diol [FC8-DOD]; and perfluoro-2-methyl-3-oxahexanoic acid [HFPO-DA]) that showed varying levels of in vitro estrogenic potency. In agreement with in vitro screening results, exposure to FC8-diol, FC10-diol, and FC8-DOD caused concentration-dependent increases in the expression of transcript coding for vitellogenin and estrogen receptor alpha and reduced expression of insulin-like growth factor and apolipoprotein eb. Once differences in bioconcentration were accounted for, the rank order of potency in vivo matched that determined in vitro. These results provide a screening level benchmark for worst-case estimates of potential estrogenic hazards of PFAS and a basis for identifying structurally similar PFAS to scrutinize for putative estrogenic activity.

Organochlorine pesticides and polychlorinated biphenyls in city drains in Makurdi, central Nigeria: Seasonal variations, source apportionment and risk assessment

A study of seasonal variation, sources and potential risks of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in open city drains in Makurdi, Central Nigeria was carried out. OCPs and PCBs were quantified using gas chromatograph-mass spectrometer. The total (∑₈OCPs) concentrations (ngL^-1) of OCPs in water was 2.99 with a mean ± SD of 0.75 ± 0.12 during wet season, while during dry season, the values were 11.43 and 2.86 ± 1.54 respectively. In sediment, the total concentration (ngg^-1) of OCPs was 5270.66 with a mean ± SD of 1756.89 ± 450.01 during wet season and a total concentration of 5837.93 and the mean ± SD of 1945.98 ± 646.04, during dry season. Source apportionment of OCPs suggested historic application of the pollutants. The total (∑₇PCBs) concentration (ngL^-1) of PCBs in water was 0.24 with a mean ± SD of 0.03 ± 0.02 during wet season and a total concentration of 0.61 with a mean ± SD of 0.09 ± 0.11 during dry season. The total concentration (ngg^-1) of PCBs in sediment was 37.88, mean ± SD of 5.41 ± 5.93 during wet season and a total of 47.07 and mean ± SD of 6.72 ± 7.27 during dry season. Ecological risk assessment based on effect range low (ERL) and effect range median (ERM) or threshold effect level (TEL) and probable effect level (PEL) that ecological risks were possible for some OCPs in this study, which calls for source control and remediation of the affected sites. Toxicity equivalency (TEQ) of PCB-118, the dioxin-like congener, indicated that it was most harmful to humans/mammals followed by birds, then fish.

Combined exposure to multiple dioxins and dioxin-like polychlorinated biphenyls on hypertension among US adults in NHANES: a cross-sectional study under three statistical models

Dioxins and dioxin-like polychlorinated biphenyls (DL-PCBs) are mainly released as by-products of human activities, often in the form of mixtures, and the potential harm on human health deserves attention. Therefore, our study aimed to analyze the combined effect of dioxins and DL-PCB exposures on hypertension (HTN) among US adults. Data of eligible participants were acquired from the National Health and Nutrition Examination Survey (NHANES). Multiple logistic regression models with adjustment for covariates were applied to explore the associations between 13 persistent organic pollutants (POPs) and HTN. Stratified analyses and interaction analyses were then conducted by age and gender. Finally, the combined effects of dioxins and DL-PCBs on HTN were assessed by the weighted quantile sum (WQS) model and the Bayesian kernel machine regression (BKMR) model. A total of 976 adults were included in our study, of whom 397 had HTN. Spearman correlations indicated positive correlations among 13 POPs. And most of them (except PCB28, PCB66, and 1,2,3,4,7,8,9-hpcdf) had significant effects on HTN. The result of WQS revealed that mixed exposure to dioxins and DL-PCBs was significantly associated with increased risk of HTN (OR: 2.205; 95% CIs: 1.555, 3.127). The BKMR model also presented a positive trend of HTN risk with exposure to multiple dioxins and DL-PCBs. And 1,2,3,4,6,7,8,9-ocdd may be the main factor for this positive association. Considering the limitations of our cross-sectional study with the small sample, further prospective studies are necessary to validate our findings.

