Polychlorinated biphenyls (PCBs) and polybrominated biphenyls (PBBs): biochemistry, toxicology, and mechanism of action

An in silico study on human carcinogenicity mechanism of polybrominated biphenyls exposure

Polybrominated biphenyls (PBBs) are associated with an increased risk of thyroid cancer; however, relevant mechanistic studies are lacking. In this study, we investigated the mechanisms underlying PBB-induced human thyroid cancer. Molecular docking and molecular dynamics methods were employed to investigate the metabolism of PBBs by the cytochrome P450 enzyme under aryl hydrocarbon receptor mediation into mono- and di-hydroxylated metabolites. This was taken as the molecular initiation event. Subsequently, considering the interactions of PBBs and their metabolites with the thyroxine-binding globulin protein as key events, an adverse outcome pathway for thyroid cancer caused by PBBs exposure was constructed. Based on 2D quantitative structure activity relationship (2D-QSAR) models, the contribution of amino acid residues and binding energy were analyzed to understand the mechanism underlying human carcinogenicity (adverse effect) of PBBs. Hydrogen bond and van der Waals interactions were identified as key factors influencing the carcinogenic adverse outcome pathway of PBBs. Analysis of non-bonding forces revealed that PBBs and their hydroxylation products were predominantly bound to the thyroxine-binding globulin protein through hydrophobic and hydrogen bond interactions. The key amino acids involved in hydrophobic interactions were alanine 330, arginine 381 and lysine 270, and the key amino acids involved in hydrogen bond interactions were arginine 381 and lysine 270. This study provides valuable insights into the mechanisms underlying human health risk associated with PBBs exposure.

Identifying epigenetic aging moderators using the epigenetic pacemaker

Epigenetic clocks are DNA methylation-based chronological age prediction models that are commonly employed to study age-related biology. The difference between the predicted and observed age is often interpreted as a form of biological age acceleration, and many studies have measured the impact of environmental and disease-associated factors on epigenetic age. Most epigenetic clocks are fit using approaches that minimize the error between the predicted and observed chronological age, and as a result, they may not accurately model the impact of factors that moderate the relationship between the actual and epigenetic age. Here, we compare epigenetic clocks that are constructed using penalized regression methods to an evolutionary framework of epigenetic aging with the epigenetic pacemaker (EPM), which directly models DNA methylation as a function of a time-dependent epigenetic state. In simulations, we show that the value of the epigenetic state is impacted by factors such as age, sex, and cell-type composition. Next, in a dataset aggregated from previous studies, we show that the epigenetic state is also moderated by sex and the cell type. Finally, we demonstrate that the epigenetic state is also moderated by toxins in a study on polybrominated biphenyl exposure. Thus, we find that the pacemaker provides a robust framework for the study of factors that impact epigenetic age acceleration and that the effect of these factors may be obscured in traditional clocks based on linear regression models.

Polybrominated biphenyls (PBBs) and prevalence of autoimmune disorders among members of the Michigan PBB registry

BACKGROUND

Polybrominated biphenyls (PBBs), a class of endocrine disrupting chemicals, were the main chemicals present in one of the largest industrial accidents in the United States. We investigated the association between serum PBB-153 levels and autoimmune disorders among members of the Michigan PBB Registry.

METHODS

Eight hundred and ninety-five members of the registry had both a serum PBB-153 measurement and had completed one or more questionnaires about autoimmune disorders. Autoimmune disorders were examined collectively and within specific organ systems. Sex-stratified unadjusted and adjusted log-binomial models were used to examine the association between tertiles of serum PBB-153 levels and autoimmune disorders. Models were adjusted by lifestage at exposure (in utero, childhood, adulthood), smoking history (never, past, current), and total serum lipid levels (continuous). We utilized cubic spline models to investigate non-linearity between serum PBB-153 levels and the prevalence of autoimmune disorders.

RESULTS

Approximately 12.9% and 20.7% of male and female participants reported having one or more autoimmune disorders, respectively. After adjustment for potential confounders, we observed no association between PBB-153 tertiles and the composite classification of 'any autoimmune disorder' in either sex. We observed some evidence for an association between serum PBB-153 levels and rheumatoid arthritis in males and females; however, this was not statistically significant in females. We also observed some evidence for an association between serum PBB-153 levels and neurological- and thyroid-related autoimmune disorders in females, but again this was not statistically significant. Additionally, we identified dose-response curves for serum PBB-153 levels and the prevalence of autoimmune disorders that differed by lifestage of exposure and sex.

CONCLUSIONS

We observed some evidence that increasing serum PBB-153 levels were associated with three specified autoimmune disorders. Studies focusing on these three autoimmune disorders and the potential non-linear trend differences by lifestage of exposure warrant further investigation.

Persistent Halogenated Organic Pollutants in Deep-Water-Deposited Particulates from South China Sea

POP data are limited in the marine environment; thus, this study aimed to investigate background persistent organic pollutant (POP) levels in oceanic deep-water-deposited particulates in the South China Sea (SCS). Six POPs, including polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs), dioxin-like polychlorinated biphenyls (DL-PCBs), polybrominated diphenyl ethers (PBDEs), polybrominated dibenzo-p-dioxins/dibenzofurans (PBDD/Fs), polychlorinated diphenyl ethers (PCDEs), and polybrominated biphenyls (PBBs), were investigated in eight pooled samples from the SCS from 20 September 2013 to 23 March 2014 and 15 April 2014 to 24 October 2014 at depths of 2000 m and 3500 m. PBDEs were the most predominant compounds, with the highest mean Σ14PBDE of 125 ± 114 ng/g dry weight (d.w.), followed by Σ17PCDD/F, Σ12PBDD/F, and Σ12DL-PCB (275 ± 1930, 253 ± 216, and 116 ± 166 pg/g d.w., respectively). Most PBDD/F, PBB, and PCDE congeners were below the detection limits. PCDDs had the highest toxic equivalency (TEQ), followed by PBDDs and DL-PCBs. Among the six POPs, PBDEs were the major components of the marine-deposited particles, regarding both concentrations and mass fluxes. Compared to 3500 m, PBDE levels were higher at a depth of 2000 m. PBDE mass fluxes were 20.9 and 14.2 ng/m2/day or 68.2 and 75.9 ng/m2/year at deep-water 2000 and 3500 m, respectively. This study first investigated POP levels in oceanic deep-water-deposited particles from existing global data.

Elimination of PBB-153; findings from a cohort of Michigan adults

BACKGROUND

An industrial accident led to the widespread contamination of polybrominated biphenyl (PBB), a flame retardant, into the food system in Michigan in the 1970's. PBB continues to be detected in Michiganders' blood some forty years later. It is necessary to understand the elimination rate and half-life of PBB because it may provide clues on how to hasten the elimination of it from the human body.

METHODS

Serum samples were taken from young adult and adult participants of the Michigan PBB registry from 1974 to 2019. A single compartment model was assumed for the elimination rate for PBB-153 in young adults and adults (≥16 years). Generalized linear mixed models were used to estimate the average elimination rate of PBB-153 and allowed for a random intercept and slope for the time between measurements. Models were adjusted for age at exposure, body mass index (BMI) at initial measurement, and smoking. Models were also stratified by demographic characteristics.

RESULTS

In total, 1974 participants contributed 4768 samples over a forty-year span. The median initial PBB-153 level was 1.542 parts per billion (ppb) (Range: 0.001-1442.48 ppb). The adjusted median participant-specific half-life for PBB-153 was 12.23 years. The half-life of PBB-153 was lengthened by higher initial PBB level (∼1.5 years), younger age at exposure (∼5.4 years), higher BMI (∼1.0 years), and increased gravidity (∼7.3 years). Additionally, the half-life of PBB-153 was shortened by smoking status (∼-2.8 years) and breastfeeding (∼-3.5 years).

CONCLUSIONS

Consistent with previous studies, PBB-153 has been demonstrated to have a long half-life in the human body and may be modified by some demographic characteristics. These updated estimates of half-life will further support evaluation of health effects associated with PBB exposure. Investigations into mechanisms to accelerate elimination and reduce body burdens of PBB-153, especially those related to body weight, are needed.

