TOKYO — A study published on Thursday by the World Health Organization on the health risks associated with the disaster at the Fukushima Daiichi Nuclear Power Plant suggested that the risk for certain types of cancers had increased slightly among children exposed to the highest doses of radioactivity, but that there would most likely be no observable increase in cancer rates in the wider Japanese population.
The study, which capped off a comprehensive, two-year analysis of the estimated doses of radioactivity from the 2011 Fukushima accident and their potential risks, also warned that the disaster’s psychological impact could have a consequence on health, and called for continued monitoring and health screenings for populations most exposed to the radiological fallout.
The study’s authors warned, however, that their assessment was based on limited scientific knowledge; much of the scientific data on health effects from radiation is based on acute exposures like those that followed the bombing of Hiroshima and Nagasaki and not chronic, low-level exposure. In Japan, some densely populated areas are expected to remain contaminated with relatively low levels of radioactive materials for decades.
“Because scientific understanding of the radiation effects, particularly at low doses, may increase in the future, it is possible that further investigation may change our understanding of the risks of this radiation accident,” the report said.
The Japanese government called the report overly cautious. “It overestimates the risks, and could lead to misunderstandings of the likelihoods of developing cancer,” Japan’s Environment Ministry said in a statement made to the public broadcaster, N.H.K. In particular, the ministry said the study failed to fully take into account government evacuations of residents closest to the plant, assuming many people were exposed for longer than they were.
According to the W.H.O. study, girls exposed as infants to radioactivity in the most contaminated regions of Fukushima Prefecture, where estimated doses ranged from 12 to 25 millisieverts for the first year, faced a 70 percent higher risk of developing thyroid cancer than what would normally be expected. The report pointed out, however, that the normal expected risk of thyroid cancer was just 0.75 percent, and that the additional lifetime risk would raise that to 1.25 percent.
Girls exposed to radioactivity as infants in the most heavily contaminated areas also had a 6 percent higher risk of developing breast cancer, and a 4 percent higher risk of developing cancers that cause tumors. Meanwhile, boys exposed as infants had a 7 percent higher chance of developing leukemia.
The study also said that about a third of the emergency workers who remained to try to stabilize the Fukushima Daiichi plant were estimated to have a slightly increased risk of developing leukemia, thyroid cancer and other types of cancer.
There would most likely be no observable increase in cancer rates for the general population in Fukushima Prefecture outside the most contaminated zones, in the rest of Japan and the world, the report said. It also said that the radiological fallout from the disaster was not expected to cause increases in miscarriages, stillbirths and other physical or mental disabilities.
Still, the study said that the psychological toll of the disaster, including the stresses of evacuation, were harmful to health and should color the Japanese government’s response.
The W.H.O. report “underlines the need for long-term health monitoring of those who are at high risk, along with the provision of necessary medical follow-up and support services,” Dr. Maria P. Neira, the Geneva-based organization’s director for public health and environment, said in a news release. “This will remain an important element in the public health response to the disaster for decades,” she said.
Dr. Angelika Tritscher, acting director for the food safety and zoonoses department at the health agency, said, “In addition to strengthening medical support and services, continued environmental monitoring, in particular of food and water supplies, backed by the enforcement of existing regulations, is required to reduce potential radiation exposure in the future.” .
W.H.O. Sees Low Health Risks From Fukushima Accident
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W.H.O. Sees Low Health Risks From Fukushima Accident
