It is formed when nitrogen from ammonia or other sources combines with oxygenated water. Nitrate is a natural constituent of plants and is found in vegetables at varying levels depending on the amount of fertilizer applied and on other growing conditions. When foods containing nitrate are eaten as part of a balanced diet the nitrate exposure is not thought to be harmful. Nitrate Levels in Drinking Water Water naturally contains less than 1 milligram of nitrate-nitrogen per liter and is not a major source of exposure.
Higher levels indicate that the water has been contaminated.
Common sources of nitrate contamination include fertilizers, animal wastes, septic tanks, municipal sewage treatment systems, and decaying plant debris. The ability of nitrate to enter well water depends on the type of soil and bedrock present, and on the depth and construction of the well. These laws apply to all city and village water supplies and are used as an advisory for private wells. Health Effects High nitrate levels in drinking water pose a risk to infants. Infants who are fed water or formula made with water that is high in nitrate can develop a condition that doctors call methemoglobinemia.