Source: A common source of excess concentrations of nitrate in drinking water is the application of fertilizers. Other sources include raw sewage and cattle feedlots. Nitrate and ammonia compounds are extremely soluble in water. Nitrate (NO3) and the ammonium ion (NH4) are converted by microorganisms in the soil or in septage to nitrite (NO2). Nitrates are also converted to nitrites in the human alimentary tract.

Health Effects: When ingested in drinking water, nitrites, and nitrates that are converted to nitrites, react with hemoglobin in the blood to form methemoglobin -- creating a condition known as methemoglobinemia. This condition reduces the efficiency of the body's blood-oxygen transport system. This is a dangerous condition for everyone. However, babies, because their relatively low blood volumes, are particularly susceptible, and methemoglobinemia (sometimes known as "Blue Baby Syndrome") is often fatal.

Maximum Contaminant Level: The highest concentration of nitrate allowed in drinking water is 10 parts per million.