Serum elimination half-lives adjusted for ongoing exposure of tri-to hexabrominated diphenyl ethers: Determined in persons moving from North America to Australia

The dose disrupts the pathway: application of Paracelsus principle to mechanistic toxicology

Arguably the most famous principle of toxicology is "The dose makes the poison" formulated by Paracelsus in the 16th century. Application of the Paracelsus's principle to mechanistic toxicology may be challenging as one compound may affect many molecular pathways at different doses with different and often nonlinear dose-response relationships. As a result, many mechanistic studies of environmental and occupational compounds use high doses of xenobiotics motivated by the need to see a clear signal indicating disruption of a particular molecular pathway. This approach ignores the possibility that the same xenobiotic may affect different molecular mechanism(s) at much lower doses relevant to human exposures. To amend mechanistic toxicology with a simple and concise guiding principle, I suggest recontextualization of Paracelsus's following its letter and spirit: "The dose disrupts the pathway". Justification of this statement includes observations that many environmental and occupational xenobiotics affect a broad range of molecular cascades, that most molecular pathways are sensitive to chemical exposures, and that different molecular pathways are sensitive to different doses of a chemical compound. I suggest that this statement may become a useful guidance and educational tool in a range of toxicological applications, including experimental design, comparative analysis of mechanistic hypotheses, evaluation of the quality of toxicological studies, and risk assessment.

Gestational PBDE concentrations, persistent externalizing, and emerging internalizing behaviors in adolescents: The HOME study

BACKGROUND

Polybrominated diphenyl ethers (PBDEs) are ubiquitous environmental chemicals used as flame retardants in commercial and consumer products. Gestational PBDE concentrations are associated with adverse behaviors in children; however, the persistence of these associations into adolescence remains understudied.

OBJECTIVE

We estimated the association of gestational PBDE serum concentrations with early adolescent self- and caregiver-reported behaviors at age 12 years and determined the consistency with previously observed associations in childhood with caregiver-reported behaviors in a prospective pregnancy and birth cohort.

METHODS

We measured maternal serum concentrations of five individual PBDE congeners and created a summary exposure variable (∑5BDE: 28, -47, -99, -100 and -153) during pregnancy. At age 12 years, we assessed behaviors for 237 adolescents using self- and caregiver-reports with the Behavioral Assessment System for Children-3 (BASC3). We used multivariable linear regression models to estimate covariate-adjusted associations of lipid standardized, log10-transformed gestational PBDE concentrations with BASC3 scores. We obtained estimates and 95% confidence intervals through a bootstrapping approach. We evaluated potential effect measure modification (EMM) of adolescent sex by examining sex-stratified regression models and estimating the EMM p-values.

RESULTS

Gestational PBDE concentrations were positively associated with adolescent-reported BASC3 composite indices for inattention & hyperactivity (BDE-28, -47, -99, -100, ∑5BDE), internalizing problems (BDE-28, -47, -99), functional impairment (BDE-28, ∑5BDE), and emotional symptoms (BDE-28). Gestational PBDE concentrations were positively associated with caregiver-reported BASC3 composite indices for externalizing problems (BDE-28, -47, -99, -100, -153, ∑5BDE) and behavioral symptoms (BDE-99). For caregiver reported behaviors, we observed stronger associations with gestational BDE concentrations among males, especially for executive functioning (BDE-28, -47, -99, -100, ∑5BDE).

DISCUSSION

Gestational PBDE serum concentrations were associated with self-reported internalizing and externalizing behavior problems in early adolescence. Caregiver-reported externalizing behaviors recognized during childhood remain associated with gestational PBDE concentrations and persist into early adolescence. Internalizing behaviors were less recognized by caregivers.

Environmental contaminants in Arctic human populations: Trends over 30 years

INTRODUCTION

Arctic Monitoring and Assessment Programme (AMAP) monitors persistent organic pollutant (POP) levels in the Arctic populations and assesses health effects related to exposure to them. Many internationally regulated POPs persist in humans and biota, while new Emerging Contaminants of Arctic Concern (ECAC), many of which are unregulated, present additional challenges. Biomonitoring offers valuable insights into temporal trends within human matrices, revealing critical information not only about the efficacy of international regulations but also serving as an early warning system for exposure and risks for human health.

METHODS

Data analyzed in this study is aggregated data presented in the AMAP Human Health in the Arctic assessments, which provide data on contaminant concentrations measured in human matrices from adults, and children across various population studies conducted in the Arctic since the 1980 s. Linear regression analyses were used to assess trends of various POPs including organochlorine (OCPs), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and per- and polyfluoroalkyl substances (PFAS), measured over time from the Arctic populations in Finland, Norway, Sweden, Denmark, Iceland, Canada and Alaska (USA).

