TOKYO, July 5 (Kyodo) — Around 45 percent of children in Fukushima Prefecture surveyed by the local and central governments in late March experienced thyroid exposure to radiation, although in all cases in trace amounts that did not warrant further examination, officials of the Nuclear Safety Commission said Tuesday.
The survey was conducted on 1,080 children aged 0 to 15 in Iwaki, Kawamata and Iitate on March 26-30 in light of radiation leakages from the Fukushima Daiichi nuclear power plant crippled after the March 11 earthquake and tsunami disaster.
Separately, a survey of soil at four locations in the city of Fukushima on June 26 found that all samples were contaminated with radioactive cesium, measuring 16,000 to 46,000 becquerels per kilogram and exceeding the legal limit of 10,000 becquerels per kg, citizens groups involved said Tuesday.
The city, about 60 kilometers northwest of the crippled plant, does not fall within the 20-km no-entry zone or nearby evacuation areas.
One location registered as much as 931,000 becquerels per square meter, surpassing the 555,000 becquerels per sq meter limit for compulsory resettlement in the 1986 Chernobyl nuclear accident. Samples from the other three locations measured between 326,000 and 384,000 becquerels per sq meter.
Among children who tested positive for thyroid exposure, the amounts measured 0.04 microsieverts per hour or less in most cases. The largest exposure was 0.1 microsieverts per hour, equivalent to a yearly dose of 50 millisieverts for a 1-year-old.
None of those surveyed was exposed to over 0.2 microsieverts per hour, the government's benchmark for conducting more detailed examinations, according to the officials.
Babies and young children are at highest risk of developing thyroid cancer after exposure to radioactive iodine released into the atmosphere in nuclear accidents. In the case of Chernobyl, most victims who developed the cancer in following years had been babies or young children living in the affected regions at the time of the accident.