Longevity is the most appropriate measure of health effects of radiation.

It has been known for about a century that large doses of radiation, which are now uncommon, increase the risk of cancer. In this communication, I present evidence that moderate-dose-rate radiation significantly increases longevity without an increase in cancer. I suggest that longevity is a more appropriate measure of health effects of radiation than is cancer mortality. A double-blind study of humans would be necessary, however, to determine the health effects of low-dose radiation (1). I believe that the 100-year (1897–1997) study of British radiologists is the most important study of health effects of moderate-dose-rate radiation ever published (2). In the study, the death rates of British radiologists from cancer, noncancer, and all causes were compared with those of all male nonradiologist physicians in England and Wales, hereafter referred to as the controls. Findings of the study showed that radiologists who joined a radiologic society between 1897 and 1920 had 75% greater cancer mortality than did the controls. There is no doubt that the significant cancer increase (P .001) was caused by their high radiation doses. The increased radiation appeared to have had an important beneficial effect on deaths from noncancer that was not noticed at the time. The 1897–1920 radiologists’ death rate from noncancer was 14% lower (P .05) than that of the controls. This reduced noncancer death rate canceled out the increased death rate from cancer. The radiologists’ deaths from all causes were slightly fewer than those of the controls. Thus, the overall longevity of the earliest radiologists’ as a group was not reduced despite their high radiation doses and despite their increased cancer. The abstract of the article (2) concludes that “[t]here was no evidence of an effect of radiation on diseases other than cancer even in the earliest radiologists, despite the fact that doses of the size received by them have been associated with more than a doubling in the death rate among the survivors of the Japanese atomic bombings.” I believe the authors overlooked the fact that the significant decrease (P .05) in radiologists’ deaths from noncancer can only be explained as a reduction of deaths from diseases other than cancer compared with that of the controls. The article (2) concludes with the true statement that “[f]or non-cancer causes of death there was not evidence of an increased risk in any group, even among those registering before 1921.” However, it does not mention the 14% decrease (P .05) in deaths from noncancer before 1921 and the 14% decrease (P .001) in deaths from noncancer for the 100 years, as was pointed out in my letter to the editor (3). A similar study of U.S. radiologists suggests that their health was better than that of other medical specialists after 1940 (4). Present radiation protection limits for workers and the public are based largely on cancer deaths of atomic bomb survivors. The significant increase in deaths from noncancer of the atomic bomb survivors who received high doses of radiation compared with the significant reduction in deaths from noncancer of the radiologists, who received higher doses but over a longer period of time, indicates that atomic bomb survivor data are not appropriate for predicting longevity for radiation workers or the public. The longevity data obtained from the study of the British radiologists indicate that the dose limit of 0.2 R/day (about 50 rad/year) recommended for radiation workers by the International Commission for Radiological Health in 1934 did not need to be lowered. The very high doses of radiation received by the earliest radiologists did not reduce their overall longevity as a group. British radiologists who joined a society after 1920 also had a 14% lower (P .001) death rate from noncancer and an 8% lower (P .01) death rate from all causes than did the controls. British radiologists who joined a radiologic society after 1920 never had a statistically significant excess of cancer mortality compared with that of the controls. This contradicts the present dogma of a linear increase of cancer with dose. The abrupt decrease in cancer Opinion