Spatial and temporal distribution of polyhalogenated carbazoles in sediments from the Yangtze River estuary and adjacent East China Sea

Polyhalogenated carbazoles (PHCZs) have been increasingly detected in marine sediment, raising concerns in recent years. In this study, sediment samples (42 surface and one core) were collected from the Yangtze River estuary and the adjacent East China Sea, and eleven PHCZs and unsubstituted carbazole were measured. The total concentration of PHCZs in surface sediments ranged from 0.19 to 2.49 ng/g dry weight (d.w.) (median 1.03 ng/g d. w.). The congener compositions of PHCZs in the surface sediment were dominated by 3,6-dichlorocarbazole (36-CCZ, 53.2%), followed by 3-chlorocarbazole (14.9%) and 3,6-dibromocarbazole (36-BCZ, 11.8%). Carbazole in the surface sediment ranged from not detected to 9.89 ng/g (median 1.25 ng/g), with a detection frequency of 81.0%. The spatial distribution of 36-CCZ in surface sediments exhibited a clear decline from the coast to offshore, while 36-BCZ showed the opposite trend. The depth profile of 36-CCZ was maintained at a relatively low and stable concentration (about 0.36 ng/g) in core segments from 1903 to 1951, followed by a steady increase to 1.5 ng/g in 2006. This increase coincides with the industrial and agricultural development in China that began in the 1950s. In contrast, the other detected PHCZs and carbazole maintained stable, low concentrations over time. These spatial and temporal patterns suggest that 36-CCZ in this area is predominantly from anthropogenic sources, while 36-BCZ has a natural origin. Toxic equivalent estimations indicated that dioxin-like effects for the observed PHCZs were low. These results provide useful information for understanding the origin of PHCZs and carbazole in this area.

New emission inventory reveals termination of global dioxin declining trend

Accurate estimates of spatiotemporally resolved Polychlorinated dibenzo-p-dioxins (PCDD/Fs, or dioxins) emissions are critical for understanding their environmental fate and associated health risks. In this study, by utilizing an empirical regression model for PCDD/Fs emissions, we developed a global emission inventory for 17 toxic PCDD/Fs congeners from 8 source sectors with a spatial resolution of 1° × 1° from 2002 to 2018. The results show that PCDD/Fs emissions decreased by 25.7 % (12.5 kg TEQ) between 2002 and 2018, mostly occurring in upper- and lower-middle income countries. Globally, open-burning processes, waste incineration, ferrous and nonferrous metal production sectors and heat and power generation were the major source sectors of PCDD/Fs. Spatially, high PCDD/Fs emissions were mainly identified in East and South Asia, Southeast Asia, and part of Sub-Saharan Africa. We find that the declining trend of dioxin emissions over the past decades terminated from the early 2010s due to increasing significance of wildfire induced emissions in the total emission. The PCDD/Fs emission inventory developed in the present study was verified by inputting the inventory as initial conditions into an atmospheric transport model, the Canadian Model for Environmental Transport of Organochlorine Pesticides (CanMETOP), to simulate PCDD/Fs concentrations in air and soil. The predicted concentrations were compared to field sampling data. The good agreement between the modeled and measured concentrations demonstrates the reliability of the inventory.

PCDD/Fs and PCBs in hen eggs from a contaminated area in Italy: a 9 years spatio-temporal monitoring study

