Long-Term Exposure to Uranium and Arsenic in Community Drinking Water and CKD Risk Among California Women.

RATIONALE & OBJECTIVE Metals/metalloids in drinking water, including uranium and arsenic, may damage kidney function and increase chronic kidney disease (CKD) risk. We evaluated exposure to these contaminants in community water supplies (CWS) and CKD risk in the California Teachers Study. STUDY DESIGN Prospective cohort study. SETTING & PARTICIPANTS 88,185 women who were California teachers and school administrators enrolled 1995-1996. EXPOSURES Time- and residence- weighted annual average uranium and arsenic concentrations from CWS serving participants' residential addresses from 1995 to 2005. OUTCOME 6,185 moderate to end-stage CKD cases from hospitalization records between 2005 and 2018. ANALYTICAL APPROACH Hazard ratios (HRs) and 95% confidence intervals (95%CIs) calculated using mixed-effects Cox models, adjusted for age as the time scale, body mass index, smoking status, race/ethnicity, neighborhood socioeconomic status, and Census region as a random effect. Analyses were also stratified by risk factors and comorbidities. RESULTS Most exposures in this population were below the current regulatory limits (uranium=30μg/L and arsenic=10 μg/L), with median (interquartile range; IQR) concentrations of 3.1 (0.9, 5.6) μg/L for uranium and 1.0 (0.6, 1.8) μg/L for arsenic. Uranium exposure was positively associated with CKD risk (continuous log, per IQR; HR=1.11, 95%CI=1.02-1.20). Compared to uranium exposure <2μg/L (World Health Organization 1998 guideline), risk was over 30% greater at 10-<15μg/L (HR=1.33, 95%CI=1.15-1.54) and similar at ≥15μg/L (HR=1.32, 95%CI=1.09-1.58). There was no evidence of a significant association between arsenic and CKD overall (log, per IQR; HR=1.02, 95%CI=0.98-1.07). However, risk from arsenic was greater among younger individuals (≤55 years), and those who developed cardiovascular disease or diabetes. LIMITATIONS Individual tap water use and consumption; limited generalizability to men and non-White and less affluent populations. CONCLUSIONS Uranium below the current regulatory limit from community water may increase CKD risk.