Lifespan Studies in Rats Exposed to²³⁹PuO₂Aerosol. III. Survival and Lung Tumours

Abstract

Female, young adult, Wistar rats were given a single inhalation exposure to a submicron sized aerosol of high-fired 239PuO2 and observed during their lifespan for primary lung tumours. Rats were distributed among sham-control (n = 1052) and exposed (n = 2105) groups. Survival was significantly reduced only in rats with lung doses > 30 Gy. A total of 99 primary lung tumours were found, of which 92% were malignant and 80% were carcinomas. Of malignant lung tumours, 49 were squamous cell carcinoma, 23 adenocarcinoma, nine hemangiosarcoma, seven adenosquamous carcinoma, and three fibrosarcoma. One adenocarcinoma was found in controls and only four adenomas were seen in the exposed rat at lung doses < 1.5 Gy. The lowest doses at which lung tumours appeared in exposed rats were 1.5 Gy for squamous cell carcinoma, 3.1 Gy for adenocarcinoma. 4.1 Gy for hemangiosarcoma, and about 9 Gy for adenosquamous carcinoma and fibrosarcoma. Pulmonary squamous metaplasia was not seen in controls and was first seen in exposed rats only at lung doses > 1 Gy. Primary lung tumours were the presumed cause of death (fatal) in 60% of rats with malignant lung tumours; causes of death were equally distributed among all tumour types and doses. The incidence of all lung tumours was 0.095% in control rats, 0.21% in 1877 rats with lung doses < 1 Gy, and 41% in 228 rats with doses > 1 Gy. Lung tumour incidence increased in a linear manner from 6.9% at 2.3 Gy to an incidence of 64-88% at 16-44 Gy. Absolute malignant lung tumour risk averaged 270 lung tumours per 10(4) rat-Gy above a lung dose of 1 Gy. All types of malignant lung tumours induced by inhaled 239PuO2 exhibited a threshold at a lung dose > 1 Gy.

Activation of Alveolar Macrophages after Plutonium Oxide Inhalation in Rats: Involvement in the Early Inflammatory Response

“…These have been described both in experimental animals and in nuclear workers, such as the cohort from Mayak (1)(2)(3).…”

“…(2) Macrophages are an important source of inflammatory mediators; (3) mild inflammatory changes are associated with proliferative lesions observed in middle and late stages of plutonium-induced lung pathologies (4,19). (4) The development of squamous metaplasia occurs almost exclusively within fibrosis foci.…”

Le stockage définitif des déchets radioactifs et la radioprotection

“…Au niveau du risque, nous savons que les émetteurs alpha peuvent conduire à des réponses différentes de la relation linéaire sans seuil (Raabe et al, 1983(Raabe et al, , 1981Park, 1992Park, , 1990Sanders et al, 1993Sanders et al, , 1991Hohryakov et Romanov, 1994). L'observation des ostéosarcomes chez les peintres de cadran lumineux montre que la relation dose-effet ne répond pas à une relation linéaire sans seuil comme le montre la figure 1 (Evans et al, 1974 ;Rowland et al, 1978 ;Rowland, 1995) alors que les carcinomes des sinus de la face et des maxillaires sont plus proches d'une représentation linéaire.…”

Radiation risks in perspective: radiation-induced cancer among cancer risks

“…The variation of natural background irradiation, which in some regions is as low as 1.5 mSv and in other regions as high as 100 mSv [50,51,52,53,54], does not seem to have any impact and does not suggest a LNT relationship. Indeed, most epidemiological and experimental data [55,56,57,58,59] support a quadratic relationship, which is also compatible with the excess of solid tumours observed in A-bomb survivors [23], particularly when the presence of a neutron component is taken into consideration [60,61]. The possibility of an effect of low doses (10-20 mSv) on the fetus irradiated in utero [49,62] deserves more investigation; it should, however, be recalled that the rapidly dividing immature cells of a fetus are not comparable to solid tissue but rather to bone marrow.…”