Gestational Exposure to Common Endocrine Disrupting Chemicals and Their Impact on Neurodevelopment and Behavior.

Endocrine disrupting chemicals are common in our environment and act on hormone systems and signaling pathways to alter physiological homeostasis. Gestational exposure can disrupt developmental programs, permanently altering tissues with impacts lasting into adulthood. The brain is a critical target for developmental endocrine disruption, resulting in altered neuroendocrine control of hormonal signaling, altered neurotransmitter control of nervous system function, and fundamental changes in behaviors such as learning, memory, and social interactions. Human cohort studies reveal correlations between maternal/fetal exposure to endocrine disruptors and incidence of neurodevelopmental disorders. Here, we summarize the major literature findings of endocrine disruption of neurodevelopment and concomitant changes in behavior by four major endocrine disruptor classes:bisphenol A, polychlorinated biphenyls, organophosphates, and polybrominated diphenyl ethers. We specifically review studies of gestational and/or lactational exposure to understand the effects of early life exposure to these compounds and summarize animal studies that help explain human correlative data.

Metabolic Profiles of Tetrabromobisphenol A in Humans Extrapolated from Humanized-Liver Mouse Data Using a Simplified Physiologically Based Pharmacokinetic Model.

Tetrabromobisphenol A, a brominated flame retardant, is increasingly prevalent worldwide and presents a potential health risk. Adjusted animal biomonitoring equivalents of tetrabromobisphenol A after orally administered doses in humanized-liver mice were scaled up to humans using known species allometric scaling factors to set up simplified physiologically based pharmacokinetic (PBPK) models. Absorbed tetrabromobisphenol A was slightly, moderately, and extensively metabolized in vivo to its glucuronide in rats, control mice, and humanized-liver mice tested, respectively. In silico estimated hepatic exposures of tetrabromobisphenol A and its glucuronide generated using the rat PBPK model-generated plasma concentration profiles were consistent with the reported values. The extent of hepatic injury in humanized-liver mice caused by tetrabromobisphenol A was evaluated by detecting human albumin mRNA in mouse plasma after oral administration of a high dose of tetrabromobisphenol A (1000 mg/kg). Reverse dosimetry analyses were carried out using two human PBPK models (set up based on the humanized-liver-mouse model and by optimizing the input parameters for reported human plasma concentrations of tetrabromobisphenol A glucuronide) to estimate the tetrabromobisphenol A daily intake based on reported human serum concentrations of total tetrabromobisphenol A from biomonitoring data. Within the predictability of the forward and reverse dosimetry estimations, the calculated daily intake was found to be far below established health benchmark levels (i.e., the suggested daily reported reference dose) with a wide (4 orders of magnitude) safety margin. These results suggest that the simplified PBPK models can be successfully applied to forward and reverse dosimetry estimations of tissue and/or blood exposures of tetrabromobisphenol A in humans after oral doses.

Tetrabromobisphenol A Disturbs Brain Development in Both Thyroid Hormone-Dependent and -Independent Manners in Xenopus laevis.

Although tetrabromobisphenol A (TBBPA) has been well proven to disturb TH signaling in both in vitro and in vivo assays, it is still unclear whether TBBPA can affect brain development due to TH signaling disruption. Here, we employed the T3-induced Xenopus metamorphosis assay (TIXMA) and the spontaneous metamorphosis assay to address this issue. In the TIXMA, 5-500 nmol/L TBBPA affected T3-induced TH-response gene expression and T3-induced brain development (brain morphological changes, cell proliferation, and neurodifferentiation) at premetamorphic stages in a complicated biphasic concentration-response manner. Notably, 500 nmol/L TBBPA treatment alone exerted a stimulatory effect on tadpole growth and brain development at these stages, in parallel with a lack of TH signaling activation, suggesting the involvement of other signaling pathways. As expected, at the metamorphic climax, we observed inhibitory effects of 50-500 nmol/L TBBPA on metamorphic development and brain development, which was in agreement with the antagonistic effects of higher concentrations on T3-induced brain development at premetamorphic stages. Taken together, all results demonstrate that TBBPA can disturb TH signaling and subsequently interfere with TH-dependent brain development in Xenopus; meanwhile, other signaling pathways besides TH signaling could be involved in this process. Our study improves the understanding of the effects of TBBPA on vertebrate brain development.

