Environmental factors in the aetiology of gastric cancer.

Gastric cancer is one of the commoner causes of death in the United Kingdom but its frequency varies considerably from one part of the country to another. The standardized mortality ratios (SMRs) for the counties and county boroughs of England and Wales for the year 1961 show a range of from 59 to 164 in the case of males and from 41 to 163 in the case of females (Registrar General, 1967). The present analysis follows that made in respect of lung cancer and bronchitis (Ashley, 1969) and is based on mortality and environmental data from 53 towns in which stations for the assay of air pollution had been set up. The standardized mortality ratios were calculated for the years 1958 to 1963 from the published data of the Registrar-General (1960a, 1960b, 1962, 1963, 1964a, 1964b, 1965). The environmental parameters used were the population density (persons per acre) from the Registrar General's statistics (1964b); a social class index which comprised the proportion of the working male population who were in classes 10 (semi-skilled manual workers), 11 (unskilled manual workers), and 15 (agricultural workers) (General Register Office, 1965); the extent of atmospheric pollution by smoke and sulphur dioxide recorded at gauges set up in residential areas (Department of Scientific and Industrial Research, 1963); and a final separation into towns in which the dusty mining and textile industries were important employers of labour (Ashley, 1967, 1969).