Water quality monitoring records for estimating tap water arsenic and nitrate: a validation study

Abstract

BackgroundTap water may be an important source of exposure to arsenic and nitrate. Obtaining and analyzing samples in the context of large studies of health effects can be expensive. As an alternative, studies might estimate contaminant levels in individual homes by using publicly available water quality monitoring records, either alone or in combination with geographic information systems (GIS).MethodsWe examined the validity of records-based methods in Washington State, where arsenic and nitrate contamination is prevalent but generally observed at modest levels. Laboratory analysis of samples from 107 homes (median 0.6 μg/L arsenic, median 0.4 mg/L nitrate as nitrogen) served as our "gold standard." Using Spearman's rho we compared these measures to estimates obtained using only the homes' street addresses and recent and/or historical measures from publicly monitored water sources within specified distances (radii) ranging from one half mile to 10 miles.ResultsAgreement improved as distance decreased, but the proportion of homes for which we could estimate summary measures also decreased. When including all homes, agreement was 0.05-0.24 for arsenic (8 miles), and 0.31-0.33 for nitrate (6 miles). Focusing on the closest source yielded little improvement. Agreement was greatest among homes with private wells. For homes on a water system, agreement improved considerably if we included only sources serving the relevant system (ρ = 0.29 for arsenic, ρ = 0.60 for nitrate).ConclusionsHistorical water quality databases show some promise for categorizing epidemiologic study participants in terms of relative tap water nitrate levels. Nonetheless, such records-based methods must be used with caution, and their use for arsenic may be limited.

Residential Proximity to Freeways and Autism in the CHARGE Study

“…Additional research from the CHARGE study has shown increased plasma levels of immunoglobulin (Ig) G-4 and reduced concentrations of tumor growth factor-β, related to immune response and inflammatory processes, in plasma of children with autism compared with typically developing controls and children with developmental delay ( Ashwood et al 2008 ; Enstrom et al 2009a , 2009b ). Other recent work indicates that exposure to air pollution exposure during pregnancy is associated with changes in IgE and in lymphocytes measured from cord blood, supporting the idea that maternal exposure to air pollution is associated with altered immune profiles in the fetus ( Herr et al 2010a , 2010b ). Moreover, published evidence links maternal antibodies to fetal brain tissue with a subset of autism cases ( Braunschweig et al 2008 ).…”

Environmental justice implications of arsenic contamination in California’s San Joaquin Valley: a cross-sectional, cluster-design examining exposure and compliance in community drinking water systems

“…Previous studies have noted the benefit of using such publicly available water quality monitoring records as an alternative to costly tap water samples [28]. Using these data points, we derived the average arsenic concentration served by each CWS for the entire compliance period.…”

Nitrate in Drinking Water during Pregnancy and Spontaneous Preterm Birth: A Retrospective Within-Mother Analysis in California

“…Although imperfect, water monitoring records have been widely used for exposure assessment (Brender et al 2013;Nuckols et al 2011;Villanueva et al 2014). In a validation study in Washington State, Searles Nielsen et al (2010) found correlation between water quality monitoring records and tap water nitrate levels (R 2 of 0.3-0.5). The authors suggest that studies reliant on public records incur largely nondifferential measurement error.…”