Inhalation and dietary exposure to PCBs in urban and rural cohorts via congener-specific measurements

Effects of 28-day nose-only inhalation of PCB52 (2,2',5,5'-Tetrachlorobiphenyl) on the brain transcriptome

A semi-volatile polychlorinated biphenyl (PCB) congener, PCB52, is present in the indoor air of schools; however, the effects of inhaled PCB52 on the brain have not been investigated. This study exposed male Sprague-Dawley rats at 39 days of age and female rats at 42 days of age to PCB52 for 4 hours per day over 28 consecutive days through nose-only inhalation. Neurobehavioral tests were conducted during the last 5 days of exposure. The total estimated PCB52 exposures after 28 days were 1080±20 µg/kg BW for male rats and 1140±10 µg/kg BW for female rats. PCB52 and its metabolites were detected by gas chromatography-tandem mass spectrometry in the brain, lung, and serum, with the lung showing the highest concentrations. PCB52 levels were higher in the brains of females than males. Males showed increased exploratory behavior compared to controls, whereas females exhibited decreased exploratory behavior compared to controls in the same tests. PCB52 exposure did not impact locomotor activity or working memory. Gene expression and pathway analysis in the striatum and cerebellum suggest that PCB52 inhalation causes mitochondrial dysfunction. No significant differences were observed by immunohistochemical evaluation in the density and percent area of total cells, astrocytes, or microglia in the striatum and cerebellar cortex. Our results indicate multilevel effects of inhaled PCB52 on the rat brain, from gene expression to behavioral effects.

Significant metabolic alterations in mouse dams exposed to an environmental mixture of polychlorinated biphenyls (PCBs) during gestation and lactation: Insights into PCB and metabolite profiles

Polychlorinated biphenyls (PCBs) and their metabolites are linked to developmental neurotoxicity, but their levels in the gestational and lactational environment remain unexplored. This study investigated the effects of dietary exposure to the Fox River Mixture (FRM) on serum levels of PCBs and their metabolites in female C57BL/6 J mice. Mice were exposed to 0.1, 1.0, or 6.0 mg/kg body weight/day of FRM beginning two weeks before mating and throughout gestation and lactation. Serum samples collected from the dams at weaning were analyzed using gas chromatograph-tandem mass spectrometry and nontarget liquid chromatography-high resolution mass spectrometry. Results showed complex and dose-dependent differences in PCB and metabolite profiles. Untargeted metabolomics revealed alterations in metabolites involved in glucuronidation. Network analysis suggested disturbances in heme and amino acid metabolism associated with higher chlorinated PCBs. These findings suggested that PCBs and metabolites present in the gestational and lactation environment of mice may contribute to developmental neurotoxicity in rodents.

Inhalation of 2,2',5,5'-tetrachlorobiphenyl (PCB52) causes changes to the gut microbiome throughout the gastrointestinal tract

Polychlorinated biphenyls (PCBs), such as PCB52, are hazardous environmental contaminants present in indoor and outdoor environments. Oral PCB exposure affects the colon microbiome; however, it is unknown if inhalation of PCBs alters the intestinal microbiome. We hypothesize that sub-acute inhalation of PCB52 affects microbial communities depending on the location in the (GI) gastrointestinal tract and the local profiles of PCB52 and its metabolites present in the GI tract following mucociliary clearance and biliary or intestinal excretion. Sprague-Dawley rats were exposed via nose-only inhalation 4 h per day, 7 days per week, for 4 weeks to either filtered air or PCB52. After 28 days, differences in the microbiome and levels of PCB52 and its metabolites were characterized throughout the GI tract. PCB52 inhalation altered taxa abundances and predicted functions altered throughout the gut, with most alterations occurring in the large intestine. PCB52 and metabolite levels varied across the GI tract, resulting in differing PCB × microbiome networks. Thus, the presence of different levels of PCB52 and its metabolites in different parts of the GI tract has varying effects on the composition and predicted function of microbial communities. Future studies need to investigate whether these changes lead to adverse outcomes.

Microglial responses to inflammatory challenge in adult rats altered by developmental exposure to polychlorinated biphenyls in a sex-specific manner

Polychlorinated biphenyls are ubiquitous environmental contaminants linkedc with peripheral immune and neural dysfunction. Neuroimmune signaling is critical to brain development and later health; however, effects of PCBs on neuroimmune processes are largely undescribed. This study extends our previous work in neonatal or adolescent rats by investigating longer-term effects of perinatal PCB exposure on later neuroimmune responses to an inflammatory challenge in adulthood. Male and female Sprague-Dawley rats were exposed to a low-dose, environmentally relevant, mixture of PCBs (Aroclors 1242, 1248, and 1254, 1:1:1, 20 μg / kg dam BW per gestational day) or oil control during gestation and via lactation. Upon reaching adulthood, rats were given a mild inflammatory challenge with lipopolysaccharide (LPS, 50 μg / kg BW, ip) or saline control and then euthanized 3 hours later for gene expression analysis or 24 hours later for immunohistochemical labeling of Iba1+ microglia. PCB exposure did not alter gene expression or microglial morphology independently, but instead interacted with the LPS challenge in brain region- and sex-specific ways. In the female hypothalamus, PCB exposure blunted LPS responses of neuroimmune and neuromodulatory genes without changing microglial morphology. In the female prefrontal cortex, PCBs shifted Iba1+ cells from reactive to hyperramified morphology in response to LPS. Conversely, in the male hypothalamus, PCBs shifted cell phenotypes from hyperramified to reactive morphologies in response to LPS. The results highlight the potential for long-lasting effects of environmental contaminants that are differentially revealed over a lifetime, sometimes only after a secondary challenge. These neuroimmune endpoints are possible mechanisms for PCB effects on a range of neural dysfunction in adulthood, including mental health and neurodegenerative disorders. The findings suggest possible interactions with other environmental challenges that also influence neuroimmune systems.

Germ-free status but not subacute polychlorinated biphenyl (PCB) exposure altered hepatic phosphatidylcholine and ether-phosphatidylcholine levels in mice

Polychlorinated biphenyls (PCBs) are persistent organic pollutants that pose a current ecosystem and human health concern. PCB exposure impacts the gut microbiome in animal models, suggesting a mechanistic link between PCB exposure and adverse health outcomes. The presence and absence of the microbiome and exposure to PCBs independently affect the lipid composition in the liver, which in turn affects the PCB disposition in target tissues, such as the liver. Here, we investigated microbiome × subacute PCB effects on the hepatic lipid composition of conventional and germ-free female mice exposed to 0, 6, or 30 mg/kg body weight of an environmental PCB mixture in sterile corn oil once daily for 3 consecutive days. Hepatic triacylglyceride and polar lipid levels were quantified using mass spectrometric methods following the subacute PCB exposure. The lipidomic analysis revealed no PCB effect on the hepatic levels. No microbiome effect was observed on levels of triacylglyceride and most polar lipid classes. The total hepatic levels of phosphatidylcholine (PC) and ether-phosphatidylcholine (ePC) lipids were lower in germ-free mice than the conventional mice from the same exposure group. Moreover, levels of several unsaturated PCs, such as PC(36:5) and PC(42:10), and ePCs, such as ePC(36:2) and ePC(4:2), were lower in germ-free than conventional female mice. Based on a KEGG pathway meta-analysis of RNA sequencing data, the ether lipid metabolism pathway is altered in the germ-free mouse liver. In contrast to the liver, extractable lipid levels, determined gravimetrically, differed in several tissues from naïve conventional vs. germ-free mice. Overall, microbiome × subacute PCB exposure effects on hepatic lipid composition are unlikely to affect PCB distribution into the mouse liver. Further studies are needed to assess how the different extractable lipid levels in other tissues alter PCB distribution in conventional vs. germ-free mice.

Quantifying 209 Polychlorinated Biphenyl Congeners in Silicone Wristbands to Evaluate Differences in Exposure among Demolition Workers

A social housing estate in Denmark was designated for demolition due to exceedance of guidance values for polychlorinated biphenyls (PCBs) in indoor air. Here, we deployed precleaned silicone wristbands (n = 46) among demolition workers of these contaminated buildings during single workdays while conducting various work tasks. We established a method to analyze all 209 PCBs in wristbands to identify prominent congeners of exposure and evaluate differences between tasks. Wristbands were extracted using microwave-assisted extraction and then concentrated for gas chromatography-tandem mass spectrometry (GC-MS/MS) analysis. Twenty-nine chromatographic peaks representing 37 congeners were detected in every wristband, and tetra-CBs were the dominant homologue group. PCB-66, -44, and -70 were the most abundant congeners measured in worker wristbands, none of which are included within the typical seven indicator or WHO 12 PCBs. Workers who cut PCB-containing sealants had wristbands with the highest PCB concentrations (geometric mean ∑209PCBs = 1963 ng/g wristband), which were followed by those handling concrete elements on the building roof. Additionally, wristbands captured a broader range of PCBs than has been previously measured in air and serum samples. Taken together, our results highlight the importance of total congener analysis in assessing current PCB exposure in demolition work and the utility of wristbands for assessing these exposures.

