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    Japan Radiation Risks: FAQ

    Answers to questions about health risks posed by Japan's damaged Fukushimi Daiichi nuclear power plant.

    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? continued...

    “Our information depends on the extent to which we’re allowed to take measurements independently on-site or close by,” Davis says.

    Most of the data released by the U.S. Department of Energy is based on aerial surveillance rather than information gathered on the ground. “We can do a good job monitoring what is coming to the U.S., for example, which is important and of great concern to people here, but for the situation in Japan, we have to rely a great deal on information coming from the Japanese government," Davis says.

    Isn’t it bad that radiation is leaking into the ocean?

    That’s actually helpful, says Royal. “Because it’s in the ocean, the radiation gets diluted very rapidly, and it’s much less likely to affect people. Since the primary element that has been released is radioiodine, which has a very short half-life, it will go away very quickly."

    What kind of radiation is coming from the plant?

    There are a number of different radioactive substances that could leak from a damaged nuclear reactor. At this point, radioactive iodine (iodine-131) is the primary component of the leaked material, although there has also been some release of cesium-137.

    With a half-life of just eight days, radioactive iodine quickly loses its potency and after a couple of months, is virtually gone. Cesium, however, has a half-life of 30 years, and so can pose a threat to public health for much longer.

    “Even so, at Chernobyl if there were going to be major effects from cesium, we should have started seeing significant increases in solid tumors by now,” says Williams. “But 25 years later, we’re only just beginning to see the hints of possibly an increase in bladder cancers. We’re still not seeing if there was a significant impact.”

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