Proposed estimates of the probability of inducing pulmonary injury sufficient to cause death from radiation pneumonitis and pulmonary fibrosis after briefly inhaling a mixture of insoluble β-emitting particles

The inhalation of relatively insoluble radioactive particles whose size distribution allow substantial pulmonary deposition may result in large radiation doses (spatial average doses to the lung). Large radiation doses to the lung can cause radiation pneumonitis and pulmonary fibrosis and lead to an early death. A method of estimating the probability of inducing pulmonary injury sufficient to cause death from radiation pneumonitis and pulmonary fibrosis, following inhalation of a mixture of beta-emitting particles, is proposed. The method utilizes dose-response relationships that depend on the effective half-life, Tsub(E), of the radioactive substance in the lung. For Class I (Tsub(E) on the order of days), Class II (Tsub(E) on the order of weeks) or Class III (Tsub(E) on the order of years) radionuclides, the proposed probability estimates are based on inhalation toxicity data for Beagle dogs after inhalation of 90Y (Tsub(E) = 2.6 days), 91Y (Tsub(E) = 7.6 weeks) or 90Sr (Tsub(E) = 1.1 yr) in relatively insoluble forms, respectively. The proposed probability estimates can be obtained by using formulas or tables given herein. (author)