MIT Study: Prolonged Low-level Radiation Exposure Poses Little Risk 142
JSBiff sends this quote from MITnews:
"A new study from MIT scientists suggests that the guidelines governments use to determine when to evacuate people following a nuclear accident may be too conservative. The study (abstract), led by Bevin Engelward and Jacquelyn Yanch and published in the journal Environmental Health Perspectives, found that when mice were exposed to radiation doses about 400 times greater than background levels for five weeks, no DNA damage could be detected. Current U.S. regulations require that residents of any area that reaches radiation levels eight times higher than background should be evacuated. However, the financial and emotional cost of such relocation may not be worthwhile, the researchers say."
Re:5 weeks = long term? (Score:5, Interesting)
The interesting thing to note (if this study is correct) is that they observed a difference between an acute dose and a chronic one. Our radiation health data is mostly based on acute doses - the Hiroshima and Nagasaki bombings, mainly. The low dose risk estimates are basically based on that, extrapolated downwards linearly.
If acute dosing behaves differently to chronic, that model wouldn't be appropriate.
Re:5 weeks = long term? (Score:5, Interesting)
The interesting thing to note (if this study is correct) is that they observed a difference between an acute dose and a chronic one. Our radiation health data is mostly based on acute doses - the Hiroshima and Nagasaki bombings, mainly. The low dose risk estimates are basically based on that, extrapolated downwards linearly.
If acute dosing behaves differently to chronic, that model wouldn't be appropriate.
Hiroshima and Nagasaki radiation victims are some of the few human models that have been studied, but the DOE (and probably other government agencies around the world) did extensive testing on the effects of radiation at various doses using animal models. In one large-scale study I know of they used two exposure groups of beagles, one using the radioactive isotopes the bomb victims were exposed to in order to establish a baseline model correlation (human effects vs. effects observed in laboratory animals) and the other group exposed to isotopes expected to result from nuclear accidents and the new generation hydrogen bombs (different fallout characteristics than the original atomic bombs). Quite a bit of research was done on this, especially during the 1960s and 1970s. They also experimented with direct gamma exposure at various levels; rumor has it (I've never seen published results on the experiments) that there was a sweet spot in the gamma ray exposure scenario that actually lead to significantly longer lifespan than the control group, with many theories as to the cause.
Re:5 weeks = long term? (Score:2, Interesting)
Re:5 weeks = long term? (Score:4, Interesting)
That's a very difficult kind of test to do though, because making sure that radiation dose is the *only* difference between groups is virtually impossible. Even the abstract of that paper says that "Further studies will be important to better assess the role of tobacco and other occupational exposures in our risk estimates.". At least this mouse study allows for a proper controlled trial, and the Hiroshima data, while not perfect, is much less prone to such factors than your linked one.
Also, reading the part that says "Among 31 specific types of malignancies studied, a significant association was found for lung cancer (ERR/Sv 1.86, 90% CI 0.49, 3.63; 1457 deaths)" rather reminded me of this [xkcd.com].
Re:5 weeks = long term? (Score:4, Interesting)
One has to take care in this case to distinguish between the bio-retention of chemically pure compounds, and what happens in the real world, which is radioactive compounds embedded in small clumps with other material that makes them stick around, e.g. in the lungs. Especially if they get pulled through a cigarette or car engine on their way there.
Re:As opposed to... (Score:4, Interesting)
Do you live near a freeway? That doubles the rate of atherosclerosis. Air pollution kills hundreds of thousands a year in the US, and also causes other significant morbidity like asthma in children. Way more dangerous that a measly radiation dose. Yet, I don't see people wanting to evacuate from around coal plants and freeways.
Re:As opposed to... (Score:2, Interesting)
Right, what special magical property of the environment is this that relegates 'particles contributing to background radiation' external to humans? You do know that the primary culprit in 'background radiation' is radon GAS (e.g. an inhalant)...
And ultimately you are making an assumption not in evidence (e.g. that 'natural sources' of radiation are primarily absorbed externally while radiation doses from some 'accident' are primarily ingested or inhaled...not necessarily true in either case).