Results of an international interlaboratory study on dioxin-like activities in drinking-, river surface- and wastewater using DR CALUX bioassay.

Aquatic animals and consumers of aquatic animals are exposed to increasingly complex mixtures of known and as-yet-unknown chemicals with dioxin-like toxicities in the water cycle. Effect- and cell-based bioanalysis can cover known and yet unknown dioxin and dioxin-like compounds as well as complex mixtures thereof but need to be standardized and integrated into international guidelines for environmental testing. In an international laboratory testing (ILT) following ISO/CD 24295 as standard procedure for rat cell-based DR CALUX un-spiked and spiked extracts of drinking-, surface-, and wastewater were validated to generate precision data for the development of the full ISO-standard. We found acceptable repeatability and reproducibility ranges below 36 % by DR CALUX bioassay for the tested un-spiked and spiked water of different origins. The presence of 17 PCDD/Fs and 12 dioxin-like PCBs was also confirmed by congener-specific GC-HRMS analysis. We compared the sum of dioxin-like activity levels measured by DR CALUX bioassay (expressed in 2,3,7,8-TCDD Bioanalytical Equivalents, BEQ; ISO 23196, 2022) with the obtained GC-HRMS chemical analysis results converted to toxic equivalents (TEQ; van den Berg et al., 2013).

Association between combined exposure to dioxins and arthritis among US adults: a cross-sectional study.

Dioxins and dioxin-like compounds (DLCs) are common pollutants hazardous to human health. We applied 12 dioxins and DLCs data of 1851 participants (including 484 arthritis patients) from National Health Examination Survey (NHANES) 2001-2004 and quadrupled them into rank variables. Multivariate logistic regression, weighted quantile sum (WQS) regression, and Bayesian kernel machine regression (BKMR) models were used to explore the relationship between individual or mixed exposure to the pollutants and arthritis after adjusting for multiple covariates. In multivariable logistic regression with an individual dioxin or DLC, almost every chemical was significantly positively associated with arthritis, except PCB66 (polychlorinated biphenyl 66) and 1,2,3,4,6,7,8-heptachlorodibenzofuran (hpcdf). The WQS model indicated that the combined exposure to the 12 dioxins and DLCs was positively linked to arthritis (OR: 1.884, 95% CI: 1.514-2.346), with PCB156 (weighted 0.281) making the greatest contribution. A positive trend between combined exposure and arthritis was observed in the BKMR model, with a posterior inclusion probability (PIP) of 0.987 for PCB156, which was also higher than the other contaminants.

Congener Variation of Genetic Dependent-Developmental Toxicology in Two Emerging Classes of Dioxin-like Compounds.

Emerging classes of dioxin-like compounds (DLCs) like hydroxylated/methoxylated polybrominated diphenyl ethers (HO-/MeO-PBDEs) and polychlorinated diphenyl sulfides (PCDPSs) could lead to diverse adverse outcomes in humans and wildlife, yet knowledge gaps exist in their molecular mechanisms associated with different structures following early life environmental exposure. This study integrated a genetic knockout technique and concentration-dependent reduced zebrafish transcriptome approach (CRZT) to unravel the toxicological pathways underpinning developmental toxicity of four HO-/MeO-PBDEs and five PCDPSs at environmentally relevant doses. Generally, the dependence of aryl hydrocarbon receptor (AhR) on the embryotoxicity and transcriptomic potencies induced by the HO-PBDEs and PCDPSs varied across different congeners. The knockout of the ahr2 gene led to 1.02- to 76.48-fold decreases of DLC-induced embryotoxicities and reduced the transcriptome-based potencies ranging from 1.38 to 2124.74 folds in the CRZT test. The fold changes denoting AhR-mediated potentials significantly increased with the increasing chlorination degrees of MeO-PBDEs and PCDPSs (p < 0.05). Moreover, ahr2 knockout primarily affected the DLC-induced early molecular responses relevant to DNA damage, enzyme activation, and organ development. Our integrated approach revealed the differential role of AhR in mediating the developmental toxicity of emerging DLCs possessing varied structures at environmentally relevant doses.

Functional characterization of common carp (Cyprinus carpio) AHRs: Subform-specific sensitivity to dioxin and interspecies differences.

