image by Zac Neulieb
東京コメディストアの創設者であり、現ディレクターのChris Wells。彼のナレーターとしての仕事は定評があり、テレビのドキュメンタリーや企業CMなど多方面で活躍しているので声だけでも聞いたことがある人は多いかもしれません。
その彼が今回の放射能関連の情報をよくまとめたものが手に入ったので転載します。
原子力の専門家ではない彼ですが、とても分かりやすく状況説明していると思いました。
原文のままなので英語のみになってしまいます。時間ができたら翻訳したいと思ってはいますが、今のところ時間がありません。取り急ぎ英語だけでも掲載します。
以下Chris Wells氏の文章：
Living in Tokyo these days
Regarding the risks of radioactive particles in the atmosphere, I think there are a few misunderstandings causing smart people to talk past each other, both on my wall and friend's walls, as well as in the press.
Just yesterday, two people on a friend's wall were having a discussion that I followed with great interest. One was arguing that background radiation levels indicated Tokyo was safe. The other was saying that nobody knows the dangers brought about by fallout, or particulate matter that is radioactive, particularly fission byproducts like Cesium. I think they were both right, just focusing on different parts of the situation.
I wrote this to try and clear things up in my own head- any thoughts backed up by links to reputable sources would be appreciated.
Naturally occurring radioactive substances vs. fallout.
First, to get us all on the same page, this is how Geiger counters work:
http://en.wikipedia.org/wiki/Geiger_counter
After reading that we all know that everyday "background radiation" is measured by particles of radioactive material in the air brought about mainly by naturally occurring radioactive material in the ground, but also coal mining, bombs dropped years ago, and other industrial processes.
"Fallout" is what we call radioactive particles created by humans in bombs or power plants.
So, "background radiation" is caused by mainly natural sources of radioactive particles plus some old fallout that's become part of the modern environment, and what we call "fallout" is caused by human-made particles of more recent vintage.
The question is, is that a distinction without a difference? It is not. The danger is that the man-made particles can be extremely dangerous, more dangerous than most naturally-occurring particles, and that is what everyone's worried about. It's also why we have two different ways of referring to radioactivity in the atmosphere.
The next question is, how exposed are people to these particles? In what concentrations? Confusion arises when we forget that concentrations in the vast atmosphere on earth expressed by geiger counters must then be converted into oncological probabilities for them to have any actual meaning in our daily lives.
Radioactive cows.
For example, closer to Fukushima, Kyodo News reported that some beef was found to contain radioactive substances 10% higher than the legal limit, but upon retesting the Japanese Health Ministry reported that the first reading was wrong and there was no need to worry, something that has raised a few eyebrows. Those cows with the disappearing Cesium were in trouble before they were slaughtered and examined if they really were contaminated, agreed. From what I've read, the cows would have passed the water-soluble Cesium out of their system in a few months. How big a dose they would have received during that time and its effects would vary by cow. But humans are not cows, and the primary ingestion route of chewing on grass for hours on end is not an issue for us, as long as we don't eat their flesh or drink their milk.
So, even if the cows 70 kilometers away from Fukushima had dangerous levels, it is entirely feasible that the farmers tending to them did not. That they washed off the radioactive particles in the shower. But, and here's the rub, there is a chance that a particle or two got into their bodies. This would not be good at all and could lead to cancer. What is that probability? That is what we are discussing here. And nobody is quite certain.
Background radiation vs. individual radioactive particles.
The use of background radiation is a stand-in for probability, something all the specialists in the field are aware of, have thought about for decades, and too often do not successfully articulate to the public. What they mean when they reassure us with those numbers is that they estimate that the statistical probability of someone in, say Tokyo, ingesting a particle and then years later dying of cancer is negligible.
They are not lying, they are not not telling us the truth. They are going by the best science they have, which is, as has been correctly point out, not as conclusive as many of us would want. We don't know for sure- that's what I keep reading about extremely low-level exposure to radioactive particles in the atmosphere around us. (Not to be confused with low-level exposure to radiation, which seems to have very little effect, and is a completely different topic. This distinction is almost never made in the press.)
It's almost as though we are discussing light and flipping between describing it as a wave and a particle, without letting people know when we're changing perspectives. As abstract oncological probabilities go, background radiation readings are comforting. But when we then focus in on actual ingestion of radioactive particulate matter, things get scarier.
But all of us do ingest things like radioactive iodine, radon and even cesium on a daily basis, just in vanishingly small amounts. Our bodies are not in a pristine, radioactivity-free state. And so we need to think in terms of oncological probabilities, or the stochastic effects of exposure miles away from the source.
And how about for Tokyoites?
But what exactly are the chances that one of us here in Tokyo ingested a particle of Cesium on the days when it was in the air in Tokyo in extremely low amounts? I think what the experts are trying to tell us is that it does not rise above the level of danger presented by all of the other carcinogens we constantly breathe in in this big city. So it is not zero. But it is not raising our cancer risks statistically.
Cold comfort if you happen to be the person who is affected! But by living here we are all increasing our risk of lung cancer, etc., simply due to the atmosphere of a big city. The anthropogenic and highly unusual nature of the threat being discussed certainly raises our levels of caution, as it should, and I think that's a healthy response.
Up further north? I wouldn't want to be within, say, 100 miles of that plant. There is a bullseye around that disaster, with each ring towards the center increasing the chance of a "man-ichi"/highly improbable health effect, all the way down to standing in water that will kill you in minutes. I wouldn't want to take the chance. If a plant closer to Tokyo had a similar problem, I'd be thinking seriously about whether to stay here.
Down here, I look at it this way: What are the chances of me breathing in a single molecule of water emitted by an onsen in Fukushima? Not zero. But not probable. Whether or not that's comforting to each of us depends on our nature. The risk is not zero, and honestly will never be for anyone on the planet. That's why I'm staying here. But if those geiger counters go up, I won't ignore that data, either.
Sources:
Beef story: http://english.kyodonews.jp/news/2011/04/82608.html
I'm really using general knowledge gleaned from many sites, but the EPA covers just about everything regarding radiation on its website:
http://www.epa.gov/radiation/index.html
PS: These were just published in the NYT yesterday- I read them after I wrote this note, and they summarize the basic information and don't contradict anything above. But again, they don't quite get to the point the way someone actually living here in Tokyo would like. Seems nobody knows if the very good study involving Hiroshima survivors is applicable to our situation.
http://www.nytimes.com/2011/04/05/health/05primer.html?src=recg
http://www.nytimes.com/2011/04/05/health/05radiation.html?src=recg
And this from the Guardian:
http://www.guardian.co.uk/commentisfree/2011/apr/05