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Fukushima Radiation Significantly Lower Than Expected, Study Says

Apr 19, 2013 04:57 PM EDT

A new study on the radiation levels in Japanese locals after the Fukushima Daiichi nuclear power plant incident states that Cesium levels in the population are much lower than expected.

Based on studies from the Chernobyl incident in Russia in 1986, researchers anticipated that the levels of Cesium in those exposed to radiation after the meltdown at the Fukushima campus to be equivalent with deposition density, or the activity of radioactive molecules in an area of ground, which in Fukushima is reportedly measured at 2 millisieverts (mSv).

"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," said Ryugo Hayano, a professor at Tokyo University's Science Research Department who published the study in the English journal Proceedings of Japan Academy Series B89, which is available here.

Fear of radiation exposure was rampant in many parts of Japan in the days and weeks after the Fukushima incident, which occurred March 11, 2011 after the largest earthquake in Japan's recorded history unleashed a tsunami that ravaged northeastern Japan's coastal communities and overcame the Daiichi reactors, causing the worst nuclear accident since Chernobyl.

Because more than two years have passed since the Fukushima incident, now the greatest risk from ongoing exposure to radioactive Cesium is through eating food grown in contaminated soil.

But of more than 100,000 people screened with whole-body scanners, the study showed 99.9 percent of them with a committed effective dose (CED) of less than 1 mSv. The safety standard and recommended maximum for artificial radiation exposure is 1 mSv.

The findings draw upon tests conducted at Hirata Central Hospital, located 45km (28 miles) southwest of the Fukushima Daiichi power station. Subjects were given a whole-body scans at different dates. Between the 12 and 20 months after the Fukushima incident, the Cesium detection frequency among the test subjects was only 1 percent; in children the level was reported as 0.09 percent.

To address for any bias in the survey, such as only residents with personal concern about radiation exposure would agree to be tested and are likely to personally lower their risk of exposure anyway, the researchers also set up an agreement with Miharu town (50 km west of the nuclear campus) and tested every child enrolled in elementary and middle school as well. Because of their proximity to the Daiichi site and because about 20 percent of Miharu households are farming families, the population was considered potentially high-risk for internal exposure. The children were scanned twice in November 2011 and September 2012. After the second scan none of the 1,383 children had a detectable level of Cesium, the study reports.

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