Co-carcinogenic effects in rats of combined exposure to radon and ozone

• Published in: Environment international 1996-01, Vol.22, p.909-915
• Main Authors: Monchaux, G., Morlier, J.P., Morin, M., Rochefort, P., Maximilien, R., Trédaniel, J.
• Format: Article
• Language: English
• ISSN: 0160-4120; 1873-6750
• DOI: 10.1016/S0160-4120(96)00201-2

The aim of this study was to estimate in rats the potential carcinogenic or co-carcinogenic risk of ozone, acting either alone as a complete carcinogen, or as a promoter after pulmonary irradiation by inhalation of radon and its decay products. Three experimental groups were used: Group 1 was exposed to radon and daughters at a cumulative exposure of 3.6 J h m −3 (1000 WLM); Group 2 was exposed first to radon in the same conditions as Group 1, and one month after the end of radon exposure, to ozone by inhalation at a concentration of 0.2 μL L −1, 6 h d −1, 5 d/week for 6 months; Group 3 was exposed to ozone alone in the same conditions as Group 2. The incidence of lung cancer was 16% in Group 1, 24% in Group 2, and 4% in Group 3, compared with 0.8% in controls. Lung carcinomas induced by ozone alone showed a trend toward a preferential differentiation pattern to the squamous cell type. These results show a direct carcinogenic effect of ozone in rats for levels of exposure in the same range as those observed during peak levels of urban airborne pollution and suggest a potential co-carcinogenic effect of combined exposure to radon and ozone.