Deborah J. Watkins

Impact of dust from multiple microenvironments and diet on PentaBDE body burden

Our objectives were to determine relative contributions of diet and dust exposure from multiple microenvironments to PentaBDE body burden, and to explore the role of handwipes as a measure of personal exposure to PentaBDE. We administered a food frequency questionnaire and collected serum, dust (office, main living area, bedroom, and vehicle), and handwipe samples from 31 participants. ΣPentaBDEs (sum of BDE 28/33, 47, 99, 100, and 153) in handwipes collected in the office environment were weakly correlated with dust collected from offices (r = 0.35, p = 0.06) and bedrooms (r = 0.39, p = 0.04), but not with dust from main living areas (r = -0.05, p = 0.77) or vehicles (r = 0.17, p = 0.47). ΣPentaBDEs in serum were correlated with dust from main living areas (r = 0.42, p = 0.02) and bedrooms (r = 0.49, p = 0.008), but not with dust from offices (r = 0.22, p = 0.25) or vehicles (r = 0.20, p = 0.41). Our final regression model included variables for main living area dust and handwipes, and predicted 55% of the variation in serum ΣPentaBDE concentrations (p = 0.0004). Diet variables were not significant predictors of ΣPentaBDEs in serum. Our research suggests that exposure to dust in the home environment may be the most important factor in predicting PentaBDE body burden in North Americans, and potential exposure pathways may involve PBDE residues on hands.

Associations between urinary phenol and paraben concentrations and markers of oxidative stress and inflammation among pregnant women in Puerto Rico.

Phenols and parabens are used in a multitude of consumer products resulting in ubiquitous human exposure. Animal and in vitro studies suggest that exposure to these compounds may be related to a number of adverse health outcomes, as well as potential mediators such as oxidative stress and inflammation. We examined urinary phenol (bisphenol A (BPA), triclosan (TCS), benzophenone-3 (BP-3), 2,4-dichlorophenol (24-DCP), 2,5-dichlorophenol (25-DCP)) and paraben (butyl paraben (B-PB), methyl paraben (M-PB), propyl paraben (P-PB)) concentrations measured three times during pregnancy in relation to markers of oxidative stress and inflammation among participants in the Puerto Rico Testsite for Exploring Contamination Threats (PROTECT) project. Serum markers of inflammation (c-reactive protein (CRP), IL-1β, IL-6, IL-10, and tumor necrosis factor-α (TNF-α)) were measured twice during pregnancy (n=105 subjects, 187 measurements) and urinary markers of oxidative stress (8-hydroxydeoxyguanosine (OHdG) and isoprostane) were measured three times during pregnancy (n=54 subjects, 146 measurements). We used linear mixed models to assess relationships between natural log-transformed exposure and outcome biomarkers while accounting for within individual correlation across study visits. After adjustment for urinary specific gravity, study visit, maternal pre-pregnancy BMI, and maternal education, an interquartile range (IQR) increase in urinary BPA was associated with 21% higher OHdG (p=0.001) and 29% higher isoprostane (p=0.0002), indicating increased oxidative stress. The adjusted increase in isoprostane per IQR increase in marker of exposure was 17% for BP-3, 27% for B-PB, and 20% for P-PB (all p<0.05). An IQR increase in triclosan (TCS) was associated with 31% higher serum concentrations of IL-6 (p=0.007), a pro-inflammatory cytokine. In contrast, IQR increases in BP-3 and B-PB were significantly associated with 16% and 18% lower CRP, a measure of systemic inflammation. Our findings suggest that exposure to BPA, select parabens, and TCS during pregnancy may be related to oxidative stress and inflammation, potential mechanisms by which exposure to these compounds may influence birth outcomes and other adverse health effects, but additional research is needed.

Rodent Thyroid, Liver, and Fetal Testis Toxicity of the Monoester Metabolite of Bis-(2-Ethylhexyl) Tetrabromophthalate (TBPH), a Novel Brominated Flame Retardant Present in Indoor Dust

