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Few methods have been used to characterize repeatedly measured biomarkers of chemical mixtures. We applied latent profile analysis (LPA) to serum concentrations of 4 perfluoroalkyl and polyfluoroalkyl substances (PFAS) measured at 4 time points from gestation to age 12 years. We evaluated the relationships between profiles and z scores of height, body mass index, fat mass index, and lean body mass index at age 12 years (n  = 218). We compared LPA findings with an alternative approach for cumulative PFAS mixtures using g-computation to estimate the effect of simultaneously increasing the area under the receiver operating characteristic curve (AUC) for all PFAS. We identified 2 profiles: a higher PFAS profile (35% of sample) and a lower PFAS profile (relative to each other), based on their average PFAS concentrations at all time points. The higher PFAS profile had generally lower z scores for all outcomes, with somewhat larger effects for males, though all 95% CIs crossed the null. For example, the higher PFAS profile was associated with a 0.50-unit lower (β = −0.50; 95% CI, −1.07 to 0.08) BMI z score among males but not among females (β = 0.04; 95% CI, −0.45 to 0.54). We observed similar patterns with AUCs. We found that a higher childhood PFAS profile and higher cumulative PFAS mixtures may be associated with altered growth in early adolescence. This article is part of a Special Collection on Environmental Epidemiology. [ABSTRACT FROM AUTHOR]

Results of toxicological studies indicate that phthalates and per-/polyfluoroalkyl substances (PFAS), 2 classes of endocrine-disrupting chemicals, may alter the functioning of the hypothalamic-pituitary-adrenocortical (HPA) axis. We evaluated the associations of urinary phthalate metabolites and serum PFAS during gestation and childhood with adolescent hair cortisol concentrations (pg/mg hair) at age 12 years, an integrative marker of HPA axis activity (n  = 205 mother-child pairs; Cincinnati, Ohio; enrolled 2003–2006). We used quantile-based g-computation to estimate associations between mixtures of urinary phthalate metabolites or serum PFAS and hair cortisol. We also examined whether associations of individual phthalate metabolites or PFAS with cortisol varied by the timing of exposure. We found that a 1-quartile increase in all childhood phthalate metabolites was associated with 35% higher adolescent hair cortisol (phthalate mixture ψ = 0.13; 95% confidence interval: 0.03, 0.22); these associations were driven by monoethyl phthalate, monoisobutyl phthalate, and monobenzyl phthalate. We did not find evidence that phthalate metabolites during gestation or serum PFAS mixtures were related to adolescent hair cortisol concentrations. We found suggestive evidence that higher childhood concentrations of individual PFAS were related to higher and lower adolescent hair cortisol concentrations. Our results suggest that phthalate exposure during childhood may contribute to higher levels of chronic HPA axis activity. [ABSTRACT FROM AUTHOR]

Autism spectrum disorder, which is characterized by impaired social communication and stereotypic behaviors, affects 1%–2% of children. Although prenatal exposure to toxicants has been associated with autistic behaviors, most studies have been focused on shifts in mean behavior scores. We used Bayesian quantile regression to assess the associations between log2-transformed toxicant concentrations and autistic behaviors across the distribution of behaviors. We used data from the Maternal–Infant Research on Environmental Chemicals study, a pan-Canadian cohort (2008–2011). We measured metal, pesticide, polychlorinated biphenyl, phthalate, bisphenol-A, and triclosan concentrations in blood or urine samples collected during the first trimester of pregnancy. Using the Social Responsiveness Scale (SRS), in which higher scores denote more autistic-like behaviors, autistic behaviors were assessed in 478 children aged 3–4 years old. Lead, cadmium, and most phthalate metabolites were associated with mild increases in SRS scores at the 90th percentile of the SRS distribution. Manganese and some pesticides were associated with mild decreases in SRS scores at the 90th percentile of the SRS distribution. We identified several monotonic trends in which associations increased in magnitude from the bottom to the top of the SRS distribution. These results suggest that quantile regression can reveal nuanced relationships and, thus, should be more widely used by epidemiologists. [ABSTRACT FROM AUTHOR]

Production of organophosphate esters (OPEs), which represent a major flame-retardant class present in consumer goods, has increased over the past 2 decades. Experimental studies suggest that OPEs may be associated with thyroid hormone disruption, but few human studies have examined this association. We quantified OPE metabolites in the urine of 298 pregnant women from Cincinnati, Ohio, in the Health Outcomes and Measures of the Environment Study (enrolled 2003–2006) at 3 time points (16 and 26 weeks' gestation, and at delivery), and thyroid hormones in 16-week maternal and newborn cord sera. Urinary bis(1,3-dichloro-2-propyl)-phosphate concentrations were generally associated with decreased triiodothyronine and thyroxine levels and increased thyroid-stimulating hormone levels in maternal and newborn thyroid hormones in quartile dose–response analyses and multiple informant models. There was weaker evidence for thyroid hormone alterations in association with diphenyl-phosphate and di- n -butyl-phosphate. Bis-2-chloroethyl-phosphate was not associated with alterations in thyroid hormones in any analyses. We did not observe any evidence of effect modification by infant sex. These results suggest that gestational exposure to some OPEs may influence maternal and neonatal thyroid function, although replication in other cohorts is needed. [ABSTRACT FROM AUTHOR]