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

Upregulation of Fatty Acid Synthesis Genes in the Livers of Adolescent Female Rats Caused by Inhalation Exposure to PCB52 (2,2',5,5'-Tetrachlorobiphenyl)

Elevated airborne PCB levels in older schools are concerning due to their health impacts, including cancer, metabolic dysfunction-associated steatotic liver disease (MASLD), cardiovascular issues, neurodevelopmental diseases, and diabetes. During a four-week inhalation exposure to PCB52, an air pollutant commonly found in school environments, adolescent rats exhibited notable presence of PCB52 and its hydroxylated forms in their livers, alongside changes in gene expression. Female rats exhibited more pronounced changes in gene expression compared to males, particularly in fatty acid synthesis genes regulated by the transcription factor SREBP1. In vitro studies with human liver cells showed that the hydroxylated metabolite of PCB52, 4-OH-PCB52, but not the parent compound, upregulated genes involved in fatty acid biosynthesis similar to in vivo exposure. These findings highlight the sex-specific effects of PCB52 exposure on livers, particularly in females, suggesting a potential pathway for increased MASLD susceptibility.

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.

Use of a polymeric implant system to assess the neurotoxicity of subacute exposure to 2,2',5,5'-tetrachlorobiphenyl-4-ol, a human metabolite of PCB 52, in male adolescent rats

Polychlorinated biphenyls (PCBs) are persistent organic pollutants (POPs) that ubiquitously exist in the environment. PCB exposure has been linked to cancer and multi-system toxicity, including endocrine disruption, immune inhibition, and reproductive and neurotoxicity. 2,2',5,5'-Tetrachlorobiphenyl (PCB 52) is one of the most frequently detected congeners in the environment and human blood. The hydroxylated metabolites of PCB 52 may also be neurotoxic, especially for children whose brains are still developing. However, it is challenging to discern the contribution of these metabolites to PCB neurotoxicity because the metabolism of PCB is species-dependent. In this study, we evaluated the subacute neurotoxicity of a human-relevant metabolite, 2,2',5,5'-tetrachlorobiphenyl-4-ol (4-52), on male adolescent Sprague Dawley rats, via a novel polymeric implant drug delivery system grafted subcutaneously, at total loading concentrations ranging from 0%, 1%, 5%, and 10% of the implant (w/w) for 28 days. Y-maze, hole board test, open field test, and elevated plus maze were performed on exposure days 24-28 to assess their locomotor activity, and exploratory and anxiety-like behavior. 4-52 and other possible hydroxylated metabolites in serum and vital tissues were quantified using gas chromatography with tandem mass spectrometry (GC-MS/MS). Our results demonstrate the sustained release of 4-52 from the polymeric implants into the systemic circulation in serum and tissues. Dihydroxylated and dechlorinated metabolites were detected in serum and tissues, depending on the dose and tissue type. No statistically significant changes were observed in the neurobehavioral tasks across all exposure groups. The results demonstrate that subcutaneous polymeric implants provide a straightforward method to expose rats to phenolic PCB metabolites to study neurotoxic outcomes, e.g., in memory, anxiety, and exploratory behaviors.

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.

Liquid crystal monomers in ventilation and air conditioning dust: Indoor characteristics, sources analysis and toxicity assessment

Indoor dust contaminated with liquid crystal monomers (LCMs) released from various commercial liquid crystal display (LCD) screens may pose environmental health risks to humans. This study aimed to investigate the occurrence of 64 LCMs in ventilation and air conditioning filters (VACF) dust, characterize their composition profiles, potential sources, and associations with indoor characteristics, and assess their in vitro toxicity using the human lung bronchial epithelial cells (BEAS-2B). A total of 31 LCMs with concentrations (ΣLCMs) ranging from 43.7 ng/g to 448 ng/g were detected in the collected VACF dust. Additional analysis revealed the potential interactions between indoor environmental conditions and human exposure risks associated with the detected LCMs in VACF dust. The service area and working time of the ventilation and air conditioning system, and the number of indoor LCD screens were positively correlated with the fluorinated ΣLCMs in VACF dust (r = 0.355 ∼ 0.511, p < 0.05), while the associations with the non-fluorinated ΣLCMs were not found (p > 0.05), suggesting different environmental behavior and fates of fluorinated and non-fluorinated LCMs in the indoor environment. Four main indoor sources of LCMs (i.e., computer (37.1%), television (28.3%), Brand A smartphone (21.2%) and Brand S smartphone (13.4%)) were identified by positive matrix factorization-multiple linear regression (PMF-MLR). Exposure to 14 relatively frequently detected LCMs, individually and in the mixture, induced significant oxidative stress in BEAS-2B cells. Among them, non-fluorinated LCMs, specifically 3cH2B and MeP3bcH, caused dominant decreased cell viability. This study provides new insights into the indoor LCMs pollution and the associated potential health risks due to the daily use of electronic devices.

