It has been some time now since the earthquake caused Fukushima nuclear disaster in March 2011. A tsunami followed, killing as many as 20,000 people. Then, a series of explosions, fires and partial meltdowns at the Fukushima Daiichi Nuclear Power Station released radioactive gas directly into the atmosphere, and traces of radioactive material later turned up in Tokyoâ€™s water supply and the ocean. With time the global health effects can now be better evaluated and were so by Stanford University researchers. The estimates have large uncertainty ranges, but contrast some with previous claims that the radioactive release would likely cause no severe health effects.
Ten Hoeve and Jacobson of Stanford used a 3-D global atmospheric model, developed over 20 years of research, to predict the transport of radioactive material. A standard health-effects model was used to estimate human exposure to radioactivity.
Because of inherent uncertainties in the emissions and the health-effects model, the researchers found a range of possible death tolls, from 15 to 1,300, with a best estimate of 130. A wide span of cancer morbidities was also predicted, anywhere from 24 to 2,500, with a best estimate of 180.
Those affected according to the model were overwhelmingly in Japan, with extremely small effects noticeable in mainland Asia and North America. The United States was predicted to suffer between 0 and 12 deaths and 0 and 30 cancer morbidities, although the methods used were less precise for areas that saw only low radionuclide concentrations.
"These worldwide values are relatively low," said Ten Hoeve. He explained they should "serve to manage the fear in other countries that the disaster had an extensive global reach."
The Japanese government's response was much more rapid and coordinated than that of the Soviets in Chernobyl, which may have mitigated some of the cancer risk.
Japanese government agencies, for example, evacuated a 20-kilometer radius around the plant, distributed iodine tablets to prevent radioiodine uptake and prohibited cultivation of crops above a radiation threshold â€“ steps that Ten Hoeve said "people have applauded."
But the paper also notes that nearly 600 deaths were reported as a result of the evacuation process itself, mostly due to fatigue and exposure among the elderly and chronically ill. According to the model, the evacuation prevented at most 245 radiation-related deaths â€“ meaning the evacuation process may have cost more lives than it saved.
Earlier this year, the U.N. Scientific Committee on the effects of Atomic Radiation (UNSCEAR) announced that the health impact from Fukushima would not be large. They found that the largest health risks will be limited to workers at the plant, not the general public.
In comparison at Chernobyl, 237 people suffered from acute radiation sickness of whom 31 died within the first three months. Most of the victims were fire and rescue workers trying to bring the accident under control, who were not fully aware of how dangerous the exposure to radiation in the smoke was.
Of the 72,000 Russian Emergency Workers being studied, 216 non-cancer deaths are attributed to the disaster, between 1991 and 1998.
For further information see Fukushima.
Reactor Room image via Wikipedia.