Radiation levels in the thyroid glands of 1-year-old children living around the crippled Fukushima No. 1 nuclear power plant are estimated to be less than 30 millisieverts in most cases, a research team at the National Institute of Radiological Sciences said Sunday.

The figure is lower than the 50 millisievert threshold set by the International Atomic Energy Agency in calling for iodine to be taken to prevent thyroid exposure.

The research team came up with the estimate by combining data, including the results of thyroid exams on around 1,000 children in the prefecture soon after the nuclear crisis started, as well as projections on the accumulation of radioactive material.

The estimate was reported at an international conference in Tokyo on Sunday.

"The finding is a relief for the residents around the complex, but the data do not reflect the actions of each resident" when the plant was damaged on March 11, 2011, said Osamu Kurihara, senior researcher at the institute.

Due to the Fukushima crisis, the Nuclear Regulation Authority is considering urging local governments to prepare for the distribution of iodine tablets, which help prevent thyroid cancer, if emergencies, such as reactor leaks, occur.

The thyroid gland regulates hormone production.