WHO says only slightly higher cancer risk for Fukushima residents
A global team of experts says residents zapped by the most radiation from the Fukushima nuclear meltdowns face an increased cancer risk so small it probably won’t be detectable.
Japan Times, Mar 2, 2013
LONDON – Two years after the Fukushima nuclear disaster, an international team of experts said Thursday that residents of areas hit by the highest doses of radiation face an increased cancer risk so small it probably won’t be detectable.
In fact, experts calculated the increase at about 1 extra percentage point added to a Japanese infant’s lifetime cancer risk.
“The additional risk is quite small and will probably be hidden by the noise of other (cancer) risks like people’s lifestyle choices and statistical fluctuations,” said Richard Wakeford of the University of Manchester, one of the authors of the report. “It’s more important not to start smoking than having been in Fukushima.”
The report was issued by the World Health Organization, which asked scientists to study the health effects of the disaster in Fukushima Prefecture.
The most exposed populations were directly under the plumes of radiation after three reactors at the Fukushima No. 1 power plant suffered meltdown and spewed radiation into the surrounding air, soil and water.
In the report, the highest increases in risk are for people exposed as babies to radiation in the most heavily affected areas. Normally in Japan, the lifetime risk of developing cancer of an organ is about 41 percent for men and 29 percent for women.
The new report says that for infants in the most heavily exposed areas, the radiation from the nuclear plant would add about 1 percentage point to those numbers.
Experts had been particularly worried about a spike in thyroid cancer, because radioactive iodine released in nuclear accidents is absorbed by the thyroid, especially in children. After the Chernobyl disaster, about 6,000 children exposed to radiation later developed thyroid cancer because many drank contaminated milk after the accident.
After Fukushima, dairy radiation levels were closely monitored, but children in Japan generally are not big milk drinkers.
The WHO report estimates that women exposed as infants to the most radiation after the Fukushima accident would have a 70 percent higher chance of getting thyroid cancer in their lifetimes. But thyroid cancer is extremely rare and one of the most treatable cancers when caught early. A woman’s normal lifetime risk of developing it is about 0.75 percent. That number would rise by 0.5 under the calculated increase for women who got the highest radiation doses as infants.
Wakeford said the increase may be so small it will probably not be observable.
For people beyond the most directly affected areas of Fukushima, Wakeford said the projected cancer risk from the radiation dropped dramatically. “The risks to everyone else were just infinitesimal.”
David Brenner of Columbia University in New York, an expert on radiation-induced cancers, said that although the risk to individuals is tiny outside the most contaminated areas, some cancers might still result, at least in theory. But they’d be too rare to be detectable in overall cancer rates, he said.
Brenner said the numerical risk estimates in the WHO report were not surprising. He also said they should be considered imprecise because of the difficulty in determining risk from low doses of radiation. He was not connected with the WHO report.
Some experts said it was surprising that any increase in cancer was even predicted.
“On the basis of the radiation doses people have received, there is no reason to think there would be an increase in cancer in the next 50 years,” said Wade Allison, a professor emeritus of physics at Oxford University, who also had no role in developing the new report. “The very small increase in cancers means that it’s even less than the risk of crossing the road.”
WHO acknowledged in its report that it relied on some assumptions that may have resulted in an overestimate of the radiation dose in the general population.
Gerry Thomas, a professor of molecular pathology at Imperial College London, accused the United Nations health agency of hyping the cancer risk.
“It’s understandable that WHO wants to err on the side of caution, but telling the Japanese about a barely significant personal risk may not be helpful,” she said.
Thomas said the WHO report used inflated estimates of radiation doses and didn’t properly take into account the quick evacuation of people from Fukushima.
“This will fuel fears in Japan that could be more dangerous than the physical effects of radiation,” she said, noting that people living under stress have higher rates of heart problems, suicide and mental illness.
The Environment Ministry on Thursday also questioned the report.
“This report is not a chart predicting the future,” an official said. “It is wrong to think what are presented as risks will materialize as shown.”
Among the problems with the report, the ministry cited the assumption that low-dose radiation of 100 millisieverts or lower has a specific impact on health, when no impact has been confirmed in epidemiological studies.
“At this moment, there is no need to change policy on health management,” the official said, noting the ministry’s estimate for radiation doses is lower than that of the WHO.
Regarding health risks for nuclear power plant workers, the ministry said it would like to continue monitoring their well-being.
Information from Kyodo added
Related: Please see Japan riled by WHO’s Fukushima cancer warning
On Thursday, the WHO said rates of thyroid cancer among women who were exposed to radiation as infants within a 20-kilometre (12-mile) radius of the plant were expected to be up to 1.25 percent.
This represented a 70-percent increase over the baseline risk of thyroid cancer over a Japanese woman’s lifetime, which is 0.75 percent, the UN health agency noted.
High radiation in fish caught off No. 1 plant
A greenling caught in the Fukushima No. 1 nuclear plant’s harbor is found to contain a level of radioactive cesium 5,100 times above the government-set limit
If someone were to eat 1 kg of fish with this level, they would be exposed to about 7.7 millisieverts of internal radiation. Also caught during efforts by Tepco to rid the harbor of all fish was a spotbelly rockfish containing 277,000 becquerels of radioactive cesium per kilogram.
At the mouth of the harbor, where the ocean is about 10 meters deep, Tepco has set up a 2-meter-high net at the seafloor to prevent bottom fish from swimming out. The harbor seabed has been seriously contaminated with radioactive substances.
“If we make the net higher, vessels won’t be able to go through,” said a Tepco official, adding the utility will continue to get rid of fish in the harbor.
The highest level of radioactive cesium found in fish had been 254,000 becquerels per kilogram, also in a spotbelly rockfish caught in the harbor.
Radiation levels fall 40 pct in 80 km of Fukushima Plant last year
Tokyo, March 1 (Jiji Press)–Radiation levels in areas within 80 kilometers of the crippled Fukushima No. 1 nuclear power plant fell about 40 pct last year, according to aircraft monitoring data released by the science ministry on Friday.
The decrease was much sharper than the expected annual fall of about 21 pct from natural radioactive decay of cesium-134 and cesium-137, due possibly to the effects of rain and other factors, the ministry said.
The recent aircraft survey was conducted in the 80-kilometer-radius zone from last October through November. The survey checked atmospheric radiation levels one meter above ground as well as the ground deposition of cesium-134 and cesium-137.
The survey also found a significant fall in levels in highly contaminated areas with more than 19 microsieverts per hour.
Outside the 80-kilometer-radius zone, the highest radiation level was some one microsievert per hour.