The residents between 4 and 77 years of age came from Iitate and Kawamata, tightly knit communities about 35 kilometers away from the tsunami-hit plant, and all went through two tests each at the beginning and end of last month.
The research team that conducted the tests urged Fukushima residents to consider the results in deciding whether or not to move away from the contaminated areas voluntarily, while assuring the public that the recorded exposures were too low to pose a direct threat to the health of the tested people.
“This won’t be a problem if they don’t eat vegetables or other products that are contaminated,” said Nanao Kamada, the radiation biologist and professor emeritus from Hiroshima University who led the research team. “But it will be difficult for people to continue living in these areas. We want residents to use these results to decide whether or not to move.”
Kamada said six people tested for iodine-131 at doses up to 3.2 millisieverts in the first round of tests, but none in the second. It is possible that most of the iodine had disappeared in the lapse between the tests, because half of any given amount of it decays every eight days, according to the New Scientist.
Iodine is a main immediate hazard in nuclear fallout, because it accumulates in the thyroid gland, leading to thyroid cancer, the magazine noted. “If they found iodine in the urine, almost all of it will have traveled through the thyroid,” Richard Wakeford of the Dalton Nuclear Institute at the University of Manchester told the magazine. Following the nuclear accident at Chernobyl in the Soviet Union 25 years ago, most cases of thyroid cancer were a result of children drinking heavily contaminated milk, he added.
All of the tested residents in Fukushima had also suffered from internal exposure to radioactive cesium, according to the Japanese research team.
Their data indicates that the cumulative external radiation exposure over a period of two months was between 4.9 and 14.2 millisieverts, not exceeding the maximum amount of 20 millisieverts per year.
In the next two weeks, 110 other residents from Iitate, Kawamata and Namie will be tested for radiation exposure.