Ground-Water Contamination by Dissolved Nitrate

Ground water containing nitrate (including nitrite) in toxic concentrations, occasionally high enough to be lethal to human beings and livestock when the water is used regularly, has been observed in Kansas, Minnesota, Wisconsin, Iowa, Illinois, Michigan, Montana, Pennsylvania, Missouri, and elsewhere as awareness of $NO 3 -$ poisoning increases. More than 5000 water samples in Missouri, mainly from water-table wells, range from nil to over 300 ppm nitrogen from $NO 3 -$ . Forty-two per cent of these used as rural water-supply samples contain more than 5 ppm nitrogen, a tentative tolerance level for babies. Concentrations above 50 (perhaps 10) ppm should be avoided for livestock. The main contaminating source, in both distribution and concentration, is nitrogenous waste matter at sites of animal habitation. Excessive application of nitrogen-fertilizers in certain soils may also contribute to $NO 3 -$ concentration. The problem is becoming more acute because $NO 3 -$ accumulates below the ground-water table where micro-organisms cannot metabolize the nitrogen to innocuous compounds. High nitrate concentrations were found in permeable loess or sandy soil over glacial clay, solution channels in limestone, and low-lying alluvial deposits. Relocation and proper construction of wells, and geological study of ground-water movement are needed to combat the trouble. No economical treatment of $NO 3 -$ -rich water has been demonstrated. Nitrate poisoning promises to increase in the United States unless precautionary measures are taken. Has nitrate poisoning been a factor in the health of ancient populations, and in the “old countries” from which ancestors of Americans emigrated?