Analysis of survival and cause of death statistics for mice under single and duration-of-life gamma irradiation.
The late effects of protracted exposure to low levels of external radiation continue to be a matter of operational concern in long-range space flight. Studies have been carried out on young adult mice exposed to daily levels of 60Co gamma irradiation ranging from 0.3 to over 30 R day-1. The lowest level is comparable with the occupational maximum permissible dose for the atomic energy industry. There is little evidence of life shortening at that level, but as exposure increases, there is an exponential decline in life expectancy. The life-shortening coefficient is approximately 4 days/100 R accumulated or 4% R-1 day-1. When life-shortening is < or = 15%, all of the increased mortality can be attributed to radiation-induced increases in death rates from neoplastic diseases, including various forms of leukemia and pulmonary tumors. Age-specific death rates for mice dying of all other causes remain the same as the controls throughout life, at the lowest doses. A non-neoplastic disease component of excess mortality rate emerges at 6 R day-1 and above. The risk of death from all and specific causes following single exposures compared with protracted lifetime irradiation shows a clear effect of protraction. Leukemia death rates are reduced by a factor of 5 or more at all daily exposure levels below 20-30 R day-1. Risks for other causes of death are also reduced, but to a variable degree.
Grahn
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Division of Biological and Medical Research, Argonne National Laboratory, Argonne, Ill., USA.
Fry
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RJ
Lea
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D000818:Animals; D002423:Cause of Death; D003037:Cobalt Radioisotopes; D004307:Dose-Response Relationship, Radiation; D005260:Female; D005720:Gamma Rays / Q000009:adverse effects*; D007938:Leukemia / Q000453:epidemiology / Q000209:etiology / Q000401:mortality; D008017:Life Expectancy; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D009381:Neoplasms, Radiation-Induced / Q000453:epidemiology / Q000209:etiology / Q000401:mortality; D011833:Radiation Injuries, Experimental / Q000453:epidemiology / Q000209:etiology / Q000401:mortality*; D016019:Survival Analysis; D013997:Time Factors
D003037:Cobalt Radioisotopes