Half of Fukushima examinees exposed to radiation above annual limit

Residents in three municipalities near the crisis-hit Fukushima Daiichi nuclear power plant have been exposed to up to some 37 millisieverts of radiation during the four months after the powerful earthquake and tsunami on March 11 crippled the plant, Fukushima prefectural government officials said Friday.

While the Japanese Government maintains it’s position that annual exposure of 1 mSv is not harmful, the figure does not include normal background radiation found in nature nor exposure due to medical treatment such as X-rays.

The doses do not include natural radiation or from internal exposure. The government has set a target of one millisievert per year as a safe exposure level.

The highest dose found in four children in Koriyama City equals 4.98 millisieverts when calculated over a one-year term. This is almost five times the annual limit.

98 percent of those tested are estimated to have been exposed to less than 5 millisieverts, which the Japanese Government continues to downplay. This in comparison with the general population in Belarus and the Ukraine, who was exposed to radiation from Chernobyl, which was estimated to be 0.26 mSv during the first year, and 0.82 mSv lifetime. (ref)

The local government is continuing to conduct health checks on all the residents in Fukushima Prefecture, a population of some 2 million.

It is also using whole body counters and conducting urine tests to measure internal radiation exposure on people who spend long hours outdoor, such as farmers and construction workers, as well as on children and mothers who were evacuated from the no-entry zone in the 20-kilometer radius from the crippled power plant.

Where the Japanese Estimates Fall Short

These dose estimates released by the Japanese Government, actually generally indicate only orders of magnitude. They were calculated using data about ground contamination levels, plausible mean transfer factors, and hypotheses of food consumption patterns. They are thus applicable to groups and do not take into account individual characteristics that may be important from an epidemiologic point of view (e.g., age at exposure).

The residents face an unknown foe, as neither TEPCO or the Japanese Government has released a complete analysis of the radiation released from the Fukushima Daiichi plant, and continually downplays the dangers of radiation to citizens.

Research needs to concentrate on screening cases, so that early treatment can be provided, and on investigating the dose-response relation in this particular epidemiologic situation.

The lifestyle of the Japanese citizens has been directly touched by the accident changed, however, and their subjection to food restrictions may have modified their vitamin

intake.

The numbers are expected to increase dramatically as more information is compiled and released about the noble gas release, and fission products most of which total release estimates have yet to be totaled.

The Japanese inhabitants of the contaminated zones have been continuously subjected to external and internal irradiation, which might have been largely reduced if the Japanese Government had responded adequately.

When an individual is homogeneously and externally exposed, each part of the body receives the same dose; whole-body dose is then an appropriate concept. When exposure is heterogeneous, however, different organs or tissues receive different quantities of energy; in such events, the use of organ dose is more appropriate.

Based on what has been learned so far, the future occurrence of thyroid cancer and leukemia is plausible, and many other various unexpected and ill-defined effects, (digestive, respiratory, endocrine) have been mentioned in relation to the event.

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The equivalent dose takes into account the biologic potency of different types of radiation (x, gamma, beta, alpha, and neutrons) by applying weighting factors (respectively, 1, 1, 1, 20, and 10). The equivalent dose unit is the Sievert (Sv).

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The effective dose, also expressed as Sv, results from a calculation that provides a single summary value to be used in different cases of irradiation. It sums and weights the equivalent doses received by tissues and/or organs according to their sensitivity to the effects of ionizing radiation.

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Yoshida Confirmed Esophageal Cancer

A utility spokesman says the former chief of Japan’s crippled Fukushima Dai-ichi nuclear plant has cancer, which Tokyo Electric Power Co., kept the details of under wraps until Friday, when it confirmed he has esophageal cancer.

TEPCO spokesman Masato Yamaguchi says Yoshida was exposed to at least 70 milliseiverts of radiation after the crisis began.

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