Dioxins are widely known to bioaccumulate in the body and produce a wide spectrum of toxic effects on both humans and wildlife. In addition, some novel sorts of compounds that were similar in structure and effect were gradually identified and termed dioxin-like compounds (DLCs). The toxicity of dioxins as well as DLCs is predominantly mediated by the dioxin receptor (aryl hydrocarbon receptor, AHR) in animals, which is usually differentially expressed and functionally distinct (especially the sensitivity to dioxins) among species, possibly resulting in species-specific variations in the toxicity of dioxins. Therefore, detailed functional exploration of the AHRs of a given species, such as the common carp (which is a vital wild and commercial species with a broad geological distribution) in the current study, will enable a comprehensive ecotoxicity evaluation. Through genome survey and phylogenetic analysis, we identified three AHRs (AHR1a, AHR1b, and AHR2) and two ARNTs (ARNT1 and ARNT2). AHR2 was observed to have greater expression abundance in the gill and brain, and may serve as the predominant subform. Those AHRs and ARNTs are functional, and the AHRs can be efficiently transactivated by the classical dioxin congener 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). We individually determined the EC50 values of AHR1a (0.41 ± 0.24 nM), AHR1b (12.80 ± 3.28 nM), and AHR2 (0.64 ± 0.49 nM), and found that: 1) The AHR sensitivities of common carp and zebrafish (phylogenetically close species) are relatively similar. AHR1a and the predominant form AHR2 have greater sensitivity to TCDD. 2) ARNT1 and ARNT2 do not produce different sensitivities, but with distinct induction fold, of a given AHR transactivation when cooperating as the partner; 3) Distinct AHR subforms of the same or distinct species can have even one or two orders of magnitude differences in sensitivity. In summary, the current study will add to the knowledge of AHR biology and help improve ecotoxicology research on dioxins and DLCs.

A Physiologically Based Pharmacokinetic (PBPK) Modeling Framework for Mixtures of Dioxin-like Compounds.

Humans are exposed to persistent organic pollutants, such as dioxin-like compounds (DLCs), as mixtures. Understanding and predicting the toxicokinetics and thus internal burden of major constituents of a DLC mixture is important for assessing their contributions to health risks. PBPK models, including dioxin models, traditionally focus on one or a small number of compounds; developing new or extending existing models for mixtures often requires tedious, error-prone coding work. This lack of efficiency to scale up for multi-compound exposures is a major technical barrier toward large-scale mixture PBPK simulations. Congeners in the DLC family, including 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), share similar albeit quantitatively different toxicokinetic and toxicodynamic properties. Taking advantage of these similarities, here we reported the development of a human PBPK modeling framework for DLC mixtures that can flexibly accommodate an arbitrary number of congeners. Adapted from existing TCDD models, our mixture model contains the blood and three diffusion-limited compartments-liver, fat, and rest of the body. Depending on the number of congeners in a mixture, varying-length vectors of ordinary differential equations (ODEs) are automatically generated to track the tissue concentrations of the congeners. Shared ODEs are used to account for common variables, including the aryl hydrocarbon receptor (AHR) and CYP1A2, to which the congeners compete for binding. Binary and multi-congener mixture simulations showed that the AHR-mediated cross-induction of CYP1A2 accelerates the sequestration and metabolism of DLC congeners, resulting in consistently lower tissue burdens than in single exposure, except for the liver. Using dietary intake data to simulate lifetime exposures to DLC mixtures, the model demonstrated that the relative contributions of individual congeners to blood or tissue toxic equivalency (TEQ) values are markedly different than those to intake TEQ. In summary, we developed a mixture PBPK modeling framework for DLCs that may be utilized upon further improvement as a quantitative tool to estimate tissue dosimetry and health risks of DLC mixtures.

Dioxin-like compounds formation mediated by Fe3+-montmorillonite: The substituent effects of halophenols.

