Experimental studies of the early effects of inhaled beta-emitting radionuclides for nuclear accident risk assessment: Phase 2 report

Abstract

This report summarizes a series of experiments concerning the effect of linear energy transfer and temporal radiation dose pattern to the lung from inhaled beta-emitting radionuclides. The results were used to test the validity of a hazard-function mathematical model for predicting death from radiation pneumonitis. Both morbidity and mortality within 18 months after exposure were examined in rats exposed to beta-emitting radionuclides, giving brief or protracted irradiation of the lung or having weak or strong beta emissions. Protraction of the radiation dose to the lung from a half-time in the lung of less than three days to a half-time with a long-term component of about 150 days has a sparing effect. The median lethal dose for the protracted irradiation is about 1.7 times the median lethal dose for the brief irradiation. Low energy beta emissions from /sup 147/Pm have a similar effectiveness in producing lethal injury as high energy beta emissions from /sup 90/Sr. Changes in three parameters of morbidity were measured: body weight, hematology and pulmonary function; only changes in pulmonary function correlated well with pulmonary radiation injury. The doses of radiation required to produce impaired function, however, were not significantly different from those that produced death. The hazard-functionmore » model for predicting death from radiation pneumonitis, which was developed from previously obtained data for inhalation exposures of dogs to beta-emitting radionuclides, adequately predicted the median lethal doses for rats receiving one of several different beta dose rate patterns to the lung, thus strengthening the validity of the mathematical model. 23 refs., 41 figs., 12 tabs.« less