Assessment of the epidemiological data relating lung cancer to air pollution.

The epidemiological data linking air pollution and lung cancer are derived from statistical associations concerning rates of cancer among urban and rural residents, migrant studies and studies of occupational groups exposed to effluents from fossil fuel combinations. Few, if any of these studies, are adequately adjusted for both relatively simple measures of cigarette smoking or the potentially more subtle effects of the duration of smoking. Because urbanization and industrial sources of air pollution correspond chronologically with the major increases in cigarette smoking, it is not likely that the specific attributable risk to each component can be adequately assessed. Interactions between cigarette smoking and specific air pollutants, similar to those seen between cigarette smoking and asbestos and or radiation, may be occurring. Considering the various estimates made over the last 25 years, it is likely that the effect of air pollution on lung cancer is something greater than zero; however, it is unlikely that the estimate exceeds 2% of all lung cancers or 5/100,000 cases in urban males. Thus, the effect on all cancers is likely to be less than 1% of all cases.