Radiation risks from Fukushima are likely to be less than for Chernobyl

Mar 23, 2012 By Jeffrey Norris
Outside of the exclusion zone in the city of Kouri, public health workers asked that children under 16, infants and pregnant women be monitored for radiation exposure. Only about one out of every 100 who were monitored received a dose due to the nuclear meltdown that exceeded the worldwide mean background exposure of 2.4 millisieverts/year, according to symposium speaker Mitsuyoshi Urashima, MD, PhD, MPH, a pediatric oncologist and molecular epidemiologist from the Jikei University School of Medicine in Tokyo. 

(PhysOrg.com) -- Radiation exposures to the public in Japan from meltdowns at three Fukushima Daiichi nuclear power plant reactors in the wake of last year’s 9.0-magnitude earthquake and 45-foot tsunami have been less than what people were exposed to in the aftermath of the Chernobyl disaster a quarter century ago, according to two experts who spoke at a daylong symposium at UCSF marking the anniversary of the catastrophe in Japan.

Speakers said at the March 19 symposium that monitoring of children living just outside the evacuated zone points to higher than background levels of exposure, but not to unsafe levels. But there is uncertainty about harms that may arise due to ingestion of short-lived radioactive iodine in the immediate aftermath of the reactor meltdowns.

James Seward, MD, medical director of Lawrence Livermore National Laboratory and a UCSF clinical professor, referred to research findings that have emerged from studies of health outcomes associated with the disaster a quarter-century ago in discussing potential health outcomes that may result from the Fukushima Daiichi reactor meltdowns.

As in Chernobyl, some rescue workers were exposed to levels of close to or exceeding the permissible acute exposure limit for such workers, which in is 100 millisieverts. But there were many fewer who received unsafe radiation doses in Fukushima compared to the number exposed in Chernobyl.

Most radiation concerns have been centered on gauging risk to the broader public. These worries are focused on risks posed by internal doses acquired by children and others outside the power plants. The main concerns are two radioactive chemical isotopes released during the meltdowns that can enter the body through inhalation or by consuming milk and other foods.

Iodine-131 has a half-life of only eight days, but concentrates in the thyroid gland. Cesium-137 has a half-life of 30 years and can be taken up by food grown in contaminated soil.

Most people in Fukushima prefecture in Japan evacuated from highly contaminated areas following reactor meltdowns, according to Japanese pediatric oncologist and epidemiologist Mitsuyoshi Urashima, and Fukushima city has the highest radiation levels among residential areas.

Based on the Chernobyl experience, the main health concern is thyroid cancer in children exposed due to ingestion of iodine-131, Seward said. About 6,000 excess cases of thyroid cancer have been attributed to the Chernobyl reactor accident.

However, although radioactive iodine quickly decays to undetectable levels, the risk to those exposed remains elevated for a lifetime, so the number of excess thyroid cancers will continue to climb, he added.

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The thyroid gland absorbs much more iodine in growing children. Radiation-related risks from Chernobyl decreased with age at exposure, and studies have not shown any increase in risk for those exposed as adults, according to analysis by UCSF epidemiologist Lydia Zablotska, MD, PhD.

Compared to the Chernobyl response, residents were evacuated more rapidly and food products were taken off the market more quickly following the Fukushima Daiichi reactor meltdowns, Seward said at the symposium. About 60 percent less radiation was released.

Mitsuyoshi Urashima, MD, PhD, MPH, a pediatric oncologist and molecular epidemiologist at the Jikei University School of Medicine in Tokyo, has taken a leading role as a government advisor and in educating the public about the health effects of nuclear radiation following the Daiichi reactor meltdowns. He has also written a book for the public on the subject.

Urashima, who also serves as a consultant for the city of Kouri, outside the evacuation zone, noted the confusion and mistrust generated by government communications about radiation releases, contamination and hazards. It has not been unusual for local officials and citizens to act more decisively than central government agencies to take the initiative in organizing clean-up or monitoring efforts, he said.

Environmental levels of radioactive contaminants in the soil vary over short distances, according to Urashima, and patterns of rainwater runoff can affect levels of radiation in soil.

About 30 percent of more than 3,000 children tested to date have had thyroid nodules, but it is unclear whether this represents an abnormally high percentage, Urashima said. No thyroid cancers have been detected thus far. However, early screening result may point to an elevated incidence of abnormal thyroid function.

Seward and Urashima both noted that thyroid cancer almost always can be treated successfully. Only about 15 extra deaths have been attributed to the Chernobyl accident. But Seward also suggested that any excess cancer deaths might be undetectable against the much higher, normal incidence of cancer. Urashima said monitoring of environmental exposures in Kouri indicates that there has been less exposure to radioactivity from the meltdowns than to radiation from normal background sources.

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Mark_Goldes
1 / 5 (4) Mar 23, 2012
The Northen Lights are more unusual in color, magnitude, and in scope because of the high atomic weight Fukushima Fallout in the atmosphere. Post Fukushima such lights are no longer a treat. In fact they are the harbingers of the creation of a whole new witches brew of radioactive Fukushima related fallout. It is a harbinger that grows more concerning as these Solar Storms are simultaneously increasing in magnitude The recent CME interacted with high atomic weight fallout (both radioactive and NON-radioactive) in the upper atmosphere and produced new radioactive fallout via nuclear spallation processes. Radioactive iodine has been reported in Europe. Evidence of Plutonium 239 spallation is expected.

See pages 8&9 at "400 Chernobyls?" on the Aesop Institute website for little recognized effects from the meltdown in Japan.
DKA
2.3 / 5 (3) Mar 23, 2012
Very dissapointed that Physorg is sponsoring such irresponsible pro-nuclear activist research totally out of touch from the reality such as using TEPCO falsified data for calculation and not taking account about the most important health impairement factor, internal exposures.
Also his baseline, 6000 excess Thyroid cancers from Chernobyl immediatly lets us know that he is using the "life is beautiful" data of the IAEA which are totally false. 30% of the children of Fukushima already have lumps in their thyroid glands. There has been alrady 50% increase in cardiac arrest due to Cesium attacking the hearth muscle. It took only several months for this to happen in Fukushima, while in Chernobyl, it took 4 years for children to come up with lumps, this tells is the real story.
And internal exposures in case of Fukushima are far exeeding those of Chernobyl.
roj2003
1 / 5 (1) Mar 24, 2012
DKA - Thyroid cancer takes 3-4 years to develope after radiation exposure to large iodine doses. Chernobyl children, when first examined at Year 1, also showed thyroid tumours. This reflected the lack of prior medical facilities (number of doctors in that region), NOT early radiation-related tumours which DID arise but much later.
Tausch
1 / 5 (2) Mar 25, 2012
Imagine any government or corporate entity where 'playing down' or 'playing up' any information - imaginary or real - is no longer PR.
Callippo
1 / 5 (2) Mar 25, 2012
About 60 percent less radiation was released.
It's difficult to compare it, because at the case of the Fukushima, most of radioactivity has been simply washed into the sea in quiet.