Developmental Exposure to the Flame Retardant Mixture Firemaster 550 Compromises Adult Bone Integrity in Male but not Female Rats.

Flame retardants (FRs) are used in a variety of common items from furniture to carpet to electronics to reduce flammability and combustion, but the potential toxicity of these compounds is raising health concerns globally. Organophosphate FRs (OPFRs) are becoming more prevalent as older, brominated FRs are phased out, but the toxicity of these compounds, and the FR mixtures that contain them, is poorly understood. Work in a variety of in vitro model systems has suggested that FRs may induce metabolic reprogramming such that bone density is compromised at the expense of increasing adiposity. To address this hypothesis, the present studies maternally exposed Wistar rat dams orally across gestation and lactation to 1000 µg daily of the FR mixture Firemaster 550 (FM 550) which contains a mixture of brominated FRs and OPFRs. At six months of age, the offspring of both sexes were examined for evidence of compromised bone composition. Bone density, composition, and marrow were all significantly affected, but only in males. The fact that the phenotype was observed months after exposure suggests that FM 550 altered some fundamental aspect of mesenchymal stem cell reprogramming. The severity of the phenotype and the human-relevance of the dose employed, affirm this is an adverse outcome meriting further exploration.

Evaluation of the Effect of Selected Brominated Flame Retardants on Human Serum Albumin and Human Erythrocyte Membrane Proteins.

Brominated flame retardants (BFRs) have been using to reduce the flammability of plastics contained in many products, such as household articles, furniture, mattresses, textiles or insulation. Considering the fact that these compounds may be released into the environment leading to the exposure of living organisms, it is necessary to study their possible effects and mechanisms of action. Proteins play a crucial role in all biological processes. For this reason, a simple model of human serum albumin (HSA) was chosen to study the mechanism of BFRs' effect on proteins. The study determined interactions between selected BFRs, i.e., tetrabromobisphenol A (TBBPA), tetrabromobisphenol S (TBBPS), 2,4-dibromophenol (2,4-DBP), 2,4,6-tribromophenol (2,4,6-TBP) and pentabromophenol (PBP), and HSA by measurement of fluorescence of intrinsic tryptophan and absorbance of circular dichroism (CD). In addition, in order to understand the possible effect of these compounds in their native environment, the effect of BFRs on membrane proteins of human erythrocytes (red blood cells, RBCs) was also assessed. Among bromophenols, PBP had the strongest oxidative effect on RBC membrane, and 2,4-DBP demonstrated the weakest fluorescence-quenching effect of both membrane tryptophan and HSA. By contrast to PBP, 2,4-DBP and 2,4,6-TBP caused spatial changes of HSA. We have observed that among all analyzed BFRs, TBBPA caused the strongest oxidation of RBC membrane proteins and the model HSA protein, causing reduction of fluorescence of tryptophan contained in them. TBBPA also changed albumin conformation properties, leading to impairment of the α-helix structure. However, TBBPS had the weakest oxidative effect on proteins among studied BFRs and did not affect the secondary structure of HSA.

Effects of tetrabromobisphenol A on maize (Zea mays L.) physiological indexes, soil enzyme activity, and soil microbial biomass.

