Exposures to drinking water contaminants in community water systems and risk of ovarian cancer in the California Teachers Study cohort
Menée en Californie auprès de 91 127 résidents (durée moyenne de suivi : 19 ans), cette étude analyse l'association entre des contaminants réglementés dans les réseaux d'eau potable et le risque de cancer de l'ovaire (424 cas)
Background: Several drinking water contaminants are known or suspected carcinogens; however, there are only a few investigations of drinking water exposures and ovarian cancer. We evaluated associations between regulated contaminants in community water systems (CWS) and ovarian cancer risk in the California Teachers Study, a prospective cohort of female California educators.
Methods: Participants were cancer-free, without bilateral oophorectomy, living in California at baseline (1995-1996) with geocoded addresses linked to a CWS (N=91,127, 92%), with follow-up through 2020 (mean=19.0 years). Among participants with a residential duration at enrollment of at least 10 years, we computed 15-year (1990-2005) averages of log2-transformed arsenic, nitrate, total trihalomethanes (TTHM) (N=59,881), and uranium concentrations (N=56,314). We estimated hazard ratios (HRs, 95% CIs) for all epithelial ovarian cancers (n=424) and the high-grade serous histotype (n=203), using Cox proportional hazards regression, adjusting for age, body mass index, menopause status, oral contraceptive use, and parity. We evaluated the mixture effect (per IQR in log2 concentrations), using quantile-based g-computation.
Results: Almost all women (>99%) had average exposures below regulatory limits for all contaminants. In single contaminant analyses, a doubling in average uranium concentrations was associated with all ovarian cancer (HRperlog2=1.09, CI 1.02-1.16), whereas a doubling in nitrate was associated with the high-grade serous histotype (HRperlog2=1.09, CI 1.02-1.17). Findings were similar in models adjusted for other contaminants. We observed positive but imprecise associations for arsenic and TTHM in single-contaminant and contaminant-adjusted analyses. HRs per increase in the mixture were 1.39 (1.00, 1.94) and 1.75 (1.09, 2.83), for all ovarian cancer and the high-grade serous histotype, respectively. Uranium was the largest contributor (55%) to the mixture effect for all ovarian cancer, and nitrate was the largest contributor (46%) for the high-grade serous histotype.
Conclusions: Novel associations between drinking water contaminants and ovarian cancer risk at levels below regulatory limits warrant further investigation.
Environmental Health Perspectives , article en libre accès, 2025