During that journey, said Williams, any radioactivity in the air would be dispersed and therefore greatly weakened.
"Just the sheer dilution factor, whether by water [nuclear plant workers in Japan have been flooding the damaged reactors with seawater in an effort to cool them] or air, it's not going to affect anyone here," she said.
And that would probably hold true "even if they [the Japanese] had the most catastrophic event, like a Chernobyl [in 1986 in the Ukraine] and you had a large amount of radioactivity being released," Williams added.
Also, heavier radiation particles would fall out of a radioactive plume, so "by the time anything reached us it would be no more than we experience normally," she said. "Everyone is being irradiated all the time."
This so-called "background" radiation isn't harmful and comes from sources in the Earth, solar rays in the atmosphere, and even drinking water.
But it's not inconceivable that the health risk in the United States might have to be reassessed if the Japan disaster reached catastrophic proportions, Rosenstein said.
"In harkening back to Chernobyl, where there was a tremendous release of radioactive isotopes, it did affect a good portion of Europe, certainly well beyond the Chernobyl area," he said.
Still, he pointed out, Europe and the Ukraine are much closer to each other than are Japan and the United States, even when talking about Hawaii or Alaska.
At this point, however, there is "no concern" about harmful effects from radioactivity this side of the Pacific, Rothstein said.
The Nuclear Regulatory Commission concurs. All the available information indicates that "weather conditions have taken the small releases from the Fukushima reactors out to sea away from the population. Given the thousands of miles between the two countries, Hawaii, Alaska, the U.S. Territories
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