A Gompertz Age-Specific Mortality Rate Model of Toxicity from Short-Term Whole-Body Exposure to Fission Neutrons in Rats

Abstract

A Gompertz age-specific mortality rate model was developed for toxicity resulting from a single dose of a toxicant resulting in nonrepaired injury that summates with natural (aging) injury. The model was applied to mortality data for male Sprague-Dawley rats subjected to short-term whole-body exposure to fission neutrons (D. Chmelevsky et al., Radiat. Res. 98, 519-535, 1984; J. LaFuma et al., Radiat. Res. 118, 230-245, 1989). The logarithmic-logistic function was used to relate the displacement of the Gompertz function with dose. Analysis of the age-specific mortality rate provides a measure of total injury over time from combined neoplastic and non-neoplastic causes and can be used to calculate the relative biological effectiveness (RBE) of different radiation sources. It is a useful adjunct to conventional risk assessment paradigms, particularly for those toxicants such as fission neutrons which result in a large number of competing causes of death other than cancer.