Extensive study detects no internal cesium exposure in Fukushima children

10 October 2015

No positive tests for radioactive cesium have been returned from among any of the 2,707 infants and other young children examined by three hospitals in Fukushima Prefecture, including one in Hirata village, for internal radiation exposure in the aftermath of the 2011 nuclear accident at Tokyo Electric Power Co.'s Fukushima Daiichi plant, according to the results of an extensive study announced on Oct. 8.

A group of experts involved in examining the children, led by Masaharu Tsubokura, a researcher at the University of Tokyo’s Institute of Medical Science, said at a news conference that the results “reconfirmed the safety of agricultural products and tap water in Fukushima.”

The children, aged 0 to 12, were examined using whole-body counters, designed especially for scanning small children, at Hirata Central Hospital, where screenings began in December 2013; Iwaki Urology Hospital in Iwaki city, where they began in March 2014; and Minamisoma Municipal General Hospital, where they began in June 2014.

The accompanying chart shows the number of examinees by age. Five-year-olds formed the largest group with 438 people, followed by the 6-year-old bracket with 383, 4-year-olds with 365 and 7-year-olds with 338. Those aged 6 and below made up about 70% of the children surveyed.

By location of residence, about 2,000 examinees, or around three-quarters of the entire group, live in Fukushima Prefecture. These include municipalities in the Hamadori region on the Pacific coast such as Iwaki, Minamisoma and Soma cities, Koriyama city, and towns like Miharu that have arrangements with Hirata Central Hospital to conduct the tests. Of the remaining examinees numbering about 700, some 200 are children who evacuated outside Fukushima while the rest are from other prefectures.

The whole-body counters designed to scan small children can detect as little as 50 becquerels of radioactive substances. This is about five to six times more precise than other devices commonly used to scan adults, but in the study, no radioactive cesium beyond the measurable level was detected in the children examined.

Tsubokura and his group also surveyed the children’s parents and guardians regarding their diet and found that many of the children examined consumed Fukushima-grown produce. In Miharu, for example, less than 4% said they avoided all rice, vegetables and tap water available in the prefecture.

It was the first time since the nuclear disaster that results of such an extensive study on internal radiation exposure focusing on children were released.

Speaking at the news conference at Hirata Central Hospital, Tsubokura said the study results "show that there has been almost no intake of radioactive cesium from daily life.”

“This is ample evidence to prove that the risk is low (even if one ate Fukushima food),” he said. “We will continue to conduct the checkups to help dispel safety concerns.”

A thesis on the study results was published in the Proceedings of the Japan Academy on Oct. 9.

(Translated by Kyodo News)