METHODS: Participants included 568 California and Ohio females enrolled at age 6–8 years and followed at annual intervals during 2004–2013. Serum concentrations of individual and summed polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), and flame-retardant polybrominated diphenyl ethers (PBDEs) were measured in specimens collected at baseline or first follow-up visit. Adjusted hazard ratios (aHRs) for menarche onset were calculated by Cox proportional regression, including race, household income, mother’s education, and environmental tobacco smoke as covariates; BMI, potentially on the causal pathway, was added to a parallel analysis.
RESULTS: During follow-up, 510 subjects achieved menarche (median age 12.4 years). Age of menarche was later among girls with higher summed PCB levels (median 11.8 years in quartile 1 [Q1] versus 12.7 in quartile 4 [Q4]) and summed OCP levels (12.1 years in Q1 versus 12.4 in Q4). The aHRs for summed PCBs was 0.88 (95% confidence interval [CI]: 0.79, 0.98 per ng/g lipid) and for the pesticide hexachlorobenzene was 0.64 (95% CI: 0.52, 0.79 per ng/g lipid). Associations were nonsignificant after adjustment for BMI, and PBDE concentrations were unassociated with age at menarche.
CONCLUSIONS: Our study revealed a delay in menarche with higher concentrations of certain POPs although it may have been mediated or confounded by lower BMI. Further research is warranted on exposure to hormonally active compounds during early development and risk for reproductive health effects and later disease risk.