Distribution of 2,2',5,5'-Tetrachlorobiphenyl (PCB52) Metabolites in Adolescent Rats after Acute Nose-Only Inhalation Exposure

Inhalation of PCB-contaminated air is increasingly recognized as a route for PCB exposure. Because limited information about the disposition of PCBs following inhalation exposure is available, this study investigated the disposition of 2,2',5,5'-tetrachlorobiphenyl (PCB52) and its metabolites in rats following acute, nose-only inhalation of PCB52. Male and female Sprague-Dawley rats (50-58 days of age, 210 ± 27 g; n = 6) were exposed for 4 h by inhalation to approximately 14 or 23 μg/kg body weight of PCB52 using a nose-only exposure system. Sham animals (n = 6) were exposed to filtered lab air. Based on gas chromatography-tandem mass spectrometry (GC-MS/MS), PCB52 was present in adipose, brain, intestinal content, lung, liver, and serum. 2,2',5,5'-Tetrachlorobiphenyl-4-ol (4-OH-PCB52) and one unknown monohydroxylated metabolite were detected in these compartments except for the brain. Liquid chromatography-high resolution mass spectrometry (LC-HRMS) analysis identified several metabolites, including sulfated, methoxylated, and dechlorinated PCB52 metabolites. These metabolites were primarily found in the liver (7 metabolites), lung (9 metabolites), and serum (9 metabolites) due to the short exposure time. These results demonstrate for the first time that complex mixtures of sulfated, methoxylated, and dechlorinated PCB52 metabolites are formed in adolescent rats following PCB52 inhalation, laying the groundwork for future animal studies of the adverse effects of inhaled PCB52.

Quantitative characterization of resident' exposure to typical semi-volatile organic compounds (SVOCs) around a non-ferrous metal smelting plant

To comprehensively characterize residents' exposure to major semi-volatile organic compounds (SVOCs), samples of indoor floor wipes, size-segregated airborne particles, gaseous air, food, and paired skin wipes were simultaneously collected from residential areas around a large non-ferrous metal smelting plant as compared with the control areas, and three typical SVOCs (including polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and halogenated PAHs (HPAHs)) were determined. Comparison and correlation analysis among matrices indicated PAHs were the major contaminants emitted from metal smelting activities compared to HPAHs and PCBs, with naphthalene verified as the most important characteristic compound, and their accumulation on skin may be a comprehensive consequence of contact with floor dust and air. While patterns of human exposure pathways for the SVOCs were found to be clearly correlated to their vapor pressure, dermal absorption was the major contributor (51.1-76.3%) to total carcinogenic risk (TCR) of PAHs and HPAHs for surrounding residents, especially for low molecular weight PAHs, but dietary ingestion (98.6%) was the dominant exposure pathway to PCBs. The TCR of PAHs exceeded the acceptable level (1 × 10-4), implying smelting activities obviously elevated the health risk. This study will serve developing pertinent exposure and health risk prevention measures.

Complex roles for sulfation in the toxicities of polychlorinated biphenyls

Polychlorinated biphenyls (PCBs) are persistent organic toxicants derived from legacy pollution sources and their formation as inadvertent byproducts of some current manufacturing processes. Metabolism of PCBs is often a critical component in their toxicity, and relevant metabolic pathways usually include their initial oxidation to form hydroxylated polychlorinated biphenyls (OH-PCBs). Subsequent sulfation of OH-PCBs was originally thought to be primarily a means of detoxication; however, there is strong evidence that it may also contribute to toxicities associated with PCBs and OH-PCBs. These contributions include either the direct interaction of PCB sulfates with receptors or their serving as a localized precursor for OH-PCBs. The formation of PCB sulfates is catalyzed by cytosolic sulfotransferases, and, when transported into the serum, these metabolites may be retained, taken up by other tissues, and subjected to hydrolysis catalyzed by intracellular sulfatase(s) to regenerate OH-PCBs. Dynamic cycling between PCB sulfates and OH-PCBs may lead to further metabolic activation of the resulting OH-PCBs. Ultimate toxic endpoints of such processes may include endocrine disruption, neurotoxicities, and many others that are associated with exposures to PCBs and OH-PCBs. This review highlights the current understanding of the complex roles that PCB sulfates can have in the toxicities of PCBs and OH-PCBs and research on the varied mechanisms that control these roles.

Predicted versus observed activity of PCB mixtures toward the ryanodine receptor

Non-dioxin-like polychlorinated biphenyls (NDL PCBs) alter the activity of the ryanodine receptor (RyR), and this activity is linked to developmental neurotoxicity. Most work to date has focused on the activity of single congeners rather than relevant mixtures. The current study assessed the RyR activity of single congeners or binary, tertiary, and complex PCB mixtures. Observed mixture activity was then compared to the expected activity calculated using the concentration addition (CA) model or a RyR-specific neurotoxic equivalency scheme (rNEQ). The predictions of the CA model were consistent with the observed activity of binary mixtures at the lower portion of the concentration-response curve, supporting the additivity of RyR1 active PCBs. Findings also show that minimally active congeners can compete for the RyR1 binding site, and congeners that do not activate the RyR1 do not interfere with the activity of a full agonist. Complex PCB mixtures that mimic PCB profiles detected in indoor air, fish tissue, and the serum of mothers and children activated the RyR1 and displayed similar efficacy and potency regardless of varying congener profiles. Neither the CA model nor the rNEQ perfectly predicted the observed activity of complex mixtures, but predictions were often within one magnitude of change from the observed response. Importantly, PCB mixtures approximating profiles found in environmental samples or human serum displayed RyR1 activity at concentrations reported in published research. The work presented will aid in the development of risk assessment platforms for NDL PCBs and similar compounds toward RyR1 activation and related neurotoxicity.

Biomonitoring of PAHs and PCBs in industrial, suburban, and rural areas using snails as sentinel organisms

There is a worldwide concern about the presence of persistent organic pollutants (POPs) in the environment because of their toxicity, bioaccumulation, and resistance to degradation. Various conventional monitoring techniques have been used to assess their presence in diverse environmental compartments. Most currently available methods, however, have limitations with regards to long-term monitoring. In the present work, juvenile Cornu aspersum (O. F. Müller, 1774) snails were tested in field microcosms as biomonitors for two major classes of organic pollutants, namely, polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs). The study assessed their deployment in one suburban, one rural, and two industrial sites over an 18-week period and monitored for temporal variations of 16 PAHs and 22 PCBs. Sampling was conducted once every 3 weeks. Targeted pollutants were extracted from the caged snails using the QuEChERS extraction procedure and subsequently analyzed using gas chromatography coupled to tandem mass spectrometry (GC-MS/MS). The results showed that the bioaccumulation of specific pollutants was site dependent; significantly higher levels of PCBs were observed at the industrial sites as compared to the suburban and rural ones. PAHs were bioaccumulated by the snails via ingestion of air and soil whereas PCBs were mainly bioaccumulated via soil contact and ingestion. The findings of this study indicate that C. aspersum is a reliable model organism for the biomonitoring of organic pollutants in air and soil compartments and can be used as part of an integrated environmental assessment.

Associations of accumulated persistent organic pollutants in breast adipose tissue with the evolution of breast cancer after surgery

Chronic exposure to persistent organic pollutants (POPs) is suspected to contribute to the onset of breast cancer, but the impact on the evolution of patients after diagnosis is unclear. We aimed to analyze the contribution of long-term exposure to five POPs to overall mortality, cancer recurrence, metastasis, and development of second primary tumors over a global follow-up of 10 years after surgery in breast cancer patients in a cohort study. Between 2012 and 2014, a total of 112 newly diagnosed breast cancer patients were recruited from a public hospital in Granada, Southern Spain. Historical exposure to POPs was estimated by analyzing their concentrations in breast adipose tissue samples. Sociodemographic data were collected through face-to-face interviews, while data on evolution tumor were retrieved from clinical records. Statistical analyses were performed using Cox regression (overall survival, breast cancer recurrence or metastasis) and binary logistic regression models (joint outcome variable). We also tested for statistical interactions of POPs with age, residence, and prognostic markers. The third vs first tertile of hexachlorobenzene concentrations was associated with a lower risk of all-cause mortality (Hazard Ratio, HR = 0.26; 95 % Confidence Interval, CI = 0.07-0.92) and of the appearance of any of the four events (Odds Ratio = 0.37; 95 % CI = 0.14-1.03). Polychlorinated biphenyl 138 concentrations were significantly and inversely associated with risk of metastasis (HR = 0.65; 95 % CI = 0.44-0.97) and tumor recurrence (HR = 0.69; 95 % CI = 0.49-0.98). Additionally, p,p'-dichlorodiphenyldichloroethylene showed inverse associations with risk of metastasis in women with ER-positive tumors (HR = 0.49; 95 % CI = 0.25-0.93) and in those with a tumor size <2.0 cm (HR = 0.39; 95 % CI = 0.18-0.87). The observed paradoxical inverse associations of POP exposure with breast cancer evolution might be related to either a better prognosis of hormone-dependent tumors, which have an approachable pharmacological target, or an effect of sequestration of circulating POPs by adipose tissue.

Organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in adipose tissue of women from Grand Tunis and their association with demographic factors and dietary habits

Dichlorodiphenyl trichloroethane and its metabolites (DDTs), hexachlorocyclohexane isomers (HCHs), hexachlorobenzene (HCB) and polychloronated biphenyls (PCBs) were measured in 25 woman adipose tissues collected in 2016 from Grand Tunis, Tunisia. p,p'-DDE, p,p'-DDT, HCB and β-HCH were the dominant organochlorine pesticides (OCPs) in decreasing order in all samples. The total OCP levels varied from 79 to 343 ng g-1 lipid with a median value of 189 ng g-1 lipid and DDTs contributed approximately 88% to sum OCP. The ratio of p,p'-DDT/p,p'-DDE across all samples is below one, which suggests mainly historic exposure but may indicate some recent exposure to the banned pesticide. The median concentration of PCBs was 109 ng g-1 lipid and ranged between 27 and 204 ng g-1 lipid. PCB-153, PCB-180, PCB-138 and PCB-170 were the most abundant congeners, which contributed about 78% of the total PCBs. Spearman analysis showed that dominant organochlorine compounds (OCs) are highly positive correlated except for PCB-28/31, indicating that women from Tunis are exposed via similar routes. Inhalation exposure could be a possible pathway for the uptake of the less chlorinated congeners. We found positive and statistically significant association with subjects age for HCB (r = 0.517; p = 0.009) and PCBs (r = 0.65; p = 0.001) levels and a weak age-dependent accumulation was found for HCHs (r = 0.375; p = 0.065) and DDTs (r = 0.388; p = 0.056). The concentrations of OC subgroups were not associated with BMI, parity and residence. No association was observed between fish, red/white meat, milk and dairy products consumption and levels of HCB, HCHs and PCBs. DDTs levels were significantly correlated only with milk (p = 0.048) and milk products (p = 0.047) intake.

Polyurethane Foam Emission Samplers to Identify Sources of Airborne Polychlorinated Biphenyls from Glass-Block Windows and Other Room Surfaces in a Vermont School

We hypothesized that emissions of polychlorinated biphenyls (PCBs) from Aroclor mixtures present in building materials explain their concentrations in school air. Here, we report a study of airborne concentrations and gas-phase emissions in three elementary school rooms constructed in 1958. We collected airborne PCBs using polyurethane foam passive air samplers (PUF-PAS, n = 6) and PCB emissions from building materials using polyurethane foam passive emission samplers (PUF-PES, n = 17) placed over flat surfaces in school rooms, including vinyl tile floors, carpets, painted bricks, painted drywall, and glass-block windows. We analyzed all 209 congeners represented in 173 chromatographic separations and found that the congener distribution in PUF-PES strongly resembled the predicted diffusive release of gas-phase PCBs from a solid material containing Aroclor 1254. Concentrations of airborne total PCBs ranged from 38 to 180 ng m-3, a range confirmed by an independent laboratory in the same school. These levels exceed action levels for all aged children set by the State of Vermont and exceed guidance levels set by the U.S. EPA for children under age 3. Emissions of PCBs from the glass-block windows (30,000 ng m-2 d-1) greatly exceeded those of all other surfaces, which ranged from 35 to 2700 ng m-2 d-1. This study illustrates the benefit of the direct measurement of PCB emissions to identify the most important building remediation needed to reduce airborne PCB concentrations in schools.

Disposition and metabolomic effects of 2,2',5,5'-tetrachlorobiphenyl in female rats following intraperitoneal exposure

The disposition and toxicity of lower chlorinated PCBs (LC-PCBs) with less than five chlorine substituents have received little attention. This study characterizes the distribution and metabolomic effects of PCB 52, an LC-PCB found in indoor and outdoor air, three weeks after intraperitoneal exposure of female Sprague Dawley rats to 0, 1, 10, or 100 mg/kg BW. PCB 52 exposure did not affect overall body weight. Gas chromatography-tandem mass spectrometry (GC-MS/MS) analysis identified PCB 52 in all tissues investigated. Hydroxylated, sulfated, and methylated PCB metabolites, identified using GC-MS/MS and nontarget liquid chromatography-high resolution mass spectrometry (Nt-LCMS), were primarily found in the serum and liver of rats exposed to 100 mg/kg BW. Metabolomic analysis revealed minor effects on L-cysteine, glycine, cytosine, sphingosine, thymine, linoleic acid, orotic acid, L-histidine, and erythrose serum levels. Thus, the metabolism of PCB 52 and its effects on the metabolome must be considered in toxicity studies.

Predicted Versus Observed Activity of PCB Mixtures Toward the Ryanodine Receptor

Non-dioxin-like polychlorinated biphenyls (NDL PCBs) alter the activity of the ryanodine receptor (RyR), and this activity is linked to developmental neurotoxicity. Most work to date has focused on the activity of single congeners rather than relevant mixtures. The current study assessed the RyR activity of single congeners or binary, tertiary, and complex PCB mixtures. Observed mixture activity was then compared to the expected activity calculated using the concentration addition (CA) model or a RyR-specific neurotoxic equivalency scheme (rNEQ). The predictions of the CA model were consistent with the observed activity of binary mixtures at the lower portion of the concentration-response curve, supporting the additivity of RyR1 active PCBs. Findings also show that minimally active congeners can compete for the RyR1 binding site, and congeners that do not activate the RyR1 do not interfere with the activity of a full agonist. Complex PCB mixtures that mimic PCB profiles detected in indoor air, fish tissue, and the serum of mothers and children activated the RyR1 and displayed similar efficacy and potency regardless of varying congener profiles. Neither the CA model nor the rNEQ perfectly predicted the observed activity of complex mixtures, but predictions were often within one magnitude of change from the observed response. Importantly, PCB mixtures approximating profiles found in environmental samples or human serum displayed RyR1 activity at concentrations reported in published research. The work presented will aid in the development of risk assessment platforms for NDL PCBs, and similar compounds, towards RyR1 activation and related neurotoxicity.

Enantiomeric Fractions Reveal Differences in the Atropselective Disposition of 2,2',3,5',6-Pentachlorobiphenyl (PCB 95) in Wildtype, Cyp2abfgs-Null, and CYP2A6-Humanized Mice

Polychlorinated biphenyls (PCBs) are environmental contaminants that can cause neurotoxicity. PCBs, such as PCB 95 (2,2',3,5',6-pentachlorobiphenyl), can be metabolized by cytochrome P450 enzymes into neurotoxic metabolites. To better understand how the metabolism of PCB 95 affects neurotoxic outcomes, we conducted a study on the disposition of PCB 95 in transgenic mouse models. The mice were given a single oral dose of PCB 95 (1.0 mg/kg) and were euthanized 24 h later for analysis. PCB 95 levels were highest in adipose tissue, followed by the liver, brain, and blood. Adipose tissue levels were significantly higher in wild-type (WT) mice than in Cyp2abfgs-null (KO) or CYP2A6-transgenic (KI) mice. We also observed genotype-dependent differences in the enrichment of aS-PCB 95 in female mice, with a less pronounced enrichment in KO than WT and KI mice. Ten hydroxylated PCB 95 metabolites were detected in blood and tissue across all exposure groups. The metabolite profiles differed across tissues, while sex and genotype-dependent differences were less pronounced. Total OH-PCB levels were highest in the blood, followed by the liver, adipose tissue, and brain. Total OH-PCB blood levels were lower in KO than in WT mice, while the opposite trend was observed in the liver. In male mice, total OH-PCB metabolite levels were significantly lower in KI than in WT mice in blood and the liver, while the opposite trend was observed in female mice. In conclusion, the study highlights the differences in the atropselective disposition of PCB 95 and its metabolites in different types of mice, demonstrating the usefulness of these transgenic mouse models for characterizing the role of PCB metabolism in PCB neurotoxicity.

Disposition and Metabolomic Effects of 2,2',5,5'-Tetrachlorobiphenyl in Female Rats Following Intraperitoneal Exposure

The disposition and toxicity of lower chlorinated PCBs (LC-PCBs) with less than five chlorine substituents have received little attention. This study characterizes the distribution and metabolomic effects of PCB 52, an LC-PCB found in indoor and outdoor air, three weeks after intraperitoneal exposure of female Sprague Dawley rats to 0, 1, 10, or 100 mg/kg BW. PCB 52 exposure did not affect overall body weight. Gas chromatography-tandem mass spectrometry (GC-MS/MS) analysis identified PCB 52 in all tissues investigated. Hydroxylated, sulfated, and methylated PCB metabolites, identified using GC-MS/MS and nontarget liquid chromatography-high resolution mass spectrometry (Nt-LCMS), were primarily found in the serum and liver of rats exposed to 100 mg/kg BW. Metabolomic analysis revealed minor effects on L-cysteine, glycine, cytosine, sphingosine, thymine, linoleic acid, orotic acid, L-histidine, and erythrose serum levels. Thus, the metabolism of PCB 52 and its effects on the metabolome must be considered in toxicity studies.

