The Modification of Acute Mortality in Mice by Variation of the Dose-rate and the Overall Time of Irradiation

Abstract

1. A method is described whereby a 250 Kvcp x-ray set has been used to simulate whole-body irradiation by the fall-out from a nuclear weapon during the first 25 hours after its explosion when the dose-rate is continuously varying. 2. LD50/30 from such a fall-out exposure was 8 per cent less than the LD50/30 for a 25-hour exposure at a constant dose-rate. Both these values were more than 50 per cent greater than the LD50/30 for a short exposure lasting less than a quarter of an hour at a dose-rate about a hundred times greater. 3. During the first 30 days after irradiation there was no qualitative difference between any of the groups in the times to death or in the manner of death. Hemorrhages were the commonest cause of death and were seen mostly in the brain and spinal cord. 4. Deaths between 30 and 200 days were seen only in the high dose-rate group. They were due to a characteristic gastrointestinal disturbance.