Toxic dioxin or/and dioxin-like compounds could be naturally formed from the reaction of halophenols on Fe3+-montmorillonite minerals under ambient conditions. Given that the toxicities and productions of dioxin or/and dioxin-like compounds are largely determined by the number, species, and position of the carried halogen atoms, it is necessary to explore the substituent effects on the reaction of halophenols with Fe3+-montmorillonite. Herein, Fe3+-montmorillonite catalyzed polymerizations of six halophenols were examined in a wide range of relative humidity (10%∼80%) using combinations of mass spectrometry identifications and density functional theory calculations. Results show that both the position and species of the substituents substantially impact the reaction rate, product species, and transformation pathways. In general, regardless of humidity ortho-substituted chlorophenols are more reactive than meta-substituted chlorophenols, which is also supported by the density functional theory calculations indicating that the ortho positions are more likely to be attacked. Regarding substituent species, bromophenols are slightly more reactive and also more easily affected by humidities than chlorophenols, which is due to the weaker electron absorbing ability of the bromine atom than the chlorine atom. Hydroxylated polyhalogenated diphenyl ethers are more frequently detected polymerization products, although hydroxylated polyhalogenated biphenyls are greater quantity of products. Overall, this study provides useful information for understanding the natural formation of dioxin or/and dioxin-like compounds mediated by clay minerals and underlying reaction mechanisms.

Unraveling the differential impact of PAHs and dioxin-like compounds on AKR1C3 reveals the EGFR extracellular domain as a critical determinant of the AHR response.

Polycyclic aromatic hydrocarbons (PAHs), dioxin-like compounds (DLCs) and structurally-related environmental pollutants may contribute to the pathogenesis of various diseases and disorders, primarily by activating the aryl hydrocarbon receptor (AHR) and modulating downstream cellular responses. Accordingly, AHR is considered an attractive molecular target for preventive and therapeutic measures. However, toxicological risk assessment of AHR-modulating compounds as well as drug development is complicated by the fact that different ligands elicit remarkably different AHR responses. By elucidating the differential effects of PAHs and DLCs on aldo-keto reductase 1C3 expression and associated prostaglandin D2 metabolism, we here provide evidence that the epidermal growth factor receptor (EGFR) substantially shapes AHR ligand-induced responses in human epithelial cells, i.e. primary and immortalized keratinocytes and breast cancer cells. Exposure to benzo[a]pyrene (B[a]P) and dioxin-like polychlorinated biphenyl (PCB) 126 resulted in a rapid c-Src-mediated phosphorylation of EGFR. Moreover, both AHR agonists stimulated protein kinase C activity and enhanced the ectodomain shedding of cell surface-bound EGFR ligands. However, only upon B[a]P treatment, this process resulted in an auto-/paracrine activation of EGFR and a subsequent induction of aldo-keto reductase 1C3 and 11-ketoreduction of prostaglandin D2. Receptor binding and internalization assays, docking analyses and mutational amino acid exchange confirmed that DLCs, but not B[a]P, bind to the EGFR extracellular domain, thereby blocking EGFR activation by growth factors. Finally, nanopore long-read RNA-seq revealed hundreds of genes, whose expression is regulated by B[a]P, but not by PCB126, and sensitive towards pharmacological EGFR inhibition. Our data provide novel mechanistic insights into the ligand response of AHR signaling and identify EGFR as an effector of environmental chemicals.

The aryl hydrocarbon receptor: A predominant mediator for the toxicity of emerging dioxin-like compounds.

The aryl hydrocarbon receptor (AHR) is a member of the basic helix-loop-helix/Per-ARNT-Sim (bHLH-PAS) family of transcription factors and has broad biological functions. Early after the identification of the AHR, most studies focused on its roles in regulating the expression of drug-metabolizing enzymes and mediating the toxicity of dioxins and dioxin-like compounds (DLCs). Currently, more diverse functions of AHR have been identified, indicating that AHR is not just a dioxin receptor. Dioxins and DLCs occur ubiquitously and have diverse health/ecological risks. Additional research is required to identify both shared and compound-specific mechanisms, especially for emerging DLCs such as polyhalogenated carbazoles (PHCZs), polychlorinated diphenyl sulfides (PCDPSs), and others, of which only a few investigations have been performed at present. Many of the toxic effects of emerging DLCs were observed to be predominantly mediated by the AHR because of their structural similarity as dioxins, and the in vitro TCDD-relative potencies of certain emerging DLC congeners are comparable to or even greater than the WHO-TEFs of OctaCDD, OctaCDF, and most coplanar PCBs. Due to the close relationship between AHR biology and environmental science, this review begins by providing novel insights into AHR signaling (canonical and non-canonical), AHR's biochemical properties (AHR structure, AHR-ligand interaction, AHR-DNA binding), and the variations during AHR transactivation. Then, AHR ligand classification and the corresponding mechanisms are discussed, especially the shared and compound-specific, AHR-mediated effects and mechanisms of emerging DLCs. Accordingly, a series of in vivo and in vitro toxicity evaluation methods based on the AHR signaling pathway are reviewed. In light of current advances, future research on traditional and emerging DLCs will enhance our understanding of their mechanisms, toxicity, potency, and ecological impacts.

