Evaluating health risks from inhaled polychlorinated biphenyls: research needs for addressing uncertainty

Polychlorinated biphenyls induced toxicities upon cell lines and stem cells: a review

Polychlorinated biphenyls (PCBs) are persistent organic pollutants emitted during e-waste activities. Upon release into the environment, PCBs can pose harmful effects to the humans and environment. The present review focused on the effects of PCBs on cell proliferation, apoptosis, functional and developmental toxicity and potential possible molecular mechanisms upon cells and stem cells. The review also highlights the effects of low- and high-chlorinated, and dioxin and non-dioxin PCBs. The review suggested that high chlorinated and dioxin like PCBs at higher concentrations posed more toxic effects to cells and stem cells. PCBs at higher levels induced hepatotoxicity, carcinogenicity, reproductive toxicity, neurotoxicity and lung cell toxicity. PCBs triggered reactive oxygen species which actives mitogen activated pathways, nuclear factor and cytochrome pathway for cell proliferation and apoptosis. Further, review highlights PCBs induced toxicity in stem cells with the focus on developmental and functional toxicity. The review could be useful to understand the PCBs toxicities and mechanisms and will guide to policy makers to design policies for e-waste pollutant.

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.

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.

Comprehensive evaluation of skin exposure to PBDEs and PCBs in diverse South China populations via dermal wipe sampling

This study analyzed skin wipe samples from the forehead, palm, forearm, and lower leg of 120 volunteers across different age groups-preschoolers, thresholders, middle-aged, and elderly-with each group comprising 30 individuals with a balanced sex ratio from a city in South China. The research aimed to assess the occurrence, concentration, and associated health risks of polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) adsorbed onto human skin from environmental sources. We identified 13 PBDE congeners and 10 PCB congeners across all samples, with average detection frequencies of 48% for PBDEs and 16% for PCBs, with concentrations ranging from non-detectable (ND) to 4200 and ND to 2300 ng/m2, respectively. Skin concentrations of both PBDEs and PCBs decreased in the order of face > hand > arm > shank (ANOVA, P < 0.001), suggesting higher exposure to uncovered skin areas than to those covered by clothing, regardless of age or sex. The daily average dose of dermal (DADderm) and oral (DADoral) for PBDEs spanned from 7.0 × 10-4-0.19 ng/kg/d and ND-15 ng/kg/d, respectively, whereas the PCB exposure doses ranged from ND-7.8 ng/kg/d (DADderm) and ND-2.0 ng/kg/d (DADoral), respectively. Preschool children displayed notably higher DADoral levels than the other groups (P < 0.0001), which was attributed to their more frequent hand-to-mouth activity. Preschool boys exhibiting a higher DADderm (P < 0.05) and both preschool boys and university women showing elevated DADoral levels (P < 0.01 and P < 0.05, respectively). Health risk assessments concluded that the carcinogenic risks from BDE209 and PCBs were within acceptable limits (10-4) for all sampled populations.

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.

Advances in polychlorinated biphenyls-induced female reproductive toxicity

Polychlorinated biphenyls (PCBs) are a class of endocrine-disrupting chemicals (EDCs) widely present in the environment. PCBs have been of concern due to their anti/estrogen-like effects, which make them more toxic to the female reproductive system. However, there is still a lack of systematic reviews on the reproductive toxicity of PCBs in females, so the adverse effects and mechanisms of PCBs on the female reproductive system were summarized in this paper. Our findings showed that PCBs are positively associated with lower pregnancy rate, hormone disruption, miscarriage and various reproductive diseases in women. In animal experiments, PCBs can damage the structure and function of the ovaries, uterus and oviducts. Also, PCBs could produce epigenetic effects and be transferred to the offspring through the maternal placenta, causing development retardation, malformation and death of embryos, and damage to organs of multiple generations. Furthermore, the mechanisms of PCBs-induced female reproductive toxicity mainly include receptor-mediated hormone disorders, oxidative stress, apoptosis, autophagy, and epigenetic modifications. Finally, we also present some directions for future research on the reproductive toxicity of PCBs. This detailed information provided a valuable reference for fully understanding the reproductive toxicity of PCBs.

A mode of action-based probabilistic framework of dose-response assessment for nonmutagenic liver carcinogens: a case study of PCB-126

A main function of dose-response assessment is to estimate a "safe" dose in the target population to support chemical risk assessment. Typically, a "safe" dose is developed differently for cancer and noncancer effects based on a 2-step procedure, ie, point of departure (POD) derivation and low-dose extrapolation. However, the current dose-response assessment framework is criticized for its dichotomized strategy without integrating the mode of action (MOA) information. The objective of this study was, based on our previous work, to develop a MOA-based probabilistic dose-response framework that quantitatively synthesizes a biological pathway in a dose-response modeling process to estimate the risk of chemicals that have carcinogenic potential. 3,3',4,4',5-Pentachlorobiphenyl (PCB-126) was exemplified to demonstrate our proposed approach. There were 4 major steps in the new modeling framework, including (1) key quantifiable events (KQEs) identification and extraction, (2) essential dose calculation, (3) MOA-based POD derivation, and (4) MOA-based probabilistic reference dose (RfD) estimation. Compared with reported PODs and traditional RfDs, the MOA-based estimates derived from our approach were comparable and plausible. One key feature of our approach was the use of overall MOA information to build the dose-response relationship on the entire dose continuum including the low-dose region. On the other hand, by adjusting uncertainty and variability in a probabilistic manner, the MOA-based probabilistic RfDs can provide useful insights of health protection for the specific proportion of population. Moreover, the proposed framework had important potential to be generalized to assess different types of chemicals other than nonmutagenic carcinogens, highlighting its utility to improve current chemical risk assessment.

Exposure to airborne polychlorinated biphenyls and type 2 diabetes in a Danish cohort

BACKGROUND

Previous research indicates an association between higher-chlorinated polychlorinated biphenyls (PCBs) and type 2 diabetes (T2D). However, less is known about the extent to which PCB exposure in indoor air, composed primarily of lower-chlorinated PCBs, affects T2D risk. We assessed the association between indoor air exposure to PCBs in residential buildings and T2D incidence.

METHODS

The register-based 'Health Effects of PCBs in Indoor Air' (HESPAIR) cohort comprises 51,921 Danish residents of two residential areas with apartments built with and without PCB-containing materials (reference apartments). We assessed exposure status by combining register-based information on relocation history with extrapolated values of exposure based on PCB-measurements in indoor air from subsets of the apartments. T2D cases were identified in the Danish registers during 1977-2018. We estimated adjusted hazard ratios (HR) and 95% confidence intervals (CI) using Cox regression analyses with time-varying exposure.

