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

Abstract

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.

Exposure

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 and 95% confidence intervals calculated using mixed-effects Cox models, adjusted for age as the time scale, body mass index, smoking status, race and 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: 30 μg/L; arsenic: 10 μg/L), with median concentrations of 3.1 μg/L (IQR, 0.9-5.6 μg/L) for uranium and 1.0 μg/L (IQR, 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 with uranium exposure < 2 μg/L (World Health Organization 1998 guideline), the risk was over 30% greater at 10 to <15 μg/L (HR, 1.33 [95% CI, 1.15-1.54]) and similar at ≥15 μg/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, the 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.

Plain-Language Summary

Metals, including uranium and arsenic, can damage kidney function and may increase chronic kidney disease (CKD) risk. These contaminants are often present in groundwater and are regulated in US community water supplies. In a cohort of California women, we examined long-term uranium and arsenic exposure from households using community water. Higher uranium concentrations were associated with CKD. Those exposed to 10-15 μg/L (or one-third to one-half the regulatory limit) had an approximately 30% greater risk compared with those below the World Health Organization 1998 guideline (2 μg/L). Arsenic was not clearly associated with risk of CKD overall. However, we observed a higher risk among younger individuals and those who developed cardiovascular disease or diabetes. Uranium in community water may be linked to CKD, underscoring the need for further clinical investigation and policy evaluation.