Using In Vitro and Machine Learning Approaches to Determine Species-Specific Dioxin-like Potency and Congener-Specific Relative Sensitivity among Birds for Brominated Dioxin Analogues.

There is a paucity of experimental data regarding dioxin-like toxicity of polybrominated dibenzo-p-dioxins/dibenzofurans (PBDD/Fs) and non-ortho polybrominated biphenyls (PBBs). In this study, avian aryl hydrocarbon receptor 1 (AHR1)-luciferase reporter gene assays were used to determine their species-specific dioxin-like potencies (DLPs) and congener-specific interspecies relative sensitivities in birds. The results suggested that DLPs of the brominated congeners for chicken-like (Ile324_Ser380) species did not always follow World Health Organization toxicity equivalency factors of their chlorinated analogues. For ring-necked pheasant-like (Ile324_Ala380) and Japanese quail-like (Val324_Ala380) species, the difference in DLP for several congeners was 1 or even 2 orders of magnitude. Moreover, molecular docking and molecular dynamics simulation were performed to explore the interactions between the brominated congeners and AHR1-ligand-binding domain (LBD). The molecular mechanics energy (EMM) between each congener and each individual amino acid (AA) residue in AHR1-LBD was calculated. These EMM values could finely characterize the final conformation of species-specific AHR1-LBD for each brominated congener. Based on this, mechanism-driven generalized linear models were successfully built using machine learning algorithms and the spline approximation method, and these models could qualitatively predict the complex relationships between AHR1 conformations and DLPs or avian interspecies relative sensitivity to brominated dioxin-like compounds (DLCs). In addition, several AAs conserved among birds were found to potentially interact with species-specific AAs, thereby inducing species-specific interactions between AHR1 and brominated DLCs. The present study provides a novel strategy to facilitate the development of mechanism-driven computational prediction models for supporting safety assessment of DLCs, as well as a basis for the ecotoxicological risk assessment of brominated congeners in birds.

Polychlorinated Diphenyl Sulfides: An Emerging Class of Persistent, Bioaccumulative, and Toxic Substances in the Environment.

Polychlorinated diphenyl sulfides (PCDPSs) have recently attracted increasing attention due to their potential adverse effects on human and ecosystem health. We present a review regarding their environmental occurrence, persistence, bioaccumulation, toxicity, and biotransformation. The existing literature demonstrates that PCDPSs are ubiquitous in various environmental matrices, are persistent in the environment, and have long-range transport potential. In addition, the high bioaccumulation potential of these emerging pollutants, especially the low chlorinated PCDPS congeners, has been confirmed based on both theoretical calculations and experimental investigations. Moreover, a spectrum of adverse effects, such as acute liver injury, retardation of development, reproductive disorders, and increased mortality have been widely reported in vertebrates. These adverse outcomes were associated with oxidative stress and activation of aryl hydrocarbon receptors. Given these findings, PCDPSs represent candidate persistent, bioaccumulative, and toxic substances and thus deserve further research to fully elucidate their environmental behavior and fate, and evaluate the risks to human and ecosystem health. Environ Toxicol Chem 2021;40:2657-2666. © 2021 SETAC.

Occurrence and spatial distribution of dioxin and dioxin-like compounds in topsoil of Taranto (Apulia, Italy) by GC-MS analysis and DR-CALUX® bioassay.

