The radiation effects from the Fukushima Daiichi nuclear disaster are the observed and predicted effects resulting from the release of radioactive isotopes from the Fukushima Daiichi Nuclear Power Plant after the 2011 Tōhoku earthquake and tsunami. Radioactive isotopes were released from reactor containment vessels as a result of venting to reduce gaseous pressure, and the discharge of coolant water into the sea. This resulted in Japanese authorities implementing a 20 km exclusion zone around the power plant, and the continued displacement of approximately 156,000 people as of early 2013. Trace quantities of radioactive particles from the incident, including iodine-131 and caesium-134/137, have since been detected around the world.
The World Health Organization (WHO) released a report that estimates an increase in risk for specific cancers for certain subsets of the population inside the Fukushima Prefecture. A 2013 WHO report predicts that for populations living in the most affected areas there is a 70% higher risk of developing thyroid cancer for girls exposed as infants (the risk has risen from a lifetime risk of 0.75% to 1.25%), a 7% higher risk of leukemia in males exposed as infants, a 6% higher risk of breast cancer in females exposed as infants and a 4% higher risk, overall, of developing solid cancers for females.
Preliminary dose-estimation reports by WHO and the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) indicate that, outside the geographical areas most affected by radiation, even in locations within Fukushima prefecture, the predicted risks remain low and no observable increases in cancer above natural variation in baseline rates are anticipated. In comparison, after the Chernobyl accident, only 0.1% of the 110,000 cleanup workers surveyed have so far developed leukemia, although not all cases resulted from the accident. However, 167 Fukushima plant workers received radiation doses that slightly elevate their risk of developing cancer. Estimated effective doses from the accident outside of Japan are considered to be below, or far below the dose levels regarded as very small by the international radiological protection community. The United Nations Scientific Committee on the Effects of Atomic Radiation is expected to release a final report on the effects of radiation exposure from the accident by the end of 2013.
A June 2012 Stanford University study estimated, using a linear no-threshold model, that the radioactivity release from the Fukushima Daiichi nuclear plant could cause 130 deaths from cancer globally (the lower bound for the estimate being 15 and the upper bound 1100) and 199 cancer cases in total (the lower bound being 24 and the upper bound 1800), most of which are estimated to occur in Japan. Radiation exposure to workers at the plant was projected to result in 2 to 12 deaths. However, a December 2012 UNSCEAR statement to the Fukushima Ministerial Conference on Nuclear Safety advised that because of the great uncertainties in risk estimates at very low doses, UNSCEAR does not recommend multiplying very low doses by large numbers of individuals to estimate numbers of radiation-induced health effects within a population exposed to incremental doses at levels equivalent to or lower than natural background levels.”