By Reid Kuenzi, Natasha Krieger, Paul Mathewson, Ph.D.
Summary
Nitrates are Wisconsin’s most widespread groundwater contaminant, threatening the drinking water of over two-thirds of Wisconsinites who rely on groundwater as their primary source of drinking water. Nitrogen is an essential nutrient for plant and animal growth and is commonly used as a fertilizer for agricultural crops. While valuable for crop production, not all the nitrogen applied to fields is taken up by crops. When nitrate is applied as fertilizer, manure, or in other forms, it does not bind to soil particles as other nutrients like phosphorus do. Instead, nitrate is highly mobile and will move with water down through the soil and into groundwater aquifers used for drinking water.
Key takeaways:
- Typically, less than half of the nitrogen that is applied to fields actually gets used by crops, leaving most of it to escape into the environment. This includes contaminating drinking water sources.
- DATCP sampling suggested that 7-8% of private wells in the state exceed the 10 ppm drinking water standard and 20-25% of private wells in the state have nitrate levels above 5 ppm.
- Based on elevated drinking water nitrate exposure rates, an estimated 170 cases of cancer, 95 cases of very low birth weights, 51 cases of very preterm births, and 2 neural tube defects annually could be attributed to nitrate-contaminated drinking water in Wisconsin.
- Current drinking water standards may be inadequate to protect against all types of harm from nitrate contamination in drinking water.
