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The article "100 years of observation on British radiologists: mortality from cancer and other causes 1897–1997" [1] is, I am sure, welcomed by all those in the field, particularly those who have harboured some lingering doubt as to the safety of working a lifetime with low dose radiation. In the abstract the authors state that there was no evidence of an increase in cancer mortality among radiologists who first registered after 1954 in whom radiation exposures are likely to have been lower. Indeed, inspection of Table 2 confirms this. When we look at the entry for all cancers as a cause of death amongst those who first registered with a professional body between 1955 and 1979 we see that our standardized mortality is a meagre 0.46, which goes to say that aged-matched men are twice as likely to die of cancer as radiologists. When this is corrected for socioeconomic class the figure becomes 0.61, and when it is compared with all male medical practitioners it is 0.71, a remarkable reduction in the likelihood of dying from cancer amongst this group of workers in the radiation industry. The authors attribute this low death rate, at least in part, to the healthy worker effect.
The healthy worker effect, although accepted by health physicists and epidemiologists, is nevertheless a "catch-all" that is used irrespective of the extent or degree of benefit obtained within the workplace, to avoid invoking the other scientific conclusion, i.e. there is a benefit to be had, in this case, from low level radiation.
Although all would agree to a "healthy hire" effect, the extent of "benefit" seen in this review appears out of proportion. In any event, Baillargeon [2], in his excellent review of the healthy worker effect published in 2001, underlines that the healthy worker effect is usually substantially weaker for mortality from all cancers than for all causes of death, and he references no less than eight reviews to support that statement. As many of the readers of this journal will realize (although perhaps relatively few of the radiologists), there has been a healthy and acrimonious debate increasing over the last 20 years with respect to the veracity of the linear no-threshold hypothesis.
This paper is in line with many others in demonstrating a reduced standardized mortality rate for cancer amongst radiation workers, and it may be informative for the interested reader to refer to, for example, the occupational radiation exposure analysis from Canada by Sont et al [3], also published in 2001, to see another example of this reduction in standardized mortality. Now that we have plausible radiobiological evidence of (1) the beneficial effects of low level radiation on DNA function and repair and (2) the extraordinary low rate of radiation-induced DNA changes in comparison with those that occur in normal every day life — facts reviewed recently by Pollycove and Feinendegen [4, 5] — it is perhaps time for scientific honesty to be established in those that are strongly opposed to any alteration in the status quo with respect to the linear no-threshold hypothesis.
There is one more point to be made. A standardized mortality ratio of 0.71 for all cancers and 0.68 for all deaths compared with other medical practitioners (who presumably also registered with professional bodies) effectively excludes a health worker effect in this group (I'm sure other doctors don't think of radiologists as being more healthy!).
I personally believe that the abstract and the discussion on this paper should go further than just saying that there was no evidence of an increase in cancer mortality among radiologists who first registered after 1954. The statement should carry on to say that there was a significant decrease in cancer mortality compared with a normal population as well as compared with medical practitioners and that, although this may to some extent be related to the healthy worker effect, a beneficial effect from low level radiation is not excluded.
Queensland X-Ray, PO Box 109, Sunnybank, Queensland 4109, Australia
Received for publication March 19, 2002. Accepted for publication May 9, 2002.
References
This article has been cited by other articles:
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  L. K. Wagner The "Healthy Worker Effect": Science or Prejudice? Radiology, October 1, 2003; 229(1): 16 - 17. [Full Text] [PDF]
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 D J Brenner and E J Hall Mortality patterns in British and US radiologists: what can we really conclude? Br. J. Radiol., January 1, 2003; 76(901): 1 - 2. [Full Text] [PDF]
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