The aim of the present study was to assess the occurrence and spatial distribution of PCDD/Fs and dioxin-like compounds in topsoils of Taranto (Apulia Region), one of the most heavily industrialized and contaminated area of Southern Italy. A combined approach of chemical analysis by GC-MS/MS and AhR reporter gene bioassay was applied in a subset of topsoil samples (n = 20) collected in 2017-18 from ten sites embracing three levels of risk (from high to low) in the framework of a large survey inside Taranto municipality. TCDD-BEQs and GC-MS/MS TEQWHO and TEQTHEORETICAL revealed a decreasing trend with the distance from main industrial settings and landfill areas. A strong correlation between TCDD-BEQs and TEQWHO values (R2 = 0.85) and TEQTHEORETICAL (R2 = 0.88) was also found. In 3 out of 10 topsoil investigated, BEQs and TEQWHO/THEORETICAL resulted above Italian National Regulatory Limits for ∑PCDD/Fs in green, private and recreational used soils (10 ng TEQ/kg d.w. D.Lgs 152/2006) and for ∑PCDD/F/dl-PCBs in agricultural and farming soil (6 ng TEQ/kg d.w. D.M. 46/2019). GC-MS/MS pattern revealed the highest prevalence of dl-PCBs in 6 out of 10 sites, followed by PCDFs and PCDDs. Those sites are all located in proximity of main industrial steel and iron ore sinter plant, steel plant's landfills and illegal dumping sites. An update on occurrence and spatial distribution of PCDD/Fs and dl-PCBs contamination of Taranto urban soils was obtained and the DR-CALUX® bioassay was further recommended as a suitable screening tool for environmental and human risk assessment.

Development of a Range of Plausible Noncancer Toxicity Values for 2,3,7,8-Tetrachlorodibenzo-p-Dioxin Based on Effects on Sperm Count: Application of Systematic Review Methods and Quantitative Integration of Dose Response Using Meta-Regression.

Regulatory agencies have derived noncancer toxicity values for 2,3,7,8-tetrachlorodibenzo-p-dioxin based on reduced sperm counts relying on single studies from a large body of evidence. Techniques such as meta-regression allow for greater use of the available data while simultaneously providing important information regarding the uncertainty associated with the underlying evidence base when conducting risk assessments. The objective herein was to apply systematic review methods and meta-regression to characterize the dose-response relationship of gestational exposure and epididymal sperm count. Twenty-three publications (20 animal studies consisting of 29 separate rat experimental data sets, and 3 epidemiology studies) met inclusion criteria. Risk of bias evaluation was performed to critically appraise study validity. Low to very low confidence precluded use of available epidemiological data as candidate studies for dose-response due to inconsistencies across the evidence base, high risk of bias, and general lack of biological coherence, including lack of clinical relevance and dose-response concordance. Experimental animal studies, which were found to have higher confidence following the structured assessment of confidence (eg, controlled exposure, biological consistency), were used as the basis of a meta-regression. Multiple models were fit; points of departure were identified and converted to human equivalent doses. The resulting reference dose estimates ranged from approximately 4 to 70 pg/kg/day, depending on model, benchmark response level, and study validity integration approach. This range of reference doses can be used either qualitatively or quantitatively to enhance understanding of human health risk estimates for dioxin-like compounds.

Levels of omega 3 fatty acids, vitamin D, dioxins and dioxin-like PCBs in oily fish; a new perspective on the reporting of nutrient and contaminant data for risk-benefit assessments of oily seafood.

Oily seafood is an important food source which contains several key nutrients beneficial for human health. On the other hand, oily seafood also contains persistent organic pollutants (POPs), including the dioxin-like compounds (DLCs) polychlorinated dibenzo-p-dioxins/polychlorinated dibenzofurans (PCDD/Fs) and dioxin-like-polychlorinated biphenyls (dl-PCBs), potentially detrimental to human health. For a comprehensive comparison of the beneficial and potentially adverse health effects of seafood consumption, risk-benefit analyses are necessary. Risk-benefit analyses require reliable quantitative data and sound knowledge of uncertainties and potential biases. Our dataset comprised more than 4000 analyses of DLCs and more than 1000 analyses each of docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA) and vitamin D in the three most important Norwegian commercial oily seafood species: Atlantic herring (Clupea harengus), Atlantic mackerel (Scomber scombrus) and farmed Atlantic salmon (Salmo salar). The levels of several DLC congeners were below the limit of quantification (LOQ), making estimation of true levels challenging. We demonstrate that the use of upper bound substitution of censored data will overestimate, while lower bound substitution will underestimate the actual levels of DLCs. Therefore, we implement an alternative robust statistical method by combining Maximum Likelihood Estimation, Regression on Order Statistics and Kaplan-Meier analyses, which is better suited for providing estimations of levels of these contaminants in seafood. Moreover, we illustrate the impact of the toxic equivalency factor (TEF) system on estimation of the sums of DLCs by comparing the TEF system to an alternative system of relative effect potency (REP) factors (Consensus Toxicity Factors). The levels of nutrients and contaminants were related to adequate intake (AI) and tolerable weekly intake (TWI), respectively. We used AI and the TWI values established by the European Food Safety Authority (EFSA). The benefit and the risk were further viewed in the context of the Norwegian average intake of oily fish, and the Norwegian governmental official dietary recommendations of oily fish. Our results showed that both benefit and risk are met at the levels found of nutrients and DLCs in oily seafood. The comprehensive quantitative data presented here will be a key for future risk-benefit assessment of oily fish consumption. Together, our results underline that a refined formalized integrative risk-benefit assessment of oily fish in the diet is warranted, and that the data and methodology presented in this study are highly relevant for future integrated and multidisciplinary assessment of both risks and benefits of seafood consumption for human health.

