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Japan Radiation Risks: FAQ

Answers to questions about health risks posed by Japan's damaged Fukushimi Daiichi nuclear power plant.
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On April 11, a month after the disaster, Japan raised the radiation alert status to its highest level, level 7 -- the same as the Chernobyl plant meltdown in Russia. It had previously been at level 5. What does this new status mean?

 The reclassification doesn’t mean that the situation has gotten worse, says Henry Royal, MD, professor of radiology and associate director of the Mallinckrodt Institute of Radiology at Washington University in St. Louis. Rather, it’s acknowledging that the scope of the radiation leaked from the plant was larger than originally thought.

“The reason that the accident was reclassified was because it’s now obvious that the radioactive material has escaped the plant, particularly into the ocean. That’s why it’s been classified a level 7 as opposed to a level 5.”

An assessment released by the U.S. Department of Energy on April 7 found that beyond a 25-mile radius surrounding the plant, radiation levels were consistently below those that would require people to be evacuated. Since March 19, the report says, radiation levels have continued to decline. "The headlines are making it sound like something has gotten worse, but when you look at where people are living, the situation is getting better,” Royal says.

Nonetheless, the new classification does mean that it’s more likely that there will be environmental and health consequences for Japan from this event. 

“It indicates that there is more radioactive material being dispersed over a wider, broader geographic area,” says Scott Davis, professor and chair of the epidemiology department in the School of Public Health at the University of Washington and a member of Fred Hutchinson Cancer Research Center’s Radiation and Environmental Exposure Studies group.

On March 25, the Japanese government expanded the recommended evacuation zone around the Fukushima Daiichi plant from 12 miles to 19 miles. The U.S. Embassy recommends evacuation from areas within 50 miles of the plant. Since the radiation has not spread in even circles, but rather in varying patterns due to weather and the terrain, communities in certain “hot spots” outside the Japanese government’s 19-mile zone may also soon be evacuated.

It’s also important to remember that the information we have in the U.S. about the situation immediately surrounding the plant is limited.

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