RESULTS

We identified 2737 incident T2D cases during the follow-up. Exposure to ≥3300 ng/m3 PCB × year (3rd tertile of PCByear) was associated with higher risk of T2D (HR 1.15, 95% CI 1.02-1.30) compared with exposure to <300 ng/m3 PCB × year (reference). However, among individuals with lower cumulated PCByear, the risk was similar to residents with exposure <300 ng/m3 PCB × year (300-899 ng/m3 PCB × year: HR 0.98, 95% CI 0.87-1.11; 900-3299 ng/m3 PCB × year: HR 0.96, 95% CI 0.83-1.10).

DISCUSSION

We observed a marginally higher risk of T2D, but there was no evidence of an exposure-response relationship. The results should be interpreted with caution until confirmed in other independent studies of PCB exposure in indoor air.

Deeper insights into the effects of low dietary levels of polychlorinated biphenyls on pig metabolism using gas chromatography-high resolution mass spectrometry metabolomics

Polychlorinated biphenyls (PCBs) are a class of contaminants of great concern, linked to the development of many chronic diseases. Adverse effects of PCBs have been documented in humans after accidental and massive exposure. However, little is known about the effect of chronic exposure to low-dose PCB mixtures, and studies regarding scattered lifetime exposures to non-dioxin-like (NDL)-PCBs are especially missing. In this work, serum samples from pigs chronically exposed through their diet during 22 days to Aroclor 1260 (i.e. a commercially available mixture of NDL-PCBs) underwent a metabolomics analysis using gas chromatography-high resolution mass spectrometry (GC-HRMS), with the objective to investigate the effect of exposure to low doses of NDL-PCBs (few ng/kg body weight (b.w.) per day). The study showed that the serum profiles of 84 metabolites are significantly altered by the administration of Aroclor 1260, of which 40 could be identified at level 1. The aggregate interpretation of the results of this study, together with the outcome of a previous one involving LC-HRMS profiling, provided a substantial and concise overview of the effect of low dose exposure to NDL-PCBs, reflecting the hepatotoxic and neurotoxic effects already reported in literature at higher and longer exposures. These results are intended to contribute to the debate on the current toxicological reference values for these substances.

Plant -microbe assisted emerging contaminants (ECs) removal and carbon cycling

Continuous increase in the level of atmospheric CO₂ and environmental contaminates has aggravated various threats resulting from environmental pollution and climate change. Research into plant -microbe interaction has been a central concern of ecology for over the year. However, despite the clear contribution of plant -microbe to the global carbon cycle, the role of plant -microbe interaction in carbon pools, fluxes and emerging contaminants (ECs) removal are still a poorly understood. The use of plant and microbes in ECs removal and carbon cycling is an attractive strategy because microbes operate as biocatalysts to remove contaminants and plant roots offer a rich niche for their growth and carbon cycling. However, bio-mitigation of CO₂ and removal of ECs is still under research phase because of the CO₂ capture and fixation efficiency is too low for industrial purposes and cutting-edge removal methods have not been created for such emerging contaminants.

A case study of neurodevelopmental risks from combined exposures to lead, methyl-mercury, inorganic arsenic, polychlorinated biphenyls, polybrominated diphenyl ethers and fluoride

We performed a mixture risk assessment (MRA) case study of dietary exposure to the food contaminants lead, methylmercury, inorganic arsenic (iAs), fluoride, non-dioxin-like polychlorinated biphenyls (NDL-PCBs) and polybrominated diphenyl ethers (PBDEs), all substances associated with declines in cognitive abilities measured as IQ loss. Most of these chemicals are frequently measured in human biomonitoring studies. A component-based, personalised modified reference point index (mRPI) approach, in which we expressed the exposures and potencies of our chosen substances as lead equivalent values, was applied to perform a MRA for dietary exposures. We conducted the assessment for four different age groups (toddlers, children, adolescents, and women aged 18-45 years) in nine European countries. Populations in all countries considered exceeded combined tolerable levels at median exposure levels. NDL-PCBs in fish, other seafood and dairy, lead in grains and fruits, methylmercury in fish and other seafoods, and fluoride in water contributed most to the combined exposure. We identified uncertainties for the likelihood of co-exposure, assessment group membership, endpoint-specific reference values (ESRVs) based on epidemiological (lead, methylmercury, iAs, fluoride and NDL-PCBs) and animal data (PBDE), and exposure data. Those uncertainties lead to a complex pattern of under- and overestimations, which would require probabilistic modelling based on expert knowledge elicitation for integration of the identified uncertainties into an overall uncertainty estimate. In addition, the identified uncertainties could be used to refine future MRA for cognitive decline.

Risk of cardiovascular diseases following residential exposure to airborne polychlorinated biphenyls: A register-based cohort study

BACKGROUND

Indoor air in buildings constructed with materials containing polychlorinated biphenyls (PCBs) may be contaminated with especially lower-chlorinated PCBs. So far, the cardiovascular consequences of living with such contamination are unknown.

OBJECTIVES

To determine the risk of cardiovascular disease (CVD) following residential exposure to predominantly lower-chlorinated PCBs in indoor air.

METHODS

The Health Effects of PCBs in Indoor Air (HESPAIR) cohort is register-based with 51 921 residents of two residential areas near Copenhagen: Farum Midtpunkt and Brøndby Strand Parkerne. Here, indoor air was contaminated with PCB in one third of the apartments due to construction with materials containing PCB. Individual PCB exposure was estimated based on register-based information on relocation dates and indoor air PCB measurements in subsets of the apartments. Information on CVD was retrieved from the Danish National Patient Register for the follow-up period of 1977-2018. We estimated adjusted hazard ratios using Cox regression with time-varying exposure.

RESULTS

Cumulative residential exposure to airborne PCB was not associated with a higher overall risk for CVD (HR for highly exposed (≥3300 ng/m³ PCB × year): 1.02, 95% CI 0.94-1.10). This was also the case for most of the specific cardiovascular diseases, apart from acute myocardial infarction where a higher risk was observed for residents exposed to ≥3300 ng/m³ PCB × year compared to the reference group (HR 1.17, 95% CI 1.00-1.35). However, no exposure-response relationship was apparent and additional adjustment for education attenuated the risk estimate.

