Environmental factors

The incidence of many types of cancer varies greatly between geographical areas. There are changes of rates following migration between areas of contrasting incidence, changes in incidence over time, and variation within populations according to socio-economic status. Thus environmental factors appear to have a major role in the aetiology of most types of cancer, accounting for over 80% of human cancer. Identification of the precise causes depends on multi-disciplinary research, with analytical epidemiological studies an essential component. Based on evidence from analytical studies, a number of estimates of the proportion of cancer attributable to specific exposures have been made1,2.

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