[ RadSafe ] BBC Reports "Nuclear workers' cancer risk rise

[Otto G. Raabe]

June 29, 2005

Today's publication on the British Medical Journal of the paper "Risk of 
cancer after low doses of ionizing radiation:retrospective cohort study in 
15 counties" by Cardis, and 49 other prominent authors promises to be 
treated as the definitive study of radiation-induced cancer among radiation 
workers. The is probably the most reliable of all the radiation worker 
epidemiology studies because of its size and excellently qualified and 
unbiased authors. A cohort of 407,391 radiation workers in Canada, Sweden, 
the United Kingdom, and the United States. It concludes that "...1-2% of 
deaths from cancer among workers in this cohort may be attributable to 
radiation." It concludes that the findings are consistent with the linear 
risk estimates obtained from the RERF studies of Atomic Bomb survivors.

A reading of the paper shows that there was a significant increase in solid 
cancer cases (increased relative risk of 0.97 with 95% confidence range 
from 0.14-0.97) in radiation workers based on a linear dose-response model. 
(Leukemia was not significantly increased.) The shape of the dose-response 
curve is, therefore, uncertain since these results may be driven by cancer 
in the most highly exposed workers. There is no independent control group 
in the study.

When lung cancer is separated from the other solid cancers, there is no 
significant increase in cancer rate for all the other types of cancers 
combined. Although the researchers cite reasons for assuming that the 
results are not seriously affected by smoking, almost all lung cancer is 
caused by cigarette smoking and it may not be possible to appropriately 
correct these data for the action of this strong carcinogen among the 
workers. The Canadian cohort was the only cohort reported that showed a 
significantly increased cancer risk. If the Canadian data are omitted, the 
data from the other 14 countries did not demonstrate a significant increase 
in cancer rates as a function of radiation dose.

Even though this is a well-done study it depends on a linear model and its 
main conclusion is depends on assuming that lung cancer rates are not 
confounded by smoking or other possible factors among the workers.

Otto

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Prof. Otto G. Raabe, Ph.D., CHP
Center for Health & the Environment
(Street Address: Bldg. 3792, Old Davis Road)
University of California, Davis, CA 95616
E-Mail: ograabe at ucdavis.edu
Phone: (530) 752-7754   FAX: (530) 758-6140
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