Archives de octobre 2011
Before and After Photos of 2011 Japan Earthquake and Tsunami Destruction Show 6 Months of Speedy Cleanup
Health minister Yoko Komiyama announced Friday that the government will lower the allowable amount of radiation in food products from 5 millisieverts per year to 1, but some experts are puzzled.
Permanent limits for various categories of food will be set based on recommendations submitted Thursday by the government’s food panel.
The current limit of 500 becquerels per kilogram of radiation for meat, fish and vegetables is also expected to be lowered by about one-fifth in April.
Citing findings from various studies, the food safety panel concluded Thursday that a cumulative dose of 100 millisieverts or more throughout one’s lifetime poses significant health risks.
But experts question the focus solely on internal exposure from food and drink, while ignoring external exposure from radioactive materials, such as fallout on the ground, roofs and in ditches.
« I can’t think of a reason why they decided to omit external exposure as a factor in the proposal this time, » said Dr. Eisuke Matsui, who heads the Gifu Environmental Medicine Research Institute.
The radiology expert noted that while consuming food contaminated with radiation is a far bigger risk to human health than being exposed to radiation from the environment, it does not mean it can be disregarded.
« Think of the children in the cities of Fukushima or Minamisoma, where there is a relatively high level of radiation in the environment, » Matsui said. « Any guideline on radiation should consider the total exposure and not only the limit of contaminated food one can consume. »
According to the International Commission on Radiological Protection, a cumulative dose of 100 millisieverts increases the risk of dying from cancer by 0.5 percent. An organization of scientists, the ICRP’s recommendations serve as the basis for radiation regulations of many developed countries, including Japan.
The current limits for food and drink were set on a provisional basis soon after the nuclear crisis broke out in March at the troubled Fukushima nuclear power plant.
In July the same panel proposed in a preparatory report that 100 millisieverts be the combined limit of both internal and external exposure to radiation.
Questioned by reporters about the decision to drop external exposure from consideration, panel Chairwoman Naoko Koizumi offered no clear explanation.
Members of the panel, consisting of independent experts, asserted fallout across eastern parts of the country from the March meltdowns at the Fukushima No. 1 nuclear plant did not dramatically increase the risk from external exposure.
Koizumi also noted that other branches of the government should conduct studies on the matter, not just the food safety panel.
There are few studies of the effects of low-level radiation for extended periods, a key subject of debate among experts for years.
One study cited by the panel to explain the 100-millisievert regulation looked at cancer rates among survivors of one-time exposure to high levels of radiation, such as in the nuclear bombings of Hiroshima and Nagasaki in 1945.
Radiology expert Matsui argued that the government should make certain of the facts before advancing policies.
« Personally, I think the cumulative 100-millisievert limit is too high, whether it is only for internal exposure to radiation or not. For children, I think it should be at least one-tenth of that, » he said.
Study: Japan nuke radiation higher than estimated
NEW YORK (AP) — The Fukushima nuclear disaster released twice as much of a radioactive substance into the atmosphere as Japanese authorities estimated, reaching 40 percent of the total from Chernobyl, a preliminary report says.
The estimate of much higher levels of radioactive cesium-137 comes from a worldwide network of sensors. Study author Andreas Stohl of the Norwegian Institute for Air Research says the Japanese government estimate came only from data in Japan, and that would have missed emissions blown out to sea.
The study did not consider health implications of the radiation. Cesium-137 is dangerous because it can last for decades in the environment, releasing cancer-causing radiation.
The long-term effects of the nuclear accident are unclear because of the difficulty of measuring radiation amounts people received.
In a telephone interview, Stohl said emission estimates are so imprecise that finding twice the amount of cesium isn’t considered a major difference. He said some previous estimates had been higher than his.
The journal Atmospheric Chemistry and Physics posted the report online for comment, but the study has not yet completed a formal review by experts in the field or been accepted for publication.
Last summer, the Japanese government estimated that the March 11 Fukushima accident released 15,000 terabecquerels of cesium. Terabecquerels are a radiation measurement. The new report from Stohl and co-authors estimates about 36,000 terabecquerels through April 20. That’s about 42 percent of the estimated release from Chernobyl, the report says.
An official at the Nuclear and Industrial Safety Agency, the Japanese government branch overseeing such findings, said the agency could not offer any comment on the study because it had not reviewed its contents.
It also says about a fifth of the cesium fell on land in Japan, while most of the rest fell into the Pacific Ocean. Only about 2 percent of the fallout came down on land outside Japan, the report concluded.
Experts have no firm projections about how many cancers could result because they’re still trying to find out what doses people received. Some radiation from the accident has also been detected in Tokyo and in the United States, but experts say they expect no significant health consequences there.
Still, concern about radiation is strong in Japan. Many parents of small children in Tokyo worry about the discovery of radiation hotspots even though government officials say they don’t pose a health risk. And former prime minister Naoto Kan has said the most contaminated areas inside the evacuation zone could be uninhabitable for decades.
Stohl also noted that his study found cesium-137 emissions dropped suddenly at the time workers started spraying water on the spent fuel pool from one of the reactors. That challenges previous thinking that the pool wasn’t emitting cesium, he said.
JAPANESE RESIDENTS NEEDLESSLY EXPOSED TO RADIATION
TOKYO IGNORED CALLS TO ISSUE IODINE DURING CRISIS
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Radiation contamined cars sold in Japan: