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Environmental justice and drinking water quality: are there socioeconomic disparities in nitrate levels in U.S. drinking water?

ABSTRACT: BACKGROUND:Low-income and minority communities often face disproportionately high pollutant exposures. The lead crisis in Flint, Michigan, has sparked concern about broader socioeconomic disparities in exposures to drinking water contaminants. Nitrate is commonly found in drinking water, especially in agricultural regions, and epidemiological evidence suggests elevated risk of cancer and birth defects at levels below U.S. EPA's drinking water standard (10?mg/L NO3-N). However, there have been no nationwide assessments of socioeconomic disparities in exposures to nitrate or other contaminants in U.S. drinking water. The goals of this study are to identify determinants of nitrate concentrations in U.S. community water systems (CWSs) and to evaluate disparities related to wealth or race/ethnicity. METHODS:We compiled nitrate data from 39,466?U.S. CWSs for 2010-2014. We used EPA's Safe Drinking Water Information System (SDWIS) to compile CWS characteristics and linked this information with both city- and county-level demographic data gathered from the U.S. Census Bureau. After applying multiple imputation methods to address censored nitrate concentration data, we conducted mixed-effects multivariable regression analyses at national and regional scales. RESULTS:5.6 million Americans are served by a CWS that had an average nitrate concentration???5?mg/L NO3-N between 2010 and 2014. Extent of agricultural land use and reliance on groundwater sources were significantly associated with nitrate. The percent of Hispanic residents served by each system was significantly associated with nitrate even after accounting for county-level cropland and livestock production, and CWSs in the top quartile of percent Hispanic residents exceeded 5?mg/L nearly three times as often as CWSs serving the lowest quartile. By contrast, the percent of residents living in poverty and percent African American residents were both inversely associated with nitrate. CONCLUSIONS:Epidemiological evidence for health effects associated with drinking water above 5?mg/L NO3-N raises concerns about increased risk for the 5.6 million Americans served by public water supplies with average nitrate concentrations above this level. The associations we observed between nitrate concentrations and proportions of Hispanic residents support the need for improved efforts to assist vulnerable communities in addressing contamination and protecting source waters. Future studies can extend our methods to evaluate disparities in exposures to other contaminants and links to health effects.

SUBMITTER: Schaider LA

PROVIDER: S-EPMC6335696 | biostudies-literature | 2019 Jan

REPOSITORIES: biostudies-literature

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Environmental justice and drinking water quality: are there socioeconomic disparities in nitrate levels in U.S. drinking water?

Schaider Laurel A LA Swetschinski Lucien L Campbell Christopher C Rudel Ruthann A RA

Environmental health : a global access science source 20190117 1

<h4>Background</h4>Low-income and minority communities often face disproportionately high pollutant exposures. The lead crisis in Flint, Michigan, has sparked concern about broader socioeconomic disparities in exposures to drinking water contaminants. Nitrate is commonly found in drinking water, especially in agricultural regions, and epidemiological evidence suggests elevated risk of cancer and birth defects at levels below U.S. EPA's drinking water standard (10 mg/L NO<sub>3</sub>-N). However, ...[more]

PMID: 30651108

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Project description:BACKGROUND:Nitrate is a common water contaminant that has been associated with birth defects, although the evidence is limited. The purpose of this study was to examine whether maternal consumption of nitrate through drinking water is associated with an increased risk of congenital anomalies. METHODS:The study included a total of 348,250 singletons births from the state of Missouri between January 1, 2004 and December 31, 2008. Individual-level birth defect data and maternal and child characteristics were obtained from the Missouri birth defects registry and state vital statistics records. Outcomes were linked with county-specific monthly estimates of the nitrate concentration in finished water, based on data collected for compliance with the Safe Drinking Water Standard. Poisson models were fit to examine the association between nitrate exposure and birth defects. Average nitrate exposure during the first trimester and over 12 months prior to birth were modeled as continuous variables. Sensitivity analyses included restriction of the sample to counties with <20% and <10% private well usage to reduce exposure misclassification as well as limiting the analyses to residents of rural counties only to account for potential confounding by urbanicity. RESULTS:Estimated water concentrations of nitrate were generally low and below the Environmental Protection Agency's maximum contaminant level of 10?mg/L. Nitrate exposure was associated with a significantly increased risk of limb deficiencies (RR for 1?mg/L (RR1)?=?1.26, 95% CI?=?1.05, 1.51) in models without well restriction. Nitrate was also weakly associated with an increased risk of congenital heart defects (RR1?=?1.13, 95%CI?=?0.93, 1.51) and neural tube defects (RR1?=?1.18, 95%CI?=?0.93, 1.51) in models with well restriction (<10%). CONCLUSION:The positive associations found between nitrate exposure via drinking water and congenital abnormalities are largely consistent with some previous epidemiologic studies. The results of this study should be interpreted with caution given limitations in our ability to estimate exposures and the lack information on some risk factors for congenital abnormalities. Our findings may have serious policy implications given that exposure levels in our study were well below current EPA standards for nitrate in drinking water.

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Environmental justice and drinking water quality: are there socioeconomic disparities in nitrate levels in U.S. drinking water?

Publications

Environmental justice and drinking water quality: are there socioeconomic disparities in nitrate levels in U.S. drinking water?

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