Determination of Polychlorinated Biphenyls in Water Samples Using a Needle Trap Device Combined with Gas Chromatography

In this study, a fiber-packed needle trap device (NTD) was developed by packing heat-resistant fibers with a polyethylene glycol sol-gel coating into a 21-gauge, stainless steel needle. The polyethylene glycol sol-gel coating has numerous advantages, including uniform roughness and a large specific surface area. The prepared NTD was used for headspace extraction of five polychlorinated biphenyls (PCBs) in water samples, determined by gas chromatography with a flame ionization detector (GC-FID). The main experimental parameters, including the extraction and desorption conditions, ionic strength, and fiber bundles, were investigated to improve the extraction efficiency. After optimization, satisfactory linearity (r > 0.99) in the concentration range of 0.02–500 μg/L was obtained, and the enrichment factor of NTD for the five PCBs was between 1150 and 9537 times. The limit of detection (S/N = 3) of five PCBs were measured in ranges of 0.0021–0.01 μg/L. Furthermore, the fiber-packed NTD has excellent durability, and can be reused for 60 cycles. After being stored at room temperature for three days, the storage ability of the NTD had a loss of PCBs less than 10%, and the relative standard deviation (RSD) was less than 10%. When analyzing the PCBs in real water samples, good accuracies (spiked recoveries were in the range of 92.19–98.56%) and precision (the RSD was lower than 12.8%) was obtained.

PCBs in indoor air and human blood in Pittsfield, Massachusetts

Concentrations of polychlorinated biphenyls (PCBs) and three chlorinated pesticides were determined in serum from 21 residents of Pittsfield, MA and in the basement, living room and outdoor air of the 10 homes in which they lived. Median serum PCB levels were 4.2 ng/g, which are at least four times the average level in the US population, and consisted primarily of more highly chlorinated, persistent congeners. This reflects contamination with PCBs coming from the local General Electric facility. Median basement air concentration was 20.3 ng/m³, while the median living room air was 11.4 ng/m³ and median outdoor air concentration was 3.0 ng/m³. The PCB congeners detected in air were primarily low chlorinated (four and fewer) congeners, reflecting the greater volatility of PCBs with fewer chlorines. The congener pattern between basement and living room air showed a 95% correlation, while correlation with outdoor air was much less. While the congener pattern in air is very different from that of the PCB products used in Pittsfield (Aroclors 1254 and 1260), low chlorinated PCBs are detected in the vapor phase after air is blown across the commercial mixtures. The human serum samples did not show detectible levels of many of the congeners seen in the basement air samples, reflecting rapid metabolism of lower chlorinated PCBs by the human body. However, with continuous inhalation of indoor air, especially in the living room, the exposure to these non-persistent congeners may still have adverse health effects. Cellular studies of some of these non-persistent, low chlorinated congeners indicate that they are neurotoxic, mutagenic and cytotoxic. These results demonstrate the importance of consideration of inhalation of PCBs as a route of exposure, especially in indoor sites, and suggest that monitoring serum PCB concentration may not always provide a good measurement of exposure, especially to congeners that are relatively rapidly metabolized but have significant toxicity.

Forty years studies on polychlorinated biphenyls pollution, food safety, health risk, and human health in an e-waste recycling area from Taizhou city, China: a review

E-waste generation has become a serious environmental challenge worldwide. Taizhou of Zhejiang Province, situated on the southeast coastline of China, has been one of the major e-waste dismantling areas in China for the last 40 years. In this review, we focused on the polychlorinated biphenyl (PCB) trends in environmental compartments, burden and impact to humans, food safety, and health risk assessment from Taizhou, China. The review suggested that PCBs showed dynamic trends in air, soil, water, biodiversity, and sediments. Soils and fish samples indicated higher levels of PCBs than sediments, air, water, and food items. PCB levels decreased in soils with the passage of time. Agriculture soils near the e-waste recycling sites showed more levels of total PCBs than industrial soils and urban soils. Dioxin-like PCB levels were higher in humans near Taizhou, suggesting that e-waste pollution could influence humans. Compared with large-scale plants, simple household workshops contributed more pollution of PCBs to the environment. Pollution index, hazard quotient, and daily intake were higher for PCBs, suggesting Taizhou should be given priority to manage the e-waste pollution. The elevated body burden may have health implications for the next generation. The areas with stricter control measures, strengthened laws and regulations, and more environmentally friendly techniques indicated reduced levels of PCBs. For environment protection and health safety, proper e-waste dismantling techniques, environmentally sound management, awareness, and regular monitoring are very important.

Polluted porpoises: Generational transfer of organic contaminants in harbour porpoises from the southern North Sea

Persistent organic pollutants (POPs), including polychlorinated biphenyls (PCBs), polybrominated diphenylethers (PBDEs) and hexachlorobenzene (HCB), bioaccumulate in marine ecosystems. Top predators contain high levels of POPs in their lipid-rich tissues, which may result in adverse effects on their reproductive, immune and endocrine functions. Harbour porpoises (Phocoena phocoena) are among the smallest of cetaceans and live under high metabolic demand, making them particularly vulnerable to environmental pressures. Using samples from individuals of all maturity classes and sexes stranded along the southern North Sea (n = 121), we show the generational transfer of PCBs, PBDEs and HCB from adults to foetuses. Porpoise placentas contained 1.3-8.2 mg/kg lipid weight (lw) Sum-17PCB, <dl-0.08 mg/kg lw Sum-17PBDE and 0.14-0.16 mg/kg lw HCB, which were similar to concentrations in foetus blubber. Contaminant levels increased significantly after birth through suckling. Milk samples contained 0.20-33.8 mg/kg lw Sum-17PCB, 0.002-0.51 mg/kg lw Sum-17PBDE and 0.03-0.21 mg/kg lw HCB. Especially lower halogenated and more toxic contaminants were transferred to calves, exposing them to high levels of contaminants early in life. Of all animals included in this study, 38.5% had PCB concentrations exceeding a threshold level for negative health effects (>9 mg/kg lw). This was particularly true for adult males (92.3% >9 mg/kg lw), while adult females had relatively low PCB levels (10.5% >9 mg/kg lw) due to offloading. Nutritional stress led to higher offloading in the milk, causing a greater potential for toxicity in calves of nutritionally stressed females. No correlation between PCB concentration and parasite infestation was detected, although the probability of a porpoise dying due to infectious disease or debilitation increased with increasing PCB concentrations. Despite current regulations to reduce pollution, these results provide further evidence of potential health effects of POPs on harbour porpoises of the southern North Sea, which may consequently increase their susceptibility to other pressures.

Oyster Crassostrea gigas, a good model for correlating viral and chemical contamination in the marine environment

To establish a relationship between viruses and chemicals, they were analysed in oyster Crassostrea gigas from an Italian experimental station. The chemicals concentrations were: Σ6 NDL-PCBs 0.82-7.12 ng g^-1; BaP LOQ (<0.2 μg kg^-1) to 1.2 μg kg^-1; PAH4 LOQ (<0.2 μg kg^-1) to 9.8 μg kg^-1; Cd 0.073-0.365 mg kg^-1; Pb 0.010-0.487 mg kg^-1; and Hg < LOQ (0.089 mg kg^-1). The viruses identified included: noroviruses (NoVGI/GII), astrovirus (AsV), rotavirus (RV), adenovirus (AdV), and sapovirus (SaV), while hepatitis A, hepatitis E, and Aichi viruses were not detected. Significant correlations were observed for NDL-PCBs with NoVGI, NoVGII, and AdV; BaP and PAH4 with NoVGI and AsV; Cd with RV; Pb with NoVGI and AsV; PAHs with Pb; AsV with NoVGI; and AdV with NoVGII. The study indicated as C. gigas is a model for correlating pollutants and foodborne viruses, whose co-presence may represent an additional food safety risk.

Characterization of chlordecone distribution and elimination in ewes during daily exposure and depuration

To reduce the exposure of the French West Indies population to the pollutant chlordecone (CLD), the contamination of consumed products must be reduced. One of the strategies to secure safe animal products is related to the depuration of contaminated animals. In order to set up this strategy in situ, characterizing CLD distribution and elimination appears to be essential. The aim of this study is to characterize CLD distribution and elimination in ewes, and establish correlations between CLD concentrations in tissues following a continuous oral contamination period and a depuration period. The experiment consisted in a 90-d period of CLD exposure via daily feeding at 0.01 mg kg^-1 body weight, followed by a 127-d period of depuration. A total of 24 ewes were sequentially slaughtered and serum, liver, perirenal fat, subcutaneous fat, shaft muscle, longissimus dorsi muscle and heart samples were collected. CLD concentrations in serum and tissues were analyzed by GC-MS/MS and LC-MS/MS, respectively. Whatever the time of sampling, CLD concentrations in liver were significantly higher than in other collected tissues. However, the results showed that fat tissues stored the higher portion of CLD body burden, followed by muscle, liver, serum and heart. CLD half-lives did not differ significantly between tissues including serum and ranged between 20.2 ± 4.0 and 24.1 ± 4.9 d. Two linear models were developed to estimate CLD concentration in tissues from a blood sample. This study illustrates the theoretical methodology to estimate the time required to decontaminate farm animals from a blood sample.