Highlights

PCB 52 was present in adipose, brain, liver, and serum 3 weeks after PCB exposureLiver and serum contained hydroxylated, sulfated, and methylated PCB 52 metabolitesMetabolomics analysis revealed minor changes in endogenous serum metabolitesLevels of dopamine and its metabolites in the brain were not affected by PCB 52.

Hydroxylation markedly alters how the polychlorinated biphenyl (PCB) congener, PCB52, affects gene expression in human preadipocytes

Polychlorinated biphenyls (PCBs) accumulate in adipose tissue and are linked to obesity and diabetes. The congener, PCB52 (2,2',5,5'-tetrachorobiphenyl), is found at high levels in school air. Hydroxylation of PCB52 to 4-OH-PCB52 (4-hydroxy-2,2',5,5'-tetrachorobiphenyl) may increase its toxicity. To understand PCB52's role in causing adipose dysfunction, we exposed human preadipocytes to PCB52 or 4-OH-PCB52 across a time course and assessed transcript changes using RNAseq. 4-OH-PCB52 caused considerably more changes in the number of differentially expressed genes as compared to PCB52. Both PCB52 and 4-OH-PCB52 upregulated transcript levels of the sulfotransferase SULT1E1 at early time points, but cytochrome P450 genes were generally not affected. A set of genes known to be transcriptionally regulated by PPARα were consistently downregulated by PCB52 at all time points. In contrast, 4-OH-PCB52 affected a variety of pathways, including those involving cytokine responses, hormone responses, focal adhesion, Hippo, and Wnt signaling. Sets of genes known to be transcriptionally regulated by IL17A or parathyroid hormone (PTH) were found to be consistently downregulated by 4-OH-PCB52. Most of the genes affected by PCB52 and 4-OH-PCB52 were different and, of those that were the same, many were changed in an opposite direction. These studies provide insight into how PCB52 or its metabolites may cause adipose dysfunction to cause disease.

Networks of placental DNA methylation correlate with maternal serum PCB concentrations and child neurodevelopment

BACKGROUND

Gestational exposure to polychlorinated biphenyls (PCBs) has been associated with elevated risk for neurodevelopmental disorders. Placental epigenetics may serve as a potential mechanism of risk or marker of altered placental function. Prior studies have associated differential placental DNA methylation with maternal PCB exposure or with increased risk of autism spectrum disorder (ASD). However, sequencing-based placental methylomes have not previously been tested for simultaneous associations with maternal PCB levels and child neurodevelopmental outcomes.

OBJECTIVES

We aimed to identify placental DNA methylation patterns associated with maternal PCB levels and child neurodevelopmental outcomes in the high-risk ASD MARBLES cohort.

METHODS

We measured 209 PCB congeners in 104 maternal serum samples collected at delivery. We identified networks of DNA methylation from 147 placenta samples using the Comethyl R package, which performs weighted gene correlation network analysis for whole genome bisulfite sequencing data. We tested placental DNA methylation modules for association with maternal serum PCB levels, child neurodevelopment, and other participant traits.

RESULTS

PCBs 153 + 168, 170, 180 + 193, and 187 were detected in over 50% of maternal serum samples and were highly correlated with one another. Consistent with previous findings, maternal age was the strongest predictor of serum PCB levels, alongside year of sample collection, pre-pregnancy BMI, and polyunsaturated fatty acid levels. Twenty seven modules of placental DNA methylation were identified, including five which significantly correlated with one or more PCBs, and four which correlated with child neurodevelopment. Two modules associated with maternal PCB levels as well as child neurodevelopment, and mapped to CSMD1 and AUTS2, genes previously implicated in ASD and identified as differentially methylated regions in mouse brain and placenta following gestational PCB exposure.

CONCLUSIONS

Placental DNA co-methylation modules were associated with maternal PCBs and child neurodevelopment. Methylation of CSMD1 and AUTS2 could be markers of altered placental function and/or ASD risk following maternal PCB exposure.

A systematic evidence map for the evaluation of noncancer health effects and exposures to polychlorinated biphenyl mixtures

Assessing health outcomes associated with exposure to polychlorinated biphenyls (PCBs) is important given their persistent and ubiquitous nature. PCBs are classified as a Group 1 carcinogen, but the full range of potential noncancer health effects from exposure to PCBs has not been systematically summarized and evaluated. We used systematic review methods to identify and screen the literature using combined manual review and machine learning approaches. A protocol was developed that describes the literature search strategy and Populations, Exposures, Comparators, and Outcomes (PECO) criteria used to facilitate subsequent screening and categorization of literature into a systematic evidence map of PCB exposure and noncancer health endpoints across 15 organs/systems. A comprehensive literature search yielded 62,599 records. After electronic prioritization steps, 17,037 studies were manually screened at the title and abstract level. An additional 900 studies identified by experts or supplemental searches were also included. After full-text screening of 3889 references, 1586 studies met the PECO criteria. Relevant study details such as the endpoints assessed, exposure duration, and species were extracted into literature summary tables. This review compiles and organizes the human and mammalian studies from these tables into an evidence map for noncancer health endpoints and PCB mixture exposure to identify areas of robust research as well as areas of uncertainty that would benefit from future investigation. Summary data are available online as interactive visuals with downloadable metadata. Sufficient research is available to inform PCB hazard assessments for most organs/systems, but the amount of data to inform associations with specific endpoints differs. Furthermore, despite many years of research, sparse data exist for inhalation and dermal exposures, which are highly relevant human exposure routes. This evidence map provides a foundation for future systematic reviews and noncancer hazard assessments of PCB mixtures and for strategic planning of research to inform areas of greater uncertainty.

Toxicity Impacts on Human Adipose Mesenchymal Stem/Stromal Cells Acutely Exposed to Aroclor and Non-Aroclor Mixtures of Polychlorinated Biphenyl

Polychlorinated biphenyl (PCB) accumulates in adipose where it may impact the growth and function of cells within the tissue. This is particularly concerning during adolescence when adipocytes expand rapidly. Herein, we sought to understand how exposure to PCB mixtures found in U.S. schools affects human adipose mesenchymal stem/stromal cell (MSC) health and function. We investigated how exposure to Aroclor 1016 and Aroclor 1254, as well as a newly characterized non-Aroclor mixture that resembles the PCB profile found in cabinets, Cabinet Mixture, affects adipose MSC growth, viability, and function in vitro. We found that exposure to all three mixtures resulted in two distinct types of toxicity. At PCB concentrations >20 μM, the majority of MSCs die, while at 1-10 μM, MSCs remained viable but display numerous alterations to their phenotype. At these sublethal concentrations, the MSC rate of expansion slowed and morphology changed. Further assessment revealed that PCB-exposed MSCs had impaired adipogenesis and a modest decrease in immunosuppressive capabilities. Thus, exposure to PCB mixtures found in schools negatively impacts the health and function of adipose MSCs. This work has implications for human health due to MSCs' role in supporting the growth and maintenance of adipose tissue.

Inhalation and dermal absorption as dominant pathways of PCB exposure for residents of contaminated apartment buildings

Applications of polychlorinated biphenyls (PCBs) in buildings and their persistence in indoor environments have led to cases of current and highly elevated exposure in humans, despite the global cease of production decades ago. Personal exposure to PCBs was assessed among residents in a social housing estate in Denmark containing both contaminated (n = 67) and non-contaminated (n = 23) apartments. Samples and estimated daily intakes (EDIs) were assessed for 15 PCB congeners, and body burden, which was limited by the dietary data availability, was compared across 7 indicator PCBs, with its sum (PCB_sum7) often applied in European regulation of PCBs. Median PCB_sum7 EDI across measured pathways for exposed residents was 101 ng· (kg bodyweight)^-1· day^-1, with the majority of exposure (60%) coming from inhalation of contaminated indoor air. Calculated from both PCBs measured in indoor air and on hand wipes, dermal absorption estimates showed comparable results and served as a secondary exposure pathway, accounting for 35% of personal exposure and considering selected assumptions and sources of physical-chemical parameters. Estimates revealed that diet was the primary PCB source among the reference group, accounting for over 75% of the PCB_sum7 EDI across exposure routes. When evaluating overall EDIs across the two study groups and including dietary estimates, PCB exposure among exposed residents was around 10 times higher than the reference group. Solely within the exposed population, pathway-specific body burdens were calculated to account for exposure across years of residence in contaminated apartments, where lower chlorinated PCBs were dominant in indoor air. Among these dominant congeners, estimated body burdens of PCB-28 and -52 were significantly correlated with measured serum (r_s = 0.49, 0.45; p < 0.001). This study demonstrates that inhalation and dermal absorption serve as dominant exposure pathways for residents of apartments contaminated with predominantly lower chlorinated PCBs and suggest that predictions of body burden from indoor environment measurements may be comparable to measured serum PCBs.