DISCUSSION

In this, to our knowledge, first study ever to examine the risk of CVD following residential exposure to PCBs in indoor air, we observed limited support for cardiovascular effects of living in PCB-contaminated indoor air. Considering the prevalence of exposure to airborne PCBs and lack of literature on their potential health effects, these findings need to be corroborated in other studies.

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.

Lab-scale biodegradation assay using passive samplers to determine microorganisms' ability to reduce polychlorinated biphenyl (PCB) volatilization from contaminated sediment

Many PCB-degrading aerobes have been identified which may serve as bioaugmentation strains for aerobic, in situ bioremediation or in combination with dredging operations. The present work describes a lab-scale PCB biodegradation assay which can be used to screen potential bioaugmentation strains or consortia for their ability to decrease PCB mass flux from contaminated sediment to air through biodegradation of freely dissolved PCBs that have desorbed from sediment particles. The assay uses two types of passive samplers to simultaneously measure PCB mass that is freely dissolved in aqueous solution and PCB mass that has volatilized to the headspace of the bioreactor. Using this approach, relative comparisons of PCB mass accumulated in passive samplers between bioaugmented treatments and controls allow for practical assessment of a microbial strain's ability to reduce both freely dissolved and vapor phase PCB concentrations. The method is designed to be conducted using aliquots of homogenized, well-characterized, PCB-contaminated sediment gathered from a field site. This work details the experimental design methodology, required materials, bioreactor set-up, passive sampling, PCB-extraction, sample cleanup, and quantification protocols such that the biodegradation assay can be conducted or replicated. A step-by-step protocol is also included and annotated with photos, tips, and tricks from experienced analysts.•Relative comparisons of PCB mass accumulated in passive samplers between experimental treatments and controls allow for practical assessment of bioaugmentation strain's ability to reduce both freely dissolved and vapor phase PCB concentrations•Passive sampler preparation, deployment, PCB-extraction, cleanup procedures, and quantification are detailed step-by-step and annotated by experienced analysts.

Using a dynamic mass balance model to predict fate and transport of PCBs in a polluted boreal lake in Sweden

In 2013, a screening survey including fish (European perch, Perca fluviatilis) from 20 locations in the Stockholm region of Sweden indicated exceptionally high levels of PCBs (>450 ng ΣPCB₇/g ww) in Lake Oxundasjön. An extensive sampling program was launched to define the magnitude and area of impact of PCBs. Moreover, a dynamic mass balance model approach was applied to identify and quantify key transport processes and predict the long-term turnover of PCBs given various remediation scenarios. Based on the dating of sediment profiles, primary emissions of PCBs to Lake Oxundasjön have likely occurred from the end of the 1940s until 1980, reaching the lake via one of its tributaries. Presently, the main source of PCBs is diffusion from the lake sediments. From the lake outlet, >400 g ΣPCB₇/yr are transported to Lake Mälaren (the third largest lake in Sweden), supplying drinking water for parts of the Stockholm area. Remediation actions are necessary to reduce the PCB levels in fish below today's marketing limits and environmental quality standards. With natural recovery, our results indicate that the PCB levels in non-migratory fish from Lake Oxundasjön will be elevated for decades to come. The mass of PCBs stored in the lake sediments was estimated, and to our knowledge, Lake Oxundasjön is the most heavily PCB contaminated lake in Sweden. The system constitutes a unique opportunity to test and develop a mathematical mass balance model for PCBs, with substantial data acquired from different aquatic matrices. The model presented in the paper is applicable for risk assessments of PCBs, and the results contribute to the general understanding of the transport and turnover dynamics of PCBs in aquatic ecosystems.

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.

Aerobic Bioaugmentation to Decrease Polychlorinated Biphenyl (PCB) Emissions from Contaminated Sediments to Air

We conducted experiments to determine whether bioaugmentation with aerobic, polychlorinated biphenyl (PCB)-degrading microorganisms can mitigate polychlorinated biphenyl (PCB) emissions from contaminated sediment to air. Paraburkholderia xenovorans strain LB400 was added to bioreactors containing PCB-contaminated site sediment. PCB mass in both the headspace and aqueous bioreactor compartments was measured using passive samplers over 35 days. Time-series measurements of all 209 PCB congeners revealed a 57% decrease in total PCB mass accumulated in the vapor phase of bioaugmented treatments relative to non-bioaugmented controls, on average. A comparative congener-specific analysis revealed preferential biodegradation of lower-chlorinated PCBs (LC-PCBs) by LB400. Release of the most abundant congener (PCB 4 [2,2'-dichlorobiphenyl]) decreased by over 90%. Simulations with a PCB reactive transport model closely aligned with experimental observations. We also evaluated the effect of the phytogenic biosurfactant, saponin, on PCB bioavailability and biodegradation by LB400. Time-series qPCR measurements of biphenyl dioxygenase (bphA) genes showed that saponin better maintained bphA abundance, compared to the saponin-free treatment. These findings indicate that an active population of bioaugmented, aerobic PCB-degrading microorganisms can effectively lower PCB emissions and may therefore contribute to minimizing PCB inhalation exposure in communities surrounding PCB-contaminated sites.

Cancer Risk following Residential Exposure to Airborne Polychlorinated Biphenyls: A Danish Register-Based Cohort Study

BACKGROUND

Polychlorinated biphenyls (PCBs) are biopersistent chemicals classified as human carcinogens. This classification is primarily based on evidence on higher-chlorinated PCBs found in food. The carcinogenic potential of airborne lower-chlorinated PCBs remains largely unexplored.

OBJECTIVES

We aimed to investigate cancer risk following residential exposure to airborne PCBs.

METHODS

Cancer risk was examined in the Health Effects of PCBs in Indoor Air (HESPAIR) cohort of 38,613 residents of two partly PCB-contaminated residential areas in Greater Copenhagen, identified by nationwide registries. PCB exposure was based on relocation dates and indoor air PCB measurements in subsets of apartments. Cancer diagnoses were extracted from the Danish Cancer Registry for the follow-up period of 1970-2018. We estimated adjusted hazard ratios with time-varying cumulative exposure and a 10-y lag using Cox regression.

RESULTS

Overall risk of cancer was not associated with PCByear, [hazard ratio (HR) for high-exposed vs. low-exposed =0.98; 95% confidence interval (CI): 0.88, 1.09], but residents exposed to ≥3,000 ng/m3 PCB×year had higher risk of liver cancer (HR =2.81; 95% CI: 1.28, 6.15) and meningiomas (HR =3.49; 95% CI: 1.84, 6.64), with indications of exposure-response relationships. Results were suggestive of a higher risk of pancreatic cancer (HR =1.59; 95% CI: 0.95, 2.64) at the highest aggregated PCB level. For testis cancer, a higher risk was observed among residents exposed to 300-949 ng/m3 PCB×year relative to residents exposed to <300 ng/m3 PCB×year (HR =2.97; 95% CI: 1.41, 6.28), but the risk was not higher for residents exposed to ≥950 ng/m3 PCB×year. Apart from this, the risk of specific cancers was similar across exposure groups.

