Epidemiologic identification of occupational carcinogens.

Epidemiology has a role to play in the identification of occupational carcinogens through hypothesis testing and surveillance for new carcinogenic hazards. Hypothesis testing is undertaken mainly by retrospective (non-concurrent) cohort studies and case-control studies. The former are limited particularly by difficulties in follow-up and inadequacy of data on exposure to the agent of interest and possible confounding or interacting factors. The latter are limited mainly by the problem of bias in the retrospective determination of exposure. Several studies giving similar results are therefore usually required before an association can be considered with any confidence as established. Surveillance for new hazards may be maintained by the regular analysis of routinely collected cancer incidence or mortality data. For early detection of hazards this should be supplemented by special studies, either on-going case control studies of cancers which are commonly due to occupation (e.g. lung, bladder, liver and nasal cancers) or linkage of personnel records from high risk industries to cancer registry or death records.