Nitrate is a compound made up of nitrogen and oxygen. It is formed when nitrogen from ammonia or other sources combines with oxygen in water.
Nitrate is naturally found in plants and in vegetables and can be found in groundwater, depending on how much fertilizer and manure is applied to fields.
According to the U.S. Environmental Protection Agency, most adults who are eating a balanced diet may consume 10 to 25 milligrams of nitrate or nitrogen per day in their food. Most comes from leafy vegetables such as lettuce, cabbage, celery and spinach but also from cured meats such as bacon.
Additional exposure to nitrate from contaminated drinking water may pose significant health risks. Potentially fatal “blue baby syndrome” has been linked to the presence of nitrate in drinking water. It is also suspected of causing thyroid disease, diabetes and certain types of cancer.
Common sources of nitrate include nitrogen fertilizers, manure, septic systems and sewage treatment practices. Nitrate can be carried into the groundwater by rainwater and melting snow that percolates through the soil and bedrock into the underlying aquifer.
Nitrate can also run off fields and pollute surface water, causing overstimulation of aquatic plants and algae, resulting in unsightly scum and occasional fish kills.
Sources: Wisconsin Department of Natural Resources Nitrate in Drinking Water fact sheet and U.S. Geological Survey Water Science School website.