The major UN report on the health impacts of the Fukushima accident concluded that any radiation-induced effects would be too small to identify. People were well protected and received "low or very low" radiation doses.
The latest report on the accident comes from the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) - the independent international body set up in the 1950s to give impartial advice on the effects of radiation on people and the environment. In January 2012 UNSCEAR was asked by the UN General Assembly to undertake a "full assessment of the levels of exposure and radiation risks" attributable to Fukushima accident.
Released today, the study concluded that the rates of cancer or hereditary diseases were unlikely to show any discernible rise in affected areas because the radiation doses people received were too low. People were promptly evacuated from the vicinity of the nuclear power plant, and later from a neighbouring area where radionuclides had accumulated. This action reduced their radiation exposure by a factor of ten, said UNSCEAR, to levels that were "low or very low."
Overall, people in Fukushima are expected on average to receive less than 10 mSv due to the accident over their whole lifetime, said UNSCEAR, comparing this to the 170 mSv lifetime dose from natural background radiation that people in Japan typically receive.
Health issues from radiation only become apparent in people known to have received 100 mSv or more in a short space of time. This criteria does apply to a group of 160 plant workers, who are to be monitored in the long term.
Despite the evacuation's success in minimizing radiation exposure to a level where, "No discernible increased incidence of radiation-related health effects are expected among exposed members of the public or their descendants," the mass movement of people had repercussions of its own, including the deaths of some vulnerable people and social effects of the relocation. UNSCEAR said, "The most important health effect is on mental and social well-being, related to the enormous impact of the earthquake, tsunami and nuclear accident, and the fear and stigma related to the perceived risk of exposure to radiation."
Agneta Rising, head of the World Nuclear Association, said the UNSCEAR report was the "most detailed yet... and should greatly reassure those thinking of returning to evacuated areas." She continued: "Experience has taught us that some measures to prevent radiation dose can be more damaging than the doses avoided. They also exacerbate fears that lead to social and economic suffering. We need practical measures for protecting people that also help them get on with their lives when the emergency is over."
UNSCEAR's conclusions agree with those of its preliminary report from late 2012. The extra time was used in compiling the most detailed possible models to describe people's individual radiation doses based on their age, their movements and the distribution of radionuclides. Another study from the World Health Organisation in early 2013 was based on broad theoretical risk calculations. Overall, WHO's conclusions were the same as UNSCEAR's - that any health effects from radiation were expected to be too small to identify.
Children are more vulnerable than adults to the effects of radiation and after a nuclear accident, the principal risk is for the youngest children to absorb iodine-131 which would accumulate in the thyroid gland, increasing the chance of thyroid cancer. This rare disease is treatable with a high success rate, but to guard against potential extra cases the thyroid glands of some 360,000 young people up to the age of 18 are being surveyed by ultrasound.
UNSCEAR said, "Increased rates of detection of nodules, cysts and cancers have been observed during the first round of screening; however, these are to be expected in view of the high detection efficiency. Data from similar screening protocols in areas not affected by the accident imply that the apparent increased rate of detection among children in Fukushima prefecture are unrelated to radiation exposure."
Effects on wildlife and nearby ecosystems were similar in magnitude to the predicted human health impact. UNSCEAR said it expected no effects beyond the areas where highly radioactive water was released - i.e. the immediate environs of the plant itself. Even there the effects would be "transient" it said. In the wider area of the Pacific Ocean, "the potential for effects on biota is insignificant."
Researched and written
by World Nuclear News