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The rates nitrate risks from “low or none� to “very high� for each square mile of the county. It considers local land cover, soil type, septic system density and irrigation to determine possible nitrate dangers.

Users of the map are able to input their home addresses and identify what the nitrate risks are in the area.

Nick Zupan, an epidemiologist at the Rock County Public Health Department, debuted the map at the Rock County Board of Health meeting Wednesday night. He said the tool has been an ongoing project for three years and is designed to strengthen communication with residents who own private wells.

Nitrates are found in fertilizers and food and waste materials. They can leach into groundwater if they are not carried away in runoff or absorbed by plants.

Officials say the countyÃÛèÖÊÓƵ nitrate levels are among the highest in the state. The county estimates at least 30% of private wells have high nitrates levels, or more than 10 parts per million.

Drinking water with high nitrate levels carries heightened risks of blue baby syndrome, and there are possible links to diabetes and some cancers.

Rock CountyÃÛèÖÊÓƵ map does not indicate nitrate levels in drinking water. It only rates the risks of nitrates in groundwater, which might signal that the drinking water in that area is a health hazard, officials said.

In areas with very high nitrate levels, county officials encourage homeowners with wells to test their water annually.

Rick Wietersen, environmental health director at the public health department, said low or no-risk areas still could have nitrate contamination in the groundwater.

Groundwater with high nitrate levels might flow to nearby areas, he said. Nitrate levels also could vary depending on the groundwaterÃÛèÖÊÓƵ depth. He said the risk tool essentially determines the nitrate level at the top of the groundwater, but not necessarily the well water.

“Even when itÃÛèÖÊÓƵ a low risk, we really encourage people to test their wells,â€� Wietersen said.

To reduce nitrates, treatment techniques for homeowners include reverse osmosis, ion exchange and distillation, Wietersen said.

Rock County launched the online tool Monday afternoon. Zupan said the department now will promote it by doing social media outreach, tracking website usage and ideally increasing water tests.

A grant from the National Environmental Health Association helped pave the way for the tool, allowing the county to use state Department of Health Services’ data expertise to build it.

Rock County was the only recipient of the $2,500 grant in the country.

In his presentation, Zupan said students from UW-WhitewaterÃÛèÖÊÓƵ geography department helped determine the four main ingredients that contribute to high nitrate levels in the county. The students then combined the data into a map, which eventually blossomed into the interactive tool.

“We want it to be a communication tool. The main message is we want people to be testing their well water,� Zupan said. “If we can increase that, then we can get down the road of what people need to do to mitigate some of the risks.