This map shows the approximate locations of community water systems in each of the 10 states – California, Illinois, Iowa, Kansas, Maryland, Nebraska, Oklahoma, Pennsylvania, Texas and Wisconsin – where nitrate contamination of drinking water got worse between 2003 and 2017. The Oklahoma map shows systems that had worsening nitrate between 2007 and 2017.
These 10 states were chosen because a previous EWG study and map, released in October 2019, showed that the drinking water in these states had the worst nitrate contamination in the country. A community system is what most people think of as a water utility, mainly serving places where people live, such as cities and towns.
Yellow points represent systems with at least one nitrate test at or above 3 milligrams per liter, or mg/L. Orange points had at least one test at or above 5 mg/L, and dark orange points had at least one test at or above 10 mg/L. See map key above for more information.
The Environmental Protection Agency considers 3 mg/L of nitrate in groundwater used for drinking water an indication of contamination above naturally occurring levels. The map includes only systems with at least one test at or above that level.
Clicking on a state will take you to that state’s profile, which has summary statistics about the communities in that state with worsening nitrate contamination. Each state profile also contains a link to a state-level map, which provides details about each state’s water systems.
The data were obtained by EWG under the states’ public record laws. Some of the data can also be found on the EPA’s Safe Drinking Water Information System website.
To see a summary report of systems with worsening nitrate contamination across all 10 states, click here.