After an infant's digestive system becomes developed, the child is no longer susceptible to nitrate poisoning. As a precautionary measure, children under three, nursing mothers, and pregnant mothers should not consume high nitrate water. Although nitrates can occur naturally from decaying organic material such as on-site septic systems, the greatest source of nitrates in most areas is crop fertilizers. Fertilizers typically contain nitrogen compounds which either are in the form of nitrates or turn into nitrates in the soil. These fertilizers produce excellent crop yields, and conversely, they produce elevated nitrate levels in ground water in many rural areas.
Nitrates are water soluble.
Once nitrates are applied to the soil, heavy rains can wash any nitrates not used by plant roots into ground water where they are no longer beneficial to plant roots above ground water level. The result is local wells that are contaminated with nitrates. Nitrate levels are affected by rain patterns and fertilizer application by local farmers. Heavy rainfall can increase or even decrease nitrates in a well, and nitrate results, like other parameter results, can vary greatly. Therefore, regular testing for nitrates is recommended.