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Nitrate in Drinking Water, 2003-2017: Texas

Between 2003 and 2017, tests detected elevated levels of nitrate (3 milligrams per liter, or mg/L) in the tap water supplies of 384 towns and cities in Texas, serving approximately 1.9 million people.

Contamination is getting worse in 218 of those community water systems1 – 57 percent, serving approximately 691,000 people. Larger towns and cities tend to depend on surface water for drinking, whereas smaller, often rural communities depend on groundwater. In Texas, just over 468,000 residents of 59 larger towns and cities that rely on surface water faced increased contamination. But 159 mostly small, rural communities, serving approximately 223,000 people, that depend on groundwater also saw nitrate contamination increase.

Texas Communities With Increases in Nitrate Contamination, 2003 to 2017

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Average nitrate contamination across these communities jumped by 21 percent between 2003 and 2017. In 2003, average contamination was 5.16 mg/L. By 2009, average contamination had increased to 5.77 mg/L and continued climbing to 6.01 mg/L in 2017.

Average Nitrate Levels in Texas Communities Where Contamination Rose, 2003 to 2017

Source: EWG, from Texas Commission on Environmental Quality data.

Health Hazards of Nitrate

Nitrate is a primary chemical component of fertilizer and manure that can run off farm fields and seep into drinking water supplies. Under the federal Safe Drinking Water Act, the legal limit for nitrate, measured as nitrogen, in drinking water is 10 mg/L. This limit was set in 1962 to guard against so-called blue baby syndrome, a potentially fatal condition that starves infants of oxygen if they ingest too much nitrate.

But more recent studies show strong evidence of an increased risk of colorectal cancer, thyroid disease and neural tube birth defects at levels at 5 mg/L or even lower. During the period studied, drinking water was getting worse in 115 Texas communities, serving approximately 463,000 people, that already had tested at or above 5 mg/L at least once.

Drinking water for approximately 47,000 of those people, in 46 communities, had already tested at or above the legal limit at least once and had increasing nitrate levels during the period studied. Of the 102 communities where nitrate exceeded the Environmental Protection Agency’s legal limit at least once, 38 systems, serving approximately 34,000 people, tested at or above the legal limit in 2017.

People who want to know the level of nitrate in their community’s water system can visit the Texas page of EWG’s Tap Water Database.

Who Is Affected?

Contamination was more likely to get worse in smaller communities between 2003 and 2017. Eighty-two percent of systems where contamination increased served 3,300 people or fewer. For our analysis, systems were put into the EPA-designated size categories based on how many water customers they serve.

Nitrate contamination was also more likely to get worse for people living in rural areas. In Texas, 69 percent of communities with growing nitrate levels were rural, whereas 31 percent were urban, as defined by the U.S. Census Bureau.

Notes

1 Community water systems are public water supplies that serve residents in cities and towns year-round.