Analysis of lung tumour risk in radon-exposed rats: an intercomparison of multi-step modelling.

Three carcinogenesis modelling groups have both jointly and separately applied a multi-step carcinogenesis model with clonal expansion to one data set of lung tumours in rats exposed to radon (CEA, France). This study was designed to investigate the differences in modelling approach and fitting procedures used by the three groups in detail, and to explore possible discrepancies in the results. Using the same model assumptions and a (linear) radiation dependence on the first model step only, the three groups arrived at identical best fits, proving that the mathematical formalisms and fitting procedures do not lead to different results.

Neutron RBE for induction of tumors with high lethality in Sprague-Dawley rats.

The effectiveness of fission neutrons is compared to that of gamma rays and X rays with regard to the induction of malignancies in male Sprague-Dawley rats. The analysis is based on autopsy results. It is focused on tumors that tend to be present in animals dying early, which is indicative of a high degree of lethality.

Carcinogenic and cocarcinogenic effects of radon and radon daughters in rats.

It has been previously established that lung cancer could be induced in rats by exposure to radon and radon daughters. Although the oat-cell carcinomas that are common in humans were not found in rats, other histological types of lung carcinomas, especially squamous cell carcinomas and primitive lung adenocarcinomas, were similar to those observed in humans. A dose-effect relationship was established for cumulative doses varying from 25 to 3000 working-level-months (WLM), which was similar for medium and high cumulative doses to that observed in uranium miners.

[Experimental study of different histologic types of pulmonary cancers induced by irradiation].

Recent epidemiologic studies suggested that some histologic types of carcinomas were preferentially induced in the lung by irradiation, whatever the mode of exposure and the radiation quality. Since smoking and other environmental airborne pollutants may be strong confounding factors in humans, we have investigated whether histological subtypes were dependent or not on the mode of exposure, in a large series of 9000 rats exposed to external and internal sources at high and low Linear Energy Transfer. Despite comparable overall risk coefficients in rats and humans, our results show that histological types are influenced not only by dose but also by radiation quality and heterogeneity of dose delivering.

[Importance of the role of dose rate on tumor induction in rats after radon inhalation].

Lung cancer can be induced in rats, by radon daughter products, after exposure as low as 25 WLM (80 mJ.h.m-3) protracted over 4 to 6 months with a dose rate of 100 to 150 WL (2 to 3 mJ.