Water as a relevant source of inorganic arsenic exposure in U.S. cities

Abstract

BACKGROUND AND AIM: Water arsenic represents a health concern for US residents served by community water systems (CWS) exceeding the Environmental Protection Agency (EPA) Maximum Contaminant Level (MCL) of 10 µg/L, and for residents reliant on unregulated private wells. Little is known on the contribution of CWS arsenic exposures below the MCL, particularly in urban areas. We evaluated whether water arsenic is a relevant source of urinary arsenic in urban settings in the Multi-Ethnic Study of Atherosclerosis (MESA). METHODS: We examined the association of CWS arsenic with urinary arsenic concentrations (µg/L) for 910 MESA participants from Baltimore, Chicago, Los Angeles, New York City, St. Paul, MN, and Winston-Salem, NC. We assigned three-year population weighted averages of CWS arsenic concentrations using 2006-2008 EPA data (before MCL implementation) to participants by zip code. Dietary information and urinary samples were collected in 2000-2002. Urinary arsenic species were measured using HPLC-ICPMS. We accounted for seafood intake using a residual based method. Linear models adjusted for race/ethnicity, income, smoking status, diet (rice) and urinary creatinine to account for urine dilution. RESULTS:CWS arsenic levels ranged from 0.5 µg/L (LOD) in several cities to 3.05 µg/L in Chicago (median 0.44 µg/L). CWS arsenic was positively correlated (p 0.05) with urinary inorganic arsenic (Spearman’s rho 0.11), dimethylarsinate (DMA) (0.09), monomethylarsonate (MMA) (0.16) and their sum (0.10). In adjusted models, a 1 µg/L change in CWS arsenic was associated with 1.29 (95%CI 1.01, 1.64) higher inorganic arsenic and 1.19 (1.03, 1.38) higher MMA. The association with DMA, sum of inorganic and methylated species was not statistically significant. CONCLUSIONS:Drinking water arsenic is a relevant source of exposure and internal dose in US urban areas, determined by urinary arsenic biomarkers. Research is needed to determine health implications of chronic exposure to water arsenic below the MCL, including vulnerable subpopulations. KEYWORDS: arsenic, drinking water, exposure assessment, environmental epidemiology