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News Release

U.S. Department of the Interior
U.S. Geological Survey

Release: December 4, 2008
Lonna Frans

John Clemens

Study Maps Nitrate in Washington Ground Water

[Editors: The report can be viewed on the Web at .]

Results of the first statewide study to predict elevated concentrations of nitrate in ground water are summarized in a report published by the U.S. Geological Survey (USGS), in cooperation with the Washington State Department of Health.

Scientists found that agricultural areas are most at risk of having elevated nitrate concentrations in ground water, followed by urban areas. Undeveloped areas have a low probability of having elevated nitrate concentrations.

Shallow wells in eastern Washington have a greater than 90-percent probability of nitrate concentrations greater than 2 milligrams per liter. In urban and agricultural areas of Puget Sound, shallow wells have a greater than 50-percent probability of nitrate concentrations exceeding 2 milligrams per liter.

Nitrate concentrations at or greater than 2 milligrams per liter generally are greater than naturally occurring levels and indicate human-related sources of nitrate such as fertilizer and sewage. Federal safe drinking water rules for public water systems set a maximum contaminant level of 10 milligrams per liter for nitrate.

More than 60 percent of Washington residents use ground water for drinking and cooking. Although public water systems routinely monitor nitrate levels in well water, there is no requirement to monitor private wells. To inform private well users, health officials worked with USGS scientists to develop a way to estimate the vulnerability of private wells to nitrate.

Elevated levels of nitrate pose a risk to babies and pregnant women as well as people with a rare blood enzyme disorder. Ingesting high levels of nitrate reduces the ability of red blood cells to carry oxygen. Although older children and adults rapidly recover from this condition, babies can be severely harmed. Information about the health effects of nitrate is available on the Department of Health Web site (

The report, "Distribution of Elevated Nitrate Concentrations in Ground Water in Washington State," by Lonna Frans, is published as U.S. Geological Survey Fact Sheet 2008-3063. Copies are available from the U.S. Geological Survey, Information Services, Box 25286, Federal Center, Denver, CO 80225-0286, toll-free 1-888-ASK-USGS (1-888-275-8747). The report can also be viewed on the Web at .

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