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 industry and the environment, the assessment of intake and dose is based frequently on biokinetic studies of the materials in laboratory animals. The ICRP 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 lungs into blood for a given material are independent of the mammalian species. To address this uncertainty, biokinetic studies involving five chemical compounds and four mammalian species are being conducted. The compounds, with the species in parenthesis, are Pu-nitrate (man, primate, rat), Gd-oxide (man, primate, dog, rat), Np- oxide and nitrate (primate, rat), and U-octoxide (primate, dog rat). This paper describes progress to date