Perinatal effects of persistent organic pollutants on thyroid hormone concentration in placenta and breastmilk

Thyroid hormones (TH) are known to play a critical role in regulating many biological processes including growth and development, energy homeostasis, thermogenesis, lipolysis and metabolism of cholesterol. Severe TH deficiency especially during fetal development results in cretinism, but can also lead to an imbalance in metabolism with, among others, an alteration in body weight composition. Over the past two decades, increasing evidence has shown that certain persistent organic pollutants (POP) can interfere with the endocrine system. These POP referred to as "endocrine disrupting chemicals" are widely present in the environment and populations are exposed globally. Moreover, epidemiological studies have shown that a particularly sensitive period is the pre- and postnatal time. Indeed, perinatal exposure to such chemicals could lead to the onset diseases in later life. It is known, that, maternal thyroid hormones are transported by the placenta to the fetus from 6 weeks of gestation and it seems that during the first trimester, and part of the second, the fetus is entirely dependent on maternal TH supply for its development. Interferences in the TH-network as a consequence of the exposure to such pollutants could cause variations in TH concentration. Only small changes in maternal thyroid hormone levels in early stages of pregnancy can influence fetal neurological and cardiovascular development, as well as according to recent studies, have effect on childhood body composition. With this review, we will report the most recent and important studies concerning the association between thyroid hormone concentration and POP levels measured during the perinatal period. We will mostly focus on the data recently reported on placenta and breastmilk as main sources for understanding the potential consequences of exposure. The possible link between exposure to pollutants, TH dysregulation and possible adverse outcome will also be briefly discussed. From our literature search, several studies support the hypothesis that pre- and postnatal exposure to different pollutants might play a role in causing variation in thyroid hormone concentration. However, few research papers have so far studied the relationship linking exposure to pollutants, TH concentration and possible health consequences. Therefore, this review highlights the need for further research in this direction.

Reduction of PVA Aerogel Flammability by Incorporation of an Alkaline Catalyst

Sodium hydroxide was used as a base catalyst to reduce the flammability of poly(vinyl alcohol) (PVA) aerogels. The base-modified aerogels exhibited significantly enhanced compressive moduli, likely resulting in decreased gallery spacing and increased numbers of “struts” in their structures. The onset of decomposition temperature decreased for the PVA aerogels in the presence of the base, which appears to hinder the polymer pyrolysis process, leading instead to the facile formation of dense char. Cone calorimetry testing showed a dramatic decrease in heat release when the base was added. The results indicate that an unexpected base-catalyzed dehydration occurs at fire temperatures, which is the opposite of the chemistry normally observed under typical synthesis conditions.

In silico exploration of hydroxylated polychlorinated biphenyls as estrogen receptor β ligands by 3D-QSAR, molecular docking and molecular dynamics simulations

Hydroxylated polychlorinated biphenyls (HO-PCBs), as the major metabolites of PCBs, have been reported to act as estrogen receptor β (ERβ) agonists. However, the chemical-biological interactions governing their activities toward ERβ have not been elucidated. Therefore, three dimensional quantitative structure-activity relationship (3D-QSAR), molecular docking and molecular dynamics (MD) simulations, to the best of our knowledge, for the first time were performed to explore the correlation between the structures and activities. The best 3D-QSAR model presented higher predictive ability (R²_cv=0.543, R²_pred=0.5793/R²_cv=0.543, R²_pred=0.6795) based on comparative molecular field analysis (CoMFA) and comparative similarity indices analysis (CoMSIA), respectively. At the same time, the derived contour maps indicated the important structural features required for improving the activity. Furthermore, molecular docking studies and MD simulations predicted the binding mode and the interactions between the ligand and the receptor. All the results would lead to a better understanding of the specific mechanism of HO-PCBs on estrogen receptor β (ERβ).Communicated by Ramaswamy H. Sarma.

Structure-based mimicking of hydroxylated biphenyl congeners (OHPCBs) for human transthyretin, an important enzyme of thyroid hormone system

In humans, transthyretin (hTTR) is a plasma protein act as a transporter of thyroxine (T4) in the blood. Polychlorinated biphenyls (PCBs) are used in coolants, transformers, plasticizers, and pesticide extenders, etc. due to their physical properties, chemical stability, and dielectric properties. Cytochrome P450 can oxidize the PCBs into hydroxylated PCBs (OHPCBs) which can further interact with hTTR results in hepatoxicity, loss of metabolic rate, memory problems, and neurotoxicity. Molecular docking results show that OHPCBs bind at the active site of hTTR with a more binding affinity as compared to T4. Further, molecular dynamics simulation has been done to confirm the stability of hTTR-OHPCBs complexes. Several analysis parameters like RMSD, RMSF, Rg, SASA, hydrogen bonds numbers, PCA, and FEL revealed that binding of OHPCBs with hTTR results in the formation of stable hTTR-OHPCBs complexes. Individual residues decomposition analysis confirms that Lys15, Leu17, Ala108, Ala109, Leu110, Ser117, and Thr119 of hTTR plays a major role in the binding of OHPCBs to form the lower energy hTTR-OHPCBs complexes. Molecular docking and simulations results emphasize that OHPCBs can efficiently bind at the active site of hTTR, which further leads to inhibition of transportation of T4 in human blood.

Brain Disorders and Chemical Pollutants: A Gap Junction Link?

The incidence of brain pathologies has increased during last decades. Better diagnosis (autism spectrum disorders) and longer life expectancy (Parkinson's disease, Alzheimer's disease) partly explain this increase, while emerging data suggest pollutant exposures as a possible but still underestimated cause of major brain disorders. Taking into account that the brain parenchyma is rich in gap junctions and that most pollutants inhibit their function; brain disorders might be the consequence of gap-junctional alterations due to long-term exposures to pollutants. In this article, this hypothesis is addressed through three complementary aspects: (1) the gap-junctional organization and connexin expression in brain parenchyma and their function; (2) the effect of major pollutants (pesticides, bisphenol A, phthalates, heavy metals, airborne particles, etc.) on gap-junctional and connexin functions; (3) a description of the major brain disorders categorized as neurodevelopmental (autism spectrum disorders, attention deficit hyperactivity disorders, epilepsy), neurobehavioral (migraines, major depressive disorders), neurodegenerative (Parkinson's and Alzheimer's diseases) and cancers (glioma), in which both connexin dysfunction and pollutant involvement have been described. Based on these different aspects, the possible involvement of pollutant-inhibited gap junctions in brain disorders is discussed for prenatal and postnatal exposures.

Human exposure to PCBs, PBDEs and bisphenols revealed by hair analysis: A comparison between two adult female populations in China and France

Humans are exposed to various anthropogenic chemicals in daily life, including endocrine-disrupting chemicals (EDCs). However, there are limited data on chronic, low-level exposure to such contaminants among the general population. Here hair analysis was used to investigate the occurrence of four polychlorinated biphenyls (PCBs), seven polybrominated diphenyl ethers (PBDEs) and two bisphenols (BPs) in 204 Chinese women living in the urban areas of Baoding and Dalian and 311 pregnant French women. All the PCBs and PBDEs tested here were more frequently detected in the hair samples of the French women than in those of the Chinese women. In both cohorts, PCB 180 and BDE 47 were the dominant PCB and PBDE congener, respectively. PCB 180 was found in 82% of the French women and 44% of the Chinese women, while the corresponding values of BDE 47 were 54% and 11%, respectively. A discriminant analysis further demonstrated the difference in PCBs and PBDEs exposure profile between the two cohorts. These results demonstrate that hair analysis is sufficiently sensitive to detect exposure to these pollutants and highlight differences in exposure between populations even at environmental levels. Although BPA and BPS were found in 100% of the hair samples in both cohorts, the French women had significantly higher levels of BPA and BPS than the Chinese women. The median concentrations of BPA were one order of magnitude higher than BPS in both the Chinese (34.9 versus 2.84 pg/mg) and the French women (118 versus 8.01 pg/mg) respectively. Our results suggest that both French and Chinese populations were extensively exposed to BPA and BPS.

