WHO Estimates Radiation Dose From Fukushima Accident

The World Health Organization has released its estimates on the radiation dose uptake from the Fukushima Dai-ichi nuclear site during the March 2011 earthquake and tsunami.

AsianScientist (May 29, 2012) – The World Health Organization (WHO) has released its estimates on the radiation dose uptake from the Fukushima Dai-ichi nuclear site during the March 2011 earthquake and tsunami.

The report, written by an International Expert Panel of more than 30 scientists, is part of an overall health risk assessment on the global impact of the March 2011 accident. A separate health risk assessment will be published this summer.

Conservatively, the report estimated that individuals in the Fukushima prefecture with a relatively high exposure during the first year after the accident received a total effective dose of 10 to 50 mSv.

To put these numbers in perspective, 10,000 mSv of radiation in a single dose is fatal within weeks, while the recommended limit for radiation workers every five years is 100 mSv.

In the rest of Fukushima prefecture the effective dose was estimated to be within 1 to 10 mSv. The majority of Japanese received an estimated 0.1 to 1 mSv, and the rest of the world received doses far below 0.01 mSv.

For thyroid exposure, the characteristic doses in the most exposed locations of Fukushima prefecture were estimated to be within 10 to 100 mSv.

Assuming a relatively high exposure during the first year after the accident, the characteristic thyroid dose to one-year-old infants would be within 100 and 200 mSv, mainly through inhalation.

Thyroid doses in the rest of Japan were approximately 1 to 10 mSv and in the rest of the world doses are estimated to be far below 0.01 mSv. Outside the most affected areas of Fukushima prefecture, radiation exposure mainly occurs from food.

While all efforts were made to avoid any underestimation of doses, a number of caveats exist.

The report gave estimates based on “characteristic” individual doses for each region considered, which may not represent the full dose range. It also was based on a number of assumptions of the radioactive cloud composition and dispersion, time spent indoors/outdoors, and consumption levels.

In particular, it assumed that people in the most affected areas outside the 20-kilometer radius continued to live there for four months after the accident which may lead to a dose overestimation.

The full report can be downloaded here (PDF, 1.81 MB): Preliminary dose estimation from the nuclear accident after the 2011 Great East Japan.

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Copyright: Asian Scientist Magazine.
Source: World Health Organization.
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.

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