Methaemoglobinaemia in areas with high nitrate concentration in drinking water

Background. An epidemiological investigation was undertaken in all age grou ps to assess the prevalence of methaemoglobinaemia in areas with high nitra te concentration in drinking water. Methods. Five areas were selected with an average nitrate concentration las nitrate) of 26, 45, 95, 222 and 459 mg nitrate ions/litre in drinking wate r. These areas were visited and the house schedule (containing name, age, s ex and weight of the family members) prepared in accordance with the statis tically designed protocol. In all, 178 persons, matched for age and weight, were selected and arranged in five age groups. They constituted 10% of the total population of each of these areas. A detailed history of the selecte d population was taken, medical examination conducted and blood samples tak en to ascertain the level of methaemoglobin, The collected data were subjec ted to statistical analysis to ascertain a relationship between nitrate con centration and methaemoglobinaemia, Results. High nitrate concentrations cause severe methaemoglobinaemia (7%-2 7% of Hb) in all age groups, especially in the age group of less than 1 yea r and above 18 years. The lower levels of methaemoglobin in the age group o f 1-18 years is probably due to better reserve of cytochrome b(5) reductase activity and its adaptation to increasing nitrate concentration in water t o compensate for methaemoglobinaemia in this age group. Conclusion. We conclude that high nitrate ingestion causes methaemoglobinae mia in all age groups. Cytochrome b(5) reductase activity and its adaptatio n with increasing water nitrate ingestion plays a role in compensating for the methaemoglobinaemia.