Cancer rates are not expected to rise after Japan's Fukushima nuclear accident as people quickly left the area hit by the world's worst such disaster in 25 years, a UN scientific committee said on Friday.
Wolfgang Weiss, a senior member of the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), said the evacuation of tens of thousands of people had sharply lowered radiation exposure.
The dose levels were "so low that we don't expect to see any increase in cancer in the future in the population", he told reporters during an UNSCEAR meeting to discuss a draft report to be presented to the UN General Assembly later this year.
A magnitude 9 earthquake and tsunami on March 11, 2011, killed nearly 19,000 people and devastated the Fukushima Daiichi nuclear plant, spewing radiation and forcing about 160,000 people to flee their homes.
It was the biggest nuclear accident since a reactor exploded at the Chernobyl power plant in Ukraine in 1986. Studies into that accident have linked thyroid cancer to radioactive iodine from Chernobyl.
UNSCEAR's findings appeared to differ somewhat from a World Health Organisation (WHO) report published in February which said people in the area worst affected have a slightly higher risk of developing certain cancers.
Weiss suggested the UNSCEAR study, carried out by 80 experts and with the involvement of five international organisations including the United Nations health agency, was based on information covering a longer period after the accident.
"So they (the WHO) didn't have the full picture. We don't have the full picture either but we have more than one year in addition," he said.
UNSCEAR's 27 member states and 180 experts met this week in Vienna to scrutinise the report.
"The results are very straightforward ... the evacuation of many, many thousands of people resulted in a reduction of the dose that they would have received if they had stayed in the evacuation zone by a factor of 10," he said.
Highlighting the differences between Chernobyl and Fukushima, he said people close to the plant in the then Soviet Union were exposed to radioactive iodine that contaminated milk.
The thyroid 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. "The doses through the thyroid in Japan are much, much lower."
Also when it came to exposure to another radioactive contaminant, the longer-lasting caesium, "we wouldn't expect any increase of...cancers during the next decades", he said.
But he said a few workers at the plant had received very high radioactive doses in the early stages of the accident and they continued to be under medical surveillance.
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