In its report on April 2, the U.N. Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) also said there was no discernible rise in overall cancer rates among residents of Fukushima Prefecture.
However, the internal dose levels among subcontract company workers that were reported tended to be lower compared with the estimates of the U.N. experts.
In several cases concerning dose levels detected in the thyroid glands of contracted workers, the report said TEPCO’s levels were less than half of those calculated by the committee.
The committee also pointed out that no consideration was given to the possibility that TEPCO or contract workers were exposed to the shorter-lived isotopes of iodine than iodine-131 through inhalation.
“As a result, the assessed doses from internal exposure could have been underestimated by about 20 percent,” the report said.
Doubts raised by UNSCEAR on the effective exposure by workers from affiliated companies reported in an earlier study prompted the Japanese government last year to instruct TEPCO and its contractors to re-evaluate the internal dose levels.