The application of epidemiology to the prevention of occupational cancer

Epidemiology attempts to establish a quantitative causality which is essential in preventive medicine strategies for occupational cancer. By studying carefully exposure effect relationships and populations at risk, subtle causes of occupational cancer can be identified. The nature of epidemiological reasoning and the criticism of this methodology are outlined. Using combined epidemiological and industrial hygiene data, a quantitative risk assessment of a lifetime exposure of workers to benzene and its association with leukemia is presented. In a population of 1,000 workers exposed for a working lifetime to 100 ppm benzene vapor, 140 excess deaths from leukemia would occur. At a lifetime exposure of 10 ppm, it is calculated that 14 excess leukemia deaths would occur. Because the current legal standard is 10 ppms for occupational exposure, this epidemiological risk assessment indicates that an unexpectedly large number of excess leukemia deaths will result in a population of workers exposed to 10 ppm.