April 20, 2013
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.” 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.
In addition, the report contradicts the exposure estimates for communities that have the higher levels of soil contamination outside the government-mandated exclusion zone. 10,000 of the people tested live in locations reported to have more than 100,000 Bq/m2. Only 4.7% showed detectible Cesium radioactivity in March 2011. Only 1% of those re-tested since then have detectible Cesium in their systems. After August 2012, no children have shown even a trace of internal contamination. The team believes the lower than expected exposure levels are because residents have been keenly aware of the foods they buy, and also because food restrictions began almost immediately after the first week of the crisis at F. Daiichi. Professor Hayano says, “Results have shown that even the minority of people whose radiation exposure was high can reduce or eliminate exposure through regular health monitoring and avoiding contaminated food.”
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.
Dr. Hayano believes that the team’s findings ought to ease the public’s deep-rooted fear of radiation, and dispel negative rumors about Fukushima, its foods and its people. However, it does not appear the Japanese public will know of this good news because their politicians and popular press are not telling anyone. The politicians are probably remaining mum because it would seem they have been needlessly frightening hundreds of thousands of Fukushima residents, and tens of thousands of evacuees could have safely returned home a long time ago. Tokyo should tell those who can safely go home to “go home”, and be done with it. The Press is probably remaining silent because this extremely good news conflicts with their publically-admitted antinuclear agenda. But, it seems Japan’s news media only wants to keep the radiophobic demographic cowering in fear.
References:
(1) Hayano, Ryugo S., et.al.; ”Internal radiocesium contamination of adults and children in Fukushima 7 to 20 months after the Fukushima NPP accident measured by extensive whole-body-counter surveys”; Proceedings of Japan Academy: Series B89; 2013. https://www.jstage.jst.go.jp/article/pjab/89/4/89_PJA8904B-01/_pdf
(2) “Fukushima Prefecture Produces First Thesis on the Effects of Internal Radiation Exposure: Children of Fukushima Unaffected?”; Rocket News 24; April 19, 2013. http://en.rocketnews24.com/2013/04/20/fukushima-prefecture-produces-first-thesis-into-the-effects-of-internal-radiation-exposure-children-of-fukushima-unaffected/
