Nitrate in Private Wells

Nitrate is found across Wisconsin

Nitrate naturally occurs in plants and animals. Nitrate can enter groundwater from fertilizers and animal and human waste. While most exposure to nitrate comes from our diet, drinking water with high levels of nitrate may cause health problems.

Nitrate is one of the most common groundwater contaminants in Wisconsin. It is estimated that at least 10% of private wells in Wisconsin have high levels of nitrate. If you have a private well, we recommend that you test your well for nitrate every year and take action to reduce your exposure if nitrate levels are high.

High levels of nitrate may be harmful to our health

Wisconsin’s drinking water and groundwater standards for nitrate are 10 milligrams per liter (mg/L). This is based on nitrate-nitrogen levels and is what your test result will read as.

Nitrate can impact the blood’s ability to carry oxygen. High levels of nitrate can cause methemoglobinemia or “blue baby syndrome” in infants.

Seek medical help immediately if the skin color of your baby appears bluish or gray. Sometimes color change is first noticed around the mouth, or on the hands and feet.

Some studies suggest that high levels of nitrate may also cause birth defects, thyroid problems, and certain kinds of cancer.

Learn what to do if you have high levels of nitrate in your well (P-02128 - English, Spanish, Hmong) and what is happening around the state to address nitrate issues in groundwater.

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Last Revised: October 1, 2019