TetrabromobisphenolA (TBBPA) is the most widely used brominated flame retardant, and it has the characteristics of persistent organic pollutants (POPs), attracting considerable attention. Many studies mainly focus on TBBPA toxicological effects in aquatic animals and rodents, but the ecotoxicology data of TBBPA on plant-soil system are limited so far. In this study, we assessed the impacts of TBBPA on maize (Zea mays L.) physiological indexes, soil enzyme activity, and soil microbial biomass at different concentrations of TBBPA (0, 0.75, 3.75, 7.5, 15, 37.5 and 75 mg·kg-1) and explored their relationships. Results showed that the maize physiological indexes and chlorophyll contents were significantly decreased by TBBPA, the activities of anti-oxidative enzymes including catalase (CAT), peroxidase (POD) and polyphenol oxidase (PPO) and the contents of malondialdehyde (MDA) were remarkably enhanced. Meanwhile, TBBPA activated the CAT, POD and PPO activities in soil. The low concentrations TBBPA promoted the activities of soil urease (S-UE), neutral phosphatase (S-PE) and increased the soil microbial biomass carbon (SMBC) and nitrogen (SMBN) while the high concentrations TBBPA suppressed them. Notably, the data indicated microbial biomass had respectively a significant correlation with CAT, PPO and S-UE in soil in the presence of TBBPA, and maize chlorophyll contents were associated with SMBN, CAT, and PPO. Taken together, TBBPA caused soil pollution, affected soil enzyme activities and microbial biomass, and hindered maize growth under the current experimental condition, suggesting the interactions among maize growth, soil enzyme, soil microorganism in maize rhizosphere of TBBPA-polluted soils are very important aspects to comprehensively evaluate the ecotoxicological effects of TBBPA.

[Tetrabromobisphenol A - Toxicity, environmental and occupational exposures]. / Tetrabromobisfenol A ­ toksycznosc, narazenie srodowiskowe i zawodowe.

Brominated flame retardants (BFR), including tetrabromobisphenol A (TBBPA) represents 25% of the global market of flame retardants. Among them, TBBPA is used on the largest scale (approx. 60%) because of its firebreak properties and widespread occurrence in every day products such as furniture, upholstery, adhesives and electronic equipment. A broad application of TBBPA can contribute to environmental pollution. Tetrabromobisphenol A has been determined in soil, water, river sediments and the atmosphere. Tetrabromobisphenol A is characterized by a high value of coefficient n-octanol/water (log P = 4.5), low acidity, and it may exist in undissociated or dissociated form. Due to the high hydrophobicity, TBBPA may accumulate in living organisms, including humans at different food chain levels. The occurrence of TBBPA in humans, e.g., in blood, fat tissue and mother milk, has been reported. Tetrabromobisphenol A is classified as hazard statements (H) H400/H410, which means that it is toxic to aquatic biota, causing long-term changes in these organisms. Up to now, only a few studies have been conducted to assess potential toxicity of high doses of TBBPA to mammals. Although many people are occupationally exposed to TBBPA during production or processing of this substance in their workplaces, there are only a few studies that have assessed the real hazard associated with TBPPA exposure. The aim of the study was to discuss the latest literature (mainly from the years 2010-2016) referring to the presence of TBBPA in the environment and its effects to living organisms. Data concerning occupational exposure to TBBPA were also presented. Med Pr 2017;68(1):121-134.

Breast cancer among women in Michigan following exposure to brominated flame retardants.

In this updated follow-up, we investigated the breast cancer experience among women in Michigan exposed to brominated flame retardants, some 30 years following exposure. Michigan residents were enrolled in a study cohort after exposure to polybrominated biphenyls (PBBs) through the consumption of contaminated food products. PBB concentrations were measured in serum at the time of enrolment. Cancer experience was determined by linkage to the Michigan Cancer Registry. We conducted a nested case-control study that included 51 women diagnosed with breast cancer during 1974-2004 and 202 age-matched controls. While the data suggest an increase in breast cancer risk with higher PBB exposure, this did not reach statistical significance. The OR of having breast cancer among women with PBB concentrations ≥10 ng/mL compared to women with PBB concentrations at or below the limit of detection of 1 ng/mL was 2.60, 95% CI 0.93 to 7.27, (p=0.07), when adjusted for age and family history of cancer in a first-degree female relative. It remains important to examine exposure to brominated chemicals and possible health effects, and to continue following the cancer experience of participants in this study.

