Reanalysis of Hanford data: 1944-1986 deaths.

Reanalysis of Hanford data by a method, which is new only in the sense that it makes new uses of standard epidemiological procedures, has produced evidence of a cancer risk at low dose levels. By a conservative estimate, about three per cent of the pre-1987 cancer deaths of Hanford workers had occupational exposures to external radiation as the critical (induction) event. These radiogenic cancers were evenly distributed between five diagnostic groups, but as a result of there being much greater sensitivity to "cancer induction by radiation" after, rather than before, 50 years of age, they were concentrated among the cancers which proved fatal after 70 years of age. The reanalysis provides no support for the idea that radiation is more likely to cause leukemia than solid tumors, or the idea that there is reduced cancer effectiveness of radiation at low dose levels (dose rate effectiveness factor or DREF hypothesis), but the estimated proportion of radiogenic cancers was much higher for the 175 nonfatal cancers (which had other certified causes of death) than for the 1,732 fatal cases. Finally, according to the latest publication of the US Committee on Biological Effects of Ionizing Radiation (BEIR V), dose rate is more important than exposure age, and even a single exposure to 10 rem would only increase the normal cancer risk by four percent. Nevertheless, for all recorded exposures of Hanford workers, the estimated doubling dose was close to 26 rem; for exposures after 58 years, it was close to 5 rem, and for exposures after 62 years, it was less than 1 rem.