Characterization of different contaminants and current knowledge for defining chemical mixtures in human milk: A review

Hundreds of xenobiotics, with very diverse origins, have been detected in human milk, including contaminants of emerging concern, personal care products and other current-use substances reflecting lifestyle. The routes of exposure to these chemicals include dermal absorption, ingestion and inhalation. Specific families of chemicals are dominant among human milk monitoring studies (e.g., organochlorine pesticides, bisphenol A, dioxins), even though other understudied families may be equally toxicologically relevant (e.g., food-processing chemicals, current-use plasticizers and flame retardants, mycotoxins). Importantly, the lack of reliable human milk monitoring data for some individual chemicals and, especially, for complex mixtures, is a major factor hindering risk assessment. Non-targeted screening can be used as an effective tool to identify unknown contaminants of concern in human milk. This approach, in combination with novel methods to conduct risk assessments on the chemical mixtures detected in human milk, will assist in elucidating exposures that may have adverse effects on the development of breastfeeding infants.

Probing the Role of CYP2 Enzymes in the Atropselective Metabolism of Polychlorinated Biphenyls Using Liver Microsomes from Transgenic Mouse Models

Chiral polychlorinated biphenyls (PCB) are environmentally relevant developmental neurotoxicants. Because their hydroxylated metabolites (OH-PCBs) are also neurotoxic, it is necessary to determine how PCB metabolism affects the developing brain, for example, in mouse models. Because the cytochrome P450 isoforms involved in the metabolism of chiral PCBs remain unexplored, we investigated the metabolism of PCB 91 (2,2',3,4',6-pentachlorobiphenyl), PCB 95 (2,2',3,5',6-pentachlorobiphenyl), PCB 132 (2,2',3,3',4,6'-hexachlorobiphenyl), and PCB 136 (2,2',3,3',6,6'-hexachlorobiphenyl) using liver microsomes from male and female Cyp2a(4/5)bgs-null, Cyp2f2-null, and wild-type mice. Microsomes, pooled by sex, were incubated with 50 μM PCB for 30 min, and the levels and enantiomeric fractions of the OH-PCBs were determined gas chromatographically. All four PCB congeners appear to be atropselectively metabolized by CYP2A(4/5)BGS and CYP2F2 enzymes in a congener- and sex-dependent manner. The OH-PCB metabolite profiles of PCB 91 and PCB 132, PCB congeners with one para-chlorine substituent, differed between null and wild-type mice. No differences in the metabolite profiles were observed for PCB 95 and PCB 136, PCB congeners without a para-chlorine group. These findings suggest that Cyp2a(4/5)bgs-null and Cyp2f2-null mice can be used to study how a loss of a specific metabolic function (e.g., deletion of Cyp2a(4/5)bgs or Cyp2f2) affects the toxicity of chiral PCB congeners.

Gene×environment interactions in autism spectrum disorders

There is credible evidence that environmental factors influence individual risk and/or severity of autism spectrum disorders (hereafter referred to as autism). While it is likely that environmental chemicals contribute to the etiology of autism via multiple mechanisms, identifying specific environmental factors that confer risk for autism and understanding how they contribute to the etiology of autism has been challenging, in part because the influence of environmental chemicals likely varies depending on the genetic substrate of the exposed individual. Current research efforts are focused on elucidating the mechanisms by which environmental chemicals interact with autism genetic susceptibilities to adversely impact neurodevelopment. The goal is to not only generate insights regarding the pathophysiology of autism, but also inform the development of screening platforms to identify specific environmental factors and gene×environment (G×E) interactions that modify autism risk. Data from such studies are needed to support development of intervention strategies for mitigating the burden of this neurodevelopmental condition on individuals, their families and society. In this review, we discuss environmental chemicals identified as putative autism risk factors and proposed mechanisms by which G×E interactions influence autism risk and/or severity using polychlorinated biphenyls (PCBs) as an example.

Occurrence and spatial distribution of individual polychlorinated biphenyl congeners in residential soils from East Chicago, southwest Lake Michigan

We report individual polychlorinated biphenyl congeners and the sum of all congeners (ΣPCB) in residential soils of East Chicago, Indiana. ΣPCB in soils ranged from 20 to 1700 ng/g dry weight (DW), with a geometric mean of 120 ng/g DW. These values are significantly higher than other locations, but similar or lower to locations nearby well-known PCB contamination sites. No PCB spatial distribution pattern was observed. PCB concentrations increase with total organic carbon in the soils and proximity to Indiana Harbor and Ship Canal (IHSC), where sediments are contaminated with PCBs. Most samples are similar in their PCB distribution and Aroclor 1254 yielded the highest similarity to all the samples. A fifth of the samples highly resemble other PCB profiles such as EPA background and Cedar Rapids Iowa soils, and volatilization from Lake Michigan, whereas volatilization from IHSC could not explain the PCBs found in soils. IHSC was expected to be the main source of PCBs in the nearby soils. It is possible that soils are impacted by variety of known and unknown sources, including volatilization from Lake Michigan, resulting in a regional PCB signal. Although PCB concentrations are higher than other locations, samples were below the current US EPA non-cancer residential soil level remediation goal for dioxin TEQ.

An evidence map of polychlorinated biphenyl exposure and health outcome studies among residents of the Akwesasne Mohawk Nation

From the 1950s to the 1970s, three Superfund sites discharged polychlorinated biphenyl (PCB)-contaminated waste upstream of the Mohawk Nation at Akwesasne, resulting in PCB contamination of groundwater, soil, and sediment in the surrounding area. Given the persistence of PCBs in the environment and in human tissues, there are continued concerns regarding PCB exposures and the potential for adverse health effects in the community. We developed an evidence map of PCB research at Akwesasne in order to characterize the available data and to highlight potential research needs. Human health and exposure biomarker studies were identified from a literature search based on population, exposure, comparator, and outcome (PECO) criteria. Data extracted from references that met the inclusion criteria after full-text review included study characteristics (e.g., sample size, study design, sampling years), details on PCB measurements (e.g., analytical method, number of congeners analyzed, method detection limits), and results (e.g., PCB levels and summary of study conclusions). We identified 33 studies, conducted between 1986 and 2013, that examined PCB exposure characteristics and health effects in residents of the Akwesasne Mohawk Nation. Organizing this literature into an evidence map including information on study cohort, congener groupings, exposure biomarker characteristics, and health effects allowed us to identify research gaps and to suggest future research priorities for the community. We identified current PCB exposure levels and PCB source characterization as major uncertainties, both of which could be addressed by new studies of PCB concentrations in environmental media.

A Review of Polychlorinated Biphenyls (PCBs) Pollution in the Air: Where and How Much Are We Exposed to?

Polychlorinated biphenyls (PCBs) were widely used in industrial and commercial applications, until they were banned in the late 1970s as a result of their significant environmental pollution. PCBs in the environment gained scientific interest because of their persistence and the potential threats they pose to humans. Traditionally, human exposure to PCBs was linked to dietary ingestion. Inhalational exposure to these contaminants is often overlooked. This review discusses the occurrence and distribution of PCBs in environmental matrices and their associated health impacts. Severe PCB contamination levels have been reported in e-waste recycling areas. The occurrence of high PCB levels, notably in urban and industrial areas, might result from extensive PCB use and intensive human activity. Furthermore, PCB contamination in the indoor environment is ten-fold higher than outdoors, which may present expose risk for humans through the inhalation of contaminated air or through the ingestion of dust. In such settings, the inhalation route may contribute significantly to PCB exposure. The data on human health effects due to PCB inhalation are scarce. More epidemiological studies should be performed to investigate the inhalation dose and response mechanism and to evaluate the health risks. Further studies should also evaluate the health impact of prolonged low-concentration PCB exposure.

Toxicity of polychlorinated biphenyls in aquatic environments - A review

The assessment of polychlorinated biphenyls (PCBs) and their congeners resulting from the pollution of all environmental media is inherently related to its persistence and ubiquitous nature. In principle, determination of this class of contaminants are limited to the determination of their concentrations in the various environmental matrices. For solving many problems in this context, knowledge of the emission sources of PCBs, transport pathways, and sites of contamination and biomagnification is of great benefit to scientists and researchers, as well as many regulatory organizations. By far the largest amounts of PCBs, regardless of their discharged points, end up in the soil, sediment and finally in different aquatic environments. By reviewing relevant published materials, the source of origin of PCBs in the environment particularly from different pollution point sources, it is possible to obtain useful information on the nature of different materials that are sources of PCBs, or their concentrations and their toxicity or health effects and how they can be removed from contaminated media. This review focuses on the sources of PCBs in aquatic environments and critically reviews the toxicity of PCBs in aquatic animals and plants. The review also assesses the toxicity equivalency factors (TEFs) of PCBs providing valuable knowledge to other scientists and researchers that enables regulatory laws to be formulated based on selective determination of concentrations regarding their maximum permissible limits (MPLs) allowed. This review also supplies a pool of valuable information useful for designing decontamination technologies for PCBs in media like soil, sediment, and wastewaters.

