In wastewater irrigation, the primary concern with respect to nitrogen is the possibility of nitrate contamination of domestic water supplies and the attendant risk of methemoglobinemia in human infants. Although the incidence of methemogl obi nemi a, or “blue baby disease,” in the United States is very low, the Public Hea7th Service has set 10 mg/L nitrate-N as the level that should not be exceeded in drinking water. The risk is based on the possibility of reduction of nitrate to nitrite in the digestive tract of infants below the age of 6 months. Nitrite absorbed into the blood stream can combine with hemoglobin, thereby reducing its capacity to carry oxygen. 07 der humans are much less susceptible to the disease than are very young infants. Methemogl obi nemi a is much more common in ruminant animals than in humans, but its occurrence is usually associated with high nitrate concentrations in forage rather than in drinking water.