Professor Shinji Tokonami, Department of Radiation Physics, Institute of Radiation Emergency Medicine, Hirosaki University and his researchers say people who escaped from the coastal areas of Fukushima Prefecture after the accident and people who continued to live in Namie-machi after the March 11, 2011 nuclear accident were found with high levels of radiation exposure on the thyroid.
They tested 65 residents in April 2011, and it is in the news on March 9, 2012. Another case of nearly one-year delay in disclosing the information that would have made the difference if known earlier. Like 11 months ago.
From Asahi Shinbun (3/9/2012):
From Asahi's extremely convoluted tabulation, here's what I've figured out (I think, maybe):
It has been disclosed that someone was exposed to nearly 90 millisievert radiation [equivalent dose] on the thyroid from radioactive iodine during the Fukushima I Nuclear Power Plant accident. Professor Shinji Tokonami, Department of Radiation Physics, Institute of Radiation Emergency Medicine, Hirosaki University and his researchers analyzed the test result of 65 Fukushima residents. The test was conducted 1 month after the accident. Of people who were exposed to radiation, about half had equivalent dose of 10 millisieverts or less, but 5 people had equivalent dose exceeding 50 millisieverts.
The radiation exposure on the thyroid increases the risk of cancer. However, radioactive iodine has a short half life, and the exposure was not measured properly in the confusion right after the accident and the details were not known.
From April 11 to 16 last year, Professor Tokonami's group measured the density of radioactive iodine in the thyroid of 48 people who evacuated from Hamadori (coastal 1/3 of Fukushima) to Fukushima City and 17 people who remained in Tsushima District of Namie-machi, right outside the 30 kilometer radius from the nuclear power plant. Radioactive iodine was found in 50 people, nearly 80% of people tested.
From the actual measurement, the researchers calculated the equivalent dose at the thyroid. Assuming they had inhaled radioactive iodine immediately after the accident on March 12 and were exposed to radiation, the calculation showed that 34 people had equivalent dose of 20 millisieverts and less, and 5 people exceeded 50 millisieverts, which is an international standard for intervention to prevent negative effect on health.
The maximum equivalent dose was 87 millisieverts, from an adult who remained in Namie-machi after the accident. The second highest was 77 millisieverts from an adult who had spent more than 2 weeks in Tsushima District of Namie-machi on his/her way to evacuate to Fukushima City. The highest dose in children was 47 millisieverts. There is no information of whereabouts of the child during the weeks in March and April.
In the test done by the national government late last March on 1,080 children in Iwaki City, Kawamata-machi, and Iitate-mura, 35 millisievert equivalent dose was announced as the maximum.
48 people from Hamadori (coastal 1/3), 17 people who remained in Tsushima District of Namie-machi, total 65 people
Radioactive iodine detected in 50 people
25 people below 10 millisieverts equivalent dose
9 people between 10 and 20
11 people between 20 and 50
- 5 people above 50
NHK, reporting on the same news, says the researchers are yet to tell the residents about the test result:
The researchers plans to tell the residents about the test result in the near future.
How nice of them.
Hirosaki University is one of the 86 national universities in Japan.