RESULTS

Overall, decreasing trends were observed for PCBs and OCPs. Regulated PFAS showed decreasing trends, but increasing trends were observed for unregulated PFAS in certain populations. PBDEs showed decreasing or inconsistent trends in certain Arctic populations.

CONCLUSIONS

Decreasing trends are observed for legacy POPs, but the trends for new emerging contaminants are inconsistent. More focus is needed on biomonitoring the new emerging contaminants of concern in the Arctic and their implications on human health.

Biomarkers of Organophosphate and Polybrominated Diphenyl Ether (PBDE) Flame Retardants of American Workers and Associations with Inhalation and Dermal Exposures

This study evaluated workers' exposures to flame retardants, including polybrominated diphenyl ethers (PBDEs), organophosphate esters (OPEs), and other brominated flame retardants (BFRs), in various industries. The study aimed to characterize OPE metabolite urinary concentrations and PBDE serum concentrations among workers from different industries, compare these concentrations between industries and the general population, and evaluate the likely route of exposure (dermal or inhalation). The results showed that workers from chemical manufacturing had significantly higher (p <0.05) urinary concentrations of OPE metabolites compared to other industries. Spray polyurethane foam workers had significantly higher (p <0.05) urinary concentrations of bis(1-chloro-2-propyl) phosphate (BCPP) compared to other industries. Electronic scrap workers had higher serum concentrations of certain PBDE congeners compared to the general population. Correlations were observed between hand wipe samples and air samples containing specific flame-retardant parent chemicals and urinary metabolite concentrations for some industries, suggesting both dermal absorption and inhalation as primary routes of exposure for OPEs. Overall, this study provides insights into occupational exposure to flame retardants in different industries and highlights the need for further research on emerging flame retardants and exposure reduction interventions.

Socio-demographic inequalities influence differences in the chemical exposome among Swedish adolescents

Relatively little is known about the relationship between socio-demographic factors and the chemical exposome in adolescent populations. This knowledge gap hampers global efforts to meet certain UN sustainability goals. The present work addresses this problem in Swedish adolescents by discerning patterns within the chemical exposome and identify demographic groups susceptible to heightened exposures. Enlisting the Riksmaten Adolescents 2016-17 (RMA) study population (N = 1082) in human-biomonitoring, and using proportional odds ordinal logistic regression models, we examined the associations between concentrations of a diverse array of substances (N = 63) with the determinants: gender, age, participant/maternal birth country income per capita level, parental education levels, and geographic place of living (longitude/latitude). Participant/maternal birth country exhibited a significant association with the concentrations of 46 substances, followed by gender (N = 41), and longitude (N = 37). Notably, individuals born in high-income countries by high-income country mothers demonstrated substantially higher estimated adjusted means (EAM) concentrations of polychlorinated biphenyls (PCBs), brominated flame retardants (BFRs) and per- and polyfluoroalkyl substances (PFASs) compared to those born in low-income countries by low-income country mothers. A reverse trend was observed for cobalt (Co), cadmium (Cd), lead (Pb), aluminium (Al), chlorinated pesticides, and phthalate metabolites. Males exhibited higher EAM concentrations of chromium (Cr), mercury (Hg), Pb, PCBs, chlorinated pesticides, BFRs and PFASs than females. In contrast, females displayed higher EAM concentrations of Mn, Co, Cd and metabolites of phthalates and phosphorous flame retardants, and phenolic substances. Geographical disparities, indicative of north-to-south or west-to-east substance concentrations gradients, were identified in Sweden. Only a limited number of lifestyle, physiological and dietary factors were identified as possible drivers of demographic inequalities for specific substances. This research underscores birth country, gender, and geographical disparities as contributors to exposure differences among Swedish adolescents. Identifying underlying drivers is crucial to addressing societal inequalities associated with chemical exposure and aligning with UN sustainability goals.

