50 years ago
During the latter half of October 1957, following the Windscale reactor accident, we observed that the gamma-ray activity of certain members of the staff ... was higher than expected ... The source of the greater part of this increased activity was identified as iodine-131 ... We decided, therefore, to make some measurements of the iodine-131 in human thyroids ... Eighteen persons were measured, the majority of whom were resident either in, or on the fringe of, the Greater London area ... Since the main route of entry to the human thyroid was via milk, then as the cloud with its iodine-131 from Windscale passed over Britain on October 11, we may expect that the first day on which the milk contained this isotope was October 12 ... If we assume the same pattern of uptake throughout the group, then it is evident that the average person received about 0.04 rad. The magnitude of the radiation dose to adult human thyroids in the people measured was therefore comparable with that expected each year from natural background radiation.
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