Chiral signatures of polychlorinated biphenyls in serum from e-waste workers and their correlation with hydroxylated metabolites

Elevated concentrations of polychlorinated biphenyls (PCBs) found in environmental media and biota from typical e-waste dismantling sites have raised concerns regarding their human body burden and potential negative health effects. In the present study, the enantiomeric compositions of three typical chiral congeners (PCB-95, PCB-132, and PCB-149) were measured in 24 serum samples from e-waste workers by using gas chromatography coupled to triple quadrupole tandem mass spectrometry. The mean enantiomer fractions (EFs) of chiral congeners in serum from the workers were 0.655 ± 0.103, 0.679 ± 0.164, and 0.548 ± 0.095 for PCB-95, PCB-132, and PCB-149, respectively. The (+) enantiomers of PCB-95, PCB-132, and PCB-149 were enantioselectively enriched in serum. Significant positive correlations were observed between the EF of the chiral congener PCB-95 and the total concentration of OH-PCBs, suggesting that EF values of chiral PCBs could be used to indicate the extent of biological metabolism. In addition, the EF of PCB-95 in serum samples increased with increasing work duration of the e-waste workers, thus demonstrating the usefulness of EF values of chiral PCBs as tracers of human exposure to PCBs. Because of the enantioselective enrichment of (+) enantiomers of PCB-95, PCB-132, and PCB-149, further studies are needed to explore the metabolism and toxicity of chiral contaminants in humans.

A Generic Pharmacokinetic Model for Quantifying Mother-to-Offspring Transfer of Lipophilic Persistent Environmental Chemicals

Lipophilic persistent environmental chemicals (LPECs) can accumulate in a woman's body and transfer to her developing child across the placenta and via breast milk. To assess health risks associated with developmental exposures to LPECs, we developed a pharmacokinetic (PK) model that quantifies mother-to-offspring transfer of LPECs during pregnancy and lactation and facilitates internal dosimetry calculations for offspring. We parameterized the model for mice, rats, and humans using time-varying functions for body mass and milk consumption rates. The only required substance-specific parameter is the elimination half-life of the LPEC in the animal species of interest. We used the model to estimate whole-body concentrations in mothers and offspring following maternal exposures to hexachlorobenzene (HCB) and 2,2',4,4',5,5'-hexachlorobiphenyl (PCB 153) and compared these with measured concentrations from animal studies. We also compared estimated concentrations for humans to those generated using a previously published human LPEC PK model. Finally, we compared human equivalent doses (HEDs) calculated using our model and an allometric scaling method. Estimated and observed whole-body concentrations of HCB and PCB 153 in offspring followed similar trends and differed by less than 60%. Simulations of human exposure yielded concentration estimates comparable to those generated using the previously published model, with concentrations in offspring differing by less than 12%. HEDs calculated using our PK model were about 2 orders of magnitude lower than those generated using allometric scaling. Our PK model can be used to calculate internal dose metrics for offspring and corresponding HEDs and thus informs assessment of developmental toxicity risks associated with LPECs.

Inadvertently Generated PCBs in Consumer Products: Concentrations, Fate and Transport, and Preliminary Exposure Assessment

Although commercial polychlorinated biphenyl (PCB) production was banned in 1979 under the Toxics Substance Control Act, inadvertent generation of PCBs through a variety of chemical production processes continues to contaminate products and waste streams. In this research, a total of 39 consumer products purchased from local and online retailer stores were analyzed for 209 PCB congeners. Inadvertent PCBs (iPCBs) were detected from seven products, and PCB-11 was the only congener detected in most of the samples, with a maximum concentration exceeding 800 ng/g. Emission of PCB-11 to air was studied from one craft foam sheet product using dynamic microchambers at 40 °C for about 120 days. PCB-11 migration from the product to house dust was also investigated. The IAQX program was then employed to estimate the emissions of PCB-11 from 10 craft foam sheets to indoor air in a 30 m3 room at 0.5 h-1 air change rate for 30 days. The predicted maximum PCB-11 concentration in the room air (156.8 ng/m3) and the measured concentration in dust (20 ng/g) were applied for the preliminary exposure assessment. The generated data from multipathway investigation in this work should be informative for further risk assessment and management for iPCBs.

Health risk assessment of polychlorinated biphenyls (PCBs) in baby clothes. A preliminary study

Clothes may contain a large range of chemical additives and other toxic substances, which may eventually pose a significant risk to human health. Since they are associated with pigments, polychlorinated biphenyls (PCBs) may be especially relevant. On the other hand, infants are very sensitive to chemical exposure and they may wear some contact and colored textiles for a prolonged time. Consequently, a specific human health risk assessment is required. This preliminary study was aimed at analyzing the concentrations of PCBs in ten bodysuits purchased in on-line stores and local retailers. The concentrations of 12 dioxin-like and 8 non-dioxin-like PCB congeners were determined by gas chromatography coupled to high resolution mass spectrometry, with detection limits ranging between 0.01 and 0.13 pg/g. The dermal absorption to PCBs of children at different ages (6 months, 1 year and 3 years old) was estimated, and the non-cancer and cancer risks were evaluated. Total levels of PCBs ranged from 74.2 to 412 pg/g, with a mean TEQ concentration of 13.4 pg WHO-TEQ/kg. Bodysuits made of organic cotton presented a total mean PCB concentration substantially lower than clothes made of regular cotton (11.0 vs. 15.8 pg WHO-TEQ/kg). The dermal absorption to PCBs for infants was calculated in around 3·10^-5 pg WHO-TEQ/kg·day, regardless the age. This value is > 10,000-fold lower than the dietary intake of PCBs, either through breastfeeding or food consumption. Furthermore, this exposure value would not pose any health risks for the infants wearing those bodysuits. Anyhow, as it is a very preliminary study, this should be confirmed by analyzing larger sets of textile samples. Further investigations should be also focused on the co-occurrence of PCBs and other toxic chemicals (i.e., formaldehyde, bisphenols and aromatic amines) in infant clothes.

Assessment of Polychlorinated Biphenyls and Their Hydroxylated Metabolites in Postmortem Human Brain Samples: Age and Brain Region Differences

Exposure to polychlorinated biphenyls (PCBs) and their hydroxylated metabolites (OH-PCBs) has been implicated in neurodevelopmental disorders. However, the distribution of PCBs and OH-PCBs in the human brain has not been characterized. This study investigated the age-, sex-, and brain region-specific distribution of all 209 PCBs using gaschromatography-tandem mass spectrometry (GC-MS/MS) in neonatal (N = 7) and adult (N = 7) postmortem brain samples. OH-PCB analyses were performed by GC-MS/MS (as methylated derivatives) and, in a subset of samples, by nontarget liquid chromatography high-resolution mass spectrometry (Nt-LCMS). Fourteen higher chlorinated PCB congeners were observed with a detection frequency >50%. Six lower chlorinated PCBs were detected with a detection frequency >10%. Higher chlorinated PCBs were observed with higher levels in samples from adult versus younger donors. PCB congener profiles from adult donors showed more similarities across brain regions and donors than younger donors. We also assess the potential neurotoxicity of the PCB residues in the human brain with neurotoxic equivalency (NEQ) approaches. The median ΣNEQs, calculated for the PCB homologues, were 40-fold higher in older versus younger donors. Importantly, lower chlorinated PCBs made considerable contributions to the neurotoxic potential of PCB residues in some donors. OH-PCBs were identified for the first time in a small number of human brain samples by GC-MS/MS and Nt-LCMS analyses, and all contained four or fewer chlorine.

Elevated mercury and PCB concentrations in Dolly Varden (Salvelinus malma) collected near a formerly used defense site on Sivuqaq, Alaska

Environmental pollution causes adverse health effects in many organisms and contributes to health disparities for Arctic communities that depend on subsistence foods, including the Yupik residents of Sivuqaq (St. Lawrence Island), Alaska. Sivuqaq's proximity to Russia made it a strategic location for U.S. military defense sites during the Cold War. Two radar surveillance stations were installed on Sivuqaq, including at the Northeast Cape. High levels of persistent organic pollutants and toxic metals continue to leach from the Northeast Cape formerly used defense (FUD) site despite remediation efforts. We quantified total mercury (Hg) and polychlorinated biphenyl (PCB) concentrations, and carbon and nitrogen stable isotope signatures, in skin and muscle samples from Dolly Varden (Salvelinus malma), an important subsistence species. We found that Hg and PCB concentrations significantly differed across locations, with the highest concentrations found in fish collected near the FUD site. We found that 89% of fish collected from near the FUD site had Hg concentrations that exceeded the U.S. Environmental Protection Agency's (EPA) unlimited Hg-contaminated fish consumption screening level for subsistence fishers (0.049 μg/g). All fish sampled near the FUD site exceeded the EPA's PCB guidelines for cancer risk for unrestricted human consumption (0.0015 μg/g ww). Both Hg and PCB concentrations had a significant negative correlation with δ¹³C when sites receiving input from the FUD site were included in the analysis, but these relationships were insignificant when input sites were excluded. δ¹⁵N had a significant negative correlation with Hg concentration, but not with PCB concentration. These results suggest that the Northeast Cape FUD site remains a point source of Hg and PCB pollution and contributes to higher concentrations in resident fish, including subsistence species. Moreover, elevated Hg and PCB levels in fish near the FUD site may pose a health risk for Sivuqaq residents.