Chemical identity and cardiovascular toxicity of hydrophobic organic components in PM2.5

Numerous experimental and epidemiological studies have demonstrated that exposure to PM_2.5 may result in pathogenesis of several major cardiovascular diseases (CVDs), which can be attributed to the combined adverse effects induced by the complicated components of PM_2.5. Organic materials, which are major components of PM_2.5, contain thousands of chemicals, and most of them are environmental hazards. However, the contamination profile and contribution to overall toxicity of PM_2.5-bound organic components (OCs) have not been thoroughly evaluated yet. Herein, we aim to provide an overview of the literature on PM_2.5-bound hydrophobic OCs, with an emphasis on the chemical identity and reported impairments on the cardiovascular system, including the potential exposure routes and mechanisms. We first provide an update on the worldwide mass concentration and composition data of PM_2.5, and then, review the contamination profile of PM_2.5-bound hydrophobic OCs, including constitution, concentration, distribution, formation, source, and identification. In particular, the link between exposure to PM_2.5-bound hydrophobic OCs and CVDs and its possible underlying mechanisms are discussed to evaluate the possible risks of PM_2.5-bound hydrophobic OCs on the cardiovascular system and to provide suggestions for future studies.

Spatial and temporal trends of polychlorinated biphenyls in water and sediment from Nairobi River, Kenya

Polychlorinated biphenyls (PCBs) are chemicals that have become ubiquitous environmental pollutants due to their past use, persistence, and long-range transport thus requiring continuous monitoring. Therefore, this research was carried out to investigate spatial and temporal trends of seven indicator PCBs and two others (PCB 105 and PCB 156) in the Nairobi River. Levels of PCBs ranged from below detection limit (bdl) to 157.64 ± 1.52 ng g^-1 and bdl to 718.78 ± 1.71 ng L^-1 for sediment and water, respectively. PCBs 28, 138, and 153 were the most dominant contributing 33.4%, 17.9%, and 14.5% to the total PCBs in sediments and 54.6%, 19.3%, and 14.1% to the total PCBs in water. There was a general increase in ΣPCBs from 18.89 to 151.18 ng g^-1 for sediments and 275.52 to 429.84 ng L^-1 for water as the River flowed downstream. The dry season recorded the highest ΣPCB in sediments while the rainy season recorded the highest ΣPCBs in water, with levels exceeding the WHO water quality guidelines. Risk assessment revealed that populations living downstream are exposed to high levels of PCBs through the consumption of water. Levels of ΣPCBs downstream also exceeded the sediment quality guidelines meaning that aquatic organisms are threatened.

Cross-Sectional and Longitudinal Effects of PCB Exposure on Human Stress Hormones in the German HELPcB Surveillance Program

Multiple pathological associations are attributed to PCBs (polychlorinated biphenyls). Research shows a positive association of PCBs with dehydroepiandrosterone sulfate (DHEAS) concentration but the results on the stress hormone cortisol have been inconsistent so far. This study is the first to examine not only the cross-sectional but also the longitudinal effects of PCB exposure on the stress hormones DHEAS and cortisol. Over a period of three years, 112 former employees occupationally exposed to PCBs were tested for their body burden with different types of PCBs (lower and higher chlorinated, dioxin-like and hydroxylated) and for their stress hormone concentration. Highly exposed employees showed a significantly higher risk for higher DHEAS values. Multiple linear regression analysis revealed a positive relationship between the exposure to lower chlorinated PCBs and DHEAS. Mixed models also revealed a significantly positive correlation between lower chlorinated PCBs with DHEAS when controlled for a cross-section. However, an effect for cortisol was not found. These results suggest a causal pathophysiological relationship between PCB exposure and DHEAS concentration, but not with cortisol. The health consequences of high DHEAS concentrations are discussed.

Renal changes and apoptosis caused by subacute exposure to Aroclor 1254 in selenium-deficient and selenium-supplemented rats

Aroclor 1254 (A1254), a mixture of polychlorinated biphenyls, exerts hepatic, renal, and reproductive toxicity in rodents. This study aimed to determine a protective role of selenium on histopathological changes, oxidative stress, and apoptosis caused by A1254 in rat kidney. It included a control group, which received regular diet containing 0.15 mg/kg Se (C), a Se-supplemented group (SeS) receiving 1 mg/kg Se, a Se-deficient group (SeD) receiving Se-deficient diet of ≤0.05 mg/kg Se, an A1254-treated group (A) receiving 10 mg/kg of Aroclor 1254 and regular diet, an A1254-treated group receiving Se-supplementation (ASeS), and an A1254-treated group receiving Se-deficient diet (ASeD). Treatments lasted 15 days. After 24 h of the last dose of A1254, the animals were decapitated under anaesthesia and their renal antioxidant enzyme activities, lipid peroxidation (LP), glutathione, protein oxidation, and total antioxidant capacity levels measured. Histopathological changes were evaluated by light and electron microscopy. Apoptosis was detected with the TUNEL assay. Kidney weights, CAT activities, and GSH levels decreased significantly in all A1254-treated groups. Renal atrophic changes and higher apoptotic cell counts were observed in the A and ASeD groups. Both groups also showed a significant drop in GPx1 activities (A – 34.92 % and ASeD – 86.46 %) and rise in LP (A – 30.45 % and ASeD – 20.44 %) vs control. In contrast, LP levels and apoptotic cell counts were significantly lower in the ASeS group vs the A group. Histopathological changes and renal apoptosis were particularly visible in the ASeD group. Our findings suggest that selenium supplementation provides partial protection against renal toxicity of Aroclor 1254.

Sex-specific DNA methylation differences in people exposed to polybrominated biphenyl

Aim: Michigan residents were exposed to polybrominated biphenyls (PBBs) when it was accidentally added to the food supply. Highly exposed individuals report sex-specific health problems, but the underlying biological mechanism behind these different health risks is not known. Materials and methods: DNA methylation in blood from 381 women and 277 men with PBB exposure was analyzed with the MethylationEPIC BeadChip. Results: 675 CpGs were associated with PBBs levels in males, while only 17 CpGs were associated in females (false discovery rate <0.05). No CpGs were associated in both sexes. These CpGs were enriched in different functional regions and transcription factor binding sites in each sex. Conclusion: Exposure to PBBs may have sex-specific effects on the epigenome that may underlie sex-specific adverse health outcomes.

Halogen Bonding Interactions of Polychlorinated Biphenyls and the Potential for Thyroid Disruption

Polychlorinated biphenyl (PCB) flame retardants are persistent pollutants and inhibit neurodevelopment, particularly in the early stages of life. Halogen bonding (XB) to the iodothyronine deiodinases (Dio) that modulate thyroid hormones (THs) is a potential mechanism for endocrine disruption. Cl⋅⋅⋅Se XB interactions of PCBs with SeMe- , a small model of the Dio active site selenocysteine, are compared with previous results on polybrominated diphenylethers (PBDEs) and THs using density functional theory. PCBs generally display weaker XB interactions compared to PBDEs and THs, consistent with the dependence of XB strength on the size of the halogen (I>Br>Cl). PCBs also do not meet a proposed energy threshold for substrates to undergo dehalogenation, suggesting they may behave as competitive inhibitors of Dio in addition to other mechanisms of endocrine disruption. XB interactions in PCBs are position-dependent, with ortho interactions slightly more favorable than meta and para interactions, suggesting that PCBs may have a greater effect on certain classes of Dio. Flexibility of PCBs around the biphenyl C-C bond is limited by ortho substitutions relative to the biphenyl linkage, which may contribute to the ability to inhibit Dio and other TH-related proteins.

Juvenile harbor porpoises in the UK are exposed to a more neurotoxic mixture of polychlorinated biphenyls than adults

Polychlorinated biphenyls (PCBs) are a group of 209 persistent and bio-accumulative toxic pollutants present as complex mixtures in human and animal tissues. Harbor porpoises accumulate some of the highest levels of PCBs because they are long-lived mammals that feed at a high trophic level. Studies typically use the sum of a suite of individual chlorobiphenyl congeners (CBs) to investigate PCBs in wildlife. However, toxic effects and thresholds of CB congeners differ, therefore population health risks of exposure may be under or over-estimated dependent on the congener profiles present. In this study, we found congener profiles varied with age, sex and location, particularly between adult females and juveniles. We found that adult females had the highest proportions of octa-chlorinated congeners whilst juveniles had the highest proportions of tri- and tetra-chlorinated congeners. This is likely to be a consequence of pollutant offloading between mothers and calves during lactation. Analysis of the individual congener toxicities found that juveniles were exposed to a more neurotoxic CB mixture at a time when they were most vulnerable to its effects. These findings are an important contribution towards our understanding of variation in congener profiles and the potential effects and threats of PCB exposure in cetaceans.

