I will state up front that I am not an expert in human health. I am, however, a student of words and language and must make an observation about an article in the August 30, 2008 issue of The Lancet titled “Can low-dose radiation increase risk of cardiovascular disease?”.
For people that read just headlines and article summaries, the news of this article has been touted as providing more evidence that there are important negative health effects from even “low doses” of radiation, but it is very important to understand more details about the study that the article is reporting.
According to the researchers, they have found a correlation between radiation exposure and cardiovascular disease in patients that had received cardiac doses of between 1.6 and 3.9 Gray (Gy) during treatment for peptic ulcer. Because treatments for that disease could range as high as 30-40 Gy, finding a dose related response at 1.6-3.9 Gy seems to qualify as news about “low dose” radiation.
This “news” has nothing to do with nuclear power plant operation.
Here’s why. One Gray (Gy)=100 rad. Nuclear plant operators in the US normally think in terms of measuring radiation doses in Rem (Roentgen Equivalent Man). With the kinds of gamma exposures that represent the lion’s share of doses associated with reactors, 1 rad=1 rem. Therefore 1.6 – 3.9 Gy = 160 – 390 rem.
The legal limit for occupational exposure is 5 Rem per year, but most plants use a much lower control dose limit of 2 Rem per year and some use even lower limits for average exposures. No power plant radiation worker would consider short term doses of between 160-390 rem – significantly more than most will receive in their entire careers – to be “low dose” exposures. (My lifetime occupational dose is less than 0.5 rem.)
The Lancet article might very well be discussing an important finding about a radiation dose risk that must be understood for medical uses of radiation, but it dose not include a cause for concern about the dose levels associated with nuclear power plant operation.