Exposure sources of polychlorinated biphenyls (PCBs) and health risk assessment: a systematic review in Iran

This systematic review aims to identify the sources of exposure to polychlorinated biphenyls (PCBs), portioning, and human health risk assessment in Iran. The literature was searched in the international databases of Web of Science, PubMed, Scopus, Google Scholar, and the national databases of SID and MagIran up to November 14, 2020. Among all 153 articles, 21 eligible papers were identified. Among them, only one article was related to drinking water, the rest was related to food and soil, and no article was found on ambient air. The corrected portion of each exposure source was determined to be 90% for food, 9% for water, and 1% for air. The total hazard quotient (HQ) was determined to be within an unsafe range, and the total excess lifetime cancer risk (ELCR) was determined to be at a high risk of oral carcinogenesis. It is suggested that a comprehensive study be conducted in a specific period for all sources of exposure in all counties of Iran. Moreover, it is recommended that the policymakers set national standards for this pollutant in near future in some sources of exposure (e.g., drinking water) which have no standards in Iran.

PCB Sulfates in Serum from Mothers and Children in Urban and Rural U.S. Communities

Serum samples from 24 subjects (6 mother-daughter and 6 mother-son dyads) in a rural community (Columbus Junction, Iowa) and 24 subjects (6 mother-daughter and 6 mother-son dyads) in an urban community (East Chicago, Indiana) were analyzed for 74 sulfated metabolites of polychlorinated biphenyls (PCBs). We detected significantly higher mean concentrations of total assessed PCB sulfates in the urban group (110-8900 ng/g fresh weight of serum, mean = 3400 ng/g, standard error = 300) than in the rural cohort (530-6700 ng/g fresh weight of serum, mean = 1800 ng/g, standard error = 500). Eight PCB sulfate congeners (4-PCB 2 sulfate, 4'-PCB 2 sulfate, 2'-PCB 3 sulfate, 4'-PCB 3 sulfate, 4-PCB 11 sulfate, 4'-PCB 18 sulfate, 4'-PCB 25 sulfate, and 4-PCB 52 sulfate) contributed over 90% of the total assessed PCB sulfates in most individuals. The serum samples were enriched in PCB sulfates with fewer than 5 chlorine atoms, and this congener distribution differed from those of PCBs and hydroxylated PCBs in previous studies in the same communities. Regression analysis indicated several significant congener-specific correlations in mother-child dyads, and these relationships differed by location and by mother-daughter or mother-son dyads. This is the first study reporting a broad range of PCB sulfates in populations from urban and rural areas.

Developmental polychlorinated biphenyl (PCB) exposure alters voiding physiology in young adult male and female mice

The impact of developmental exposure to environmental chemicals on lower urinary tract function is not well understood, despite the fact that these chemicals could contribute to etiologically complex lower urinary tract symptoms (LUTS). Polychlorinated biphenyls (PCBs) are environmental toxicants known to be detrimental to the central nervous system, but their impact on voiding function in mouse models is not known. Therefore, we test whether developmental exposure to PCBs is capable of altering voiding physiology in young adult mice. C57Bl/6J female mice received a daily oral dose of the MARBLES PCB mixture for two weeks prior to mating and through gestation and lactation. The mixture mimics the profile of PCBs found in a contemporary population of pregnant women. Voiding function was then tested in young adult offspring using void spot assay, uroflowmetry and anesthetized cystometry. PCB effects were sex and dose dependent. Overall, PCBs led to increases in small size urine spots in both sexes with males producing more drop-like voids and greater peak pressure during a voiding cycle while females displayed decreases in void duration and intervoid interval. Together, these results indicate that developmental exposure to PCBs are capable of altering voiding physiology in young adult mice. Further work to identify the underlying mechanisms driving these changes may help develop more effective preventative or therapeutic strategies for LUTS.

Intracity occurrence and distribution of airborne PCB congeners in Chicago

To evaluate the magnitude and extent of airborne PCBs in an urban area, we measured and investigated the temporal and spatial behavior of atmospheric concentrations of individual polychlorinated biphenyl (PCB) congeners as well as the sum of all congeners (ΣPCB) in both gas and particle phases at 27 locations across the City of Chicago in a single year (2009). In total, 141 gas-phase air samples were collected, including 22 pairs (44 samples) deployed at the same time but at two different locations, and 46 particle-phase samples. ΣPCB in the gas-phase ranged from 80 to 3000 pg/m³, with a geometric mean (GM) of 530 pg/m³, whereas particle-phase ranged from 8 to 160 pg/m³, with a GM of 28 pg/m³. We found the temporal variability to be about three times larger than the variability over space for all gas-phase congeners and ΣPCB. Around 50% of the sample PCB profiles resembled a mixture of a 1:1 vapor Aroclor mixture of 1016 + 1254, with most of the rest (30%) showing enrichment of PCB 3 (>0.1), which did not match any Aroclor profiles. PCB 11 contributed to ~5% in all samples. The fractions of PCB congeners bound to particles ranged from 0.001 to 0.97. Our analysis shows that airborne PCBs are widely distributed across Chicago and confirms that most locations have a similar PCB distribution, but differ in the concentration levels. Volatilization continues to be the main release process of PCBs into the atmosphere, including both Aroclor and non-Aroclor congeners.

PCB126 induced toxic actions on liver energy metabolism is mediated by AhR in rats

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor involved in the regulation of biological responses to more planar aromatic hydrocarbons, like TCDD. We previously described the sequence of events following exposure of male rats to a dioxin-like polychlorinated biphenyl (PCB) congener, 3,3',4,4',5-pentachlorobiphenyl (PCB126), that binds avidly to the AhR and causes various types of toxicity including metabolic syndrome, fatty liver, and disruption of energy homeostasis. The purpose of this study was, to investigate the role of AhR to mediate those toxic manifestations following sub-acute exposure to PCB126 and to examine possible sex differences in effects. For this goal, we created an AhR knockout (AhR-KO) model using CRISPR/Cas9. Comparison was made to the wild type (WT) male and female Holtzman Sprague Dawley rats. Rats were injected with a single IP dose of corn oil vehicle or 5 μmol/kg PCB126 in corn oil and necropsied after 28 days. PCB126 caused significant weight loss, reduced relative thymus weights, and increased relative liver weights in WT male and female rats, but not in AhR-KO rats. Similarly, significant pathologic changes were visible which included necrosis and regeneration in female rats, micro- and macro-vesicular hepatocellular vacuolation in males, and a paucity of glycogen in livers of both sexes in WT rats only. Hypoglycemia and lower IGF1, and reduced serum non-esterified fatty acids (NEFAs) were found in serum of both sexes of WT rats, low serum cholesterol levels only in the females, and no changes in AhR-KO rats. The expression of genes encoding enzymes related to xenobiotic metabolism (e.g. CYP1A1), gluconeogenesis, glycogenolysis, and fatty acid oxidation were unaffected in the AhR-KO rats following PCB126 exposure as opposed to WT rats where expression was significantly upregulated (PPARα, females only) or downregulated suggesting a disrupted energy homeostasis. Interestingly, Acox2, Hmgcs, G6Pase and Pc were affected in both sexes, the gluconeogenesis and glucose transporter genes Pck1, Glut2, Sds, and Crem only in male WT-PCB rats. These results show the essential role of the AhR in glycogenolysis, gluconeogenesis, and fatty acid oxidation, i.e. in the regulation of energy production and homeostasis, but also demonstrate a significant difference in the effects of PCB126 in males verses females, suggesting higher vulnerability of glucose homeostasis in males and more changes in fatty acid/lipid homeostasis in females. These differences in effects, which may apply to more/all AhR agonists, should be further analyzed to identify health risks to specific groups of highly exposed human populations.

Developmental Exposure to a Human-Relevant Polychlorinated Biphenyl Mixture Causes Behavioral Phenotypes That Vary by Sex and Genotype in Juvenile Mice Expressing Human Mutations That Modulate Neuronal Calcium

Polychlorinated biphenyls (PCBs) are putative environmental risks for neurodevelopmental disorders. Here, we tested two hypotheses: (1) developmental exposure to a human-relevant PCB mixture causes behavioral phenotypes relevant to neurodevelopmental disorders; and (2) expression of human mutations that dysregulate neuronal Ca2+ homeostasis influence sensitivity to behavioral effects of developmental PCB exposures. To test these hypotheses, we used mice that expressed a gain-of-function mutation (T4826I) in ryanodine receptor 1 (RYR1), the X-linked fragile X mental retardation 1 (FMR1) CGG repeat expansion or both mutations (double mutant; DM). Transgenic mice and wildtype (WT) mice were exposed to the MARBLES PCB mix at 0, 0.1, 1, and 6 mg/kg/day in the maternal diet throughout gestation and lactation. The MARBLES PCB mix simulates the relative proportions of the 12 most abundant PCB congeners found in the serum of pregnant women at increased risk for having a child with a neurodevelopmental disorder. We assessed ultrasonic vocalizations at postnatal day 7 (P7), spontaneous repetitive behaviors at P25-P30, and sociability at P27-P32. Developmental PCB exposure reduced ultrasonic vocalizations in WT litters in all dose groups, but had no effect on ultrasonic vocalizations in transgenic litters. Developmental PCB exposure significantly increased self-grooming and decreased sociability in WT males in the 0.1 mg/kg dose group, but had no effect on WT females in any dose group. Genotype alone influenced ultrasonic vocalizations, self-grooming and to a lesser extent sociability. Genotype alone also influenced effects of PCBs on sociability. PCB levels in the brain tissue of pups increased in a dose-dependent manner, but within any dose group did not differ between genotypes. In summary, developmental PCB exposure phenocopied social behavior phenotypes observed in mice expressing human mutations that modify intracellular Ca2+ dynamics, and expression of these mutations alleviated PCB effects on ultrasonic vocalizations and repetitive behavior, and modified the dose-response relationships and sex-dependent effects of PCB effects on social behavior. These findings suggest that: (1) developmental PCB exposure causes behavioral phenotypes that vary by sex and genotype; and (2) sex-specific responses to environmental factors may contribute to sex biases in the prevalence and/or severity of neurodevelopmental disorders.

