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March 10, 2012

High radioiodine levels found in thyroids of Fukushima residents post-meltdown



HIROSAKI, Aomori -- Radioactive iodine levels exceeding international limits were detected in the thyroid glands of five people who lived near the Fukushima No. 1 nuclear plant during the meltdowns there, researchers here have revealed.

Findings by the research team, led by professor Shinji Tokonami from Hirosaki University, showed that 50 of 65 people checked from April 11 to 17 last year had radioactive iodine-131 in their thyroids, with 26 absorbing radiation doses over 10 millisieverts, and five with doses over 50 millisieverts -- the upper limit set by the International Atomic Energy Agency (IAEA).

"After detecting high levels of radiation exposure in people who stayed in Namie, we were able to grasp part of the reality of the disaster," says Tokonami.

All five people with doses exceeding 50 millisieverts -- the point at which the IAEA recommends taking iodine pills to prevent thyroid cancer -- were from Namie, Fukushima Prefecture -- three who were still living in the town's Tsushima district at the time, and two who had moved to the prefectural capital about two weeks after the outbreak of the nuclear crisis. Most of Namie lies within the 20-kilometer radius no-go zone around the Fukushima plant.

The survey covered 12 other people from Namie's Tsushima district, and 48 people from other municipalities along the prefecture's coast who had evacuated to the city of Fukushima shortly after the March 11 disasters. The team made their dosage calculations based on the assumption that the residents, who varied from infants to people in their 80s, had inhaled radioactive iodine -- which has a short half-life -- immediately after the outbreak of the disaster.

The highest exposure from radioiodine overall was 87 millisieverts, while the highest among children under 15 was 47 millisieverts.

The researchers' findings exceed data collected by the government in a similar survey in March 2011. Among the total of 1,080 children the government surveyed in Iwaki and other Fukushima Prefecture municipalities at the time, the highest estimated doses stood at around 30 millisieverts.

"The central and prefectural governments should conduct follow-up surveys and take other measures to deal with potential health issues," Tokonami stated.

The Hirosaki University team will submit its findings to the Ministry of Internal Affairs and Communications, and brief the residents.

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