Cancer incidence in an urban community: an historical cohort study.

This historical cohort study tested the hypothesis that residents of an industrialized urban community were at higher risk of cancer than residents of a comparable, but non-industrialized, community. The exposed (C1) and the unexposed (C2) cohorts resided in their respective neighbourhoods between 1952 and 1956. All incident cancers were identified through linkage with the Ontario Cancer Registry for 1964-1982. Cancer incidence rates in the two cohorts were 7.0 and 7.3 per 1,000 person-years, respectively. Relative risk estimates for all cancers, lung cancer and cancers associated with environmental exposure, were not significantly different from 1.0. Only colorectal cancers were significantly more frequent in the C1 than the C2 cohort, and these only in one sub-analysis. Overall, we conclude that if there was increased risk of cancer related to environmental pollution in the industrially exposed community, it was less than a two-fold increase.