Eggs can represent a food susceptible to contamination, with bioaccumulation potential for POPs. The Province of Taranto, Southern Italy, is of particular relevance in this context because of the presence of industrial sources of PCDD/Fs and PCBs. The aim of this study was to analyze and report the levels of these contaminants in hen eggs sampled in farms located within a radius of 20 km from the industrial area of Taranto. Between 2013 and 2021, 227 hen eggs were collected, according to a special monitoring plan of the Prevention Department. Samples were analyzed by the National Reference Laboratory for Halogenated POPs in Feed and Food. Median (IQR) values were: 0.28 (0.59) pg WHO-TEQ/g fat for PCDD/Fs, 0.89 (1.70) pg WHO-TEQ/g fat for PCDD/Fs + DL-PCBs, 0.57 (1.16) pg WHO-TEQ/g fat for DL-PCBs, 2.24 (5.51) ng/g fat for NDL-PCBs. Samples not-compliant (Reg. 1881/2006/EC and amendments) for at least one contaminant were 17 (7.5%). No contaminants values or exceedances showed a statistically significant correlation with distance from industrial area (p > 0.05). Higher PCDD/Fs values were observed in first and second quarters (p < 0.05). All contaminants' values pairwise combinations showed significant (p < 0.0001) strong (ρ > 0.7) correlation. According to our epidemiological investigations, the exceedances are to be attributed to factors mainly related to farmers' wrong habits. These results confirmed the importance of the monitoring of contaminants' levels in the matrices at risk as well as to focus on enhancing good management practices on eggs-producing farms.

Persistent organic pollutants in human milk from primiparae - correlations, global, regional, and national time-trends

Human breast milk reflects body burden of chemicals and has been used for exposure assessment to estimate risks of humans from pollutants. Harmonized protocols for sampling and analysis of persistent organic pollutants (POPs) have become widely available after the entry-into-force of the Stockholm Convention on POPs and activities coordinated by the United Nations Environment Programme (UNEP). These protocols promote the generation of national pools consisting of breast milk from first mothers directed to assess at national level but have not been assessed comprehensively. Early surveys date back to the mid-1980s, but the majority of the pools and high numbers of POPs analytes were available after the year 2000. Our assessment of pools from 90 countries for 29 POPs showed declining time trends for almost all POPs and significant differences between all 5-year time periods. However, in general, the most recent data from samples collected between 2015 and 2019, were no longer different from the period immediately prior. The strongest declines were seen for POPs that have already been measured for more than 30 years, i.e., dioxin-like POPs and polychlorinated biphenyls (PCB). For certain initial and newly listed POPs, such as aldrin, endrin, mirex, toxaphene, α-HCH, chlordecone, endosulfan, pentachlorobenzene, hexachlorobutadiene, decabromo diphenyl ether, hexabromobiphenyl 153, and perfluorohexane sulfonate, the median values in pools were always zero, and some of them were never quantified in these human milk pools. Since these POPs may be present at national level, we recommend including all listed POPs into surveys related to the Stockholm Convention.

Endocrine-Disrupting Chemicals and Their Effects in Pet Dogs and Cats: An Overview

Over the past few decades, several pollutants classified as environmental endocrine-disrupting chemicals (EDCs) have become a matter of significant public health concern. Companion animals play a major role in human society, and pet ownership is substantially increasing worldwide. These intimate human-pet relationships imply sharing much of the same environment, thus including exposure to similar levels of EDCs in daily routine. Here, we review the current knowledge on the sources and routes of exposure to EDCs in domestic indoor and outdoor environments and discuss whether endocrine disruption is a health concern in pets. We summarize the phenomenon of endocrine disruption, providing examples of EDCs with a known impact on dog and cat health. Then, we propose an overview of the literature on the adverse effects of EDCs in domestic pets, with a special focus on the health of reproductive and thyroid systems. Finally, we explore the potential role of companion animals as unintentional sentinels of environmental exposure to EDCs and the implications for public health risk assessment in a "shared risk" scenario. Overall, this review supports the need for an integrated approach considering humans, animals, and the environment as a whole for a comprehensive assessment of the impact of EDCs on human and animal health.

New insight into the perplexing toxic features of PCBs: A study of nephrotoxicity in an animal model

The present study investigated the effects of PCBs on the rat kidneys with attention given to the determination critical effect dose (CED) using the Benchmark dose (BMD) approach. Male albino Wistar rats (7 animals per group) were given by oral gavage Aroclor 1254 dissolved in corn oil at doses of 0.0, 0.5, 1, 2, 4, 8, or 16 mg/kg b.w./day for 28 days. The PCB nephrotoxicity was manifested by a dose-dependent changes in serum urea levels. The study has also revealed PCB-induced oxidative stress induction in kidneys. The observed nephrotoxic effects can be partly explained by oxidative damage of lipids and proteins in the kidneys due to observed reduced CuZnSOD activity and disturbances in antioxidant protection. Аll the renal oxidative stress parameters showed dependence on PCB oral doses as well as internal, measure kidney PCB levels. Calculated BMDL values were lower than estimated no observed adverse effect levels (NOAEL) based on the study, suggesting the importance of BMD approach use in future risk assessment.

