A nuclear advisor to the Cabinet has resigned in protest against government stopgap measures that deal with the ongoing nuclear crisis in Fukushima Prefecture.
Toshiso Kosako, 61, a University of Tokyo professor specializing in radiation safety, submitted a letter of resignation to the Prime Minister's Office on April 29.
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In particular, Kosako protested against the government's decision to revise the maximum permissible level of radiation exposure among children up to 20 millisieverts per year, saying, "Should I approve that decision, I would no longer be a researcher. I would not want my children to be exposed to that amount of radiation."
Kosako revealed the Cabinet did not accept his advice that outdoor school activities for elementary and junior high school students near the crippled power station be restricted to prevent them from being exposed to over 1 millisievert of radiation per year.
"It is quite rare for nuclear power plant workers dealing with radioactive materials to be exposed to 20 millisieverts of radiation per year. I cannot allow infants and children to be exposed to such high levels of radiation from an academic as well as humanitarian point of view."
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In a tearful news conference, Kosako said he could not stay and allow the government to set what he called improper radiation limits of 20 millisieverts an hour for elementary schools in areas near the plant.
"I cannot allow this as a scholar," he said. "I feel the government response has been merely to bide time."
I am not a health physicist (i.e. radiation expert), but I think Professor Kosako is correct. 20 mSv/year (which is also the evacuation threshold) is not a dose to be subjected to without good cause. It is ten times background radiation; it is comparbale to a CT scan every year. Based on ICRP recommendations, 20 mSv (1 year) should be estimated to cause an excess fatal-cancer risk of 0.1% (general population -- for children this should be higher?):
[Google Books excerpt] Radiobiology for the radiologist By Eric J. Hall, Amato J. Giaccia
Admittedly there is signficiant uncertainty about such a prediction, as 20 mSv is a sufficiently low dose that emprical data does not exist (you can only extrapolate from known effects at much higher doses). The Health Physics Society, for instance, recommends against quantiative estimation below 50 mSv (5 rem). But 20 mSv is pretty close to 50 mSv; I should think there's a good chance there are substantial health risks at this dose rate, even if the linear extrapolation is an overestimate.
As a related issue (one I've been repeatedly bringing up), some people in yet-to-be-evacuated areas have already received doses of up to 20 mSv (in Namie, measured), or maybe 50 mSv (extrapolated). Actually these are outdoors doses, so actual exposures are attenuated (by maybe a half).
Excuse me, uvdiv - 20mSv is NOT close to 50mSv. A factor of 2.5 is a large safety margin, and in itself 50mSv has a generous safety margin. No health effects have been evidenced below 100mSv.
ReplyDeleteThe professor's point on the variation for children is accurate, however; they do appear to be more vulnerable to radiation, and not just because they have more natural life in front of them. So the 20mSv level is reasonable - but resigning in protest at a level that will almost certainly not be reached for any child, and would not be harmful to them if it were, seems the height of pointlessness.
His insistence that 1mSv/year is a reasonable boundary is insupportable. It is radiation fearmongering of an order that makes me glad he has resigned. I am ever mindful that excess fear of radiation was directly implicated in self-damaging behaviour by people post-Chernobyl - as the principal adverse health consequence.
I was interested enough in your link to "Radiobiology for the radiologist" to go to look for the Doll & Wakeford paper, which to my delight is freely available. They have undertaken a tough task, to try to demonstrate an effect from a population subjected to changing doses over time with contradicting evidence such as the lack of any effect in twins. Still an interesting piece of evidence, even though not conclusive, by their own admission.
I don't think it's a safety margin, because 50 mSv isn't a "maximum safe" dose. HPS' position isn't that doses below 50 mSv are safe; it is that quantitative prediction isn't supportable below that level (because of the lack of empirical data).
ReplyDeleteAnd as you probably perceive, I disagree that we should regard something for which no harm has been shown to be regarded as harmful. If quantitative prediction is not possible - in something that has been studied so thoroughly - I regard that as the same as saying there is no adverse health effect.
ReplyDeleteHow about his 1mSv suggestion? Any thoughts on that?
http://bravenewclimate.com/2011/05/02/would-sir-like-a-caesium-salad-with-his-steak/
ReplyDeletehas an article which compares the DNA damage from 20 mSv/year with the DNA damage from eating meat or dairy products. The hysteria and ignorance is astounding.
If we want to save lives, in order to be safe, I think we should evacuate everyone that lives in an area that has over 10x the background carginoginic particulate matter from fossil fuel combustion. It has been demonstrated to give a significant carginogenic added risk.
ReplyDeleteHowever, if we do that, my entire country, the Netherlands, has to be evacuated, and closed permanently, or we have to stop driving cars and shut down all fossil boilers.
If the alternatives are either
ReplyDelete-- to expose everyone who has been displaced to 20 mSv, total, this year, and a small fraction of that from next year to forever, or
-- to forbid them to return to their homes,
I favour the first one.
It seems to me there might be some stage-managing going on. Many of the people directly involved may share my preference; by having this "maverick" act as if the big bad government were trying to harm them by letting them go back, the big bad government seeks to move the Overton window in the desired direction, the one that lets it harm them by not letting them go back.