Dear Editor,
In his Feb. 9 letter, Jeremy Whitlock wrote that one reader claimed Whitlock would lie about the effects of radiation since he works in the nuclear field. I only pointed out he had a conflict of interest.
My conflict of interest: I’m a physician, interested in the health of patients. As such I am responsible for our greatest “body burden” of ionizing radiation. I co-authored a book on ionizing radiation and health.
The myth: “The dose at which we see the earliest onset of observed negative health effects is about 100 millisieverts (mSv).” This comes from the Radiation Research Effects Foundation (originally the ABCC, following survivors of the atomic bomb blasts in Japan). There are limits to applying the RREF to other populations.
We do know: Doing a PET scan (after a heart attack, delivering one-time dose of ~14 mSv) results in a three per cent risk of cancer per five years per 10 mSv delivered. X-raying a woman during pregnancy (delivering a dose of less than 0.1 mSv to her fetus) doubles the risk of leukemia in her child.
Cancer radiotherapy on a tumour before surgery results in increases of secondary cancers by eight per cent. Radon in basements accounts for ~20 per cent of lung cancers at an exposure of five to 10 mSv per year.
All of these are less than 100 mSv. There is a growing body of evidence that we should be extremely careful in our use of therapeutic and diagnostic ionizing radiation.
We live in a “sea of radiation”; more is not good for us nor is there proof that radiation has ever had any beneficial effect upon health, or upon evolution.
“Hormesis theory” exists for vitamins. Vitamin A is good for us, too much is a problem; micro amounts of selenium is good, too much poisons us – etc. for vitamin D, iron, copper, etc. The US Biological Effects of Ionizing Radiation VII (BEIR VII) concluded that no level of radiation is safe for living beings.
Applause to the Canadian Nuclear Safety Commission for the standards they set. They are dependent upon fees from the very industry that they regulate and upon the government for their authority. (Remember Linda Keen, fired for applying safety standards to the Chalk River reactor?).
As physicians, we try to apply the precautionary principle – if uncertain, don’t do it; the nuclear industry applies the ALARA principle – As Low As Reasonably Acceptable given economic and physical barriers. Which would you choose?
