The latest round of results in the Southwest Wisconsin Groundwater and Geology (SWIGG) study have found nitrate contamination levels consistent with pollution found in the first round of sampling, indicating that nitrate pollution is a serious problem in the region that must be addressed.

“Two rigorous rounds of sampling show that nitrate pollution is a big problem in Grant, Iowa, and Lafayette Counties,” said Scott Laeser, Clean Wisconsin water program director. “The high number of wells with nitrate pollution above the health standard from both sampling rounds tell us we need to tackle this problem sooner rather than later. Southwest Wisconsin families deserve safe, clean drinking water, and right now it’s clear many of them don’t have it.”

The study found that 27% of wells tested during the spring sampling event were contaminated with bacteria and/or nitrates. Fifteen percent of wells exceeded the nitrate health standard of 10 mg/l, similar to levels found in the first round of the study when 16% of samples exceeded this threshold. Thirteen wells sampled this spring exceeded 20mg/l, which is double the health standard.

Nitrate pollution in Wisconsin’s groundwater originates primarily from farming operations and some septic systems, but studies conducted by University of Wisconsin researchers and others have found that most nitrate pollution comes from agricultural sources such as manure and commercial fertilizer.

Based on research from the Center for Watershed Science and Education at the University of Wisconsin-Stevens Point, Clean Wisconsin estimates that nitrogen leaching annually from corn fields is 29 times higher than nitrogen leaching annually from septic systems in Grant, Iowa, and Lafayette Counties.

“Instead of getting bogged down in debating whose fault this is, we need to be honest with ourselves about what the science tells us. We need to work together to reduce nitrate pollution so rural residents throughout Wisconsin can draw safe, clean drinking water from their taps,” Laeser said.

Understanding of the health risks associated with consuming nitrate-contaminated water is growing. Blue baby syndrome and central nervous system birth defects are potentially fatal risks of exposure to nitrates for fetuses or young children. For adults, an increased risk of thyroid disease and colorectal cancer has been associated with high nitrate exposure.

“Thanks to the counties and researchers involved in the SWIGG Study, we have definitive evidence of widespread nitrate contamination in private wells in Southwest Wisconsin. The first round of sampling led to the formation of Speaker’s Task Force on Water Quality, and this second round of testing continues to point to the need for bold action by lawmakers to address this problem,” said Laeser. “We know enough at this point that the legislature should feel compelled to start taking steps to fix this problem now.”