The extent of nitrate contamination, and how quickly it occurs, depends both on soil type and on depth of the water source. Nitrates can leach more easily in light sandy soils than in clay-based soils. Contamination is more common in shallow wells than in wells drilled into deeper aquifers. Heavy rains and flooding also affect the amount of nitrate that reaches both ground and surface water. High nitrate levels in drinking water can have adverse effects on human health.
Most cases occur in infants under one year of age.
Therefore, water high in nitrates should not be used to prepare infant formula or food, and should not be given to infants to drink. As nitrates may be present in breast milk, nursing mothers also should avoid ingestion of water high in nitrates. Pregnant women should also avoid using water with excess nitrates. Nitrate is converted to nitrite in the stomach, then absorbed into the bloodstream. There it interferes with the ability of red blood cells to carry oxygen.