Will U.S. citizens face any danger from the fallout from nuclear reactors? Over the next week, you’ll hear exaggerated estimates of the danger. Some news reports are saying that low levels of radiation have been detected as far away as 200 miles from the nuclear plant, but the radioactivity that has been released into the atmosphere appears to be coming from a storage pond that caught fire (since extinguished) where fuel rods are kept cool. This is not a nuclear explosion, and it is helpful to remember that Seattle—the nearest city to northern Japan—is 4,792 miles away from the potential meltdown sites, or about a fifth of the circumference of the Earth.
Some might remember when Soviet Russia set off a 50-megaton hydrogen bomb 4,000 meters (13,000 feet) over the Arctic island of Novaya Zemlya in far northern Siberia on October 30, 1961, at a time when prevailing winds were reportedly blowing over the North Pole toward Canada. The blast, which shattered windows as far away as Norway and Finland, threw up many many orders of magnitude more radiation than exists in the Japanese core reactors, and it was much closer to the U.S. mainland than is Fukushima Dai-ichi. The subsequent evaluation of Russia’s political stunt was that the detonation was extremely unwise, but the only health concerns it raised were warnings that children should avoid eating the snow. A Wikipedia article on the Chernobyl meltdown (a far greater disaster in terms of spread of radiation) suggests that there were moderate health impacts in France, the Czech Republic and, of course, Belarus and the Ukraine, but not on other continents.
As you continue to see images from Japan, recognize that we are all exposed to some risk of tragedy. The best method of protection is to be aware and be prepared.