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FBaggins

(26,697 posts)
Mon Apr 22, 2013, 02:52 PM Apr 2013

Tokyo has greatly overestimated Fukushima resident’s exposures

A team at Tokyo University’s Science Research Dept. reports that Fukushima resident’s exposures due to ingestion since October, 2011, have been negligible. In addition, the results indicate that previous official exposure assessments for the prefecture’s most contaminated communities have been greatly over-estimated. Unfortunately, the Japanese Press has refrained from covering this good news.

This is believed to be the first study of its kind relative to the Fukushima accident. Team leader Dr. Ryugo Hayano says, “Findings suggest that the level of internal radiation exposure brought about by pollution from the soil within the Fukushima Prefecture is much less than originally believed. The amount is so negligible that it is difficult to imagine there being any risk to the health.” (Poster's note... he underestimated the imagination of the anti-nuke fringe) Hayano’s group found that nearly 120,000 Fukushima residents were given sensitive Whole Body Counter scans between March 2011 and November 2012. 99.9% show an internal exposure of less than 1 millisievert, which is the national standard. All of those above the criterion were examined before May, 2011, with the majority of positive results occurring in March of that year. Since then, thousands have been reexamined and found to have no detectible radioactive Cesium in their systems. This includes the more than 1,000 students who were tested at Miharamachi elementary school, 50 kilometers from Fukushima Daiichi.

Up to this point, residential exposure estimates were created out of worst-case, upper limit ingestion assumptions, but did not use any actual data. Hayano’s team used only actual data, and their findings were stunning. First, of course, were the results of a comprehensive study of the Whole Body Count outcomes, mentioned above. When he actual numbers were much lower than expected, they wanted to know why. Ministry of Health records contain over 40,000 radiological analyses on foodstuffs since 3/11/11. 10% failed Tokyo’s exceedingly restrictive limit of 100 Becquerels per kilogram. However, only 2% of the failed foods were over the health standard. In other words, only a tiny fraction of each specific food banned for distribution actually had contamination levels above 100 Bq/kg. 98% of the volume was below the limit. This strongly indicates that the actual ingestion of radioactive Cesium has been many times lower than prior government estimates.

...snip...

Even with all this good news, the research team wanted to know more; where did the original, flawed exposure estimates come from? They feel it has to do with a line of thought prominent after the Chernobyl accident in 1986. Exposures were assumed to be proportional to soil contamination levels, similar to what was the case with the Chernobyl-area population. At Chernobyl, food restrictions were not put in place until weeks after the accident, plus contamination was much-more wide-spread and the concentrations much higher than around F. Daiichi. When these Chernobyl-based assumptions were applied to a community like Koriyama, which had many areas above 100,000 Bq/m2, it was estimated that the population’s Cesium intake would result in a 5 mSv/yr exposure. This was assuming that the population was consuming the banned foodstuffs at a rate similar to their ingestion before the Fukushima accident. However, the actual levels of intake were considerably less and the resulting exposures more than 5 times lower than the long-standing official estimates. It also suggests that a majority of food products from areas of higher soil contamination were not as contaminated as first thought. Again, the previous estimates for contamination up-takes from the soil were centered on Chernobyl-based assumptions that no longer seem to be valid for Fukushima.


I don't see a direct link. It's currently the second post on: http://www.hiroshimasyndrome.com/fukushima-commentary.html
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