Background: Bis-(2-ethylhexyl) tetrabromophthalate (TBPH) is widely used as a replacement for polybrominated diphenyl ethers (PBDEs) in commercial flame retardant mixtures such as Firemaster 550. It is also used in a commercial mixture called DP 45. Mono-(2-ethyhexyl) tetrabromophthalate (TBMEHP) is a potentially toxic metabolite. Objectives: We used in vitro and rodent in vivo models to evaluate human exposure and the potential metabolism and toxicity of TBPH. Methods: Dust collected from homes, offices, and cars was measured for TBPH by gas chromatography followed by mass spectrometry. Pregnant rats were gavaged with TBMEHP (200 or 500 mg/kg) or corn oil on gestational days 18 and 19, and dams and fetuses were evaluated histologically for toxicity. We also assessed TBMEHP for deiodinase inhibition using rat liver microsomes and for peroxisome proliferator-activated receptor (PPAR) α and γ activation using murine FAO cells and NIH 3T3 L1 cells. Results: TBPH concentrations in dust from office buildings (median, 410 ng/g) were higher than in main living areas in homes (median, 150 ng/g). TBPH was metabolized by purified porcine esterases to TBMEHP. Two days of TBMEHP exposure in the rat produced maternal hypothyroidism with markedly decreased serum T3 (3,3´,5-triiodo-l-thyronine), maternal hepatotoxicity, and increased multinucleated germ cells (MNGs) in fetal testes without antiandrogenic effects. In vitro, TBMEHP inhibited deiodinase activity, induced adipocyte differentiation in NIH 3T3 L1 cells, and activated PPARα- and PPARγ-mediated gene transcription in NIH 3T3 L1 cells and FAO cells, respectively. Conclusions: TBPH a) is present in dust from indoor environments (implying human exposure) and b) can be metabolized by porcine esterases to TBMEHP, which c) elicited maternal thyrotoxic and hepatotoxic effects and d) induced MNGs in the fetal testes in a rat model. In mouse NIH 3T3 L1 preadipocyte cells, TBMEHP inhibited rat hepatic microsome deiodinase activity and was an agonist for PPARs in murine FAO and NIH 3T3 L1 cells.

Exposure to Perfluoroalkyl Acids and Markers of Kidney Function among Children and Adolescents Living near a Chemical Plant

Background: Serum levels of perfluorooctanoic acid (PFOA) have been associated with decreased renal function in cross-sectional analyses, but the direction of the association is unclear. Objectives: We examined the association of measured and model-predicted serum PFOA concentrations with estimated glomerular filtration rate (eGFR), a marker of kidney function, in a highly exposed population (median serum PFOA, 28.3 ng/mL). Methods: We measured serum creatinine, PFOA, perfluorooctane sulfonate (PFOS), perfluorononanoic acid (PFNA), and perfluorohexane sulfonate (PFHxS) and calculated eGFR in 9,660 children 1 to < 18 years of age at study enrollment. We predicted concurrent and historical serum PFOA concentrations using a validated environmental, exposure, and pharmacokinetic model based on individual residential histories, and used linear regression to estimate the association between eGFR and measured and predicted serum PFOA concentrations. We hypothesized that predicted serum PFOA levels would be less susceptible to reverse causation than measured levels. Results: An interquartile range increase in measured serum PFOA concentrations [IQR ln(PFOA) = 1.63] was associated with a decrease in eGFR of 0.75 mL/min/1.73 m2 (95% CI: –1.41, –0.10; p = 0.02). Measured serum levels of PFOS, PFNA, and PFHxS were also cross-sectionally associated with decreased eGFR. In contrast, predicted serum PFOA concentrations at the time of enrollment were not associated with eGFR (–0.10; 95% CI: –0.80, 0.60; p = 0.78). Additionally, predicted serum PFOA levels at birth and during the first ten years of life were not related to eGFR. Conclusions: Our findings suggest that the cross-sectional association between eGFR and serum PFOA observed in this and prior studies may be a consequence of, rather than a cause of, decreased kidney function.

In utero and peripubertal exposure to phthalates and BPA in relation to female sexual maturation

