Association of arsenic and uranium concentrations in private wells and community water systems with urinary biomarkers in American Indian adults: The Strong Heart Family Study

BACKGROUND AND AIM: Chronic exposure to inorganic arsenic (iAs) and uranium (U) has been associated with adverse health risks. High As and U levels occur in unregulated private wells and regulated community water systems (CWSs) serving tribal communities in the Southwest, Central Midwest, and Northern Plains. Our objective was to examine the contribution of CWS and private well As and U concentrations to urinary biomarkers of total internal dose in American Indian adults in the Strong Heart Family Study (SHFS). METHODS: 2,688 SHFS participants had dietary recall information and spot urine concentrations of U and iAs, estimated as the sum of inorganic and methylated species, collected between 2001-2003. We assigned participants zip code level area- and population- weighted CWS and private well As and U estimates based on previously developed nationwide estimates derived from US Environmental Protection Agency and US Geological Survey datasets, respectively. We used generalized linear mixed models to evaluate the geometric mean ratio (GMR) of urinary iAs or U concentrations per log unit increase in water As or U, respectively. Models were adjusted for sex, age, reported intake of As- and U- containing foods, and smoking status. Random effects were applied for zip code and family group. RESULTS: In fully adjusted models, the GMR of estimated iAs and U per log µg/L increase in CWS As and U was 1.11 (1.08-1.14) and 1.26 (1.15-1.39), respectively. The fully adjusted GMR of estimated iAs per unit (100%) increase in the probability of private well As >10 µg/L was 1.81 (1.35-2.41). Per log µg/L increase in mean private well U, the GMR of urinary U was 1.04 (0.91-1.19). CONCLUSIONS: Both regulated CWSs and unregulated private wells are important sources of iAs and U exposure for tribal communities in the SHFS, as reflected in urinary biomarkers. KEYWORDS: arsenic, uranium, environmental epidemiology