The relationship between water quality and health in the London area.

In a retrospective study of the relationship between reuse of water and hazards to health, the mortality experience from different causes, principally cancer, was examined for 29 boroughs and districts in the London area for the period 1968 to 1974. Information concerning the source of water supply to each borough was obtained both for the current situation, and historically back to 1926. Socioeconomic characteristics of the boroughs were extracted from 1971 census data. Differential mortality experiences for each sex were analysed using the standardised mortality ratio for ages 25 to 74. Most of the causes of death examined were associated with one or more of the socioeconomic characteristics of the boroughs. These socioeconomic characteristics accounted for the statistical associations between water reuse and mortality for each cause studied, except male stomach cancer, where a weak residual association remained. This association disappeared when variation in the size of boroughs was taken into account.