A recent study has found high levels of uranium in two major aquifers in the United States that may pose a great health risk to people living over groundwater containing the chemical.
The high levels of uranium are linked to the presence of nitrates, scientists say.
Nearly 2 million people living in California and the Great Plains are situated over groundwater contaminated with uranium. Researchers at the University of Nebraska-Lincoln (UNL) studied about 275,000 water samples from the aquifers in Central Valley and the High Plains to determine uranium contamination and find out what risks the contamination has to health. They published their findings in the journal Environmental Science & Technology Letters.
In the study, the researchers noted that many Americans live close to wells with very high uranium content. That's less than two-thirds of a mile from contaminated wells whose levels of uranium exceed Environmental Protection Agency (EPA) guidelines.
Some 78 percent of the sites contaminated with uranium also had high levels of nitrate, which mainly comes from animal waste and chemical fertilizers, and is a common contaminant found in groundwater. Through a series of reactions, both chemical and bacterial, nitrate oxidizes the radioactive mineral and makes it soluble in groundwater. Nitrate was found to mobilize naturally occurring uranium in groundwater.
According to researchers Jason Nolan and Karrie Weber from UNL, uranium content in the High Plains aquifer is significantly higher than EPA standards by 89 times. Nitrate concentrations, on the other hand, are approximately 189 times higher. Concentrations at the aquifer in Central Valley are greater than EPA standards by 180 times for uranium and 34 times for nitrate.
"It needs to be recognized that uranium is a widespread contaminant," said Weber, who is also an assistant professor of biological, Earth and atmospheric sciences. She added that when we allow the production of a primary contaminant, a secondary one follows, causing problems.
In a previous research, prolonged drinking of water contaminated with uranium was found to be linked to a susceptibility to kidney damage and increased blood pressure. Also, peer-reviewed studies have found that food crops can also get contaminated with uranium through irrigated water from uranium-contaminated water sources, Weber said.
The High Plains aquifer is the largest aquifer in the U.S., providing drinking water and irrigation that runs from South Dakota to Nebraska to northern Texas. Central Valley is the largest reservoir in California, situated under some of the most fertile agricultural lands in the state. These two aquifers generate about one-sixth of the annual agricultural revenue in the U.S.
The UNL researchers also highlighted that uranium contamination does not necessarily result from mining or spent nuclear fuel, after they determined that only one out of six wells located near a current or former mining site had high levels of uranium.
