| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Opinion |
1 From the Department of Radiology, University of Wisconsin-Madison. Received February 20, 2003; accepted April 7. Address correspondence to the author, 2678 SW 14th Dr, Gainesville, FL 32608-2050 (e-mail: jrcamero@wisc.edu).
Index terms: Opinions • Radiations, exposure to patients and personnel • Radiology and radiologists
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 cancerdeaths of the radiologists after 1920 suggests that x-ray induction of cancer may have a threshold, as was suggested by findings of two earlier studies. Radium-induced bone cancer of the watch dial painters had a threshold of 1,000 rad to the skeleton (5). Lung cancer induction from fluoroscopic exposures had a threshold of about 200 rad to the lungs (6).
The British radiologists’ death rate for the century from noncancer causes was 14% lower (P < .001) than that of the controls. Their death rate from all causes was 8% lower (P < .01). Thus, is moderate radiation exposure harmful?
The healthiest British radiologists were those who joined a radiologic society between 1955 and 1979. Their death rate from cancer was 29% lower (not significant), that from noncancer was 36% lower (P < .001), and that from all causes was 32% lower (P < .001) than that of the controls. Their longevity would be about 3 years longer than that of the controls. The chance of this greater longevity being accidental is less than one in 1,000.
In my opinion, the best epidemiologic study of radiation workers ever performed is the U.S. Department of Energy–supported nuclear shipyard worker study (1980–1988) (7). The 28,000 nuclear shipyard workers with the largest cumulative doses had a death rate from all causes 24% lower than did the 32,000 age-matched and job-matched unexposed shipyard workers. The probability of such a very low death rate from all causes being accidental is less than one in 10 million billion. No other study of radiation workers had the important advantage of having job-matched controls. The details of this important study still have not been published. The Department of Energy news release about the study did not mention that the deaths from all causes of the nuclear workers were 16 SDs lower than those of the controls (8). It does not seem realistic to me to suggest that this great health improvement can be explained by selection bias, as was suggested in a recent report (9).
In summary, I believe that longevity is a better measure of the health effects of radiation than is cancer mortality. The aforementioned data strongly support this belief. Is a low level of radiation therefore potentially beneficial, rather than harmful?
 |
FOOTNOTES |
|---|
|
REFERENCES |
|---|
 TOP REFERENCES |
|---|
Related Articles
This article has been cited by other articles:
|
|
 |
|
  C. D. Furtado, D. A. Aguirre, C. B. Sirlin, D. Dang, S. K. Stamato, P. Lee, F. Sani, M. A. Brown, D. L. Levin, and G. Casola Whole-Body CT Screening: Spectrum of Findings and Recommendations in 1192 Patients Radiology, November 1, 2005; 237(2): 385 - 394. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J R Cameron Moderate dose rate ionizing radiation increases longevity Br. J. Radiol., January 1, 2005; 78(925): 11 - 13. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. S. Welsh, E. J. Hall, and D. J. Brenner Further Thoughts on Low-Level Radiation: An Evolutionary Biologist's Perspective [letter] * Drs Hall and Brenner respond: Radiology, June 1, 2004; 231(3): 922 - 923. [Full Text] [PDF]
|
|
|
|
|
|
L. K. Wagner The "Healthy Worker Effect": Science or Prejudice? Radiology, October 1, 2003; 229(1): 16 - 17. [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| RADIOLOGY | RADIOGRAPHICS | RSNA JOURNALS ONLINE |
