Evaluation of Threshold Levels for Effects of Chronic Exposure of Mammals with Different Life Expectancies

The lower threshold of chronic exposure rate values, above which negative radiobiological effects occur, are estimated and compared for mammals with low and high natural life expectancy. A dataset has been prepared containing information on observed radiobiological effects of chronic exposure in mammals depending on the dose rate. The dataset includes 118 records for mammals with high life expectancy and 92 records for mammals with low life expectancy. The data were analyzed with the nonparametric statistics. The lower threshold for deterministic radiation effects of chronic exposure for long-lived mammals is shown to be 0.1 mGy/day with a 95% confidence interval of 0.04 to 0.3 mGy/day. For mammals with a short natural life cycle, this threshold value is one order of magnitude higher, being—1 mGy/day with a 95% confidence interval of 0.5 to 1.1 mGy/day. It is concluded that the quantitative radiation safety criteria for long-lived and short-lived mammal species differ, which should be taken into account when assessing the environmental risk of radioactive contamination