Long-lived epigenetic interactions between perinatal PBDE exposure and Mecp2308 mutation.

The widespread use of persistent organic polybrominated diphenyl ethers (PBDEs) as commercial flame retardants has raised concern about potential long-lived effects on human health. Epigenetic mechanisms, such as DNA methylation, are responsive to environmental influences and have long-lasting consequences. Autism spectrum disorders (ASDs) have complex neurodevelopmental origins whereby both genetic and environmental factors are implicated. Rett syndrome is an X-linked ASD caused by mutations in the epigenetic factor methyl-CpG binding protein 2 (MECP2). In this study, an Mecp2 truncation mutant mouse (Mecp2(308)) with social behavioral defects was used to explore the long-lasting effects of PBDE exposure in a genetically and epigenetically susceptible model. Mecp2(308/+) dams were perinatally exposed daily to 2,2',4,4'-tetrabromodiphenyl ether 47 (BDE-47) and bred to wild-type C57BL/6J males, and the offspring of each sex and genotype were examined for developmental, behavioral and epigenetic outcomes. Perinatal BDE-47 exposure negatively impacted fertility of Mecp2(308/+) dams and preweaning weights of females. Global hypomethylation of adult brain DNA was observed specifically in female offspring perinatally exposed to BDE-47 and it coincided with reduced sociability in a genotype-independent manner. A reversing interaction of Mecp2 genotype on BDE-47 exposure was observed in a short-term memory test of social novelty that corresponded to increased Dnmt3a levels specifically in BDE-47-exposed Mecp2(308/+) offspring. In contrast, learning and long-term memory in the Morris water maze was impaired by BDE-47 exposure in female Mecp2(308/+) offspring. These results demonstrate that a genetic and environmental interaction relevant to social and cognitive behaviors shows sexual dimorphism, epigenetic dysregulation, compensatory molecular mechanisms and specific behavioral deficits.

In-utero exposure to polybrominated biphenyl (PBB) and menstrual cycle function in adulthood.

BACKGROUND: There is evidence that in-utero exposure to PBBs, and similar chemicals, are associated with several adverse reproductive health outcomes including altered pubertal timing. However, less is known about the effects of in-utero exposure to PBBs on menstrual cycle function and reproductive hormone levels in adulthood. METHODS: For this menstrual cycle study, we recruited reproductive-aged women in the Michigan PBB Registry who were not pregnant, lactating, or taking hormonal medications (2004-2014). A total of 41 women who were born after the PBB contamination incident (1973-1974) and were prenatally exposed to PBBs, were included in this analysis. We estimated in-utero PBB exposure using maternal serum PBB measurements taken after exposure and extrapolated to time of pregnancy using a PBB elimination model. Women were followed for up to 6 months during which they provided daily urine samples and completed daily diaries. The urine samples were assayed for estrone 3-glucuronide (E13G), pregnanediol 3-glucuronide (Pd3G), and follicle stimulating hormone (FSH). RESULTS: Women in our study were, on average, 27.5 (SD:5.3) years old and contributed 4.9 (SD:1.9) menstrual cycles of follow-up. Compared to women with low in-utero PBB exposure (≤1 ppb), women with medium (>1.0-3.0 ppb) and high (>3.0 ppb) exposure had higher maximum 3-day mean Pd3G levels during the luteal phase. Specifically, the age- and creatinine-adjusted maximum 3-day mean luteal phase Pd3G levels (95% CI) in increasing categories of in-utero PBB exposure were 9.2 (4.6,13.9), 14.8 (11.6,18.0), and 16.1 (12.9,19.3) µg/mg creatinine. There were no meaningful differences in average cycle length, follicular or luteal phase cycle length, bleed length, or creatinine-adjusted E13G or FSH levels by category of in-utero PBB exposure. CONCLUSION: Higher exposure to PBB in-utero was associated with increased progesterone levels across the luteal phase, however, most other menstrual cycle characteristics were largely unassociated with in-utero PBB exposure. Given our modest sample size, our results require cautious interpretation.