Human hepatic microsomal sulfatase catalyzes the hydrolysis of polychlorinated biphenyl sulfates: A potential mechanism for retention of hydroxylated PCBs

Polychlorinated biphenyls (PCBs) are persistent environmental contaminants that continue to be of concern due to their varied toxicities. Upon human exposure, many PCBs with lower numbers of chlorine atoms are metabolized to hydroxylated derivatives (OH-PCBs), and cytosolic sulfotransferases can subsequently catalyze the formation of PCB sulfates. Recent studies have indicated that PCB sulfates bind reversibly with a high affinity to human serum proteins, and that they are also taken up by cells and tissues. Since PCB sulfates might be hydrolyzed to the more toxic OH-PCBs, we have investigated the ability of human hepatic microsomal sulfatase to catalyze this reaction. Twelve congeners of PCB sulfates were substrates for the microsomal sulfatase with catalytic rates exceeding that of dehydroepiandrosterone sulfate as a comparison substrate for steroid sulfatase (STS). These results are consistent with an intracellular mechanism for sulfation and de-sulfation that may contribute to retention and increased time of exposure to OH-PCBs.

BMI modifies the association between dietary intake and serum levels of PCBs

Polychlorinated biphenyls (PCBs) are a group of persistent organic pollutants that are carcinogenic, neurotoxic, and endocrine disrupting in humans. Although diet is the primary source of exposure, there is no consensus on the association between dietary intake and serum PCBs. Additionally, body mass index (BMI) - with its inverse association with serum PCBs - may play a role in the association, which has never been studied. Therefore, we aimed to examine the association between dietary intake and serum levels of PCBs, and whether the association was modified by BMI. We used data from the National Health and Nutrition Examination Survey (NHANES) 2003-2004, including 1531 participants. We estimated dietary intake of PCBs using the 24-hour diet recall, USDA Food Composition Intake Database, and PCB content in foods from the Canada Total Diet Study. Serum PCBs were measured by high-resolution gas chromatography-mass spectrometry (HRGC-HRMS). We used linear regression to examine the associations of dietary PCB intake with serum levels of seven PCB congeners and six PCB metrics. Further, we explored the role of BMI in the associations. We found that participants who were older and non-Hispanic tended to have a higher serum level of ∑37-PCB. In addition, we observed positive associations between dietary intake and serum PCBs for: PCB 105, 118, 126, 138 + 158, and 153 (P value ranges 0.005-0.03); seven PCB indicators (P value = 0.03) and the sum of 37 PCBs (P value = 0.04). Furthermore, we observed an effect modification by BMI (P for interaction = 0.01 for ∑37-PCBs), with stronger associations in underweight or normal-weight individuals, and no association in overweight and obese individuals. In conclusion, within a cross-sectional, nationally representative sample of the US population, dietary PCB intake was positively associated with serum PCBs and the association was modified by BMI. Additional studies are warranted to replicate and confirm this effect modification.

Polychlorinated biphenyls in indoor dust from urban dwellings of Lahore, Pakistan: Congener profile, toxicity equivalency, and human health implications

This study is the pioneer assessment of the PCBs in indoor dust particles (from air conditioners) of an urbanized megacity from South Asian. The ∑₃₅ PCB concentration ranged from 0.27 to 152.9 ng/g (mean: 24.84 ± 22.10 ng/g). The tri- and tetra-PCBs were dominant homologues, contributing 57.36% of the total PCB concentrations. The mean levels of Σ₈ -dioxin-like (DL), Σ₆ -indicator PCBs and WHO₂₀₀₅ -TEQ for DL-PCBs were 2.22 ± 2.55 ng/g, 9.49 ± 8.04 ng/g and 4.77 ± 4.89 pg/g, respectively. The multiple linear regression indicated a significant correlation of dusting frequency (p = 1.06 × 10-04) and age of the house (p = 1.02 × 10-06) with PCB concentrations in indoor environment. The spatial variation of PCB profile revealed relatively higher concentrations from sites near to illegal waste burning spots, electrical locomotive workshops, and grid stations. Human health risk assessment of PCBs for adults and toddlers through all three exposure routes (ie, inhalation, ingestion, and dermal contact) demonstrated that toddlers were vulnerable to high cancer risk (4.32 × 10^-04 ), while adults were susceptible from low to moderate levels of risk (3.16 × 10^-05 ). Therefore, comprehensive investigations for PCBs in the indoor settings, focusing particularly on the sensitive populations with relationship to the electronic devices, transformers, and illegal waste burning sites, are recommended.

Room-to-Room Variability of Airborne Polychlorinated Biphenyls in Schools and the Application of Air Sampling for Targeted Source Evaluation

Airborne polychlorinated biphenyl (PCB) concentrations are higher indoors than outdoors due to their historical use in building materials and their presence in modern paints and surface treatments. For some populations, including school children, PCB levels indoors result in inhalation exposures that may be greater than or equivalent to exposure through diet. In a school, PCB exposure may come from multiple sources. We hypothesized that there are both Aroclor and non-Aroclor sources within a single school and that PCB concentration and congener profiles differ among rooms within a single building. To evaluate this hypothesis and to identify potential localized sources, we measured airborne PCBs in nine rooms in a school. We found that schoolroom concentrations exceed outdoor air concentrations. Schoolroom concentrations and congener profiles also varied from one room to another. The concentrations were highest in the math room (35.75 ng m-3 ± 8.08) and lowest in the practice gym (1.54 ng m-3 ± 0.35). Rooms in the oldest wing of the building, originally constructed between 1920 and 1970, had the highest concentrations. The congener distribution patterns indicate historic use of Aroclor 1254 as well as modern sources of non-Aroclor congeners associated with paint pigments and surface coatings. Our findings suggest this noninvasive source identification method presents an opportunity for targeted source testing for more cost-effective prioritization of materials remediation in schools.

A state-of-the-science review of polychlorinated biphenyl exposures at background levels: relative contributions of exposure routes

Exposure to polychlorinated biphenyls (PCBs) can occur through multiple routes and sources, including dietary intake, inhalation, dermal contact, and ingestion of dust and soils. Dietary exposure to PCBs is often considered the primary exposure route for the general population; however, recent studies suggest an increasing contribution from indoor inhalation exposure. Here, we aim to estimate the relative contribution of different PCB exposure pathways for the general population, as well as for select age groups. We conducted a targeted literature review of PCB concentrations in environmental media, including indoor and outdoor air, indoor dust, and soils, as well as of total dietary intake. Using the average concentrations from the studies identified, we estimated PCB exposure through different routes for the general population. In addition, we assessed exposure via environmental media for select age groups. We identified a total of 70 studies, 64 that provided background PCB concentrations for one or more of the environmental media of interest and 6 studies that provided estimates of dietary intake. Using estimates from studies conducted worldwide, for the general population, dietary intake of PCBs was the major exposure pathway. In general, our review identifies important limitations in the data available to assess population exposures, highlighting the need for more current and population-based estimates of PCB exposure, particularly for indoor air and dietary intake.

Non-dioxin-like polychlorinated biphenyl neurotoxic equivalents found in environmental and human samples

Non-dioxin like polychlorinated biphenyls (NDL PCB) are recognized neurotoxicants with implications on altered neurodevelopment and neurodegeneration in exposed organisms. NDL PCB neurotoxic relative potency schemes have been developed for a single mechanism, namely activity toward the ryanodine receptor (RyR), or combined mechanisms including, but not limited to, alterations of RyR and dopaminergic pathways. We compared the applicability of the two neurotoxic equivalency (NEQ) schemes and applied each scheme to PCB mixtures found in environmental and human serum samples. A multiple mechanistic NEQ predicts higher neurotoxic exposure concentrations as compared to a scheme based on the RyR alone. Predictions based on PCB ortho categorization, versus homologue categorization, lead to a higher prediction of neurotoxic exposure concentrations, especially for the mMOA. The application of the NEQ schemes to PCB concentration data suggests that PCBs found in fish from US lakes represent a considerable NEQ exposure to fish consuming individuals, that indoor air of schools contained high NEQ concentrations representing an exposure concern when inhaled by children, and that levels already detected in the serum of adults and children may contribute to neurotoxicity. With further validation and in vivo exposure data the NEQ scheme would help provide a more inclusive measure of risk presented by PCB mixtures.