PROLONGED use of chlorinated drinking water can cause cancer, says a study by scientists at the Indian Council for Medical Research (ICMR). When chlorine gas reacts with naturally occurring organic contaminants in water, minute concentrations of carcinogenic compounds are formed. The risk is greater in water got from rivers and reservoirs than that from the ground or tubewells.

Another study published in the American Journal of Public Health estimates about 9 per cent of all bladder cancers and 15 per cent of rectal cancers in USA results from long-term consumption of chlorinated water. The US Environment Protection Agency has been in the process of reviewing permissible chlorine concentrations in water since 1979.