Lung Tumours in Rats After Inhalation of Actinides

Purpose: To assess the risks of lung tumors after inhalation of different alpha-emitting actinides and help to understand the problem of "hot spots"

Status: 1965 - 1975, terminated; data in ERAD.

Treatment: Inhalation, intramuscular (IM) or intravenous (IV) injection of Th-227 (chloride) Pu-238 (oxide and nitrate), Pu-239 (oxide and nitrate), Am-241, (oxide and nitrate), Cm-244 (nitrate) with or without cofactor.

Dosimetry: Activity inhaled, activity retained, calculated average lung doses for a group.

Endpoints: Life-span study (spontaneous death) with macroscopic/microscopic pathology

Animal: Male Sprague-Dawley SPF rats aged 3 months; for controls see 02.01

Results: The data demonstrate very clearly that the more a dose was homogeneously distributed the more it was efficient in causing cancer and that the opinion that a heterogeneous distribution of exposure in hot spots represents a greater cancer risk is untenable. The degree of homogeneity of dose was varied by inhalation different physicochemical forms of various actinides. Inhalation of oxides caused a heterogeneous distribution of dose whereas that of salt solution which formed hydroxides at higher pH resulted in a nearly homogeneous solution . Other experiments were carried out to study the role of dose rate which depended on the speed of dissolution of the aerosols deposited in lung, the possible synergy with smoking tobacco, the therapy with DTPA and the influence of im or iv injection on the induction of osteosarcoma and leukemia.

When actinides were inhaled in a soluble physico-chemical form not only excess lung cancers but also extra-pulmonary cancers were observed. In order to analyse the the dose-effect relation-ships from these studies correctly, a study on exposure to fission neutrons delivered at various doses and dose rates was carried out (02.12).