Indoor environment, physiological factors, and diet as predictors of halogenated flame retardant levels in stool and plasma of children from a Canadian cohort

Exposure to halogenated flame retardants (HFRs) has been associated with various adverse effects on human health. Human exposure to HFRs mainly occurs through diet, ingesting contaminated dust, and inhaling contaminated air. Understanding and characterizing the variables linked to these exposure pathways is essential for developing effective risk assessment and mitigation strategies. We investigated indoor environment quality, physiological factors, and diet as potential predictors of HFRs concentration in children's plasma and stool. A selected number of HFRs, including polybrominated diphenyl ethers (PBDEs), Dechlorane-like compounds, and emerging halogenated flame retardants, were measured in children from eastern Quebec (Canada). Information on indoor environment quality, physiological factors, and diet was obtained through self-report questionnaires. Our results show that lower brominated compounds, which are more volatile, were primarily correlated to indoor environment quality. Notably, the use of air purifiers was associated with lower BDE47 and BDE100 levels in blood and newer residential buildings were associated with higher concentrations of BDE47. A significant seasonal variation was found in stool samples, with higher levels of lower brominated PBDEs (BDE47 and BDE100) in samples collected during summer. No association between household income or maternal education degree and HFRs was found. Among emerging compounds, Dec602 and Dec603 were associated with the most variables, including the use of air dehumidifiers, air conditioning, and air purifiers, and the child's age and body fat percentage.

Magnetically separable Pd-iron-oxides composites as highly efficient and recyclable catalysts for ultra-rapid degradation and debromination of polybrominated diphenyl ethers

When precious nano-metals are used as environmental catalysts, it is important to tune the particle sizes and the reusability of the nano-metals for achieving their highly efficient catalytic performance at a low cost. In the present work, magnetic iron oxides (FeOx-Y) nanoparticles were pre-prepared as supports of nano-metals, where Y represented the mole percentage of Fe(III) in the total iron (Y ≥ 50 %). FeOx-Y (support), PdCl42- (Pd source) and NaBH4 (reducing agent) were added into the organic pollutant solution containing 2,2',4,4'-tetrabromodiphenyl ether (BDE47). After the NaBH4 was added, the followed reaction realized not only the rapid in-situ preparation of a Pd-loaded FeOx-Y composite catalyst (Pd-FeOx-Y), but also the ultra-fast and complete debromination of BDE47 within 30 s. Comparing the case without adding FeOx-Y, the debromination efficiency of BDE47 was much promoted in the presence of FeOx-Y. The support-induced enhancing effect on the catalytic ability of Pd nanoparticles was improved by increasing the Fe(III) content in the support, being attributed to the much more hydroxyl groups on the support surface. Considering both the catalytic and recovery abilities of Pd-FeOx-Y, Pd-FeOx-75 was the optimal choice because it could be magnetically recovered and re-used for multiple cycles with high catalytic activities. The presently developed "catalyst preparation-pollutant degradation" one-pot system could be applied to conduct complete debromination of all the PBDEs.

Using in vitro data to derive acceptable exposure levels: A case study on PBDE developmental neurotoxicity

BACKGROUND

Current acceptable chemical exposure levels (e.g., tolerable daily intake) are mainly based on animal experiments, which are costly, time-consuming, considered non-ethical by many, and may poorly predict adverse outcomes in humans.

OBJECTIVE

To evaluate a method using human in vitro data and biological modeling to calculate an acceptable exposure level through a case study on 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) developmental neurotoxicity (DNT).

METHODS

We reviewed the literature on in vitro assays studying BDE-47-induced DNT. Using the most sensitive endpoint, we derived a point of departure using a mass-balance in vitro disposition model and benchmark dose modeling for a 5% response (BMC05) in cells. We subsequently used a pharmacokinetic model of gestation and lactation to estimate administered equivalent doses leading to four different metrics of child brain concentration (i.e., average prenatal, average postnatal, average overall, and maximum concentration) equal to the point of departure. The administered equivalent doses were translated into tolerable daily intakes using uncertainty factors. Finally, we calculated biomonitoring equivalents for maternal serum and compared them to published epidemiological studies of DNT.

RESULTS

We calculated a BMC05 of 164 μg/kg of cells for BDE-47 induced alteration of differentiation in neural progenitor cells. We estimated administered equivalent doses of 0.925-3.767 μg/kg/day in mothers, and tolerable daily intakes of 0.009-0.038 μg/kg/day (composite uncertainty factor: 100). The lowest derived biomonitoring equivalent was 19.75 ng/g lipids, which was consistent with reported median (0.9-23 ng/g lipids) and geometric mean (7.02-26.9 ng/g lipids) maternal serum concentrations from epidemiological studies.

CONCLUSION

This case study supports using in vitro data and biological modeling as a viable alternative to animal testing to derive acceptable exposure levels.