Polychlorinated biphenyls: Hazardous properties and environmentally sound management in Ukraine

Polychlorinated biphenyls are one of the most dangerous compounds for human health and the environment and are included to Annex C of the Stockholm Convention on Persistent Organic Pollutants. Since Ukraine joined the Stockholm Convention in 2007, the National Implementation Plan of the Stockholm Convention provides the environmentally sound disposal of polychlorinated biphenyls, as well as creation of a monitoring system and sharing information about toxicants. Polychlorinated biphenyls’ have fire resistance, low volatility and stability. Therefore, these substances have been widely used in industry, but on the other hand, they are a problem for the environment. The main hazardous properties of polychlorinated biphenyls are bioaccumulation, stability in the environment, the possibility of formation in accidents (especially in fires) of extremely persistent and toxic aromatic compounds, such as dioxins and furans. Toxic responses to polychlorinated biphenyls are: acute lethality; body weight loss; carcinogenesis; dermal toxi­city; fatty liver; genotoxicity; hepatomegaly; immunosuppressive effects; neurotoxicity; porphyria; reproductive and developmental toxicity; thymic atrophy; thyroid hormone-level alterations. The most likely risks of polychlorinated biphenyls contamination in Ukraine are in the areas of operation, repair or storage of electrical equipment. According to quantity, the leading regions for accumulated polychlorinated biphenyls in Ukraine, are Dnipropetrovsk (459 tons), Volyn (280 tons) and Kyiv regions (255 tons). A comprehensive approach to reducing the risk of polychlorinated biphenyls for human health and the environment involves the improvement of the regulatory framework for managing in all stages of “life cycle”. Obtaining complete and accurate information on the volumes and forms of polychlorinated biphenyls accumulation and creation of modern effective technological support for polychlorinated biphenyls’ degradation are a necessary part of environmentally sound management of polychlorinated biphenyls in Ukraine. The “Polychlorinated Biphenyls Database in Ukraine” information system (2017) was created as a National Polychlorinated Biphenyls Registry in Ukraine. It was designed to systematize, structure, and analyze the large amount of information collected during the inventorising of polychlorinated biphenyls. The best technology of polychlorinated biphenyls degradation must not only provides a high degree of polychlorinated biphenyls’ destruction, but also not lead to the formation of new toxic compounds.

Examining Reproductive Health Outcomes in Females Exposed to Polychlorinated Biphenyl and Polybrominated Biphenyl

In 1973, accidental contamination of Michigan livestock with polybrominated biphenyls (PBBs) led to the establishment of a registry of exposed individuals that have been followed for > 40 years. Besides being exposed to PBBs, this cohort has also been exposed to polychlorinated biphenyls (PCBs), a structurally similar class of environmental pollutants, at levels similar to average US exposure. In this study, we examined the association between current serum PCB and PBB levels and various female reproductive health outcomes to build upon previous work and inconsistencies. Participation in this cross-sectional study required a blood draw and completion of a detailed health questionnaire. Analysis included only female participants who had participated between 2012 and 2015 (N = 254). Multivariate linear and logistic regression models were used to identify associations between serum PCB and PBB levels with each gynecological and infertility outcome. Additionally, a generalized estimating equation (GEE) model was used to evaluate each pregnancy and birth outcome in order to account for multiple pregnancies per woman. We controlled for age, body mass index, and total lipid levels in all analyses. A p-value of <0.05 was used for statistical significance. Among the women who reported ever being pregnant, there was a significant negative association with higher total PCB levels associating with fewer lifetime pregnancies ( β = −0.11, 95% CI = −0.21 to −0.005, p = 0.04). There were no correlations between serum PCB levels and the self-reported gynecological outcomes (pelvic inflammatory disease, endometriosis, polycystic ovarian syndrome, or uterine fibroids). No associations were identified between serum PCB levels and the prevalence of female infertility in women reporting ever having sexual intercourse with a male partner. There were no associations identified between serum PCB levels and pregnancy outcomes (singleton live births or miscarriages) or birth outcomes (preterm birth, birth weight, birth defects, hypertensive disorders of pregnancy, or gestational diabetes). PBB was not associated with any outcome. Further research is needed to determine if and how PCB may reduce pregnancy number.

Separation of halogenated benzenes enabled by investigation of halogen-π interactions with carbon materials

We report the existence of bimodal interactions, the π–π and halogen–π interactions, between the halogenated benzenes and aromatic materials.

The halogen–π (X–π) interaction is an intermolecular interaction between the electron-poor region of bonded halogen atoms and aromatic rings. We report an experimental evaluation of the halogen–π (X–π) interaction using liquid chromatography with carbon-material coated columns providing strong π interactions in the normal phase mode. A C₇₀-fullerene (C70)-coated column showed higher retentions for halogenated benzenes as the number of halogen substitutions increased as a result of X–π interactions. In addition, the strength of the X–π interaction increased in the order of F < Cl < Br < I. Changes to the UV absorption of C70 and the brominated benzenes suggested that the intermolecular interaction changed from the π–π interaction to X–π interaction as the number of bromo substitutions increased. Computer simulations also showed that the difference in dipole moments among structural isomers affected the strength of the π–π interaction. Furthermore, we concluded from small peak shifts in ¹H NMR and from computer simulations that the orbital interaction contributes to the X–π interactions. Finally, we succeeded in the one-pot separation of all isomers of brominated benzenes using the C70-coated column by optimizing the mobile phase conditions.

Binding and activity of sulfated metabolites of lower-chlorinated polychlorinated biphenyls towards thyroid hormone receptor alpha

There has been long-standing evidence that the lower-chlorinated polychlorinated biphenyls (LC-PCBs) can be metabolized to hydroxylated metabolites (OH-PCBs), which play important roles in the LC-PCBs induced toxicity. Recently, multiple studies have demonstrated the further metabolic transformation of OH-PCBs to LC-PCB sulfates in vitro and in vivo. Several studies found LC-PCB sulfates could bind with thyroid hormone (TH) transport proteins in the serum, indicating the potential relevance of these metabolites in the TH system disruption effects. However, the interaction of LC-PCB sulfates with the TH nuclear receptor (TR), another kind of important functional protein in the TH system, has not been explored. Here, by using a fluorescence competitive binding assay, we demonstrated that LC-PCB sulfates could bind with TRα. Moreover, the LC-PCB sulfates had higher binding potency than their corresponding OH-PCB precursors. By using a luciferase reporter gene assay, we found the LC-PCB sulfates showed agonistic activity towards the TRα signaling pathway. Molecular docking simulation showed all the tested LC-PCB sulfates could fit into the ligand binding pocket of the TRα. The LC-PCB sulfates formed hydrogen bond interaction with arginine 228 residue of TRα by their sulfate groups, which might facilitate the TR binding and agonistic activity. The present study suggests that interaction with the TR might be another possible mechanism by which LC-PCB sulfate induce TH system disruption effects.

Thyroid hormone levels associate with exposure to polychlorinated biphenyls and polybrominated biphenyls in adults exposed as children

BACKGROUND

Michigan residents were directly exposed to endocrine-disrupting compounds, polybrominated biphenyl (PBB) and polychlorinated biphenyl (PCB). A growing body of evidence suggests that exposure to certain endocrine-disrupting compounds may affect thyroid function, especially in people exposed as children, but there are conflicting observations. In this study, we extend previous work by examining age of exposure's effect on the relationship between PBB exposure and thyroid function in a large group of individuals exposed to PBB.

METHODS

Linear regression models were used to test the association between serum measures of thyroid function (total thyroxine (T4), total triiodothyronine (T3), free T4, free T3, thyroid stimulating hormone (TSH), and free T3: free T4 ratio) and serum PBB and PCB levels in a cross-sectional analysis of 715 participants in the Michigan PBB Registry.

RESULTS

Higher PBB levels were associated with many thyroid hormones measures, including higher free T3 (p = 0.002), lower free T4 (p = 0.01), and higher free T3: free T4 ratio (p = 0.0001). Higher PCB levels were associated with higher free T4 (p = 0.0002), and higher free T3: free T4 ratio (p = 0.002). Importantly, the association between PBB and thyroid hormones was dependent on age at exposure. Among people exposed before age 16 (N = 446), higher PBB exposure was associated with higher total T3 (p = 0.01) and free T3 (p = 0.0003), lower free T4 (p = 0.04), and higher free T3: free T4 ratio (p = 0.0001). No significant associations were found among participants who were exposed after age 16. No significant associations were found between TSH and PBB or PCB in any of the analyses conducted.

CONCLUSIONS

This suggests that both PBB and PCB are associated with thyroid function, particularly among those who were exposed as children or prenatally.