Infant dietary exposure to dioxin-like polychlorinated biphenyls (dlPCBs), polybrominated and mixed halogenated dibenzo-p-dioxins and furans (PBDD/Fs and PXDD/Fs) in milk samples of lactating mothers in Accra, Ghana.

In this study, polybrominated and mixed halogenated dibenzo-p-dioxins and furans (PBDD/Fs and PXDD/Fs), and dioxin-like polychlorinated biphenyls (dlPCBs) were quantified in 24 human milk samples of first-time lactating mothers from Greater Accra region in Ghana. The aims of the study were to determine the concentrations and toxic equivalent concentrations of PBDD/F, PXDD/F and dlPCBs in human milk, and to estimate an infant's daily intake. The samples were analysed for 12 dioxin-like PCBs, 7 congeners of 2,3,7,8-polybrominated dibenzo-p-dioxins and furans (PBDD/Fs), and 7 congeners of 2,3,7,8-mixed halogenated dioxins and furans (PXDD/Fs, where X = Br/Cl). The mean concentrations in human milk ranged from 0.15 to 212.9 pg/g lipid for dlPCB congeners (mean TEQ: 1.67 pg WHO2005-TEQ/g lipid). Lesser concentrations for 2,3,7,8-PXDD/Fs (and PBDD/Fs congeners) ranged between <0.01-1.67 pg/g lipid, with a total mean tentative TEQ of 0.56 pg WHO2005-TEQ/g lipid. For an infant of average weight 7 kg, consuming an estimated volume of 600 mL human milk, the estimated average daily intake of dlPCBs in 21 human milk samples was 4.95 pg TEQ/kg bw/day; contributions from dlPCBs, PXDD/Fs and PBDD/Fs resulted in an average estimated daily intake of 6.56 pg TEQ/kg bw/day. The results obtained in this study, although lower than infant dietary intake estimates in human milk from industrialized countries, exceeded the recommended safety standards of 1 pg TEQ/kg bw/day and 1-4 pg TEQ/kg bw/day from the Agency for Toxic Substances and Disease Registry (ATSDR) and the World Health Organization (WHO), respectively.

Shotgun metagenomics of indigenous bacteria collected from the banks of the San Jacinto River for biodegradation of aromatic waste.

Several Eastern Harris County communities lie near the now enclosed San Jacinto River (SJR) Waste Pit Superfund, a dumping ground for chlorinated dioxins and other paper mill waste products. Currently, no active monitoring of the SJR is conducted for these toxins with the exact concentration and health impact to the area unknown. As such, remediation and monitoring efforts outside of the Superfund itself could be necessary. To better understand the possible environmental fate of these aromatics, here we provide a shotgun metagenomic analysis of the structural and putative functional diversity of the SJR microbiome from two impacted Channelview, Texas communities bordering the Superfund. Results show that the underlying SJR microbiome possesses a core of metabolic enzymes related to the ß-ketoadipate and benzoate degradation pathways. This suggests possible endpoints for many aromatics found deposited in the SJR including dioxin-like compounds. However, degradation biomarkers related to the priming and initial cleavage of chlorinated dioxin-like aromatics while present, are poorly concentrated across sampled sites. This may be due in part to decreased coverage of low abundance bacterial species, but also be a contributing factor leading to increased recalcitrance of these compounds in this environment compared to other aromatics.

Validation of the micro-EROD assay with H4IIE cells for assessing sediment contamination with dioxin-like chemicals.

