[Significance of chemical carcinogens in the atmosphere for carcinogenesis]

After some remarks on air pollution by chemical carcinogens from natural or man-made sources a few figures area given on the production of chemicals and their emission, to characterize the situation. Our little knowledge on the carcinogenic risk from carcinogens in the ambient air is demonstrated with benzo[a]pyrene as an example. The role of nitroaromatic hydrocarbons as possible carcinogenic factors is indicated. We know, that carcinogens exist in the ambient air. Their quantity and sources are partially known. Their activity as a complex is as well unknown as the resulting level of health risk for humans.