“No one wants people getting sick from their drinking water,” Abbott said.

It’s possible that faulty septic systems are causing some portion of the contamination, or that wells need to be upgraded.

Before the study is completed in 2020, researchers plan to investigate a variety of factors that could contribute to contamination, Bradbury said.

For example, in the southwest part of the state at least some of the soil is composed of clay, which can slow the downward flow of pollutants. The clay areas need to be better mapped to understand the extent to which they may protect drinking water, Bradbury said.

“The shallow bedrock and thin soils in southwest Wisconsin make this a vulnerable setting from the standpoint of groundwater contamination,” Bradbury said.

“Now that we’re beginning to get some solid data sets we can begin to compare the results to physical parameters such as bedrock depth, soil type, and well construction in order to determine the most important factors controlling well vulnerability,” he said.

[Editor's note: This story has been updated to clarify two items in the sixth paragraph. The original said research links "the malady" to health risks in adults but should have said "high nitrate consumption." Also, while diabetes is one of the risks, the link has not been as well established as thyroid disease and cancer.]

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