§ Mr. Gareth WardellTo ask the Secretary of State for Health what information he has on studies on the morbidity rates of populations subjected to drinking water which has been chlorinated.
§ Mr. FreemanAdequate disinfection by chlorination has had a marked effect in reducing morbidity rates from water-borne infectious diseases. However, this treatment leads to the production of chlorination by-products, some of which have been shown to cause cancer in laboratory animals when administered in large doses for long periods. Numerous studies of chlorinated water and disease rates, particularly cancer morbidity and mortality have been published, and the Department sought advice from its independent expert advisory committee on the medical aspects of the contamination of air, soil and water. It said
We have found no sound reason to conclude that the consumption of the by-products of chlorination in drinking water which has been treated and chlorinated according to current practices, increases the risk of cancer in humans.401WThe effective disinfection of water supplies is clearly of great importance in maintaining public health. In our opinion, modification of chlorination processes which have proved effective over many years, or the replacement of chlorination by other disinfectants, is not required by the available data on cancer epidemiology, animal carcinogenicity, and mutagenicity in relation to chlorination by-products in drinking water.This advice was conveyed to water authorities and water companies in England and Wales in DoE/Welsh Office letter WP 12/1986, and republished in annex 1 of "Guidance on Safeguarding the Quality of Public Water Supplies" (HMSO, 1989). Relevant epidemiological and other research is kept under review.