DISCUSSION

In this, to our knowledge, first population-based cohort study of residential exposure to airborne PCBs, we found no association between exposure to PCBs in indoor air in private homes and the risk for most of the specific cancers. Higher risk of liver cancer and meningiomas were observed. https://doi.org/10.1289/EHP10605.

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.

Metabolomics and lipidomics to identify biomarkers of effect related to exposure to non-dioxin-like polychlorinated biphenyls in pigs

Recent epidemiological studies show that current levels of exposure to polychlorinated biphenyls (PCBs) remain of great concern, as there is still a link between such exposures and the development of chronic environmental diseases. In this sense, most studies have focused on the health effects caused by exposure to dioxin-like PCBs (DL-PCBs), although chemical exposure to non-dioxin-like PCB (NDL-PCB) congeners is more significant. In addition, adverse effects of PCBs have been documented in humans after accidental and massive exposure, but little is known about the effect of chronic exposure to low-dose PCB mixtures. In this work, exposure to Aroclor 1260 (i.e. a commercially available mixture of PCBs consisting primarily of NDL-PCB congeners) in pigs is investigated as new evidence in the risk assessment of NDL-PCBs. This animal model has been selected due to the similarities with human metabolism and to support previous toxicological studies carried out with more frequently used animal models. Dietary exposure doses in the order of few ng/kg body weight (b.w.) per day were applied. As expected, exposure to Aroclor 1260 led to the bioaccumulation of NDL-PCBs in perirenal fat of pigs. Metabolomics and lipidomics have been applied to reveal biomarkers of effect related to Aroclor 1260 exposure, and by extension to NDL-PCB exposure, for 21 days. In the metabolomics analysis, 33 metabolites have been identified (level 1 and 2) as significantly altered by the Aroclor 1260 administration, while in the lipidomics analysis, 39 metabolites were putatively annotated (level 3) and associated with NDL-PCB exposure. These biomarkers are mainly related to the alteration of fatty acid metabolism, glycerophospholipid metabolism and tryptophan-kynurenine pathway.

Toxicity Assessment of 91-Day Repeated Inhalation Exposure to an Indoor School Air Mixture of PCBs

School indoor air contaminated with polychlorinated biphenyls (PCBs) released from older building materials and paint pigments may pose health risks to children, as well as teachers and staff, by inhalation of PCBs. The health effects of long-term inhalation exposure to PCBs are poorly understood. We conducted a comprehensive toxicity assessment of 91-day repeated inhalation exposure to a lab-generated mixture of PCBs designed to emulate indoor school air, combining transcriptomics, metabolomics, and neurobehavioral outcomes. Female Sprague-Dawley rats were exposed to school air mixture (SAM+) at a concentration of 45.5 ± 5.9 μg/m3 ∑209PCB or filtered air 4 h/day, 6 days/week for 13 weeks using nose-only exposure systems. The congener-specific PCB body burden was quantified in major tissues using GC-MS/MS. The generated SAM+ vapor recapitulated the target school air profile with a similarity coefficient, cos θ of 0.91. PCB inhalation yielded 875-9930 ng/g ∑209PCBlipid weight levels in tissues in the following ascending order: brain < liver < lung < serum < adipose tissue. We observed that PCB exposure impaired memory, induced anxiety-like behavior, significantly reduced white blood cell counts, mildly disrupted metabolomics in plasma, and influenced transcription processes in the brain with 274 upregulated and 58 downregulated genes. With relatively high exposure and tissue loading, evidence of toxicity from half the end points tested was seen in the rats.

Environmental contamination and human exposure of polychlorinated biphenyls (PCBs) in China: A review

Polychlorinated biphenyls (PCBs), together with 11 other organic compounds, were initially listed as persistent organic pollutants (POPs) by the Stockholm Convention because of their potential threat to ecosystems and humans. In China, many monitoring studies have been undertaken to reveal the level of PCBs in environment since 2005 due to the introduced stricter environmental regulations. However, there are still significant gaps in understanding the overall spatial and temporal distributions of PCBs in China. This review systematically discusses the occurrence and distribution of PCBs in environmental matrices, organisms, and humans in China. Results showed that PCB contamination in northern and southern China was not significantly different, but the PCB levels in East China were commonly higher than those in West China, which might have been due to the widespread consumption of PCBs and intensive human activities in East China. Serious PCB contamination was found in e-waste disassembling areas (e.g., Taizhou of Zhejiang Province and Qingyuan and Guiyu of Guangdong Province). Higher PCB concentrations were also chronicled in megalopolises and industrial clusters. The unintentionally produced PCBs (UP-PCBs) formed during industrial thermal processes may play an increasingly significant role in PCB pollution in China. Low PCB levels were recorded in rural and underdeveloped districts, particularly in remote and high-altitude localities such as the Tibetan Plateau and the South China Sea. However, these data are limited. Human exposure to PCBs is closely related to the characteristics of environmental pollution. This review also discusses existing issues and future research prospects on PCBs in China. For instance, the accumulation characteristics and migration regularities of PCBs in food webs should be further studied. More investigations should be undertaken to assess the quantitative relationship between external and internal exposure to PCBs. For example, bioaccessibility and bioavailability studies should be supplemented to evaluate human health risks more accurately.

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.

Bioremediation strategies with biochar for polychlorinated biphenyls (PCBs)-contaminated soils: A review

Polychlorinated biphenyls (PCBs) are hazardous organic contaminants threatening human health and environmental safety due to their toxicity and carcinogenicity. Biochar (BC) is an eco-friendly carbonaceous material that can extensively be utilized for the remediation of PCBs-contaminated soils. In the last decade, many studies reported that BC is beneficial for soil quality enhancement and agricultural productivity based on its physicochemical characteristics. In this review, the potential of BC application in PCBs-contaminated soils is elaborated as biological strategies (e.g., bioremediation and phytoremediation) and specific mechanisms are also comprehensively demonstrated. Further, the synergy effects of BC application on PCBs-contaminated soils are discussed, in view of eco-friendly, beneficial, and productive aspects.

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.