Complementarity of plasma and stool for the characterization of children's exposure to halogenated flame retardants: Update on analytical methods and application to a Canadian cohort

Sixteen halogenated flame retardants including Polybrominated diphenyl ethers (PBDEs), Dechlorane-like compounds, and emerging halogenated flame retardants were measured in stool and plasma samples from children aged 8.9-13.8 years old. Samples were obtained from a Canadian cohort investigating the effect of contaminants on children's neurodevelopment in the Estrie region, Québec, Canada. The method for stool analysis developed for this study showed good recovery for all targeted compounds (73%-93%) with associated relative standard deviation (RSD) in the range of 16.0%-30.7% for most compounds except for the thermosensitive BDE209, OBTMBI, and BTBPE, which showed slightly higher RSD, i.e., 49.3%, 37.2%, and 34.9% respectively. Complementarity investigation of stool and blood samples allowed us to better characterize human exposure to these halogenated flame retardants. Exposure patterns differed significantly between stool and blood, notably in the relative abundance of BDE47, BDE100, BDE99, and BDE153 and the detection frequencies of BDE209, syn-DP, anti-DP, and DBDPE. There was no correlation between the two matrices' PBDEs concentration levels except for BDE153 (rho = 0.44, p < 0.01). Our results indicate that future epidemiological studies may benefit from the use of stool as a complementary matrix to blood, especially investigations into chemical impacts on the gut microbiome. Results also revealed that children from the GESTE cohort, an Eastern Canadian semi-rural cohort, are exposed to both historical and emergent flame retardants.

Cadmium (Cd) and 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) co-exposure induces acute kidney injury through oxidative stress and RIPK3-dependent necroptosis

Environmental pollution is complex, and co-exposure can accurately reflect the true environmental conditions that are important for assessment of human health. Cadmium (Cd) is a widespread toxicant that can cause acute kidney injury (AKI), while its combined effect with 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) is not fully understood. Thus, we used an in vivo model where C57BL/6J mice were treated with low dietary intake of Cd (5 mg/kg/day) and/or BDE-47 (1 mg/kg/day) for 28 days to examine AKI, and in vitro experiments to investigate the possible mechanism. Results showed that Cd or BDE-47 caused pathological kidney damage, accompanied by elevated urea nitrogen (BUN) and urinary creatinine, as well as increased interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α), and reduced IL-10 in kidney tissues. In vitro Cd or BDE-47 exposure decreased cell viability and induced cell swelling and blebbing of human embryonic kidney 293 (HEK-293) and renal tubular epithelial cell lines (HKCs), and changes in co-exposure was larger than that in Cd and BDE-47 treatment. Oxidative stress indicators of the reactive oxygen species (ROS) and malondialdehyde (MDA) were elevated, while the antioxidant superoxide dismutase (SOD) was decreased. Necrosis occurred with increased lactate dehydrogenase (LDH) release and propidium iodide (PI) staining, which was attenuated by the ROS scavenger N-acetyl-L-cysteine (NAC). Furthermore, necroptotic genes of receptor-interacting protein kinase-3 (RIPK3), classical mixed lineage kinase domain-like protein-dependent (MLKL), IL-1β and TNF-α were up-regulated, whereas RIPK1 was down-regulated, which was attenuated by the RIPK3 inhibitor GSK872. These findings demonstrate that Cd or BDE-47 alone produces kidney toxicities, and co-exposure poses an additive effect, resulting in AKI via inducing oxidative stress and regulating RIPK3-dependent necroptosis, which offers a further mechanistic understanding for kidney damage, and the combined effect of environmental pollutants should be noticed.

Insight into the application of magnetic molecularly imprinted polymers in soil-washing effluent: Selective removal of 4,4'-dibromodiphenyl ether, high adaptivity of material and efficient recovery of eluent

Soil washing techniques can effectively remove soil polybrominated diphenyl ethers (PBDEs), but further removal of PBDEs from washing effluent is disrupted by environmental factors and coexisting organic matter. Hence, this work prepared novel magnetic molecularly imprinted polymers (MMIPs) to selectively remove PBDEs in soil washing effluent and recycling surfactants, with Fe₃O₄ nanoparticles as the magnetic core, methacrylic acid (MAA) as the functional monomer, and ethylene glycol dimethacrylate (EGDMA) as the cross-linker. Later, the prepared MMIPs were applied to adsorb 4,4'-dibromodiphenyl ether (BDE-15) in Triton X-100 soil-washing effluent and characterized by scanning electron microscopy (SEM), infrared spectrometry (FT-IR), nitrogen adsorption and desorption experiments. According to our observations, BDE-15 equilibrium adsorptions on dummy-template magnetic molecularly imprinted adsorbent (D-MMIP, 4-bromo-4'-hydroxyl biphenyl as template) and part-template magnetic molecularly imprinted adsorbent (P-MMIP, toluene as template) were reached within 40 min, and their equilibrium adsorption capacities were 164.54 μmol/g and 145.55 μmol/g, respectively, with imprinted factor α > 2.03, selectivity factor β > 2.14, and selectivity S > 18.05. MMIPs exhibited good adaptability to pH, temperature, and cosolvent. Our Triton X-100 recovery rate reached as high as 99.9%, and MMIPs maintained a more than 95% adsorption capacity after being recycled five times. Our results offer a novel approach to selectively remove PBDEs in soil-washing effluent, with efficient recovery of surfactants and adsorbents in soil-washing effluent.

