Clearance of radioactivity deposited in the respiratory tract to blood: Progress in a multinational interspecies comparison project

Dire to the diversity of the chemical forms of radionuclides inhaled in ind ustry and the environment, the assessment of intake and dose is based frequ ently on biokinetic studies of the materials in laboratory animals. The ICR P respiratory tract and systemic models provide an effective framework for extrapolating the results of such studies to humans, but there is a paucity of data concerning the crucial assumption that the absorption rates from l ungs into blood for a given material are independent of the mammalian speci es. To address this uncertainty, biokinetic studies involving five chemical compounds and four mammalian species are being conducted. The compounds, w ith the species in parenthesis, are Pu-nitrate (man, primate, rat), Gd-oxid e (man, primate, dog, rat), Np- oxide and nitrate (primate, rat), and U-oct oxide (primate, dog rat). This paper describes progress to date.