A review of radiation accidents involving whole body exposure and the relevance to the LD50/60 for man.

The absorbed dose of low LET radiation that would be lethal (due to bone marrow failure) to 50% of an exposed human population is a matter for concern in planning for the consequences of an accident to a nuclear reactor and in the event of nuclear war. Since accidents with radiation-generating equipment or in the nuclear fuel processing industry might provide relevant human data, published accounts of these are reviewed. Two accidents, one in the USA, the other in Yugoslavia, both involving exposure to neutrons as well as gamma-rays, are identified as possibly satisfying the criteria of uniformity of dose, magnitude of dose and dose rate necessary to provide useful information on the value of LD50/60 for man. The symptomatology of the exposed individuals is discussed in terms of the published doses. Detailed examination of the dosimetry for these two accidents revealed possible ambiguities and a thorough re-examination has been carried out, the results of which are reported in detail in the Appendix. This indicates considerable and largely unresolvable uncertainty in the magnitude of the dose to exposed individuals when expressed as the low LET equivalent dose in bone marrow. It is also shown that the relationship between severity of effects and dose to exposed individuals is not the same for both accidents and it is argued that the experience from the Yugoslavian accident is more relevant to the determination of the sensitivity to radiation of an exposed human population. Given the uncertain nature of the accident data and the small amount of other relevant human data at present available, the uncertainty of current knowledge of man's sensitivity to the acute effects of exposure to ionising radiation is discussed.