2012年8月15日水曜日

低線量被曝の影響はいかに?

 原発災害以降、枝野氏や原子力の専門家と呼ばれる錚々たる原子力ムラの村人らによって、「直ちに健康被害はない」と断定的な口調で繰り返された放射能漏れであるが、ここに来て、フクイチの原発災害の後に、福島第1の近辺で採取されたちょうちょの奇形の割合が増加しているという論文が発表されたという。

 奇形は継続的な低線量被曝の影響によるものであり、種によって放射能に対する脆弱さは異なるため、人類への影響についてはどうなのかよくわからないと専門家は結論づけているが、決して手放しで安心してよいというような結論は誰からも導きだされてはいない。

 政府は、高線度の放射能がばらまかれた地域に安易な除染を奨励し、福島復興を高々と掲げ、帰村を促し、東電の賠償額を最小限に抑えることにばかりに腐心してきた。そして故郷に戻っていった人々をメディアはことさら大きく讃え続けてきたが、「安全である」という保障すらない地域に住民を帰らせることが、国民の安全を守るべき政府がとるべき最良の判断であったとは決して思えない。薔薇っ子は震災後早い段階から主張してきたが、原発で既得権益を得てきた原子力ムラの村人以外の住民を速やかに集団疎開させることが、必要不可欠であったと思う。

 広島や長崎で被災した多くの人々がそうであるように、原発災害の後、数十年たって心疾患や癌などに罹患した多くの原発立地自治体の住民に対しても、おそらく 「直接、放射能被曝との因果関係を証明することは難しい」といって、国は責任を回避する腹づもりなのだろうから、福井であれ、北海道であれ、島根であれ、原発立地自治体の住民は、ゆめゆめ、原発で最悪の事態が起こっても、政府が自分や家族の面倒を最後までちゃんと見てくれるに違いない」などといった甘い期待など抱くべきではない。

 末代に突然変異による奇形などの大きな負債を負わせたくないとまこと願うのであれば、いかなる犠牲を払ってでも、可及的速やかに原発は断ち切るべきである。




Fukushima Watch: What Do Deformed Butterflies Mean for Humans in Fukushima?


How vulnerable are species — including humans — to radiation?

European Pressphoto Agency
Severe mutations were found in butterflies collected near the Fukushima Daiichi nuclear power plant. A healthy adult pale grass blue butterfly, top, and a mutated variety, bottom, can be seen in this photograph released by Joji Otaki on August 14.

This is a crucial question facing people around the crippled Fukushima Daiichi nuclear plant, who have to live with low-level radiation the government says is insignificant but whose long-term health consequences are still unknown.

At least one species – the pale grass blue butterfly – has been found to be vulnerable to such radiation exposure, with high rates of deformities detected among offspring, according to a research paper published in Scientific Reports last week.

This begs another question: Does that mean there will be an increase in deformities and mortality rates among humans also?

A team of Japanese scientists found a marked increase in mutations among the offspring of pale grass blue butterflies that were collected in Fukushima prefecture two months after the March 11 nuclear disaster last year.

The abnormalities included underdeveloped palpi and leg tarsus, dented eyes, rumpled or underdeveloped wings.

The incidence of deformities was even higher among butterflies collected four months after the first sample, pointing to a possibility of “mutation accumulation caused by continuous low-dose exposure through generations,” such as through the ingestion of contaminated leaves, the researchers said.

Such deformities can be recreated in the lab by applying relatively strong radiation — 55 millisieverts during the butterflies’ one-month life span, according to lead researcher, Prof. Joji Otaki of the University of the Ryukyus. “It is most likely that the abnormal phenotypes observed are produced by random mutations caused by the exposure to radiation,” the paper concludes.

No significant increase in genetic mutations was detected among samples taken in other prefectures such as Tokyo, Prof. Otaki said.

So what does this mean for humans? Not much, apparently.

Different species have different degrees of resistance to radiation. Even among insects, some species such as silk moths and melon flies are known to be highly resistant to radiation. “We just don’t know (about the likely impact on humans). Radiation sensitivity varies among species,” Prof. Otaki said.

Prof. Shinzo Kimura of Dokkyo Medical University, one of Japan’s best known radiation experts, agrees. “It is very inappropriate to apply the conclusion of this study to humans,” he said.That doesn’t mean we can ignore the safety risks of low level radiation, however.”

Many Fukushima residents are unable to move away from the area for financial reasons and continue to stay in the parts of the prefecture that are not off-limits.

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