Nitrate in Drinking Water

Nitrate is one of the most common groundwater contaminants in the United States, particularly in agricultural areas. It enters water supplies primarily through nitrogen-based fertilizers that wash off farmland during rainfall, leaking or poorly maintained septic systems, animal feedlot runoff, and municipal wastewater. Naturally occurring nitrate from geological deposits also contributes, but human activities have dramatically increased nitrate levels in many aquifers and surface waters over the past several decades.

The most acute danger from nitrate in drinking water is to infants under six months of age. When babies ingest water with high nitrate levels (or formula mixed with that water), bacteria in their digestive systems convert nitrate to nitrite, which interferes with the blood's ability to carry oxygen. This condition, known as methemoglobinemia or "blue baby syndrome," can be fatal if untreated. The symptoms include bluish skin color, shortness of breath, and lethargy. Adults can also experience health effects from high nitrate exposure, including increased risk of thyroid problems and some emerging research suggests possible links to certain cancers.

Nitrate contamination is most prevalent in rural agricultural communities, especially in the Midwest, Great Plains, and Central Valley of California. Private wells in farming areas are at particularly high risk because they are not monitored by the EPA. Nitrate levels tend to spike in spring and after heavy rainfall events when fertilizer runoff increases. If you live in a farming community or rely on a private well, regular testing is essential -- especially if there are infants in the household.