EXTERNAL ENVIRONMENT

Air pollutants arising from traffic clustering and industrial producti on include a number of chemical compounds that at high doses are carci nogenic in animal models and in some instances also in humans. Direct epidemiological evidence for a carcinogenic effect of air pollution in humans is, however, weak, and most of the available studies are limit ed by lack of adequate control of confounding factors and other method ological drawbacks. Limited evidence exists for a link between urban a ir pollution and lung cancer, with reported relative risks of 1.0-1.5. About one-third of the population of the Nordic countries, correspond ing to 7.3 million people, lives in urban areas. If there is an excess risk associated with air pollution, the annual number of lung cancer cases around the year 2000 in the Nordic countries would range from 0 (no excess risk) to 1,800 (relative risk, 1.5). As the existence of a causal link between air pollution and cancer is not uncorroborated, me asures for avoiding cancer from this source cannot be recommended.