Association of prenatal exposure to polybrominated diphenyl ethers and infant birth weight.

Polybrominated diphenyl ethers (PBDEs) are a class of persistent compounds that have been used as flame retardants in vehicles, household furnishings, and consumer electronics. This study examined whether concentrations of PBDEs in maternal serum during pregnancy were associated with infant birth weight, length, head circumference, and length of gestation. Participants were pregnant women (n = 286) enrolled in the Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS) Study, a longitudinal cohort study of low-income, predominantly Mexican families living in the Salinas Valley, California. Blood samples were collected near the 26th week of pregnancy in 1999-2000, and concentrations of 10 PBDE congeners (BDE-17, -28, -47, -66, -85, -99, -100, -153, -154, and -183) were measured. Multiple linear regression models were used to investigate the association of lipid-adjusted, log(10)-transformed PBDE concentrations and birth outcome. In adjusted analyses, negative associations with birth weight were seen with BDE-47 (ß = -115 g, 95% confidence interval (CI): -229, -2), BDE-99 (ß = -114 g, 95% CI: -225, -4), and BDE-100 (ß = -122 g, 95% CI: -235, -9). These findings were diminished slightly and were no longer statistically significant when maternal weight gain was included in the models. PBDE congeners were not associated with birth length, head circumference, or gestational duration.

Likelihood-based methods for estimating the association between a health outcome and left- or interval-censored longitudinal exposure data.

The Michigan Female Health Study (MFHS) conducted research focusing on reproductive health outcomes among women exposed to polybrominated biphenyls (PBBs). In the work presented here, the available longitudinal serum PBB exposure measurements are used to obtain predictions of PBB exposure for specific time points of interest via random effects models. In a two-stage approach, a prediction of the PBB exposure is obtained and then used in a second-stage health outcome model. This paper illustrates how a unified approach, which links the exposure and outcome in a joint model, provides an efficient adjustment for covariate measurement error. We compare the use of empirical Bayes predictions in the two-stage approach with results from a joint modeling approach, with and without an adjustment for left- and interval-censored data. The unified approach with the adjustment for left- and interval-censored data resulted in little bias and near-nominal confidence interval coverage in both the logistic and linear model setting.

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

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

Effects of brominated and organophosphate ester flame retardants on male reproduction.

BACKGROUND: Environmental chemicals that interfere with the production and/or action of hormones may have adverse effects on male reproduction. This review focuses on the possible impact of exposure to flame retardant chemicals on male reproduction. Flame retardants are added to a wide variety of combustible materials to prevent fires from starting, slow their spread, and provide time to escape. However, these chemicals are often additive so they leach out into the environment. Governments have restricted the use of polybrominated diphenyl ether flame retardants based on evidence that they are persistent and bioaccumulate and have adverse effects on health. The phasing out of these "legacy" flame retardants has resulted in their replacement with alternatives, such as tetrabromobisphenol A and the organophosphate esters. OBJECTIVE: To review the literature on the effects of brominated and organophosphate ester flame retardant chemicals on male reproduction. METHODS: PubMed database was searched for studies reporting the effects of brominated and organophosphate ester flame retardants on male reproduction. RESULTS: Cell-based, animal model, and human studies provide evidence that the polybrominated diphenyl ethers act as endocrine-disrupting chemicals; further, exposure during critical windows of development may be associated with a permanent impact on male reproduction. In vitro and animal model data are accumulating with respect to the effects of tetrabromobisphenol A and organophosphate esters, but few studies have evaluated their impact on human health. CONCLUSIONS: More research on human exposure to replacement flame retardants and the possibility that they may be associated with adverse reproductive health outcomes is a high priority.

