Martinez-Morata et al. 2022 — County-level arsenic and uranium in US public drinking water by racial/ethnic composition
This Nature Communications paper reports a nationwide geospatial analysis of US county-level community water system (CWS) arsenic and uranium concentrations from EPA compliance monitoring data, evaluating associations with county racial/ethnic composition. The study provides the most comprehensive available distribution of arsenic and uranium concentrations in US public drinking water for the 2000–2011 period. Nationwide, the county-level mean CWS arsenic concentration was 1.42 µg/L (SD 2.22), and uranium was 3.45 µg/L (SD 6.85). The study found that higher proportions of Hispanic/Latino and American Indian/Alaskan Native residents were significantly associated with higher CWS arsenic and uranium concentrations at the county level, with High-High spatial autocorrelation clusters concentrated in the Midwest and Southwest.
Key numbers
Nationwide county-level CWS concentration estimates (all counties in any analysis, N=2631):
- Arsenic (2006–2011): mean 1.42 µg/L (SD 2.22 µg/L); US EPA MCL = 10 µg/L; MCLG = 0
- Uranium (2000–2011): mean 3.45 µg/L (SD 6.85 µg/L); US EPA MCL = 30 µg/L; MCLG = 0
- High-High spatial clusters for both metals: Midwest and Southwest (Nevada, California, Arizona, New Mexico, Texas, Kansas, Nebraska)
- Low-Low clusters for arsenic: Southeast and Mid-Atlantic (Alabama, Arkansas, North Carolina, South Carolina, Virginia, Kentucky)
Racial/ethnic composition associations from spatial lag regression: higher Hispanic/Latino and American Indian/Alaskan Native county proportions were independently associated with higher CWS arsenic and uranium in nationwide models; higher non-Hispanic White proportion associated with lower concentrations.
Methods (brief)
County-level CWS arsenic and uranium concentration estimates were derived from US EPA routine compliance monitoring records (previously published by Nigra et al. 2020 and Ravalli et al. 2022). Spatial lag regression used to account for spatial autocorrelation (Moran’s I = 0.62 for arsenic, 0.68 for uranium). Locally weighted geographically weighted regression (GWR) used to assess spatial variation in associations. Counties with <100 residents of each racial/ethnic group excluded from subgroup analyses.
Implications
Certification: establishes the national baseline distribution of arsenic and uranium in US public drinking water. The mean of 1.42 µg/L As is well below the EPA MCL of 10 µg/L but above the MCLG of 0, and the geographic dispersion (SD 2.22) means high-concentration areas substantially exceed the mean. Water-processed food products and formulas are relevant downstream.
Courses: primary source for US drinking water arsenic and uranium distributions; documents environmental justice disparities in water quality.
App: drinking water arsenic and uranium concentrations are spatially heterogeneous in the US; geographic origin is a key variance factor for water-containing products.
Regulations: US EPA arsenic MCL 10 µg/L (MCLG 0); uranium MCL 30 µg/L (MCLG 0). See epa-drinking-water-arsenic-mcl.