Experimental Study of the Combined Effects of Inhalation of Radon Daughter Products and Tobacco Smoke

摘要

For 10 years, over 500 lung cancers have been induced in rats by inhalations of radon daughter products at various concentrations and cumulated doses. Considering several points and the dose-effect relationship especially, such cancers can be compared with human cancers. This type of experiments, fully mastered, has made it possible to undertake under good conditions the study of the co-carcinogenic effect of various inhaled pollutants such as tobacco smoke. In a first experiment, 100 rats were exposed to a 4000WLM cumulated dose of radon daughter products, knowing that this level induces some 30% of lung cancers. Fifty animals were then administered tobacco smoke by inhalation in a fume box during 5 months (350 h). In the group inhaling radon only, 17 cancers appeared; in the radon-tobacco group 32 cancers bigger and more invasive were observed. Under the same conditions, tobacco smoke was inhaled by rats previously exposed to lower doses of radon daughter products (2 groups of 30 rats, 500 and 100 WLM respectively). Again, the number of cancers observed was higher than the number of cancers expected if the rats had inhaled radon only. This co-carcinogenic and potentiating action of tobacco was clearly demonstrated. Further experiments are considered in order to determine the processes involved. (Atomindex citation 11:535392)