The first round of thyroid tests for about 80,000 children in Fukushima Prefecture found no direct effects from last year's accident at the Fukushima No. 1 nuclear power plant.
Although one child was found to have thyroid cancer, specialists said there was likely no link to the nuclear accident since thyroid cancer only develops four to five years after exposure to radiation.
The Fukushima prefectural government on Sept. 11 reported the results of thyroid tests for about 80,000 subjects that had been compiled as of Aug. 24 to a committee looking into the health checks of prefectural residents.
A total of 425 individuals were found to have either a lump of 5.1 millimeters or larger or a cyst of 2.1 centimeters or larger and were told to undergo further tests. Of those individuals, further tests were conducted on 38 individuals, and one was found to have thyroid cancer while 27 were diagnosed as having a benign tumor.
Citing privacy concerns, Fukushima prefectural government officials did not reveal any details about the individual diagnosed with thyroid cancer, including gender, age, symptoms and future treatment plans.
Regarding whether the Fukushima nuclear accident was the cause of the cancer, Shinichi Suzuki, professor of thyroid surgery at Fukushima Medical University, said, "Based on the experience of the Chernobyl nuclear accident, it is inconceivable that cancer would develop within four years of exposure to radiation."
The tests were part of a program that will eventually check the health of about 360,000 individuals who were 18 years old and younger and living in Fukushima Prefecture at the time of the nuclear accident. The children will be tested throughout their lives to check on whether they develop thyroid cancer due to the radiation released from the plant following the accident.
Data from victims of the Chernobyl nuclear accident as well as the atomic bombings of Hiroshima and Nagasaki has led to the theory that thyroid cancer can develop several years or several decades after exposure to radiation.
The health checks by Fukushima Prefecture will be used as fundamental data to grasp what the situation is like among those who were living in Fukushima at the time of the accident as well as to determine if any aftereffects develop in the ensuing years.
The results that were released on Sept. 11 were of tests conducted on some of the children within 18 months of the nuclear accident, so prefectural officials said it was still too early to reach conclusions about the effects from the accident as well as general health trends.
In most cases of thyroid cancer, progression of the disease is slow and treatment tends to be effective. The 30-year survival rate for children who have been diagnosed is between 90 and 99 percent.
After the Chernobyl accident, the average thyroid radiation exposure level of evacuees was about 500 millisieverts. About 6,000 people, mainly children, developed thyroid cancer, and a dozen or so died.
The Fukushima prefectural government also released the estimated external radiation exposure levels for about 97,000 residents in the first four months after the nuclear accident. Excluding individuals whose work involved exposure to radiation, there were 18 individuals with radiation exposure levels of 10 millisieverts or higher and 44 with exposure levels of between five millisieverts and less than 10 millisieverts. All the other individuals were exposed to less than five millisieverts.
(This article was written by Teruhiko Nose and Yuri Oiwa.)
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