Effects of air pollution exposure on social behavior: a synthesis and call for research

BACKGROUND

There is a growing literature from both epidemiologic and experimental animal studies suggesting that exposure to air pollution can lead to neurodevelopmental and neuropsychiatric disorders. Here, we suggest that effects of air pollutant exposure on the brain may be even broader, with the potential to affect social decision-making in general.

METHODS

We discuss how the neurobiological substrates of social behavior are vulnerable to air pollution, then briefly present studies that examine the effects of air pollutant exposure on social behavior-related outcomes.

RESULTS

Few experimental studies have investigated the effects of air pollution on social behavior and those that have focus on standard laboratory tests in rodent model systems. Nonetheless, there is sufficient evidence to support a critical need for more research.

CONCLUSION

For future research, we suggest a comparative approach that utilizes diverse model systems to probe the effects of air pollution on a wider range of social behaviors, brain regions, and neurochemical pathways.

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.

The role of epidemiology studies in human health risk assessment of polychlorinated biphenyls

Polychlorinated biphenyls (PCBs) are a public health concern given evidence that they persist and accumulate in the environment and can cause toxic effects in animals and humans. However, evaluating adverse effects of PCBs in epidemiologic studies is complicated by the characteristics of PCB exposure. PCBs exist as mixtures in the environment; the mixture changes over time due to degradation, and given physicochemical differences between specific PCB congeners, the mixture that an individual is exposed to (via food, air, or other sources) is likely different from that which can be measured in biological tissues. This is particularly problematic when evaluating toxicity of shorter-lived congeners that may not be measurable by the time biological samples are collected. We review these and other issues that arise when evaluating epidemiologic studies of PCBs and discuss how epidemiology data can still be used to inform both hazard identification and dose-response evaluation.

Comprehensive Subchronic Inhalation Toxicity Assessment of an Indoor School Air Mixture of PCBs

Few in vivo inhalation studies have explored the toxicity of environmentally relevant mixtures of polychlorinated biphenyls (PCBs). The manufacture of industrial PCBs was banned in 1978, but PCBs continue to be formed in industrial and consumer products. Schools represent a significant source of airborne exposures to legacy and nonlegacy PCBs, placing children at risk. To evaluate the impact of these exposures, we generated an airborne mixture of PCBs, called the School Air Mixture (SAM), to match the profile of an older school from our adolescent cohort study. Female Sprague-Dawley rats were exposed either to SAM or filtered air in nose-only exposure systems, 4 h/day for 4 weeks. Congener-specific air and tissue PCB profiles were assessed using gas chromatography with tandem mass spectrometry (GC-MS/MS). PCB exposures recapitulated the target school air profile with a similarity coefficient, cos θ of 0.83. PCB inhalation yielded μg/g ∑209 PCB levels in tissues. Neurobehavioral testing demonstrated a modest effect on spatial learning and memory in SAM-exposed rats. PCB exposure induced oxidative stress in the liver and lungs, affected the maturational stages of hematopoietic stem cells, reduced telomerase activity in bone marrow cells, and altered the gut microbiota. This is the first study to emulate PCB exposures in a school and comprehensively evaluate toxicity.

Investigating the presence of emerging and legacy POPs in European domestic air

Presence of organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and dechlorane plus (DP) were evaluated in indoor domestic air from four European countries (Belgium, Italy, Spain and Portugal). The main pollutants were hexachlorohexanes (sum of α-, β- and γ-HCH; ΣHCHs) and ΣPCBs (sum of PCB-28, 52, 101, 118, 138, 153 and 180), with median concentrations of 366 and 306 pg/m³, respectively. By decreasing order came hexachlorobenzene (HCB; 130 pg/m³), ΣDDXs (sum of DDTs, DDEs and DDDs; 94.4 pg/m³), ΣPBDEs (sum of BDE-17, 28, 47, 66, 99, 100, 153, 154, 183, 206, 207 and 209; 6.08 pg/m³) and DP (0.30 pg/m³). Lower ΣPCBs and ΣDDXs levels were found at Portuguese homes compared to Belgian, Italian and Spanish households. Italian samples presented also lower ΣHCHs concentrations while Spanish homes revealed higher HCB and BDE-209 indoor air concentrations than those obtained in the other countries. ΣHCHs, ΣDDXs and ΣPBDE levels mirrored lindane, dicofol and Penta-, DecaBDE use, respectively. The influence of building characteristics, surroundings and inhabitants habits on pollutant air concentrations was investigated. Data generated were used to conduct a human exposure assessment for toddlers and adults with median (P50) and upper (P95) concentrations. Results indicated that health risk posed by inhalation of ΣPCBs, ΣHCHs, ΣDDXs, HCB, ΣPBDEs and DP were 2 to 5 orders of magnitude lower than oral Reference Dose (RfD) values, and 90 (PCB-28) and 12 (γ-HCH) times lower than Minimal Risk Levels (MRLs) for toddlers at the worst case scenario.

Human health risks due to airborne polychlorinated biphenyls are highest in New Bedford Harbor communities living closest to the harbor

In response to concerns raised by communities surrounding the New Bedford Harbor Superfund site, we completed a field and modeling study that concluded the harbor is the primary source of polychlorinated biphenyls (PCBs) in air around the harbor. The follow-up question from residents was whether the PCBs measured in air pose a risk to their health. The US Environmental Protection Agency focuses their site-specific, risk-based decisions for site clean-up on cancers. We focused our assessment on the non-cancer effects on the thyroid based on the congener specific patterns and concentrations of PCBs measured in air near and distant to the harbor. Human and animal studies of PCB-induced effects on the thyroid provide evidence to support our analysis. Drawing from the published toxicological data, we used a Margin of Exposure (MOE) approach to derive a human-equivalent concentration in air associated with human health effects on the thyroid. Based on the MOEs calculated herein, evaluation of the MOE indicates that changes in thyroid hormone levels are possible among people living adjacent to the Harbor. Changes in thyroid hormone levels are more likely among people who live near the harbor compared to residents living in areas distant from the harbor. This risk assessment documents potential health risks associated with proximity to a marine Superfund Site using site-specific ambient air PCB congener data.