The age of pubertal onset for girls has declined over past decades. Research suggests that endocrine disrupting chemicals (EDCs) may play a role but exposure at multiple stages of development has not been considered. We examined in utero and peripubertal exposure to bisphenol-A (BPA) and phthalates in relation to serum hormones and sexual maturation among females in a Mexico City birth cohort. We measured phthalate metabolite and BPA concentrations in urine collected from mothers during their third trimester (n=116) and from their female children at ages 8-13 years (n=129). Among girls, we measured concurrent serum hormone concentrations, Tanner stages for breast and pubic hair development, and collected information on menarche onset. We used linear and logistic regression to model associations between in utero and peripubertal measures of exposure with hormones and sexual maturation, respectively, controlling for covariates. An interquartile range (IQR) increase in in utero urinary mono-2-ethylhexyl phthalate (MEHP) was positively associated with 29% (95% CI: 9.2-52.6%) higher dehydroepiandrosterone sulfate (DHEA-S), an early indicator of adrenarche, and 5.3 (95% CI: 1.13-24.9) times higher odds of a Tanner stage >1 for pubic hair development. Similar relationships were observed with other in utero but not peripubertal di-2-ethylhexyl phthalate (DEHP) metabolites. IQR increases in in utero monobenzyl phthalate (MBzP) and monoethyl phthalate (MEP) were associated with 29% and 25% higher serum testosterone concentrations (95% CI: 4.3-59.3; 2.1-54.1), respectively. In addition, we observed suggestive associations between in utero and peripubertal MEP concentrations and increased odds of having undergone menarche, and between peripubertal MnBP concentrations and increased odds of having a Tanner stage >1 for both breast and pubic hair development. BPA was not associated with in utero or peripubertal serum hormones or sexual maturation. Our findings suggest in utero phthalate exposure may impact hormone concentrations during peripubescence and timing of sexual maturation. Efforts to control phthalate exposure during pregnancy should be of high priority.

Variability and predictors of urinary concentrations of phthalate metabolites during early childhood.

The variability and predictors of urinary concentrations of phthalate metabolites in preschool-aged children have not been thoroughly examined. Additionally, the impact of temporal changes in the use and restriction of phthalates in children’s products has not been assessed. Our objective was to identify demographic, behavioral, and temporal predictors of urinary phthalate metabolite concentrations in young children. Between 2004 and 2011, we collected up to five urine samples from each of 296 children participating in a prospective birth cohort during annual study visits at ages 1–5 years. We used linear mixed models to calculate intraclass correlation coefficients (ICCs), a measure of within-individual reproducibility, and identify demographic predictors of urinary phthalate metabolites. We used multivariable linear regression to examine cross-sectional relationships between food packaging or personal care product use and phthalate metabolites measured at age 5 years. Across annual measurements, monoethyl phthalate exhibited the least variation (ICC = 0.38), while di-2-ethylhexyl phthalate (ΣDEHP) metabolites exhibited the most variation (ICC = 0.09). Concentrations changed with age, suggesting age-related changes in phthalate exposure and perhaps metabolism. Our findings suggest that fast food consumption may be a source of butylbenzyl phthalate and di-isononyl phthalate (DiNP) exposure, and some personal care products may be sources of diethyl phthalate exposure. Concentrations of ΣDEHP metabolites decreased over the study period; however, concentrations of DiNP metabolites increased. This finding suggests that manufacturer practices and regulations, like the Consumer Product Safety Improvement Act of 2008, may decrease DEHP exposure, but additional work characterizing the nature and toxicity of replacements is critically needed.

Associations between serum perfluoroalkyl acids and LINE-1 DNA methylation.

Perfluoroalkyl acids (PFAAs) are persistent, synthetic compounds that are used in a number of consumer products. Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) have been associated with cardiovascular risk factors, and changes in gene expression and DNA methylation in animals and cellular systems. However, whether PFAA exposure is associated with LINE-1 DNA methylation, a potential marker of cardiovascular risk, in humans remains unknown. We sought to evaluate the cross-sectional associations between serum PFAAs and LINE-1 DNA methylation in a population highly exposed to PFOA. We measured serum PFAAs twice four to five years apart in 685 adult participants (47% male, mean age±SD=42±11years). We measured percent LINE-1 DNA methylation in peripheral blood leukocytes at the second time point (follow-up), and estimated absolute differences in LINE-1 methylation associated with an interquartile (IQR) shift in mean PFAA serum levels. IQR increases in mean serum PFOA, PFOS, perfluorononanoic acid (PFNA), and perfluorohexane sulfonate (PFHxS) were associated with differences of -0.04 (p=0.16), 0.20 (p=0.001), 0.06 (p=0.19), and 0.02 (p=0.57), respectively, in % LINE-1 methylation at follow-up after adjustment for potential confounders. We observed a monotonic increase in LINE-1 DNA methylation across tertiles of PFOS and PFNA (ptrend=0.02 for both associations), but not across tertiles of PFOA or PFHxS (ptrend=0.71 and 0.44, respectively). In summary, serum PFOS was associated with LINE-1 methylation, while serum PFOA, PFHxS, and PFNA were not. Additional research is needed to more precisely determine whether these compounds are epigenetically active.

