1 Juin 2013
June 1, 2013
VIENNA--The evacuation of tens of thousands of people helped prevent rising cancer rates and other health problems after Japan's Fukushima nuclear disaster, the world's worst in 25 years, U.N. scientists said on May 31.
Radiation exposure following the reactor meltdowns more than two years ago did not cause any immediate health effects, the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) said after its annual meeting.
That would be in contrast to Chernobyl, the 1986 Soviet reactor explosion which sent radioactive dust across much of Europe and is believed to have caused thyroid cancer in some children.
A magnitude 9 earthquake and tsunami on March 11, 2011, killed nearly 19,000 people and devastated the Fukushima No. 1 nuclear plant, spewing radiation and forcing about 160,000 people to flee their homes.
Actions to protect inhabitants in the area, including evacuation and sheltering, significantly reduced the exposure to radioactive substances, the scientific body said after the session to prepare a report for the U.N. General Assembly.
"These measures reduced the potential exposure by up to a factor of 10," said senior UNSCEAR member Wolfgang Weiss.
"If that had not been the case, we might have seen the cancer rates rising and other health problems emerging over the next several decades," he said in a statement.
Weiss, who chairs work on UNSCEAR's Fukushima report, told reporters that dose levels were "so low that we don't expect to see any increase in cancer in the future in the population."
UNSCEAR's findings appeared to differ somewhat from a World Health Organization (WHO) report published in February which said people in the area worst affected have a slightly higher risk of developing certain cancers.
NO RADIATION-RELATED DEATHS
Weiss suggested the UNSCEAR study, carried out by 80 experts and with the involvement of five international organizations including the United Nations health agency, was based on information covering a longer period after the accident.
UNSCEAR's 27 member states scrutinized the draft during this week's session in Vienna, it said, adding it would be the most comprehensive scientific analysis of the issue so far.
While a few received very high doses, no radiation-related deaths or acute effects were observed among nearly 25,000 workers--including employees of the operator Tokyo Electric Power Co.--involved at the accident site, it said.
Highlighting the differences between Chernobyl and Fukushima, Weiss said people close to the then Soviet plant were exposed to radioactive iodine that contaminated milk.
The thyroid--a gland in the neck that produces hormones that regulate vital body functions--is the most exposed organ as radioactive iodine concentrates there. Children are deemed especially vulnerable.
"In Chernobyl, many children used milk which had high iodine concentrations, resulting in high thyroid doses, resulting in an increase of thyroid cancer," Weiss said, adding that the doses in Japan were "much, much lower."
In Belarus, Russia and Ukraine, the countries most affected by Chernobyl, more than 6,000 cases of thyroid cancer had been reported by 2005 in children and adolescents who were exposed at the time of the accident, UNSCEAR says on its web site.
"Many of those cancers were most likely caused by radiation exposures shortly after the accident," it adds.
VIENNA (Kyodo) -- U.N. scientists assessing the health impact of the disaster-crippled Fukushima Daiichi Nuclear Power Station said Friday their estimates based on data obtained so far show the radiation dose on residents in the region is so low they do not expect to see any increase in cancer in the future but urged that follow-up studies be conducted on residents' health.
The U.N. Scientific Committee on the Effects of Atomic Radiation also noted that the prompt evacuation of many residents from areas around Tokyo Electric Power Co.'s plant resulted in a reduction of dose they would have received from radioactive substances released after the 2011 accident.
The panel said its dose estimate of radioactive iodine, which is associated with the thyroid cancer, in most cases was below the critical 50 millisieverts, a threshold above which preventive "iodine tablets" are given to young children, but also mentioned single cases of children with a dose level up to 66 millisieverts.
The doses of cesium 134 and 137 on adults for the whole body are estimated up to 15 millisieverts, much lower than 100 millisieverts of dose considered to increase risks for solid cancers.
In the 1986 nuclear accident in Chernobyl, many children consumed milk with a high iodine concentration, leading to high thyroid doses and an increase in thyroid cancer.
The panel said the quick evacuation of the local population after the accident has reduced the radiation doses for the people by a factor of 10.
Radiation doses were also reduced because taking in food contaminated with radioactive substances was prevented.
The results presented in the report differ from those in a previous report published by the World Health Organization in February, which warned of higher cancer risks for residents and nuclear power plant workers around Fukushima than the average for the country's entire population.
On this, UNSCEAR said the WHO only had access to data from the first three months after the accident and then calculated the estimates by using models and plausible parameters, while UNSCEAR made use of precise dose distributions from an additional year of time, which helped present updated results.
About the workers at the Fukushima plant, the panel confirmed that two workers received thyroid doses up to 12 millisieverts as a result of inhalation of iodine at the beginning of the accident. They are under medical surveillance and nothing extraordinary has been observed so far, according to the panel.
The panel said it has only limited information on the impact of animals, plants and other non-human spheres, adding follow-up research, particularly in the ocean, is needed.
UNSCEAR held a meeting from Monday through Friday in Vienna to discuss the impact of the Fukushima accident on residents and others. A report is expected to be presented to the U.N. General Assembly session this fall.