Exposure to Particulate Matter Air Pollution and Age of Menarche in a Nationwide Cohort of U.S. Girls

BACKGROUND: It remains unclear whether in utero and childhood exposure to air pollution affects pubertal development, particularly age of menarche in girls. OBJECTIVE: The aim of this study was to determine whether residential ambient particulate matter (PM) exposure in utero and during childhood is associated with age of menarche. METHODS: We studied 5,201 girls in the Growing Up Today Study 2 (2004–present) who were 10–17 y of age at enrollment (47.7% premenarchal; 52.3% postmenarchal). Exposure to three size fractions of PM [fine PM with aerodynamic diameter [Formula: see text] ([Formula: see text]), PM with aerodynamic diameters [Formula: see text] ([Formula: see text]), and PM with aerodynamic diameter [Formula: see text] ([Formula: see text])] was assigned based on maternal residential address, updated every 2 y, using nationwide spatiotemporal models. We estimated average PM exposure in utero, and time-varying windows: annual average exposure in the prior 1 and 2 y and cumulative average from birth. Age of menarche was self-reported on three surveys administered in 2004, 2006, and 2008. We calculated hazard ratios (HR) for menarche for an interquartile range (IQR) increase in PM exposure using Cox proportional hazard models adjusting for potential confounders. RESULTS: Girls attained menarche at 12.3 y of age on average. In the adjusted model, higher residential exposure to ambient [Formula: see text] during all time windows was associated with earlier age of menarche. The HRs of menarche for each IQR ([Formula: see text]) increase in exposure to [Formula: see text] during the in utero period, 1 y prior to menarche, and throughout childhood were 1.03 [95% confidence interval (CI): 1.00, 1.06], 1.06 (95% CI: 1.02, 1.10) and 1.06 (95% CI: 1.02, 1.10), respectively. Effect estimates for [Formula: see text] exposure were similar, albeit attenuated, for all time windows. [Formula: see text] exposure was not associated with age of menarche. DISCUSSION: Among a large, nationwide, prospective cohort of U.S. girls, higher exposure to [Formula: see text] and [Formula: see text] in utero and throughout childhood was associated with an earlier age of menarche. Our results suggest that [Formula: see text] and [Formula: see text] may have endocrine-disrupting properties that could lead to altered timing of menarche. https://doi.org/10.1289/EHP12110