Known occupational carcinogens and their significance.

Although rates of occupational cancer can be excessive in certain industries, less than 5% of all cancers seem attributable to exposure to carcinogens in the workplace. For example, workers in hard-rock mining and the woodworking industries are at increased risk; cigarette smoking has a synergistic effect. There is conclusive evidence of carcinogenicity for fewer than 20 substances, including asbestos, arsenic, chromium, nickel, cadmium, radon, several aromatic hydrocarbons and certain herbicides. Most of the hundreds of organic compounds known to be mutagenic in in-vitro tests have not been shown to be carcinogenic in epidemiologic studies. Both laboratory and epidemiologic approaches, however, can identify probable causes of cancer and permit the application of effective preventive measures. In addition, it is still possible for the alert individual clinician to make the initial discovery of an occupational hazard.