Serum polybrominated diphenyl ether exposure and influence factors in blood donors of Wuxi adults from 2013 to 2016

Polybrominated diphenyl ethers (PBDEs) have been used as brominated flame retardants worldwide and are correlated with extensive environmental pollution and human health concerns. This study is aimed at analyzing the concentrations of PBDEs and at evaluating their temporal trends among a population of blood donors (n = 33) over a 4-year period. A total of 132 serum samples were used for PBDE detection. Nine PBDE congeners were quantified in serum samples by gas chromatography with mass spectrometry (GC-MS). The median concentrations of Σ₉PBDEs in each year were 33.46, 29.75, 30.85, and 35.02 ng/g lipid, respectively. Most of the PBDE congeners showed a downward trend from 2013 to 2014 and then increased after 2014. No correlations between age and PBDE congener concentrations were observed, while concentrations of each congener and Σ₉PBDE were nearly always lower in females than in males, especially in BDE-66, BDE-153, BDE-183, BDE-190, and Σ₉PBDE. We also found that the intake of fish, fruit, and eggs in the daily diet was related to the exposure level of PBDEs. Our results suggest that, as deca-BDE is still produced and used in China, diet is an important exposure pathway for PBDEs, and follow-up studies will be required to improve our understanding of the behaviors of PBDE isomers in humans and the exposure levels.

Association of pre-pregnancy maternal overweight/obesity and dietary intake during pregnancy with the concentrations of persistent organic pollutants in the human milk of women from Rio de Janeiro, Brazil

Persistent organic pollutants (POPs) are toxic chemical compounds that can bioaccumulate, adhere to lipid matrices, and affect human health. This study aimed to investigate the association between maternal pre-pregnancy overweight/obesity and dietary intake during pregnancy and POP concentrations in the human milk of women from Rio de Janeiro, Brazil. One hundred and forty-seven women were followed from the third trimester of pregnancy until 119 days postpartum, and 77 human milk samples were analyzed between 2 and 119 days postpartum. POP concentrations were analyzed using gas chromatography-triple quadrupole mass spectrometry. Pregnancy dietary intake was estimated using a semi-quantitative food frequency questionnaire, and pre-pregnancy body mass index at baseline was classified as normal or overweight/obesity. Multiple logistic and linear regression models were performed to investigate the association between pre-pregnancy overweight/obesity, dietary intake during pregnancy, and POP concentrations in human milk. The models were adjusted for maternal age, maternal schooling, total cholesterol serum concentrations, and time postpartum. The analyses were corrected for multiple comparisons using the Benjamini-Hochberg test. Significant associations were observed between pre-pregnancy overweight/obesity and dichlorodiphenyldichloroethane (ppDDE), polychlorinated biphenyl (PCB)74, PCB138, PCB153, PCB170, PCB180, total PCBs, total 4PCBs, total 2 organochlorine pesticides (OCPs), and total POP concentrations. Higher daily lipid intake during pregnancy increased human milk hexachlorobenzene (HCB). This study showed that pre-pregnancy overweight/obesity and total lipid intake during pregnancy were associated with POP concentrations in the milk of women from Rio de Janeiro, Brazil. To promote adequate nutritional status since preconception and surveillance and control of POP in the environment could be essential to ensure binomial mother-infant health and biomonitoring studies and programs for these POPs should be stimulated.

Current status of indoor dust PBDE pollution and its physical burden and health effects on children

Polybrominated diphenyl ethers (PBDEs) are widely detected in indoor dust, which has been identified as a more important route of PBDE exposure for children than food intake. The physical burden and health hazards to children of PBDE exposure in house dust have not been adequately summarized; therefore, this article reviews the current status of PBDE pollution in indoor dust associated with children, highlighting the epidemiological evidence for physical burden and health risks in children. We find that PBDEs remain at high levels in indoor dust, including in homes, schools, and cars, especially in cars showing a significant upward trend. There is a trend towards an increase in the proportion of BDE-209 in household dust, which is indicative of recent PBDE contamination. Conversely, PBDE congeners in car and school indoor dust tended to shift from highly brominated to low brominated, suggesting a shift in current pollution patterns. Indoor dust exposure causes significantly higher PBDE burdens in children, especially infants in early life, than in adults. Exposure to dust also affects breast milk, putting infants at high risk of exposure. Although evidence is limited, available epidemiological studies suggest that exposure to indoor dust PBDEs promotes neurobehavioral problems and cancer development in children.

