§ Mr. WallaceTo ask the Secretary of State for Heath what information his Department has on the effects of drinking chlorinated water.
§ Mr. FreemanNearly all public water supplies in England and Wales are treated with chlorine by the water undertakers in order to kill pathogenic micro-organisms. This leads to the production of chlorination by-products, at a level of a few parts per billion. Some of the chemicals formed cause cancer when administered in large doses for long periods to laboratory animals.
The Government sought advice from the Department of Health's independent expert advisory committee on 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.The 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 the Department of the Environment/Welsh Office letter WP 12/1986.