Around 45 percent of children in Fukushima Prefecture checked by the prefectural and central governments in late March experienced thyroid exposure to radiation, although in all cases in trace amounts that didn't warrant further examination, officials of the Nuclear Safety Commission said Tuesday.

The survey was conducted on 1,080 children from newborns to age 15 in Iwaki, Kawamata and Iitate from March 26 to 30 in light of radiation leaking from the Fukushima No. 1 nuclear plant.

Among children who tested positive for thyroid exposure, the amounts measured 0.04 microsievert per hour or less in most cases. The largest exposure was 0.1 microsievert per hour, equivalent to a yearly dose of 50 millisieverts for a 1-year-old.