Gene expression profiling after exposure to a chemical carcinogen, Pentabrominated Diphenyl Ether, at different life stages

Exposure to environmental hazards occurs at different stages of our lifetime-infant, child, adult. This study integrates recently published toxicogenomics data to examine how exposure to a known rat chemical carcinogen (pentabrominated diphenyl ether (PBDE)) upregulated liver transcriptomic changes at different life cycle stages (PND 4, PND 22, adult). We found that at all three life cycle stages PBDE exposure induced hepatocellular transcriptomic changes in disease pathways including cancer, metabolic, membrane function, and Nrf2 antioxidant pathways, pathways all characteristics of chemical carcinogens. In addition, in the adult rat after a 5-day exposure to the chemical carcinogen, there was upregulation of members of the Ras oncogenic pathway, a specific pathway found to be activated in the PBDE-induced tumors in rats in a previous hazard identification cancer study. The findings of liver transcript changes characteristic of carcinogenic activity after early life exposures and after short-term adult exposures provides data to support the use of transcriptomic data to predict the apical cancer endpoints in model studies. Using data from gene expression profiling studies after neonatal, young, or adult short-term chemical exposure helps to meet the 21st century toxicology goal of developing study designs to reduce, refine, and replace the use of traditional 2-year rodent cancer studies to provide hazard identification information. The studies reported here find that key transcripts associated with carcinogenesis were elevated in neonate (PND 4), young (PND 22) and adult animals after short-term exposure to PBDE, a known experimental chemical carcinogen in model systems.

Partitioning of Persistent Organic Pollutants between Adipose Tissue and Serum in Human Studies

Blood is the most widely used matrix for biomonitoring of persistent organic pollutants (POPs). It is assumed that POPs are homogenously distributed within body lipids at steady state; however, the variability underlying the partitioning of POPs between fat compartments is poorly understood. Hence, the objective of this study was to review the state of the science about the relationships of POPs between adipose tissue and serum in humans. We conducted a narrative literature review of human observational studies reporting concentrations of POPs in paired samples of adipose tissue with other lipid-based compartments (e.g., serum lipids). The searches were conducted in SCOPUS and PUBMED. A meta-regression was performed to identify factors responsible for variability. All included studies reported high variability in the partition coefficients of POPs, mainly between adipose tissue and serum. The number of halogen atoms was the physicochemical variable most strongly and positively associated with the partition ratios, whereas body mass index was the main biological factor positively and significantly associated. To conclude, although this study provides a better understanding of partitioning of POPs to refine physiologically based pharmacokinetic and epidemiological models, further research is still needed to determine other key factors involved in the partitioning of POPs.

Mechanisms of Male Reproductive Toxicity of Polybrominated Diphenyl Ethers

Polybrominated diphenyl ethers (PBDE) are a group of flame retardants used in a variety of artificial materials. Despite being phased out in most industrial countries, they remain in the environment and human tissues due to their persistence, lipophilicity, and bioaccumulation. Populational and experimental studies demonstrate the male reproductive toxicity of PBDEs including increased incidence of genital malformations (hypospadias and cryptorchidism), altered weight of testes and other reproductive tissues, altered testes histology and transcriptome, decreased sperm production and sperm quality, altered epigenetic regulation of developmental genes in spermatozoa, and altered secretion of reproductive hormones. A broad range of mechanistic hypotheses of PBDE reproductive toxicity has been suggested. Among these hypotheses, oxidative stress, the disruption of estrogenic signaling, and mitochondria disruption are affected by PBDE concentrations much higher than concentrations found in human tissues, making them unlikely links between exposures and adverse reproductive outcomes in the general population. Robust evidence suggests that at environmentally relevant doses, PBDEs and their metabolites may affect male reproductive health via mechanisms including AR antagonism and the disruption of a complex network of metabolic signaling.