In vitro bioassays have been used as a bioanalytical means of detecting dioxin-like compounds (DLCs) in environmental matrices and have been suggested as a tool for quantifying DLCs in sediments. The present study evaluated the relationship between bioanalytical results from the micro-7-ethoxyresorufin-O-deethylase (EROD) bioassay and chemical analytical results in 25 sediment samples collected from rivers across Germany. Sediments were collected, polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (DL-PCBs) were extracted from the sediments, biological toxicity equivalent quotients (BEQs) were determined by micro-EROD assay and toxicity equivalent quotients (TEQs) were calculated from chemical analysis. Correlations between BEQs and TEQs were evaluated, and linear regression modeling was performed, excluding 6 samples as validation data, to derive equations for predicting TEQs from BEQs. Validation data was tested to evaluate predictive capabilities of the models. Correlations were observed between BEQ and TEQ for PCDD/Fs (r=0.987), PCBs (r=0.623), measured sum of PCDD/F and PCBs (r = 0.975) and calculated sum of PCDD/F and PCBs (r = 0.971). The modeling equations provided low variances as evaluated by mean absolute error (MAE) (≤10.3 pg/g) and root mean square error (RMSE) (≤15.8 pg/g) indicating that expected TEQs could be reasonably well calculated from BEQs. Predicted TEQs from validation data fell within the 95% probability intervals of the test data and had low variances (MAE≤6.5 pg/g) and (RMSE≤10.7 pg/g). Our results indicate that the micro-EROD bioassay can be used as a screening tool for DLCs in sediment and has the capability to be used as an alternate method to chemical analysis for quantifying dioxin-like potential of sediments.

Dioxin-like compounds in paired maternal serum and breast milk under long sampling intervals.

Serum and breast milk are both important biological samples to evaluate body burden of dioxin-like compounds which include polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (dl-PCBs). We collected maternal serum at early pregnancy, and breast milk at 3-8 weeks after delivery from 55 mothers living in Beijing, China, and measured 29 dioxin-like compounds in these samples. The sampling intervals in this study were extended up to 10 months to analyze differences of contents between serum and breast milk under long sampling intervals. The results showed that mean TEq level of PCDD/Fs in serum (9.8 pg TEq g-1 lipid) was 1.7 times higher than that in milk (4.5 pg TEq g-1 lipid), while the TEq concentrations of dl-PCBs in serum (1.2 pg TEq g-1 lipid) was significantly lower than that in milk (2.0 pg TEq g-1 lipid). There were only two congeners, OCDD (r = 0.32) and PCB105 (r = 0.33), the correlations of which between serum and milk were significant. The differences in distributions of congeners in serum and milk might be influenced by number of chlorine substituents and structures of congeners. In addition, maternal age and BMI were positively and negatively correlated with mass concentrations of dioxin-like compounds in milk and serum respectively. These results suggest that, compared with serum, it is limited to use breast milk to assess long-term exposure for the wider population.

Generation and application of a Tg(cyp1a:egfp) transgenic marine medaka (Oryzias melastigma) line as an in vivo assay to sensitively detect dioxin-like compounds in the environment.

Large-range environmental pollution by dioxin and dioxin-like compounds (DLCs) is becoming a serious problem. To establish an in vivo method for the detection of DLCs in seawater, a Tg(cyp1a-12DRE:egfp) transgenic marine medaka (Oryzias melastigma) line was first developed with the modified cyp1a-12DRE promoter driving enhanced green fluorescent protein (EGFP) expression using Tol2 transgenesis technology. With increasing concentrations of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs), the EGFP fluorescence intensity increased significantly. The Tg(cyp1a-12DRE:egfp) medaka possessed high sensitivity (limit of detection of 1 ng/L TCDD) and specificity and low background. This transgenic line is capable of detecting DLCs in environmental seawater in which the concentration of DLCs is at least 0.12207 ng/L TCDD after sample enrichment. The fluorescence-toxic equivalency (TEQ) values from EGFP intensity were closely correlated with the chemical-TEQ values obtained from chemical analyses. Furthermore, the Tg(cyp1a-12DRE:egfp) medaka can directly detect DLCs in seawater samples after a serious pollution accident and screen unknown aryl hydrocarbon receptor (AhR) agonists for risk assessment. For the first time, a convenient method has been established that sensitively and specifically responds to DLCs using the Tg(cyp1a-12DRE:egfp) marine medaka, which could be a highly efficient tool for detecting seawater DLCs in the future.