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.

Physical exercise and persistent organic pollutants

Exposure to the legacy and emerging persistent organic pollutants (POPs) incessantly has become an important threat to individual health, which is closely related to neurodevelopment, endocrine and cardiovascular homeostasis. Exercise, on the other hand, has been consistently shown to improve physical fitness. Whereas associations between traditional air pollutants, exercise and lung function have been thoroughly reviewed, reviews on associations between persistent organic pollutants and exercise are scarce. Hence, a literature review focused on exercise, exposure to POPs, and health risk assessment was performed for studies published from 2004 to 2022. The purpose of this review is to provide an overview of exposure pathways and levels of POPs during exercise, as well as the impact of exercise on health concerns attributable to the redistribution, metabolism, and excretion of POPs in vivo. Therein lies a broader array of exercise benefits, including insulin sensitizing, mitochondrial DNA repair, lipid metabolism and intestinal microecological balance. Physical exercise is conducive to reduce POPs body burden and resistant to health hazards of POPs generally. Besides, individual lipid metabolism condition is a critical factor in evaluating potential link in exercise, POPs and health effects.

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.

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.

Spatial distribution and ecological risks of polychlorinated biphenyls in a river basin affected by traditional and emerging electronic waste recycling in South China

With development of e-waste related legislation in China, formal recycling activities are designated in some areas while informal ones are illegally transferred to emerging areas to avoid supervision. However, the resulting environmental impact and ecological risks are not clear. Here, we investigated the discharge of polychlorinated biphenyls (PCBs) to soil and aquatic environments by e-waste recycling activities in the Lian River Basin, China. The study area included a designated industrial park in the traditional e-waste recycling area (Guiyu, known as the world's largest e-waste center), several emerging informal recycling zones, and their surrounding areas and coastal area. A total of 27 PCBs were analyzed, and the highest concentration was found in an emerging site for soil (354 ng g^-1) and in a traditional site for sediment (1350 ng g^--1) respectively. The pollution levels were significantly higher in both the traditional and emerging recycling areas than in their respective upstream countryside areas (p = 0.0356 and 0.0179, respectively). Source analysis revealed that the traditional and emerging areas had similar PCB sources mainly associated with three PCB technical mixtures manufactured in Japan (KC600) and the USA (Aroclor 1260 and Aroclor 1262). The PCB pollution in their downstream areas including the coastal area was evidently affected by the formal and informal recycling activities through river runoff. The ecological risk assessments showed that PCBs in soils and sediments in the Lian River Basin could cause adverse ecotoxicological consequences to humans and aquatic organisms.

Transcriptome sequencing of 3,3',4,4',5-Pentachlorobiphenyl (PCB126)-treated human preadipocytes demonstrates progressive changes in pathways associated with inflammation and diabetes