Environmental exposure to polybrominated biphenyl (PBB) associates with an increased rate of biological aging

Advanced age increases risk for cancer, cardiovascular disease, and all-cause mortality. However, people do not age at the same rate, and biological age (frequently measured through DNA methylation) can be older than chronological age. Environmental factors have been associated with the rate of biological aging, but it is not known whether persistent endocrine-disrupting compounds (EDCs) like polybrominated biphenyl (PBB) would associate with age acceleration. Three different epigenetic age acceleration measures (intrinsic, extrinsic, and phenotypic) were calculated from existing epigenetic data in whole blood from a population highly exposed to PBB (N=658). Association between serum PBB concentration and these measures was tested, controlling for sex, lipid levels, and estimated cell type proportions. Higher PBB levels associated with increased age acceleration (intrinsic: β=0.24, 95%CI=0.01-0.46, p = 0.03; extrinsic: β=0.39, 95%CI=0.12-0.65, p = 0.004; and phenotypic: β=0.30, 95%CI=0.05-0.54, p = 0.01). Neither age when exposed to PBB nor sex statistically interacted with PBB to predict age acceleration, but, in stratified analyses, the association between PBB and age acceleration was only in people exposed before finishing puberty and in men. This suggests that EDCs can associate with the biological aging process, and further studies are warranted to investigate other environmental pollutants' effect on aging.

Exposure to polybrominated biphenyl and stochastic epigenetic mutations: application of a novel epigenetic approach to environmental exposure in the Michigan polybrominated biphenyl registry

Endocrine-disrupting compounds are associated with altered epigenetic regulation and adverse health outcomes, although inconsistent results suggest that people have varied responses to the same exposure. Interpersonal variation in response to environmental exposures is not identified using standard, population-based methods. However, methods that capture an individual's response, such as analyzing stochastic epigenetic mutations (SEMs), may capture currently missed effects of environmental exposure. To test whether polybrominated biphenyl (PBB) was associated with SEMs, DNA methylation was measured using Illumina's MethylationEPIC array in PBB-exposed individuals, and SEMs were identified. Association was tested using a linear regression with robust sandwich variance estimators, controlling for age, sex, lipids, and cell types. The number of SEMs was variable (range: 119-18,309), and positively associated with age (p = 1.23e-17), but not with sex (p = 0.97). PBBs and SEMs were only positively associated in people who were older when they were exposed (p = 0.02 vs. p = 0.91). Many subjects had SEMs enriched in biological pathways, particularly in pathways involved with xenobiotic metabolism and endocrine function. Higher number of SEMs was also associated with higher age acceleration (intrinsic: p = 1.70e-3; extrinsic: p = 3.59e-11), indicating that SEMs may be associated with age-related health problems. Finding an association between environmental contaminants and higher SEMs may provide insight into individual differences in response to environmental contaminants, as well as into the biological mechanism behind SEM formation. Furthermore, these results suggest that people may be particularly vulnerable to epigenetic dysregulation from environmental exposures as they age.

A relationship between environmental pollutants and enteric viruses in mussels(Mytilus galloprovincialis)

Mussels can be affected by environmental contaminants, as non-dioxin-like polychlorinated biphenyls (NDL-PCBs), polycyclic aromatic hydrocarbons (PAHs) and cadmium (Cd). Moreover, mussels may concentrate human enteric viruses, like noroviruses (NoVGI/GII), astrovirus (AsV) and rotavirus (RV). Herein, to establish a relationship between environmental and viral contamination, with the aim to ensure human food safety, both chemical and microbiological analysis were carried out in mussels Mytilus galloprovincialis, farmed in Campania region (Italy). Chemical analysis revealed ranges below the European maximum limits, and were: ∑6 NDL-PCBs (28, 52, 101, 138, 153, 180) 0.579-16.857 ng g^-1 wet weight (ww); BaP LOQ (<0.2 µg kg^-1)- 2.9 µg kg^-1 ww, and ∑4 PAHs (BaA, CHR, BbFA, BaP) 0.7-23.7 µg kg^-1 ww; Cd LOQ (<0.005 mg kg^-1)- 0.078 mg kg^-1 ww. In addition, mussels exhibited a prevalence of NoVGI (18%), NoVGII (43%), AsV (40%), RV (30%) and the presence of more than one viruses resulted in about 35%. Overall, a simultaneous contamination, both chemical and viral, was found in 62% of samples. Interestingly, virus-positive mussels showed levels of chemicals higher than negative ones.

Exposure to polybrominated biphenyl (PBB) associates with genome-wide DNA methylation differences in peripheral blood

In 1973, Michigan residents were exposed to polybrominated biphenyl (PBB) when it was accidentally added to farm animal feed. Highly exposed individuals and their children have experienced endocrine-related health problems, though the underlying mechanism behind these remains unknown. We investigated whether PBB exposure is associated with variation in DNA methylation in peripheral blood samples from 658 participants of the Michigan PBB registry using the MethylationEPIC BeadChip, as well as investigated what the potential function of the affected regions are and whether these epigenetic marks are known to associate with endocrine system pathways. After multiple test correction (FDR <0.05), 1890 CpG sites associated with total PBB levels. These CpGs were not enriched in any particular biological pathway, but were enriched in enhancer and insulator regions, and depleted in regions near the transcription start site or in CpG islands (p < 0.05). They were also more likely to be in ARNT and ESR2 transcription factor binding sites (p = 3.27e-23 and p = 1.62e-6, respectively), and there was significant overlap between CpGs associated with PBB and CpGs associated with estrogen (p < 2.2e-16). PBB-associated CpGs were also enriched for CpGs known to be associated with gene expression in blood (eQTMs) (p < 0.05). These eQTMs were enriched for pathways related to immune function and endocrine-related autoimmune disease (FDR <0.05). These results indicate that exposure to PBB is associated with differences in epigenetic marks that suggest that it is acting similarly to estrogen and is associated with dysregulated immune system pathways.

Structural alerts for the identification of bioaccumulative compounds

Legislators have included bioaccumulation in the evaluation of chemicals in the framework of the European Registration, Evaluation, Authorization, and Restriction of Chemicals (REACH) regulation. REACH requires information on the bioconcentration factor (BCF), which is a parameter for assessing bioaccumulation and encourages the use of a weight-of-evidence approach, including predictions from quantitative structure-activity relationships (QSARs). This study presents a novel approach, based on structural alerts, to be used as a decision-support system for the identification of substances with bioaccumulation potential. In a regulatory framework, these alerts can be integrated with other sources of information, such as experimental and in silico data, to reduce the uncertainty of the assessment, thereby supporting a weight-of-evidence approach. Moreover, the identified alerts have a direct connection with relevant structural features, thus fostering the applicability and interpretability of the approach. The structural alerts were identified on 779 chemicals annotated for their fish BCF, and the approach was then validated on 278 external molecules. The developed decision-support system allowed identification of 77% of bioaccumulative chemicals and was competitive with more complex QSAR models used in regulatory assessments. The approach is implemented in an easy-to-use workflow, provided free of charge. Integr Environ Assess Manag 2019;15:19-28. © 2018 SETAC.

Persistent organic pollutants as predictors of increased FSH:LH ratio in naturally cycling, reproductive age women

Although several recent studies suggest endocrine disrupting compounds, such as polychlorinated biphenyls (PCBs), dichlorodiphenyldichloroethylene (p,p', DDE), and hexachlorobenzene (HCB), target different organs and systems in the body, their impact on female reproductive function in humans is not well characterized. We seek to determine the relationship between several known endocrine disrupting compounds and a marker of ovarian responsivity, the FSH:LH ratio (higher ratio indicates less ovarian responsivity). For this analysis, 169 naturally cycling women between 21 and 38 years of age completed interviews and had their blood drawn on day 3 of their menstrual cycle for analyses of toxicants, gonadal sex hormones (E₂ and P₄), and gonadotropins (FSH and LH). PCB congeners were classified into five groups based on their environmental persistence, distribution in human tissue, and toxicological action, reflecting the structure, mechanism, and known biological activity of individual PCB congeners. For every unit (ppb) increase in the level of the estrogenic PCB group, there was a 5-fold greater risk of a FSH:LH ratio ≥ 2, controlling for individual differences in age, percent body fat, cycle day 3 estradiol levels, parity, alcohol use and cigarette smoking in the past year (exp[ß] = 5; p = ≤0.01). PCB congeners identified as estrogenic were analyzed individually, and, of the 19 potentially estrogenic congeners, five were significantly, and positively related to an increased FSH:LH ratio. Four of these congeners are non-persistent, easily volatilize in the environment, and are easily metabolized, and hence, are indicative of very recent or current exposure. p,p'-DDE and HCB were not associated with FSH:LH ratio. We find a clinical indicator of ovarian responsivity, FSH:LH ratio, is associated with a specific group of estrogenic PCBs. These congeners may become airborne when they volatilize from dredged PCB-contaminated soil or from indoor PCB-containing window caulk and sealants in older buildings leading to inhalation exposure. PCB exposure, particularly to non-persistent, estrogenic congeners, may pose an unrecognized threat to female fecundity within the general population.

