Cancer incidence and geochemical factors in the environment.

Between 1961 and 1987, 9875 cases of cancer were registered in the district of Zdar nad Sazavou in southern Czechoslovakia; this district covers an area of 1627 km2 and has a population of 125,000 living within 197 identifiable communities. The age-standardized cancer incidence (standardized incidence rate, SIR) for selected cancers was calculated for each of the 197 communities. Five distinct geological areas were identified in the district; the percentages of the communities with a high incidence of cancer in each of these five areas were compared and statistically tested.