Detrimental effects of flame retardant, PBB153, exposure on sperm and future generations.

In 1973, the Velsicol Chemical Company, which manufactured FireMaster, a brominated flame retardant, and NutriMaster, a nutritional supplement, mistakenly shipped hundreds of pounds of FireMaster to grain mills around Michigan where it was incorporated into animal feed and then into the food chain across the state. An estimated 6.5 million Michigan residents consumed polybrominated biphenyl (PBB)-laced animal products leading to one of the largest agricultural accidents in U.S. history. To date, there have been no studies investigating the effects of PBB on epigenetic regulation in sperm, which could explain some of the endocrine-related health effects observed among children of PBB-exposed parents. Fusing epidemiological approaches with a novel in vitro model of human spermatogenesis, we demonstrate that exposure to PBB153, the primary component of FireMaster, alters the epigenome in human spermatogenic cells. Using our novel stem cell-based spermatogenesis model, we show that PBB153 exposure decreases DNA methylation at regulatory elements controlling imprinted genes. Furthermore, PBB153 affects DNA methylation by reducing de novo DNA methyltransferase activity at increasing PBB153 concentrations as well as reducing maintenance DNA methyltransferase activity at the lowest tested PBB153 concentration. Additionally, PBB153 exposure alters the expression of genes critical to proper human development. Taken together, these results suggest that PBB153 exposure alters the epigenome by disrupting methyltransferase activity leading to defects in imprint establishment causing altered gene expression, which could contribute to health concerns in the children of men exposed to PBB153. While this chemical is toxic to those directly exposed, the results from this study indicate that the epigenetic repercussions may be detrimental to future generations. Above all, this model may be expanded to model a multitude of environmental exposures to elucidate the effect of various chemicals on germline epigenetics and how paternal exposure may impact the health of future generations.

Fathoming the link between anthropogenic chemical contamination and thyroid cancer.

Incidence and mortality of thyroid cancer are increasing, thus making mandatory to improve the knowledge of disease etiology. The hypothesis of a role for anthropogenic chemicals is raising wide consideration. A series of occupational studies revealed that job exposures with high risk of chemical contamination were usually more prone to thyroid cancer development. These include shoe manufacture, preserving industry, building activities, pulp/papermaker industry and the wood processing, agricultural activities, and other work categories characterized by contact with chemicals, such as chemists and pharmacists. However, such epidemiological analyses cannot define a causal relationship. Thyroid-disrupting activity has emerged for a broad set of anthropogenic chemicals, with the best evidence being gained for polychlorinated biphenyls, polybrominated diphenyl ethers, dioxins, bisphenols, phthalates, pesticides, and heavy metals. A series of case-control studies, assessing exposure to thyroid-disrupting agents, as measured on biological matrices, have been recently performed providing the following insights: a) positive relationship with thyroid cancer was found for phthalates, bisphenols, the heavy metals cadmium, copper, and lead; b) polybrominated diphenyl ethers exposure showed no relationship with thyroid cancer c) controversial results were reported for polychlorinated biphenyls and pesticides. However, such studies cannot demonstrate the causal link with disease occurrence, as exposure is assessed after tumour development. Studies with different methodological approach are therefore required for defining the role of anthropogenic environmental chemicals in thyroid carcinogenesis.

Memory performance of chemical workers exposed to polybrominated biphenyls.

Twenty-five chemical workers who manufactured polybrominated biphenyls (PBB's) were given objective tests of learning and memory. Although this group had high concentrations of PBB's in adipose tissue, mean scores on all memory tests were normal. The PBB concentration was not correlated with memory performance; the most contaminated workers showed no evidence of memory dysfunction.

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

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