The Risk of Polychlorinated Biphenyls Facilitating Tumors in Hawaiian Green Sea Turtles (Chelonia mydas)

The Hawaiian green turtle (Chelonia mydas) is on the list of threatened species protected under the U.S. Endangered Species Act in 1978 in large part due to a severe tumor-forming disease named fibropapillomatosis. Chemical pollution is a prime suspect threatening the survival of C. mydas. In this study, PCBs concentrations were determined in 43 C. mydas plasma samples archived on Tern Island. The total PCBs concentration in male C. mydas (mean 1.10 ng/mL) was two times more than that of females (mean 0.43 ng/mL). The relationship between straight carapace length and PCBs concentration in females has also been studied, which was negatively related. To figure out the possible existence of correlations between PCBs and tumor status, we measured the PCBs concentration in turtles with no tumor, moderate or severe tumor affliction. PCBs concentration of two afflicted groups was much higher than the healthy group, suggesting that PCBs may play a role in fibropapillomatosis in Hawaiian green turtle.

Intergenerational effects of endocrine-disrupting compounds: a review of the Michigan polybrominated biphenyl registry

Endocrine-disrupting compounds (EDCs) are a broad class of chemicals present in many residential products that can disrupt hormone signaling and cause health problems in humans. Multigenerational cohorts, like the Michigan polybrominated biphenyl registry, are ideal for studying the effects of intergenerational exposure. Registry participants report hormone-related health problems, particularly in those exposed before puberty or those in the second generation exposed through placental transfer or breastfeeding. However, more research is needed to determine how EDCs cause health problems and the mechanisms underlying intergenerational exposure. Utilizing existing data in this registry, along with genetic and epigenetic approaches, could provide insight to how EDCs cause human disease and help to determine the risk to exposed populations and future generations.

Simultaneous quantification of T4, T3, rT3, 3,5-T2 and 3,3'-T2 in larval zebrafish (Danio rerio) as a model to study exposure to polychlorinated biphenyls

Environmental toxicants that interfere with thyroid hormone (TH) signaling can impact growth and development in animals and humans. Zebrafish represent a model to study chemically induced TH disruption, prompting the need for sensitive detection of THs. Simultaneous quantification of 3,3',5-triiodo-l-thyronine (T3), thyroxine (T4), 3,3',5'-triiodo-l-thyronine (rT3), 3,5-diiodo-l-thyronine (3,5-T2) and 3,3'-diiodo-l-thyronine (3,3'-T2) in zebrafish larvae was achieved by ultra-performance liquid chromatography-tandem mass spectrometry in positive ion mode. Solid-phase extraction with SampliQ cartridges and derivatization with 3 m hydrochloric acid in n-butanol reduced matrix effects. Derivatized compounds were separated on an Acquity UPLC BEH C₁₈ column with mobile phases consisting of 0.1% acetic acid in deionized water and 0.1% acetic acid in methanol. The limits of detection ranged from 0.5 to 0.6 pg injected on column. The method was validated by evaluating recovery (77.1-117.2%), accuracy (87.3-123.9%) and precision (0.5-12.4%) using diluted homogenized zebrafish embryos spiked with all target compounds. This method was then applied to zebrafish larvae collected after 114 h of exposure to polychlorinated biphenyls (PCBs), including PCB 28, PCB 66 and PCB 95, or the technical mixture Aroclor 1254. Exposure to PCB 28 and PCB 95 increased the T4:T3 ratio and decreased the T3:rT3 ratio, demonstrating that this method can effectively detect PCB-induced alterations in THs.

Contrasting congener profiles for persistent organic pollutants and PAH monitoring in European storm petrels (Hydrobates pelagicus) breeding in Ireland: a preen oil versus feathers approach

Persistent organic pollutants (POPs) and polycyclic aromatic hydrocarbons (PAHs) are anthropogenic contaminants of environmental concern due to their persistence in the environment and capacity to accumulate in biota. Many of these contaminants have been found to have ill effects over wildlife and humans. Birds are known to be particularly affected through endocrine disruption and eggshell thinning. POPs have been banned or restricted through the Stockholm Convention (2001), making monitoring essential for tracking effects of regulation. Seabirds have been used as monitoring tools for being top predators and consuming a diverse array of prey in different trophic levels. Non-destructive sampling has become widely popular using feathers and preen oil, as opposed to carcasses and internal organs. This study aimed to set baseline levels of POP and PAH concentration in a highly pelagic and abundant seabird in Ireland and the Atlantic, the European storm petrel, Hydrobates pelagicus, and to investigate the profiles of contaminant congeners in preen oil and feathers, comparatively. Mean concentrations in preen oil followed: PCB (10.1 ng/g ww) > PAH (7.1 ng/g ww) > OCP (5.4 ng/g ww) > PBDE (3.9 ng/g ww), whilst mean concentrations in feathers followed the order: PAH (38.9 ng/g ww) > PCB (27.2 ng/g ww) > OCP (17.9 ng/g ww) > PBDE (4.5 ng/g ww). Congener profiles highly differed between preen oil and feathers, and little correlation was found between the matrices. These results demonstrate that the sampling of a single matrix alone (preen oil or feathers) might produce confounding results on contamination in seabirds and that more than one matrix is recommended to obtain a full picture of contamination by persistent organic pollutants.

Organohalogens Naturally Biosynthesized in Marine Environments and Produced as Disinfection Byproducts Alter Sarco/Endoplasmic Reticulum Ca2+ Dynamics

Contemporary sources of organohalogens produced as disinfection byproducts (DBPs) are receiving considerable attention as emerging pollutants because of their abundance, persistence, and potential to structurally mimic natural organohalogens produced by bacteria that serve signaling or toxicological functions in marine environments. Here, we tested 34 organohalogens from anthropogenic and marine sources to identify compounds active toward ryanodine receptor (RyR1), known toxicological targets of non-dioxin-like polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs). [³H]Ryanodine ([³H]Ry) binding screening (≤2 μM) identified 10 highly active organohalogens. Further analysis indicated that 2,3-dibromoindole (14), tetrabromopyrrole (31), and 2,3,5-tribromopyrrole (34) at 10 μM were the most efficacious at enhancing [³H]Ry binding. Interestingly, these congeners also inhibited microsomal sarcoplasmic/endoplasmic reticulum (SR/ER) Ca²⁺ ATPase (SERCA1a). Dual SERCA1a inhibition and RyR1 activation triggered Ca²⁺ efflux from microsomal vesicles with initial rates rank ordered 31 > 34 > 14. Hexabromobipyrroles (25) enhanced [³H]Ry binding moderately with strong SERCA1a inhibition, whereas pyrrole (24), 2,3,4-tribromopyrrole (26), and ethyl-4-bromopyrrole-2-carboxylate (27) were inactive. Of three PBDE derivatives of marine origin active in the [³H]Ry assay, 4'-hydroxy-2,3',4,5',6-pentabromodiphenyl ether (18) was also a highly potent SERCA1a inhibitor. Molecular targets of marine organohalogens that are also DBPs of emerging environmental concern are likely to contribute to their toxicity.

Occurrence, Loading, and Exposure of Atmospheric Particle-Bound POPs at the African and European Edges of the Western Mediterranean Sea

A comparative study for 62 toxic chemicals based on the simultaneous monthly collection of aerosol samples during 2015-2016 in two coastal cities at both the African (Bizerte, Tunisia) and European (Marseille, France) edges of the Western Mediterranean basin is presented. Legacy polychlorinated biphenyls (∑₁₈PCBs) and polychlorinated dibenzo-p-dioxins and dibenzofurans (∑₁₇PCDD/Fs) show generally higher median levels at the African edge (2.1 and 0.2 pg m^-3, respectively) compared to the European coastal site (1.0 and 0.08 pg m^-3, respectively). Contrarily, the "emerging" polybrominated diphenyl ethers' (∑₂₇PBDEs) median concentrations were higher in Marseille (∼9.0 pg m^-3) compared to Bizerte (∼6.0 pg m^-3). Different past usages and current emission patterns were found at both edges of the Western Mediterranean, most probably linked to the respective different regulatory frameworks for toxic chemicals. Our results indicate that the total organic carbon (TOC) and/or the elemental carbon (EC) contents in the atmospheric aerosol may have a stronger effect than the total suspended particle (TSP) content as a whole on the spatial-temporal variability and the long-range atmospheric transport potential of the studied POPs. A "jumping" of the PBDE local atmospheric stocks from the Northwestern European Mediterranean edge to the Northwestern African coast seems to be possible under favorable conditions at present. While a higher PBDE median loading is estimated for the Marseille area (∼550 ng m^-2 y^-1) compared to Bizerte (∼400 ng m^-2 y^-1), the median PCB and PCDD/F dry deposition fluxes were higher at the African site, resulting in a 3-fold higher toxic equivalent (TEQ) loading of dioxin-like pollutants (400 pg TEQ m^-2 y^-1) compared to Marseille (∼140 pg TEQ m^-2 y^-1), with potential implications for aquatic organisms. However, the inhalation exposure assessment points to a minimum risk for human health at both sites.

