The chief cabinet secretary added that the government had checked the thyroid function of 900 children up to age 15 in two villages, Iitate and Kawamata, just outside the 18-mile perimeter and none was found to have been exposed to high radiation levels. High levels of radiation have been detected in the water and on grass in Iitate. Edano said it was the third time that the government had conducted tests on children in areas just outside the 18-mile zone.