The developmental neurotoxicity of legacy vs. contemporary polychlorinated biphenyls (PCBs): similarities and differences

Although banned from production for decades, PCBs remain a significant risk to human health. A primary target of concern is the developing brain. Epidemiological studies link PCB exposures in utero or during infancy to increased risk of neuropsychiatric deficits in children. Nonclinical studies of legacy congeners found in PCB mixtures synthesized prior to the ban on PCB production suggest that non-dioxin-like (NDL) congeners are predominantly responsible for the developmental neurotoxicity associated with PCB exposures. Mechanistic studies suggest that NDL PCBs alter neurodevelopment via ryanodine receptor-dependent effects on dendritic arborization. Lightly chlorinated congeners, which were not present in the industrial mixtures synthesized prior to the ban on PCB production, have emerged as contemporary environmental contaminants, but there is a paucity of data regarding their potential developmental neurotoxicity. PCB 11, a prevalent contemporary congener, is found in the serum of children and their mothers, as well as in the serum of pregnant women at increased risk for having a child diagnosed with a neurodevelopmental disorder (NDD). Recent data demonstrates that PCB 11 modulates neuronal morphogenesis via mechanisms that are convergent with and divergent from those implicated in the developmental neurotoxicity of legacy NDL PCBs. This review summarizes these data and discusses their relevance to adverse neurodevelopmental outcomes in humans.

Prenatal exposure to PCBs and neurological and sexual/pubertal development from birth to adolescence

Several chemical compounds are resistant to degradation and end up in the food chain. One group of these chemicals is polychlorinated biphenyls (PCBs) which are used as flame retardants and plasticizers. Although PCBs were banned several decades ago, PCBs are still found in environmental media, including in the body of humans. PCBs are transferred from mother to fetus via the placenta during pregnancy. Considering that the prenatal period is a sensitive period during which essential developmental processes take place, exposure to environmental chemicals might have considerable and permanent consequences for outcomes in later life. The aim of this review is to provide an update on the latest insights on the effects of prenatal exposure to PCBs on neurological, sexual and pubertal development in children. We give an overview of recent literature, and discuss it in the light of the findings in a unique Dutch birth cohort, with data on both neurological and pubertal development into adolescence. The findings in the studies included in this review, together with the findings in the Dutch cohort, demonstrate that prenatal exposure to PCBs can interfere with normal child development, not only during the perinatal period, but up to and including adolescence. Higher prenatal exposure to PCBs was found to be both negatively and positively associated with neurodevelopmental outcomes. Regarding pubertal development, higher prenatal PCB exposure was found to be associated with more advanced pubertal development, also in the Dutch cohort, whereas other studies also found delayed pubertal development. These findings raise concern regarding the effects of man-made chemical compounds on child development. They further contribute to the awareness of how environmental chemical compounds can interfere with child development and negatively influence healthy ageing.

PCB Emissions from Paint Colorants

Polychlorinated biphenyls (PCBs) are known human carcinogens that are byproducts of pigment manufacturing and found in colorants used to tint consumer paints sold in the United States and elsewhere. PCBs have the potential to be emitted from paint containing these pigments. To quantify the gas-phase emissions of ∑PCBs, we used polyurethane foam (PUF) to capture emissions from freshly applied colorants. Some PCB emissions were detected on the PUF after 1 day. After 6 weeks, all PCBs found in the colorant were also found on the PUF. Even the fully chlorinated PCB209 was emitted from green colorant. Mono- and dichlorinated PCBs were released from the colorant at a faster rate than the higher chlorinated congeners. By the end of the experiment, all the lower chlorinated congeners were absent from the colorant while more than 75% of the higher chlorinated congeners remained in the sample. The rate of PCB emissions from paint colorants is a function of the surface/air equilibrium coefficient, and the presence of water accelerates the emissions. Although concentrations of PCBs in colorants are less than 285 ng g^-1, PCB emissions from colorants in paint can cause environmentally relevant concentrations of ≥500 pg m^-3 within hours of painting a room.

The spatial distribution of congener-specific human PCB concentrations in a PCB-polluted region

Serum PCB congener concentrations were measured in 602 adults living near a PCB pollution source in eastern Slovakia. We created isoconcentration maps for 21 PCB congeners by geocoding each participant's place of residence and kriging. Concentrations of PCB congeners were inversely associated with the distance of the participants' residence from the source of pollution. Congener-specific risk factors were derived, particularly for PCBs 52 and 153. We observed that the spatial distribution of serum concentrations was influenced by micro-climatic parameters and physicochemical properties of the congeners. PCB congener profiles strongly correlated with that of the PCB commercial product Delor 106, which was manufactured in the region. The isoconcentration maps indicate that the zones with the highest predicted congener concentration have a mean area of approximately 235.75±188.56km² and the mean enrichment of concentration of congeners in serum in these zones is about 5.12±1.36. We estimate that depending on congener approximately 23,457±18,762 individuals with PCB concentrations exceeding health-based guidance values live in these zones.

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.

Revisiting the Contributions of Far- and Near-Field Routes to Aggregate Human Exposure to Polychlorinated Biphenyls (PCBs)

The general population is exposed to polychlorinated biphenyls (PCBs) by consuming food from far-field contaminated agricultural and aquatic environments, and inhalation and nondietary ingestion in near-field indoor or residential environments. Here, we seek to evaluate the relative importance of far- and near-field routes by simulating the time-variant aggregate exposure of Swedish females to PCB congeners from 1930 to 2030. We rely on a mechanistic model, which integrates a food-chain bioaccumulation module and a human toxicokinetic module with dynamic substance flow analysis and nested indoor-urban-rural environmental fate modeling. Confidence in the model is established by successfully reproducing the observed PCB concentrations in Swedish human milk between 1972 and 2016. In general, far-field routes contribute most to total PCB uptake. However, near-field exposure is notable for (i) children and teenagers, who have frequent hand-to-mouth contact, (ii) cohorts born in earlier years, e.g., in 1956, when indoor environments were severely contaminated, and (iii) lighter chlorinated congeners. The relative importance of far- and near-field exposure in a cross-section of individuals of different age sampled at the same time is shown to depend on the time of sampling. The transition from the dominance of near- to far-field exposure that has happened for PCBs may also occur for other chemicals used indoors.