Positive association between dietary exposure to polybrominated diphenyl ethers and breast cancer risk in the French E3N cohort: The role of vegetable oil consumption

Exposure to endocrine-disrupting chemicals, like Polybrominated diphenyl ethers (PBDEs), is suspected of playing a role in the occurrence of breast cancer. Moreover, there is growing evidence that food chemical contaminants, especially lipophilic ones such as PBDEs, could interact with different components of the diet. The objective of the present study was to assess the association between dietary intake of PBDEs and breast cancer risk in the French E3N cohort study, and to investigate the potential modification of this association by vegetable oil consumption. The study included 67879 women. Intakes of eight PBDEs were estimated using food consumption data from a validated semi-quantitative food frequency questionnaire, and food contamination levels measured by the French Agency for Food, Environmental and Occupational Health and Safety (ANSES). Cox proportional hazards models were used to estimate Hazard Ratios (HR) and 95% Confidence Intervals (CI) for the association between total PBDEs dietary intake and breast cancer risk. Interaction measures for vegetable oil consumption were estimated on both additive and multiplicative scales. The women were followed for a maximum of 21.4 years, and 5 686 developed an incident breast cancer. A positive linear trend was highlighted between dietary intake of PBDEs in quintile groups and breast cancer risk, borderline with statistical significance (p-trend = 0.06, HR_Q5vsQ1 and 95% CI: 1.09 [0.99;1.20]). Interaction measures for vegetable oil consumption were significant in both additive and multiplicative scales. Higher effect sizes of the association were highlighted in high consumers of vegetable oil, i.e. ≥4.6 g/day (HR_Q5vsQ1 and 95% CI: 1.23 [1.08; 1.40]), and almost no effect were found in low consumers (HR_Q5vsQ1 and 95% CI: 0.97 [0.86; 1.10]). Highlighting such interactions between nutrients and chemicals is crucial to develop efficient dietary recommendations to limit the negative health effects associated with exposure to food chemical contaminants.

Endocrine-Disrupting Chemical Exposures in Pregnancy: a Sensitive Window for Later-Life Cardiometabolic Health in Women

Purpose of Review

Pregnancy can be seen as a “stress test” with complications predicting later-life cardiovascular disease risk. Here, we review the growing epidemiological literature evaluating environmental endocrine-disrupting chemical (EDC) exposure in pregnancy in relation to two important cardiovascular disease risk factors, hypertensive disorders of pregnancy and maternal obesity.

Recent Findings

Overall, evidence of EDC-maternal cardiometabolic associations was mixed. The most consistent associations were observed for phenols and maternal obesity, as well as for perfluoroalkyl substances (PFASs) with hypertensive disorders. Research on polybrominated flame retardants and maternal cardiometabolic outcomes is limited, but suggestive.

Summary

Although numerous studies evaluated pregnancy outcomes, few evaluated the postpartum period or assessed chemical mixtures. Overall, there is a need to better understand whether pregnancy exposure to these chemicals could contribute to adverse cardiometabolic health outcomes in women, particularly given that cardiovascular disease is the leading cause of death in women.

Characterizing exposures to flame retardants, dioxins, and furans among firefighters responding to controlled residential fires

Firefighters may encounter items containing flame retardants (FRs), including organophosphate flame retardants (OPFRs) and polybrominated diphenyl ethers (PBDEs), during structure fires. This study utilized biological monitoring to characterize FR exposures in 36 firefighters assigned to interior, exterior, and overhaul job assignments, before and after responding to controlled residential fire scenarios. Firefighters provided four urine samples (pre-fire and 3-h, 6-h, and 12-h post-fire) and two serum samples (pre-fire and approximately 23-h post-fire). Urine samples were analyzed for OPFR metabolites, while serum samples were analyzed for PBDEs, brominated and chlorinated furans, and chlorinated dioxins. Urinary concentrations of diphenyl phosphate (DPhP), a metabolite of triphenyl phosphate (TPhP), bis(1,3-dichloro-2-propyl) phosphate (BDCPP), a metabolite of tris(1,3-dichloro-2-propyl) phosphate (TDCPP), and bis(2-chloroethyl) phosphate (BCEtP), a metabolite of tris(2-chloroethyl) phosphate (TCEP), increased from pre-fire to 3-hr and 6-hr post-fire collection, but only the DPhP increase was statistically significant at a 0.05 level. The 3-hr and 6-hr post-fire concentrations of DPhP and BDCPP, as well as the pre-fire concentration of BDCPP, were statistically significantly higher than general population levels. BDCPP pre-fire concentrations were statistically significantly higher in firefighters who previously participated in a scenario (within the past 12 days) than those who were responding to their first scenario as part of the study. Similarly, firefighters previously assigned to interior job assignments had higher pre-fire concentrations of BDCPP than those previously assigned to exterior job assignments. Pre-fire serum concentrations of 2,3,4,7,8-pentachlorodibenzofuran (23478-PeCDF), a known human carcinogen, were also statistically significantly above the general population levels. Of the PBDEs quantified, only decabromodiphenyl ether (BDE-209) pre- and post-fire serum concentrations were statistically significantly higher than the general population. These results suggest firefighters absorbed certain FRs while responding to fire scenarios.