Henry's Constants of Persistent Organic Pollutants by a Group-Contribution Method Based on Scaled-Particle Theory

A group-contribution method based on scaled-particle theory was developed to predict Henry's constants for six families of persistent organic pollutants: polychlorinated benzenes, polychlorinated biphenyls, polychlorinated dibenzodioxins, polychlorinated dibenzofurans, polychlorinated naphthalenes, and polybrominated diphenyl ethers. The group-contribution model uses limited experimental data to obtain group-interaction parameters for an easy-to-use method to predict Henry's constants for systems where reliable experimental data are scarce. By using group-interaction parameters obtained from data reduction, scaled-particle theory gives the partial molar Gibbs energy of dissolution, Δg̅₂, allowing calculation of Henry's constant, H₂, for more than 700 organic pollutants. The average deviation between predicted values of log H₂ and experiment is 4%. Application of an approximate van't Hoff equation gives the temperature dependence of Henry's constants for polychlorinated biphenyls, polychlorinated naphthalenes, and polybrominated diphenyl ethers in the environmentally relevant range 0-40 °C.

Effect of solid waste landfill organic pollutants on groundwater in three areas of Sicily (Italy) characterized by different vulnerability

The aim of this study was to obtain information on the presence and levels of hazardous organic pollutants in groundwater located close to solid waste landfills. Eighty-two environmental contaminants, including 16 polycyclic aromatic hydrocarbons (PAHs), 20 volatile organic compounds (VOCs), 29 polychlorinated biphenyls (PCBs), 7 dioxins (polychlorinated dibenzo-p-dioxins, PCDDs) and 10 furans (polychlorinated dibenzofurans, PCDFs) were monitored in areas characterised by different geological environments surrounding three municipal solid waste landfills (Palermo, Siculiana and Ragusa) in Sicily (Italy) in three sampling campaigns. The total concentrations of the 16 PAHs were always below the legal threshold. Overall, the Fl/Fl + Py diagnostic ratio revealed that PAHs had a petrogenic origin. VOC levels, except for two notable exceptions near Palermo landfill, were always below the legal limit. As concerns PCB levels, several samples were found positive with levels exceeding the legal limits. It is worth noting that the % PCB distribution differs from that of commercial compositions. In parallel, some samples of groundwater containing PCDDs and PCDFs exceeding the legal threshold were also found. Among the 17 congeners monitored, the most abundant were the highest molecular weight ones.

Using energy budgets to combine ecology and toxicology in a mammalian sentinel species

Process-driven modelling approaches can resolve many of the shortcomings of traditional descriptive and non-mechanistic toxicology. We developed a simple dynamic energy budget (DEB) model for the mink (Mustela vison), a sentinel species in mammalian toxicology, which coupled animal physiology, ecology and toxicology, in order to mechanistically investigate the accumulation and adverse effects of lifelong dietary exposure to persistent environmental toxicants, most notably polychlorinated biphenyls (PCBs). Our novel mammalian DEB model accurately predicted, based on energy allocations to the interconnected metabolic processes of growth, development, maintenance and reproduction, lifelong patterns in mink growth, reproductive performance and dietary accumulation of PCBs as reported in the literature. Our model results were consistent with empirical data from captive and free-ranging studies in mink and other wildlife and suggest that PCB exposure can have significant population-level impacts resulting from targeted effects on fetal toxicity, kit mortality and growth and development. Our approach provides a simple and cross-species framework to explore the mechanistic interactions of physiological processes and ecotoxicology, thus allowing for a deeper understanding and interpretation of stressor-induced adverse effects at all levels of biological organization.

DNA Product Formation in Female Sprague-Dawley Rats Following Polyhalogenated Aromatic Hydrocarbon (PHAH) Exposure

DNA oxidation damage has been regarded as one of the possible mechanisms for the hepatic carcinogenesis of dioxin-like compounds (DLCs). In this study, we evaluated the toxic equivalency factor (TEF) from the standpoint of induced DNA oxidation products and their relationship to toxicity and carcinogenicity. Nine DNA oxidation products were analyzed in the liver of female Sprague–Dawley rats exposed to 2,3,7,8-tetrachlorodibenzo-pdioxin (TCDD) alone or the tertiary mixture of TCDD, 3,3′,4,4′,5-pentachlorobiphenyl (PCB 126), and 2,3,4,7,8-pentachlorodibenzofuran (PeCDF) by gavage for 14, 31, and 53 weeks (5 days/week) by LC–MS/MS: 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxo-dGuo); 1,N⁶-etheno-2′-deoxyadenosine (1,N⁶-εdAdo); N²,3-ethenoguanine (N²,3-εG); 7-(2-oxoethly)guanine (7-OEG); 1,N²-etheno-2′-deoxyguanosine (1,N²-εdGuo); malondialdehyde (M₁dGuo); acrolein (AcrdGuo); crotonaldehyde (CrdGuo); and 4-hydroxynonenal (HNEdGuo) derived 2′-deoxyguanosine adducts. Exposure to TCDD (100 ng/kg/day) significantly induced 1,N⁶-εdAdo at 31 and 53 weeks, while no increase of 8-oxo-dGuo was observed. Significant increases were observed for 8-oxo-dGuo and 1,N⁶-εdAdo at all time points following exposure to the tertiary mixture (TEQ 100 ng/kg/day). Exposure to TCDD for 53 weeks only significantly increased 1,N⁶-εdAdo, while increases of N²,3-εG and 7-OEG were only found in the highest dose group (100 ng/kg/day). Exposure to the tertiary mixture for 53 weeks had no effect on N²,3-εG in any exposure group (TEQ 0, 22, 46, or 100 ng/kg/day), while significant increases were observed for 1,N⁶-εdAdo (all dose groups), 8-oxo-dGuo (46 and 100 ng/kg/day), and 7-OEG (100 ng/kg/day). While no significant increase was observed at 53 weeks for 1,N²-εdGuo, M₁dGuo, AcrdGuo, or CrdGuo following exposure to TCDD (100 ng/kg/day), all of them were significantly induced in animals exposed to the tertiary mixture (TEQ 100 ng/kg/day). This oxidation DNA product data suggest that the simple TEF methodology cannot be applied to evaluate the diverse patterns of toxic effects induced by DLCs.

Polychlorinated biphenyls target Notch/Dll and VEGF R2 in the mouse placenta and human trophoblast cell lines for their anti-angiogenic effects

The intrauterine environment is particularly vulnerable to environmental exposures. We previously established a mouse model that provided evidence for pregnancy complications and placental anti-angiogenesis in response to Aroclor 1254 (A-1254), a mixture of polychlorinated biphenyls (PCBs). Importantly, these effects were observed in IL-10^-/-, but not wild type, mice, suggesting that IL-10 deficiency predisposes to pregnancy disruptive effects of environmental toxicants. However, the mechanisms by which PCBs cause anti-angiogenic effects are unclear. Here, we evaluated PCB-mediated anti-angiogenic effects by diverse but complementary approaches, including HUVEC-mediated trophoblast invasion in nude mice, in vitro three-dimensional capillary tube formation involving HUVEC and/or HTR8 trophoblasts, and aortic ring endothelial cell outgrowth/sprouting. Taken together, our data suggest that PCBs act as potent anti-angiogenic agents. Importantly, we show that treatment of pregnant IL-10^-/- mice with A-1254 resulted in placental activation of the Notch/Delta-like ligand (Dll) pathway, a master regulator of cell-cell interaction and vascular patterning. Similar results were obtained with HUVEC and HTR8 trophoblasts. Rescue of A-1254-induced disruption of HUVEC-based tube formation by γ-secretase inhibitor L1790 confirmed the critical role of the Notch/Dll pathway. Our data suggest that PCBs impart pregnancy disruptive functions by activating the Notch/Dll pathway and by inducing anti-angiogenic effects at the maternal-fetal interface.