In vitro profiling of toxic effects of prominent environmental lower-chlorinated PCB congeners linked with endocrine disruption and tumor promotion

The mechanisms contributing to toxic effects of airborne lower-chlorinated PCB congeners (LC-PCBs) remain poorly characterized. We evaluated in vitro toxicities of environmental LC-PCBs found in both indoor and outdoor air (PCB 4, 8, 11, 18, 28 and 31), and selected hydroxylated metabolites of PCB 8, 11 and 18, using reporter gene assays, as well as other functional cellular bioassays. We focused on processes linked with endocrine disruption, tumor promotion and/or regulation of transcription factors controlling metabolism of both endogenous compounds and xenobiotics. The tested LC-PCBs were found to be mostly efficient anti-androgenic (within nanomolar - micromolar range) and estrogenic (at micromolar concentrations) compounds, as well as inhibitors of gap junctional intercellular communication (GJIC) at micromolar concentrations. PCB 8, 28 and 31 were found to partially inhibit the aryl hydrocarbon receptor (AhR)-mediated activity. The tested LC-PCBs were also partial constitutive androstane receptor (CAR) and pregnane X receptor (PXR) agonists, with PCB 4, 8 and 18 being the most active compounds. They were inactive towards other nuclear receptors, such as vitamin D receptor, thyroid receptor α, glucocorticoid receptor or peroxisome proliferator-activated receptor γ. We found that only PCB 8 contributed to generation of oxidative stress, while all tested LC-PCBs induced arachidonic acid release (albeit without further modulations of arachidonic acid metabolism) in human lung epithelial cells. Importantly, estrogenic effects of hydroxylated (OH-PCB) metabolites of LC-PCBs (4-OH-PCB 8, 4-OH-PCB 11 and 4'-OH-PCB 18) were higher than those of the parent PCBs, while their other toxic effects were only slightly altered or suppressed. This suggested that metabolism may alter toxicity profiles of LC-PCBs in a receptor-specific manner. In summary, anti-androgenic and estrogenic activities, acute inhibition of GJIC and suppression of the AhR-mediated activity were found to be the most relevant modes of action of airborne LC-PCBs, although they partially affected also additional cellular targets.

Serum concentrations of organochlorine compounds and predictors of exposure in children living in agricultural communities from South-Eastern Spain

BACKGROUND

Information on exposure levels to organochlorine compounds (OCs) in child population is limited, despite their greater vulnerability to the adverse health effects of these chemicals.

OBJECTIVE

To determine serum concentrations of 10 OCs (including organochlorine pesticides and polychlorinated biphenyls -PCBs-) in children living in agricultural communities from Almería (South-Eastern Spain), and to identify the main predictors of exposure related to socio-economic characteristics, diet and lifestyle.

METHODS

A cross-sectional study was conducted on 133 children aged 6-11 years selected from public schools of the study area. OCs compounds were determined in serum samples by GC/ECD. Anthropometric measures were obtained during sample collection. Information on sociodemographic characteristics, parental occupation, residential history, lifestyle and frequency of food consumption, among other relevant factors, was obtained by questionnaires administered to the mothers.

RESULTS

Geometric means of serum concentrations (ng/ml) were 0.11 for β-hexachloro-cyclohexane (β-HCH), 0.09 for endosulfan, 0.20 for endosulfan-ether, 0.51 for hexachorobenzene (HCB), 0.08 for mirex, 0.06 for oxychlordane, 0.36 for p,p'-DDE, 0.20 for PCB 138, 0.36 for PCB 153, and 0.45 for PCB 180. Percentage of samples above the limit of detection (0.05 ppb) ranged from 32 (β-HCH) to 100 (HCB). A high variability in OC levels depending on the compound was observed between our results and others found in similar studies carried out in children. Variables related to fish consumption were found to be the major dietary determinant of PCB 138, p,p´-DDE, endosulfan-α, β-HCH, mirex and oxychlordane levels.

CONCLUSIONS

Children participating in this study showed detectable levels of many OC, despite these compounds are no longer used. Their presence in children serum can be explained by their high lipophilicity and environmental persistence, leading to contamination of fatty food. In this line, fish consumption seemed to be the most relevant determinant of OC levels found in our study.

Life cycle of PCBs and contamination of the environment and of food products from animal origin

This report gives a summary of the historic use, former management and current release of polychlorinated biphenyls (PCBs) in Germany and assesses the impact of the life cycle of PCBs on the contamination of the environment and of food products of animal origin. In Germany 60,000 t of PCBs were used in transformers, capacitors or as hydraulic oils. The use of PCB oils in these "closed applications", has been banned in Germany in 2000. Thirty to 50% of these PCBs were not appropriately managed. In West Germany, 24,000 t of PCBs were used in open applications, mainly as additive (plasticiser, flame retardant) in sealants and paints in buildings and other construction. The continued use in open applications has not been banned, and in 2013, an estimated more than 12,000 t of PCBs were still present in buildings and other constructions. These open PCB applications continuously emit PCBs into the environment with an estimated release of 7-12 t per year. This amount is in agreement with deposition measurements (estimated to 18 t) and emission estimates for Switzerland. The atmospheric PCB releases still have an relevant impact on vegetation and livestock feed. In addition, PCBs in open applications on farms are still a sources of contamination for farmed animals. Furthermore, the historic production, use, recycling and disposal of PCBs have contaminated soils along the lifecycle. This legacy of contaminated soils and contaminated feed, individually or collectively, can lead to exceedance of maximum levels in food products from animals. In beef and chicken, soil levels of 5 ng PCB-TEQ/kg and for chicken with high soil exposure even 2 ng PCB-TEQ/kg can lead to exceedance of EU limits in meat and eggs. Areas at and around industries having produced or used or managed PCBs, or facilities and areas where PCBs were disposed need to be assessed in respect to potential contamination of food-producing animals. For a large share of impacted land, management measures applicable on farm level might be sufficient to continue with food production. Open PCB applications need to be inventoried and better managed. Other persistent and toxic chemicals used as alternatives to PCBs, e.g. short chain chlorinated paraffins (SCCPs), should be assessed in the life cycle for exposure of food-producing animals and humans.

Atropisomers of 2,2',3,3',6,6'-hexachlorobiphenyl (PCB 136) exhibit stereoselective effects on activation of nuclear receptors in vitro

PCB 136 is an environmentally relevant chiral PCB congener, which has been found in vivo to be present in form of rotational isomers (atropisomers). Its atropselective biotransformation or neurotoxic effects linked with sensitization of ryanodine receptor suggest that it might interact also with other intracellular receptors in a stereospecific manner. However, possible atropselective effects of PCB 136 on nuclear receptor transactivation remain unknown. Therefore, in this study, atropselective effects of PCB 136 on nuclear receptors controlling endocrine signaling and/or expression of xenobiotic and steroid hormone catabolism were investigated. PCB136 atropisomers were found to exert differential effects on estrogen receptor (ER) activation; (+)-PCB 136 was estrogenic, while (-)-PCB 136 was antiestrogenic. In contrast, inhibition of androgen receptor (AR) activity was not stereospecific. Both PCB136 stereoisomers induced the constitutive androgen receptor (CAR)-dependent gene expression; however, no significant stereospecificity of PCB 136 atropisomers was observed. PCB136 was a partial inducer of the pregnane X receptor (PXR)-dependent gene expression. Here, (-)-PCB 136 was a significantly more potent inducer of PXR activity than (+)-PCB 136. Taken together, the present results indicate that at least two nuclear receptors participating in endocrine regulation or metabolism, ER and PXR, could be regulated in an atropselective manner by chiral PCB 136. The enantioselective enrichment of PCB atropisomers in animal and human tissues may thus have significant consequences for endocrine-disrupting effects of chiral ortho-substituted PCB congeners.

