Phthalates and pyrethroids in infants and toddlers: concentrations, stability of repeat measures, and predictors of exposure

Abstract

BACKGROUND AND AIM: Determinants of phthalate and pyrethroid exposures are not well understood in early life, a period of rapid brain development with heightened vulnerability to toxicant exposure. Our aims were to characterize concentrations, stability, and predictors of phthalate and pyrethroid metabolites in infants and toddlers. METHODS: We included a subset of participants in the UNC Baby Connectome Project, who provided≥1 urine sample(s) between birth and 77-months. We measured 8 phthalate and 4 pyrethroid metabolites in pediatric urines. At baseline, mothers completed an environmental questionnaire on household and personal care product usage and behaviors, during-and after-pregnancy. We calculated descriptive statistics of specific gravity unadjusted (Unadj) and adjusted (Adj) phthalate concentrations, estimated intraclass correlation coefficients (ICCs), and built predictive models. Detection frequencies of any pyrethroid metabolites and their Kappa statistics were calculated. RESULTS:62 children provided 125 urine samples, with near-ubiquitous detection of all phthalate metabolites (95%). Median concentrations were highest for monobutyl phthalate (MBP; Unadj: 15.35ug/L; Adj: 5.30ug/L), followed by mono-isobutyl phthalate (MiBP; 11.50ug/L; 4.59ug/L) and monobenzyl phthalate (MBzP; 4.03ug/L; 1.56ug/L). ICCs were higher for MBzP (0.58 [0.39, 0.72]; 0.46 [0.24, 0.63]) as compared to MBP (0.29 [0.05, 0.50]; 0.17 [-0.24, 0.53]) or MiBP (-0.05 [-0.29, 0.20]; 0.12 [-0.13, 0.35]). In the subset of first urine samples with questionnaire data (n=45), 54.86% of the variability in log(MBzP) was explained by specific gravity, pets, household/personal/child care product, income, pregnancy cosmetics use, race/ethnicity, pesticide use in and around the home, and infant birthweight. Besides specific gravity, having cat and dog in household was the strongest determinant. Any pyrethroid metabolites were detected in 35.2%, with a high agreement between second and third samples (0.86 [0.60, 1.00]) but not between other piecewise-comparisons. CONCLUSIONS:Phthalates, but not pyrethroids, were commonly detected during early childhood. MBzP had moderate ICCs and was partially explained by pets and household/personal care product preferences. KEYWORDS: Phthalates, pyrethroids, infants, toddlers, predictors