LINCOLN, Neb., Aug. 17 (UPI) -- Nearly two million people in the United States live above an aquifer contaminated by natural uranium.
According to new groundwater survey, aquifers flowing under the Great Plains and California's Central Valley feature significant uranium levels fueled by fertilizer runoff and animal waste.
Hundreds of the more than 280,000 collected water samples tested positive for uranium. Nearly 80 percent of the positive tests are the result of nitrate contamination, researchers at the University of Nebraska say.
Dozens of wells were found with uranium concentrations up to 89 time higher than the EPA limit for potable water.
When nitrates from agricultural runoff seeps into groundwater, a series of chemical and bacterial reactions can work to oxidize the uranium and make the radioactive mineral water soluble.
The new research shows that uranium contamination is predominantly the result of growing concentrations of nitrates, not mining or nuclear fuel pollution. Researchers found only one in six of the wells near mining sites to be contaminated.
"It needs to be recognized that uranium is a widespread contaminant," researcher Karen Weber, assistant professor of biological, earth and atmospheric sciences, said in a press release. "And we are creating this problem by producing a primary contaminant that leads to a secondary one."
Weber and her colleague, Jason Nolan, hope their work -- published in the journal Environmental Science & Technology Letters -- inspires more active monitoring of uranium contamination.
Research suggests trace amounts of the radioactive minerals can be absorbed in the body over long periods of time. Accumulation can lead to kidney damage and high blood pressure.
Smaller, rural communities often can't afford water treatment plants, meaning better groundwater management is necessary to curb contamination.
"When you start thinking about how much water is drawn from these aquifers, it's substantial relative to anywhere else in the world," Weber said. "These two aquifers are economically important -- they play a significant role in feeding the nation -- but they're also important for health."