Saturday, August 13, 2011

1 Millisievert Internal Radiation from a Man in Minami Soma City

Minami Soma City, while waiting for the lifting of the "evacuation-ready zone" designation, tested the internal radiation exposure of the residents in the high-radiation area within the city using the whole body counter.

Over 1 millisievert internal radiation was found in a man in his 60's, but the rest of the residents tested less than 1 millisievert, and the mayor of the city is pleased with the result.

From Asahi Shinbun (8/13/2011):

福島県南相馬市が住民の内部被曝(ひばく)を調べたところ、60代の男性1人から1ミリシーベルトを超える数値が検出されたことが分かった。市立総合病院が13日発表した。住民の検査で1ミリシーベルト以上の内部被曝が明らかになったのは初めて。

Minami Soma City in Fukushima Prefecture tested the internal radiation exposure of the city's residents, and found one man in his 60's with more than 1 millisievert radiation. The result was announced by the City General Hospital on August 13. It is the first time that internal radiation of more than 1 millisievert has been detected in the survey of the city residents.

 今回はホールボディーカウンターと呼ばれる機器を使い、体内に取り込まれた放射性セシウムなどによる将来にわたる被曝量を評価した。放射性物質の量が半分になる期間は、セシウム137では尿や便などに混じって排泄(はいせつ)される分も考えると0~1歳児で9日間、31歳以上で89日。放射性物質は現時点では相当減っていると見られている。

The whole body counter was used to evaluate the radiation exposure in the future from the ingested radionuclides such as radioactive cesium. Half life of cesium-137 in the body, taking into account the amount that will be expelled in urine and stools, is 9 days for children aged between 0 and 1, 89 days for people over 31. At this point, the amount of radioactive materials in the body is considered to have decreased significantly.

 調査は放射線量が高い地区で暮らしている16歳以上の569人と、原発事故時に市内に在校していた6~15歳の小中学生330人が対象。同病院によると、1.02ミリシーベルトが測定された60代男性は3月12日、水を確保するために山中に滞在していたという。

The survey was done on 569 people over the age of 16 who live in a high-radiation area in the city and 330 students aged between 6 and 15, who attended the elementary schools and junior high schools in the city at the time of the accident. According to the hospital, the man who has been found with 1.02 millisievert internal radiation stayed in the mountain on March 12 to secure water supply.

Kahoku Shinpo (local Fukushima paper) reports that the mayor of the city is pleased with the result, and thinks it will reassure the residents that it is safe to live in Minami Soma City:

桜井勝延市長は「市民1人が1ミリシーベルトに達したのは残念だが、大半の受診者は安心できる数値。市内が、生活に支障ない環境と判断してもらえるのではないか」と述べた。

Mayor Katsunobu Sakurai said "It is regrettable that one resident exceeded 1 millisievert. But the vast majority of the residents tested at the safe level. I believe the residents of the city can judge from the result that the city is safe to live and work."

And what is the result that made the mayor happy? According to Kahoku Nippo,

検査結果によると、治療が必要とされる20ミリシーベルト以上の被ばくが確認された人はいなかった。線量は成人受診者の99%に当たる561人が0.5ミリシーベルト未満、7人が0.5ミリシーベルト以上~1ミリシーベルト未満。小中学生はセシウムが検出された2人以外は、検出限界以下だった。

There was no one exceeded 20 millisieverts, the level at which a treatment may become necessary. 561 adults, 99% of the subjects, tested less than 0.5 millisievert; 7 adults tested between 0.5 and 1 millisievert (not exceeding 1 millisievert); 2 school children was found with radioactive cesium, but the rest tested below the detection limit.

5 comments:

Anonymous said...

This doesn't make sense. Saying "1 Millisievert" means nothing without a time period. It's like saying I was walking 60 kilometers. Is it per hour, per year, per day?

Anonymous said...

Kodama has already explained that Sv numbers are meaningless for internal exposure. Next they will say it's like 5 X-rays or a flight to NY or whatever.

Antony said...

The whole body counter isn't measuring much - just how much Cesium is in the body somewhere. However, Cesium is probably just a flag for other radionuclides that are probably present - Strontium-90, Plutonium, Uranium, and so on. Then there is the problem of where these are. If Plutonium and Uranium (etc.) particles are breathed in, they may lodge in the throat and lungs. Since they are very genotoxic, only very small amounts are likely to cause cancers in later years. The ICRP model figure of 100mSv - below which cancers are not supposed to occur - is almost certainly just plain wrong by 2 to 3 orders of magnitude - Chris Busby and the ECRR say 300-900 times - in the ability to predict cancers. The whole Fukushima health study just starting up now is based on the false reassurance of the ICRP/UNSCEAR model. Sorry, mayor, not much to be happy about.

Hélios said...

Hello, I'm translating this post and I think there is a mistake.

At the end:
"There was no one exceeded 20 millisieverts, the level at which a treatment may become necessary."

Is it 20 millisieverts or 20 microsieverts ?(the man in his 60's is just at 1 millisievert)

Please for an answer.

Have a nice weekend.

Anonymous said...

It was the correct translation.

The sentence started off by reminding the readers the condition for treatment.

I.e. the current rule in Japan is that if exposure is less than 20 msv no treatment is required. Meaning that anything less than 20msv is considered non-event. i.e. it is safe.

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