University of Tokio survey very reassuring

April 11, 2013

Radioactive cesium not detectable in 99% of Fukushima residents: study

JIJI

http://www.japantimes.co.jp/news/2013/04/11/national/radioactive-cesium-not-detectable-in-99-of-fukushima-residents-study/#.UWagt0psFEs

Radioactive cesium was too low to detect in 99 percent of 22,000 residents examined in Fukushima Prefecture and neighboring Ibaraki, according to a University of Tokyo survey.

The team, which included professor Ryugo Hayano, examined internal radiation exposure levels in the two prefectures between March and November 2012. Their findings were unveiled Wednesday in the Transactions of the Japan Academy.

The survey found that the rate of internal exposure in the residents surveyed stood at about one-hundredth of the level detected in people living in the area around the Chernobyl plant at the time of the 1986 disaster.

Levels of cesium-137 were shown to be below the detectable threshold of 300 becquerels per kilogram of body weight for 99 percent of the residents, according to the team.

For the remaining 1 percent, or 212 people, 10 becquerels were detected. Still, their annual internal exposure would total only 0.04 millisievert, far below the government-set limit of 1 millisievert per year, the team said.

Meanwhile, cesium levels equivalent to 1 millisievert of internal exposure at an annualized rate were found in four elderly people who routinely ate wild mushrooms and boars. The team confirmed that the figures dropped after these four changed their eating habits.

Just as with the Chernobyl crisis, soil, particularly around Fukushima, was heavily contaminated with radioactive substances following the March 2011 nuclear meltdowns at the Fukushima No. 1 power plant.

The low cesium readings were attributed to the quality of the soil in the areas surveyed, which prevented food crops from absorbing radioactive materials, the conduction of radiation checks for food and the attention local residents are paying to the produce they consume, according to Hayano.

But the team, which used a whole body counter to examine the residents, concluded that checks on internal exposure and food inspections need to be continued. The study was conducted jointly with a hospital in Fukushima Prefecture.

Fukushima schoolchildren clear of cesium

http://www3.nhk.or.jp/nhkworld/english/news/20130411_19.html

Schoolchildren living near the Fukushima Daiichi nuclear plant have come up clear of radioactive cesium in internal-exposure screenings.

Researchers led by the University of Tokyo examined roughly 1,400 elementary and junior high school children in Miharumachi, 50 kilometers from the crippled plant.

They carried out the tests from September to November last year.

Researchers said levels of cesium 137 in all tested children were below the detectable amount of 300 becquerels.

The same researchers implemented similar tests between November 2011 and February 2012. They found then up to 1,300 becquerels of cesium 137 in 54 children.

Researchers say the new results show that checks on food products have generally prevented children from ingesting radioactive material.

University of Tokyo professor and team member Ryugo Hayano said the researchers will continue to gather data so Fukushima residents can feel safe.

Researchers this time were able to test all schoolchildren in Miharumachi. Subjects of previous screenings took part on a voluntary basis, leading to doubts over the relevance of results.

April 9, 2013

No radioactive cesium found in any of 10,000 children examined

http://mainichi.jp/english/english/newsselect/news/20130411p2g00m0dm030000c.html

TOKYO (Kyodo) -- A research team of University of Tokyo and other experts said Wednesday its survey of people who used to live near the crippled Fukushima Daiichi nuclear power plant found no radioactive cesium in any of the 10,000 children 15 years or younger examined after May 2012.

"This shows that chronic internal exposure in Fukushima is very low compared with the case of the Chernobyl nuclear accident in 1986," said Ryugo Hayano, a member of the research team and University of Tokyo professor.

"Food inspections at markets appear to be working well," he added.

The research team checked 32,811 people -- residents of Fukushima and neighboring Ibaraki Prefecture and those who evacuated to other prefectures -- for the internal presence of radioactive substances. The team used whole body counters at a hospital in the village of Hirata, Fukushima Prefecture, from October 2011 to November 2012.

Radioactive cesium was found in about 1 percent of the people surveyed after March 2012, compared with 15 percent in November 2011.

Radioactive materials taken in shortly after the Fukushima Daiichi plant disaster in March 2011 are believed to have already left the body in many cases, while improvements in food inspection methods are also considered to have been effective in eliminating contaminated food.

The survey found no specific relationship between the degree of exposure and land contamination.

The minimum detection level for the whole body counters is 300 becquerels.