Polychlorinated biphenyls (PCBs) are persistent organic pollutants that accumulate in adipose tissue and have been associated with cardiometabolic disease. We have previously demonstrated that exposure of human preadipocytes to the dioxin-like PCB126 disrupts adipogenesis via the aryl hydrocarbon receptor (AhR). To further understand how PCB126 disrupts adipose tissue cells, we performed RNAseq analysis of PCB126-treated human preadipocytes over a 3-day time course. The most significant predicted upstream regulator affected by PCB126 exposure at the early time point of 9 h was the AhR. Progressive changes occurred in the number and magnitude of transcript levels of genes associated with inflammation, most closely fitting the pathways of cytokine-cytokine-receptor signaling and the AGE-RAGE diabetic complications pathway. Transcript levels of genes involved in the IL-17A, IL-1β, MAP kinase, and NF-κB signaling pathways were increasingly dysregulated by PCB126 over time. Our results illustrate the progressive time-dependent nature of transcriptional changes caused by toxicants such as PCB126, point to important pathways affected by PCB126 exposure, and provide a rich dataset for further studies to address how PCB126 and other AhR agonists disrupt preadipocyte function. These findings have implications for understanding how dioxin-like PCBs and other dioxin-like compounds are involved in the development of obesity and diabetes.

Polychlorinated Biphenyls and Pulmonary Hypertension

Polychlorinated biphenyls (PCBs) are persistent environmental pollutants that were banned because of their potential carcinogenicity. Population studies have shown that PCBs are associated with lung toxicity and hypertension. The objective of this study was to evaluate whether higher exposure to PCB congeners is associated with the risk of pulmonary hypertension. Serum levels of PCBs in 284 subjects with combined risk factors for pulmonary arterial hypertension (PAH) were compared to 4210 subjects with no risk for PAH using the National Health and Nutrition Examination Survey (NHANES) from 1999 to 2004. The major findings from this study include significantly higher PCB levels in PAH subjects compared to non-PAH subjects; for example, the geometric mean (GM) of PCB74 was 15.91 (ng/g) (14.45–17.53) vs. 11.48 (ng/g) (10.84–12.16), respectively. Serum levels of PCB congeners showed an increasing trend in the age group 20–59 years as PCB180 GM was 19.45 (ng/g) in PAH vs. 12.75 (ng/g) in the control. A higher body burden of PCB153 followed by PCB138, PCB180, and PCB118 was observed. Estimated age, race, BMI, and gender-adjusted ORs for PCB congener levels in subjects with the combined risk factors for PAH compared to controls was significant; for example, PCB99 (OR: 1.5 (CI: 1.49–1.50). In summary, these findings indicate that exposure, as well as body burden estimated based on lipid adjustment of PCBs, were higher in people with risk factors for PAH, and PCB congeners accumulated with age. These findings should be interpreted with caution because of the use of cross-sectional self-reported data and a small sample size of subjects with combined risk factors for pulmonary arterial hypertension. Nonetheless, our finding emphasizes a need for a comprehensive environmental molecular epidemiologic study to determine the potential role of environmental exposures to PCBs in the development of pulmonary arterial hypertension.

PCBs in indoor air and human blood in Pittsfield, Massachusetts

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

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 ∑₂₀₉PCB_{lipid 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.

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.

An Exploratory Study of the Relationships Between Diesel Engine Exhaust Particle Inhalation, Pulmonary Inflammation and Anxious Behavior

Recent technical developments brought negative side effects such as air pollution and large-scale fires, increasingly exposing people to diesel engine exhaust particles (DEP). Testing how DEP inhalation triggers pathophysiology in animal models could be useful in determining how it affects humans. To this end, the aim of this study was to investigate the effects of pulmonary exposure to DEP for seven consecutive days in experimental male C5BL6/N mice. Twenty-four C5BL6/N mice were treated with one of the three test materials: distilled water for control, a low DEP exposure (5 mg/kg), or a high DEP exposure (15 mg/kg). Exposure to DEP induced decreased body weight; however, it gradually increased pulmonary weight in a DEP-dose-dependent manner. DEP exposure significantly elevated soot accumulation in the lungs, with the alteration of pulmonary homeostasis. It also elevated infiltrated immune cells, thus significantly increasing inflammatory cytokine mRNA and protein production in the lungs and broncho-alveolar lavage fluid, respectively. Pulmonary DEP exposure also altered behavioral responses in the open field test (OFT). Low exposure elevated moving distance and speed, while significantly decreasing the number of trials to enter the central zone. Different concentrations of DEP resulted in different behavioral changes; however, while anxiety levels increased, their degree was independent of DEP concentrations. Results suggest that DEP exposure may possess pro-inflammatory responses in the lungs and trigger anxiety.