Need for revision of nitrates standards for drinking water: a case study of Rajasthan.

An attempt has been made to classify ground waters in various districts of Rajasthan based on distribution of nitrate in their drinking water samples. It is seen that nitrate in ground water is unevenly distributed in the state. Major parts of Churu, Alwar, Bharatpur, Jalore, Jaipur, Sikar, Tonk and Jhunjhunu, are inherited by nitrate rich ground waters while districts like Banswara, Bundi, Bikaner, Chittor, Kota and Jhalawar have low nitrates in their ground waters at many places. It is well documented internationally that water supplied containing high levels of nitrate have been responsible for cases of infantile methemoglobinemia which may ultimately lead to death. A very high infant mortality rate in Rajasthan might be a consequence of high nitrates in drinking water supply. Some recent studies have shown that nitrates in drinking water besides causing methemoglobinemia can result in various other clinical manifestations like recurrent stomatitis, recurrent respiratory tract infections (RRTI) etc. These findings have indicated that a rethinking has to be given to the existing standards for nitrates in drinking water. Based on potential nitrate toxicity studies in view of above health effects the whole region has been classified into five water quality zones, namely, safe, mild, moderately problematic, highly problematic and dangerous. For areas falling under fourth and fifth zones it is recommended that immediate measures be taken to overcome the adverse health effects.