A Guideline Value for Dioxin-Like Compounds in Marine Sediments

Sediments to be dredged as part of the installation of a harbor crossing in Sydney, Australia, contained measurable concentrations of dioxin-like compounds. To assess the suitability of these sediments for ocean disposal, a defensible sediment quality guideline value (SQGV) for dioxin-like compounds, expressed as pg toxic equivalent (TEQ)_fish /g dry weight, was required. There were deemed to be too many uncertainties associated with a value derived using effects data from field studies. A similar issue was associated with values based on equilibrium partitioning from sediment to pore water, largely associated with the wide range of reported sediment:water partition coefficients. Greater certainty was associated with the use of a tissue residue approach based on equilibrium partitioning between sediment and organisms determined using tissue concentrations in fish, the most sensitive aquatic biota, and biota:sediment accumulation factors. The calculation of an appropriate SQGV used data for dioxin-like compounds in both fish and sediments from Sydney Harbor. A conservative SQGV for dioxin-like compounds of 70 pg TEQ/g dry weight was deemed to be adequately protective of biota that might be exposed to these contaminants in sediments at the ocean spoil ground. The approach is transferable to similar situations internationally. Environ Toxicol Chem 2023;42:257-271. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

A congener-specific modelling approach for the transfer of polychlorinated dibenzo-p-dioxins and dibenzofurans and dioxin-like polychlorinated biphenyls from feed to eggs of laying hens

Calibration of a kinetic model for the transfer of PCDD/Fs and dl-PCBs from feed to the hen's body and eggs was thus far restricted to the total TEQ concentration, i.e. the summed concentrations of PCDD/Fs and dl-PCBs expressed in terms of equivalents of 2,3,7,8-TCDD. However, this approach may lead to over- or underestimation of the transfer if the mixture contains congeners with kinetic characteristics which differ considerably from those used in such a model. This paper extends a previous transfer model of PCDD/Fs and dl-PCBs from feed to egg yolk fat and abdominal fat of high production laying hens, based on the total TEQ approach, to the level of individual congeners. Both modelling approaches are compared and the new approach is presented as a webtool application. This congener-specific approach enabled the calibration of 25 of the 29 relevant PCDD/F and dl-PCB congeners with respect to their individual transfer characteristics to body fat and egg yolk fat and their clearance from the body. Limitations of the available experimental data prevented the calibration of 1,2,3,4,6,7,8-HpCDD, OCDD, OCDF and PCB 123. The fraction transferred to egg yolk fat after long-term daily intake of contaminated feed was found to be at least 0.78 for 2,3,7,8-TCDD, 0.75 for PeCDD, 0.42-0.61 for HxCDDs, 0.70 for 2,3,7,8-TCDF, 0.71 for PeCDF, 0.54-0.60 for HxCDFs, 0.18-0.24 for HpCDFs and 0.89-1.00 for dl-PCBs. Various experimental and feed incident mixtures were used to compare the total TEQ- model with the congener-specific approach. An overestimation of the transfer by the total TEQ method was shown in particular for mixtures with a substantial contribution of hexa-, hepta- and octa-PCDD/Fs to the total TEQ level.