Relating Phthalate and BPA Exposure to Metabolism in Peripubescence: The Role of Exposure Timing, Sex, and Puberty

CONTEXT Exposure to endocrine-disrupting chemicals during development may play a role in the increasing prevalence of metabolic syndrome and type 2 diabetes among children and adolescents by interfering with metabolic homeostasis. OBJECTIVE To explore associations between in utero and peripubertal urinary phthalate metabolite and bisphenol A (BPA) concentrations and markers of peripubertal metabolic homeostasis. DESIGN Early Life Exposure in Mexico to Environmental Toxicants (ELEMENT): a longitudinal cohort study of pregnant women in Mexico City and their offspring. SETTING Public maternity hospitals in Mexico City. PATIENTS OR OTHER PARTICIPANTS Women recruited during pregnancy; offspring recruited for follow-up at age 8-14 years (n = 250). INTERVENTIONS None. MAIN OUTCOME MEASURES Fasting serum c-peptide, IGF-1, leptin, and glucose concentrations among children at follow-up; calculated measures of insulin secretion and insulin resistance. RESULTS Phthalate metabolites and BPA were associated with metabolism biomarkers at age 8-14 years in patterns that varied by sex, pubertal status, and exposure timing. For example, in utero monoethyl phthalate was associated with lower insulin secretion among pubertal boys (P = .02) and higher leptin among girls (P = .04). In utero di-2-ethylhexyl phthlate was associated with higher IGF-1 among pubertal girls; peripubertal di-2-ethylhexyl phthlate was associated with higher IGF-1, insulin secretion, and resistance among prepubertal girls. In contrast, peripubertal dibutyl phthalate, monobenzyl phthalate, and mono-3-carboxypropyl phthalate were associated with lower IGF-1 among pubertal boys. Peripubertal BPA was associated with higher leptin in boys (P = .01). CONCLUSIONS Considering the long-term health effects related to metabolic syndrome, additional research on exposure and metabolic outcomes across developmental periods and early adulthood is needed.

Maternal phthalate exposure during early pregnancy and at delivery in relation to gestational age and size at birth: A preliminary analysis

Epidemiologic studies of in utero phthalate exposure and birth outcomes have had conflicting findings. The objective of this study was to characterize maternal phthalate exposure across pregnancy, examine associations between maternal phthalate levels and infant size and gestational age at birth, and investigate relationships between concurrent bisphenol A (BPA) and phthalate exposure and birth outcomes. Women in the Michigan Mother-Infant Pairs cohort provided urine and blood samples during their first trimester and at delivery. Urinary phthalate metabolites and serum BPA were measured at both time points, and birth weight, length, head circumference, and gestational age were recorded from medical records. Maternal DEHP metabolite concentrations were significantly higher at delivery compared to the first trimester (p<0.05), suggesting increased DEHP exposure late in pregnancy. A number of phthalate metabolites were associated with birth size and gestational age in patterns that varied by sex and timing of exposure, independent of BPA exposure.

Urinary 3-phenoxybenzoic acid (3-PBA) levels among pregnant women in Mexico City: Distribution and relationships with child neurodevelopment

BACKGROUND In recent years, pyrethroid pesticide use has increased in Mexico, the United States, and elsewhere, resulting in extensive human exposure. There is growing concern that pregnant women may be a particularly vulnerable population, as in utero fetal exposure during critical periods of development could adversely affect long-term neurobehavioral function. METHODS We measured maternal urinary 3-phenoxybenzoic acid (3-PBA) concentrations during the third trimester of pregnancy as a measure of in utero pyrethroid exposure to the fetus among participants in an established Mexico City birth cohort (n=187). In a subset of mothers, we measured 3-PBA during the first, second, and third trimester (n=21) to assess variability across pregnancy. We examined associations between third trimester 3-PBA concentrations and childrens scores on the Mental Development Index (MDI) and Psychomotor Development Index (PDI) from the Bayley Scales for Infant Development (BSID-IIS) at 24 and 36 months of age. RESULTS 3-PBA was detected in 46% of all urine samples, with similar detection rates and geometric mean concentrations across pregnancy among the 21 participants who provided repeat samples. Participants in the medium and high 3-PBA categories (≥LOD) had lower MDI scores at 24 months compared to those in the low 3-PBA category (<LOD) after adjustment for covariates (ptrend=0.07), with slightly stronger associations among female children. The 3-level categorical variable for third trimester in utero 3-PBA was not associated with MDI scores at 36 months, or with PDI scores at either time point. CONCLUSION Considering the widespread agricultural and residential use of pyrethroids worldwide and the implications of cognitive and behavioral deficits, our findings indicate that additional study of in utero pyrethroid exposure and neurodevelopment in a larger study population is needed.