|Fig. 1: Workers in protective clothing and masks on site of the Fukushima Daiichi Nuclear Power Station Disaster. (Source: Wikimedia Commons)|
On March 11, 2011, a 9.0 magnitude earthquake struck the east coast of Japan, with the official estimation of the death toll exceeding 14,000.  It's resultant tsunami also caused substantial damage to the Fukushima Daiichi Nuclear Power Plant, disabling all AC power to Reactors 1, 2, and 3 of the plant and detaching fuel tanks for emergency diesel generators.  Despite the best efforts of those at the plant, the reactors were unable to be sufficiently cooled in the critical first few days. Consequently, it is suspected that hydrogen gas was released into the reactor buildings, which ignited and caused devastating explosions within the facilities.  This ultimately released masses of radioactive material into the environment and resulted in the worst nuclear accident since the 1986 disaster at Chernobyl in the former Soviet Union. 
The explosions discharged volatile radionuclides including iodine, tellurium, and cesium into the atmosphere in the northern regions of Japan and also into the ocean by direct release and deposition from the atmosphere.  Furthermore, the radioactive dust that lofted following the explosion and disperse through rainfall posed a major threat.
In the early stages of radiation exposure following the accident, short-lived radionuclides such as Te-132 and Xe-133 were were noted as a major source of external exposure.  However, most residents living within the 20 km radius had been evacuated by March 15, when the strongest radioactive plume was released.  Dietary exposures is considered a major radiation exposure route, as radioactive cesium has been detected in mushrooms, wild vegetables, and meat. 
Those at the greatest risk of external exposure were the on-site workers. However, less than 1% of all such workers were exposed to a radiation dose of 100 mSv or higher; the average dose was 119 mSv.  For the emergency workers with radiation exposure of more than 100 mSv, a small increase in incidence of cancer attributable to radiation exposure might be expected. 
Research has yet to be conducted on the long-term health effects of the disaster. However, in similar nuclear accidents, such as Chernobyl, the health effects of radiation exposure have been associated with the increased risks of developing cancer, cardiovascular disease, and genetic mutations.  Ultimately, the process of decommissioning the plant and measuring its long-term effects will be protracted.
© Anthony Trinh. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
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