Monitoring OH-PCBs in PCB transport worker's urine as a non-invasive exposure assessment tool

In this study, we analyzed hydroxylated polychlorinated biphenyls (OH-PCBs) in urine of both PCB transport workers and PCB researchers. A method to monitor OH-PCB in urine was developed. Urine was solid-phase extracted with 0.1% ammonia/ methanol (v/v) and glucuronic acid/sulfate conjugates and then decomposed using β-glucuronidase/arylsulfatase. After alkaline digestion/derivatization, the concentration of OH-PCBs was determined by HRGC/HRMS-SIM. In the first sampling campaign, the worker's OH-PCB levels increased several fold after the PCB waste transportation work, indicating exposure to PCBs. The concentration of OH-PCBs in PCB transport workers' urine (0.55~11 μg/g creatinine (Cre)) was higher than in PCB researchers' urine (< 0.20 μg/g Cre). However, also a slight increase of OH-PCBs was observed in the researchers doing the air sampling at PCB storage area. In the second sampling, after recommended PCB exposure reduction measures had been enacted, the worker's PCB levels did not increase during handling of PCB equipment. This suggests that applied safety measures improved the situation. Hydroxylated trichlorobiphenyls (OH-TrCBs) were identified as a major homolog of OH-PCBs in urine. Also, hydroxylated tetrachlorobiphenyls (OH-TeCBs) to hydroxylated hexachlorobiphenyls (OH-HxCBs) were detected. For the sum of ten selected major indicators, a strong correlation to total OH-PCBs were found and these can possibly be used as non-invasive biomarkers of PCB exposure in workers managing PCB capacitors and transformer oils. We suggest that monitoring of OH-PCBs in PCB management projects could be considered a non-invasive way to detect exposure. It could also be used as a tool to assess and improve PCB management. This is highly relevant considering the fact that in the next 10 years, approx. 14 million tons of PCB waste need to be managed. Also, the selected populations could be screened to assess whether exposure at work, school, or home has taken place.

Emissions of Tetrachlorobiphenyls (PCBs 47, 51, and 68) from Polymer Resin on Kitchen Cabinets as a Non-Aroclor Source to Residential Air

Both Aroclor and non-Aroclor sources of airborne polychlorinated biphenyls (PCBs) were found in residential homes. We deployed passive air samplers at 16 residences and found PCB-47, PCB-51, and PCB-68 to account for up to 50% of measured indoor ΣPCBs (2700 pg m-3). Although PCB-47 and PCB-51 are neurotoxins present in Aroclor mixtures (<2.5 and <0.3 wt %, respectively), we found them at much higher levels than expected for any Aroclor source. PCB-68 is not present in Aroclor mixtures. Another non-Aroclor congener, PCB-11, a byproduct of pigment manufacturing, was found inside and outside of every household and was frequently the predominate congener. We conducted direct measurements of surface emissions and identified finished cabinetry to be a major source of PCB-47, PCB-51, and PCB-68. We hypothesize that these congeners are inadvertent byproducts of polymer sealant manufacturing and produced from the decomposition of 2,4-dichlorobenzoyl peroxide used as an initiator in free-radical polymerization of polyester resins. The presence of these three compounds in polymer products, such as silicone, has been widely noted, but to our knowledge they have never been shown to be a significant environmental source of PCBs.

Effects of exposure to polychlorinated biphenyls during different periods of development on ethanol consumption by male and female rats

In two experiments, male and female Sprague-Dawley rats were exposed to Polychlorinated Biphenyls (PCBs) to assess the effect PCBs, an estrogenic endocrine disrupting chemical (EEDC), would have on the voluntary consumption of alcohol. There are several EEDCs in our food that are known to increase estrogen in adolescent females. Our objective was to assess the effect that increasing estrogen, by adding the EEDC PCBs would have on volitional intake of alcohol. In Experiment 1, pregnant dams were exposed from gestational days 5-19 to a 1:1 mixture of Aroclor 1254/1260. In Experiment 2, lactating females were exposed to the same dose of 1254:1260 from postnatal days 1-21. In both experiments, a fade-in procedure was used to gradually introduce the rats to the taste of alcohol. At the end of the fade-in series all animals were given limited access (1 h/day) to a water/alcohol solution. We found that females exposed to PCBs, at two developmental periods, consumed significantly more alcohol than unexposed females and exposed and unexposed males. Results of the experiments are discussed in terms of how PCB exposure can disrupt endocrine processes (e.g., estrogenic endocrine disrupting chemicals, EEDC) that increase estrogen in females, thereby leading to increased alcohol consumption. Thus, the present findings suggest that EEDCs, such as PCBs, could contribute to the increase abuse of alcohol in adolescent females.

Mono-, di-, and trichlorinated biphenyls (PCB 1-PCB 39) in the indoor air of office rooms and their relevance on human blood burden

Exposure to polychlorinated biphenyls (PCBs) from indoor air can lead to a significant increase in lower chlorinated congeners in human blood. Lower chlorinated congeners with short biological half-lives can exhibit an indirect genotoxic potential via their highly reactive metabolites. However, little is known about their occurrence in indoor air and, therefore, about the effects of possible exposure to these congeners. We analyzed all mono-, di-, and trichlorinated biphenyls in the indoor air of 35 contaminated offices, as well as in the blood of the 35 individuals worked in these offices for a minimum of 2 years. The median concentration of total PCB in the indoor air was 479 ng/m³ . The most prevalent PCBs in the indoor air samples were the trichlorinated congeners PCB 31, PCB 18, and PCB 28, with median levels of 39, 31, and 26 ng/m³ , respectively. PCB 8 was the most prevalent dichlorinated congener (median: 9.1 ng/m³ ). Monochlorinated biphenyls were not detected in relevant concentrations. In the blood samples, the most abundant congener was PCB 28; nearly 90% of all mono-, di-, and trichlorinated congeners were attributed to this congener (median: 12 ng/g blood lipid).