TOPEKA — A 40-year comparison study of rural water wells in the Great Bend Prairie Aquifer exposed substantial escalation in nitrate levels and produced a recommendation from researchers that private well owners annually test their water quality, officials said Tuesday.

Concentration of nitrates in wells of the Great Bend Prairie Aquifer, which is part of the High Plains Aquifer, appear large relative to concentrations measured in a national study by the U.S. Geological Survey, said Matthew Kirk, associate professor of geology at Kansas State University.

Research led by Kansas State revealed nitrate levels in shallow wells of the Great Bent Prairie Aquifer to be above standards of the U.S. Environment Protection Agency for drinking water. High nitrate levels in drinking water can cause human and livestock health issues by interfering with transport of oxygen by blood and potentially raising the risk of cancer.

"The Great Bend Prairie Aquifer is very vulnerable to contamination, and if rural well owners don't know there is a problem, they obviously can't do anything about it," Kirk said. "Municipalities are required to test and provide safe drinking water for city residents, but private rural well owners should take responsibility to test their wells at least every year."

Conditions in the High Plains Aquifer were the focus of a comparison study of rural water published in Hydrogeology Journal. Kirk and geology graduate student Allie Richard Lane published the study along with Donald Whittemore, of the Kansas Geological Survey; geologist Randy Stotler, of the University of Kansas; and John Hildebrand and Orrin Feril, both with Big Bend Groundwater Management District No. 5.

Lane, who now works at the Kansas Department of Health and Environment, said kits costing about $40 could be purchased online to test water for nitrate, bacteria, pesticides, lead, copper, iron and for hardness.

"Those kits are good to use for basic readings and if anything is concerning, then residents can send a sample to a lab for further testing," Lane said.

Researchers compared water chemistry of new samples with measurements at the same sites from the 1970s. Twenty of 21 wells had increased nitrate levels compared to the 1970s samples. Seven wells exceeded EPA standards for drinking water. In the 1970s study, only one well surpassed the current EPA standard.

According to the study, wells with the highest contamination were in fields used for crop production. The chemical signature of samples showed nitrate in the aquifer was from fertilizer.

"Other parts of the High Plains Aquifer are most likely going to see changes too, but it's just taking it longer to show up because of transport time between the surface and the water table," Kirk said.