[The study of exposure levels of dioxin-like compounds in cord blood of newborns in an e-waste dismantling area in Guangdong Province].

Objective: To study the pollution status of polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCB), polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in cord blood of newborns in an e-waste dismantling area of Guangdong Province. Methods: We recruited 20 eligible mothers and newborns who could meet the inclusion criteria in local hospitals of Guiyu in 2007. The inclusion criteria included directly engaged in dismantling e-waste during pregnancy and within 1 year before pregnancy; living in the e-waste dismantling workshops or the distance between living place and the e-waste dismantling areas was ≤200 m; the father of newborn was directly engaged in electronic waste dismantling for more than 1 year; the frequency of visiting the e-waste dismantling workshop during pregnancy was ≥3 times in a week. Questionnaires and physical examinations were performed on maternal and neonatal, and cord blood was collected from newborns to detect PCDD/Fs, PCB and PBDE. The concentration level of organic pollutants was corrected by the blood lipid content, and the total toxicity equivalent was calculated. The correlation between three compounds was analyzed by Spearman correlation. Results: The mothers of the 20 newborns were (23.45±3.27) years old and lived for more than 5 years. The number of one parent engaged in e-waste dismantling, the mother or father smoking, and parent engaged in e-waste dismantling work were 3, 13, 15 and 19, respectively. The weight of newborns ranged from 2.5 to 3.6 kilogram and the Apgar score was 10 points. No adverse birth outcomes such as preterm birth, malformation or stillbirth were found. The median (maximum, minimum) concentration of PCBs, PCDD/Fs and PBDEs in cord blood were 263.22 (328.29, 244.19), 38.42 (147.49, 12.68), 39.33 (265.11, 14.81) pg/g lipid, respectively. The median (maximum, minimum) of toxic equivalence concentrations of PCDD/Fs and PCB were 3.94 (9.24, 2.69) and 15.95 (26.64, 9.28) pg TEQ/g lipid. PBDE, the proportion of PBDE, PCB and PCDD/Fs in cord blood was 50.41%, 49.25% and 0.34%, respectively. PCBs and PBDEs were positively correlated (r=0.733, P=0.039). Conclusion: The high concentrations of PCDD/Fs, PCB, and PBDE were detected in the e-waste dismantling area. It is recommended that the risk of such substances on the health of local people should be assessed in a timely manner.

Background levels of dioxin-like polychlorinated biphenyls (dlPCBs), polychlorinated, polybrominated and mixed halogenated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs, PBDD/Fs & PXDD/Fs) in sera of pregnant women in Accra, Ghana.

Human exposure data on dioxins and dioxin-like compounds (DLCs) in Ghana are limited. Based on health risks associated with dioxins and DLCs, the impact of maternal body burdens on foetal exposure is significant. This is the first study that assesses polychlorinated, polybrominated and mixed halogenated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs, PBDD/Fs and PXDD/Fs), and dioxin-like polychlorinated biphenyls (dlPCBs) in sera of primiparous Ghanaians. Our sample selection includes 34 participants from two municipalities (Accra and Tema), and explores contributions from environmental and dietary exposures using questionnaire data. Sample preparation involved C18 solid phase extraction, purification with acidified silica and lipid removal cartridges, and detection with gas chromatography-atmospheric pressure chemical ionization-tandem mass spectrometry. The calculated average toxic equivalent concentration was 5.3 pg TEQ/g lw, with contributions from dlPCBs (1.25 pg TEQ/g lw), PCDD/Fs (3.10 pg TEQ/g lw), PBDD/Fs (0.49 pg TEQ/g lw) and PXDD/Fs (0.50 pg TEQ/g lw). The calculated total TEQ concentration was lower than background TEQ concentrations reported in sera of pregnant women globally. Positive correlations were obtained for total dioxins and DLC concentrations with age and Body Mass Index (BMI). Dietary intake of seafood and dairy products had a strong influence on PCDD/F and dlPCB concentrations. Statistically significant differences were observed for dioxins and DLCs in participants from Accra (in close proximity to Agbogbloshie e-waste site) and Tema. Given the significant TEQ contribution of PBDD/Fs and PXDD/Fs (~20%), it is essential to explore these classes of dioxins and DLCs in future biomonitoring studies as they may pose health risks, and add extra diagnostic information in source exposure investigations.