Adipose to serum ratio and mixtures of persistent organic pollutants in relation to endometriosis: Findings from the ENDO Study

BACKGROUND

Endometriosis is an estrogen-dependent disease. Endocrine disrupting chemicals (EDCs) and their mixtures may play an etiologic role.

OBJECTIVES

We evaluated an adipose-to-serum ratio (ASR) of lipophilic EDCs and their mixtures associated with incident endometriosis.

METHODS

We quantified 13 polychlorinated biphenyl (PCB) congeners, 6 polybrominated diphenyl ether (PBDE) congeners, and 11 organochlorine pesticides (OCPs) in serum and omental fat among women from the ENDO Study (2007-2009) aged 18-44 years diagnosed with (n=190) or without (n=283) surgically-visualized incident endometriosis. Odds ratios (OR) and 95% confidence intervals (CI) between ASR and endometriosis were estimated using logistic regression models adjusted for age (years), body mass index (kg/m²), serum cotinine (ng/ml), and breastfeeding conditional on parity. Bayesian hierarchical models (BHM) compared estimated associations for adipose and ASR to serum. Bayesian kernel machine regression (BKMR) estimated change in latent health and 95% posterior intervals (PI) between chemical mixtures and endometriosis.

RESULTS

Select ASR for estrogenic PCBs and OCPs were associated with an increased odds of an endometriosis diagnosis, but not for anti-estrogenic PCBs or PBDEs. Across all chemicals, BHMs generated ORs that were on average 14% (95% PI: 6%, 22%) higher for adipose and 20% (95% PI: 12%, 29%) higher for ASR in comparison to serum. ORs from BHMs were greater for estrogenic PCBs and OCPs, with no differences for PBDEs. BKMR models comparing the 75th to 25th percentile were moderately associated with endometriosis for estrogenic PCBs [adipose 0.27 (95% PI: 0.18, 0.72) and ASR 0.37 (95% PI: 0.06, 0.80)] and OCPs [adipose 0.17 (95% PI: 0.21, 0.56) and ASR 0.26 (95% PI: 0.05, 0.57)], but not for antiestrogenic PCBs and PBDEs.

DISCUSSION

ASR added little insight beyond adipose for lipophilic chemicals. BKMR results supported associations between ASR and adipose estrogenic PCB and OCP mixtures and incident endometriosis. These findings underscore the importance of choice of biospecimen and considering mixtures when assessing exposure-disease relationships.

Brominated flame retardants and organochlorine pesticides and incidence of uterine leiomyomata: A prospective ultrasound study

Uterine leiomyomata (UL) are hormone-responsive benign neoplasms. Brominated flame retardants and organochlorine pesticides (OCPs) can disrupt hormones involved in UL etiology.

METHODS

The Study of Environmental, Lifestyle, and Fibroids is a Detroit-area prospective cohort of 1693 Black women 23-35 years of age. At baseline and approximately every 20 months for 5 years, women completed questionnaires and underwent transvaginal ultrasounds. Using a case-cohort study design, we selected 729 UL-free participants at baseline and analyzed baseline plasma samples for polybrominated diphenyl ethers (PBDEs), a polybrominated biphenyl ether (PBB-153), and OCPs. We used Cox proportional hazard models to estimate hazard ratios (HRs) and 95% confidence intervals (CIs).

RESULTS

Compared with total PBDE plasma concentrations <50th percentile, adjusted HRs for the 50th-74th, 75th-89th, and ≥90th percentiles were 1.00 (95% CI = 0.68, 1.47), 1.04 (95% CI = 0.63, 1.68), and 0.85 (95% CI = 0.48, 1.50), respectively. HRs for PBB-153 plasma concentrations were generally similar to total PBDE plasma concentrations. Compared with total OCP plasma concentrations <50th percentile, HRs for the 50th-74th, 75th-89th, and ≥90th percentiles were 0.86 (95% CI = 0.57, 1.29), 0.73 (95% CI = 0.43, 1.22), and 0.58 (95% CI = 0.32, 1.04), respectively. HRs for individual PBDEs and OCPs were similar to their respective totals.

CONCLUSION

We found little support for an association between brominated flame retardant plasma concentrations and UL incidence, and some evidence of lower UL incidence with the highest OCP plasma concentrations.