Endocrine disruptors and endometriosis

Endometriosis is a hormone-dependent inflammatory gynecological disease of reproductive-age women. It is clinically and pathologically characterized by the presence of functional endometrium as heterogeneous lesions outside the uterine cavity. The two major symptoms are chronic pelvic pain and infertility, which profoundly affect women's reproductive health and quality of life. This significant individual and public health concerns underscore the importance of understanding the pathogenesis of endometriosis. The environmental endocrine-disrupting chemicals (EDCs) are exogenous agents that interfere with the synthesis, secretion, transport, signaling, or metabolism of hormones responsible for homeostasis, reproduction, and developmental processes. Endometriosis has been potentially linked to exposure to EDCs. In this review, based on the robust literature search, we have selected four endocrine disruptors (i) polychlorinated biphenyls (PCB)s (ii) dioxins (TCDD) (iii) bisphenol A (BPA) and its analogs and (iv) phthalates to elucidate their critical role in the etiopathogenesis of endometriosis. The epidemiological and experimental data discussed in this review indicate that these four EDCs activate multiple intracellular signaling pathways associated with proinflammation, estrogen, progesterone, prostaglandins, cell survival, apoptosis, migration, invasion, and growth of endometriosis. The available information strongly indicates that environmental exposure to EDCs such as PCBs, dioxins, BPA, and phthalates individually or collectively contribute to the pathophysiology of endometriosis. Further understanding of the molecular mechanisms of how these EDCs establish endometriosis and therapeutic strategies to mitigate the effects of these EDCs in the pathogenesis of endometriosis are timely needed. Moreover, understanding the interactive roles of these EDCs in the pathogenesis of endometriosis will help regulate the exposure to these EDCs in reproductive age women.

On the Permeation of Polychlorinated Dibenzodioxins and Dibenzofurans through Lipid Membranes: Classical MD and Hybrid QM/MM-EDA Analysis

The permeation of dioxin-like pollutants, namely, chlorinated dibenzodioxins and dibenzofurans, through lipid membranes has been simulated using classic molecular dynamics (CMD) combined with the umbrella sampling approach. The most toxic forms of chlorinated dibenzodioxin and dibenzofuran, 2,3,7,8-tetrachloro-p-dibenzodioxin (TCDD) and 2,3,7,8-tetrachlorodibenzofuran (TCDF), and a dioleyl-phosphatidylcholine (DOPC) lipid membrane of 50 Å wide have been chosen for our study. The free energy profile shows the penetration process is largely favoured thermodynamically (ΔG ≈ -12 kcal/mol), with a progressively decrease of the free energy until reaching the energy minima at distances of 8 Å and 9.5 Å from the centre of the membrane for, respectively, TCDD and TCDF. At the centre of the membrane, both molecules display subtle local maxima with free energy differences of 0.5 and 1 kcal/mol with respect to the energy minima for TCDD and TCDF, respectively. Furthermore, the intermolecular interactions between the molecules and the lipid membrane have been characterized at the minima and the local maxima using hybrid quantum mechanics/molecular mechanics energy decomposition analysis (QM/MM-EDA). Total interaction energies of -17.5 and -16.5 kcal/mol have been found at the energy minima for TCDD and TCDF, respectively. In both cases, the dispersion forces govern the molecule-membrane interactions, no significant changes have been found at the local maxima, in agreement with the classical free energy profile. The small differences found in the results obtained for TCDD and TCDF point out that the adsorption and diffusion processes through the cell membrane are not related to the different toxicity shown by these pollutants.

Lossless enrichment of trace analytes in levitating droplets for multiphase and multiplex detection

Concentrating a trace amount of molecules from liquids, solid objects, or the gas phase and delivering them to a localized area are crucial for almost any trace analyte detection device. Analytes within a liquid droplet resting on micro/nanostructured surfaces with liquid-repellent coatings can be concentrated during solvent evaporation. However, these coatings suffer from complex manufacturing procedures, poor versatility, and limited analyte enrichment efficiency. Here, we report on the use of an acoustic levitation platform to losslessly concentrate the analyte molecules dissolved in any volatile liquid, attached to solid objects, or spread in air. Gold nanoparticles can be simultaneously concentrated with the analytes in different phases, realizing sensitive, surface-enhanced Raman scattering detection even at attomolar (10^-18 mol/L) concentration levels. The acoustic levitation platform-enabled, lossless analyte enrichment can significantly increase the analytical performance of many conventional microsensing techniques.