The distribution patterns depend on both the winds and the release intensities from the reactors. And although the current evacuation zones are concentric circles around the plant, it is more likely that dispersed radioactive material will fall in narrow bands, David Richardson, an epidemiologist at the University of North Carolina at Chapel Hill's Gillings School of Global Public Health, said during the Wednesday briefing. He added, "It's going to be quite a while until we have anything more than a crude understanding of the magnitude and the distribution."
Gathering enough data to create sturdy predictions, however, has so far proved impossible. "The infrastructure is so bad over there, I can't really tell what's going on," Clanton says. "It's very frustrating in terms of determining what is actually happening."
Nevertheless, the U.S. Nuclear Regulatory Commission (NRC) and President Obama have reassured Americans that there will not be harmful levels of radiation reaching the U.S. "Whether it's the west coast, Hawaii, Alaska or U.S. territories in the Pacific, we do not expect harmful levels of radiation," Obama said Thursday.
Even as higher-than-normal levels of background radiation are detected in the U.S., it is unlikely to pose a health risk. Simply living at high altitudes or frequent air travel exposes people to extra radiation (via the sun's rays)—commercial flight crews, for example, can in a year accumulate more than three times normal annual U.S. background radiation found at sea level. And safety standards for nuclear industry employees allow for more than six times average U.S. background radiation, which is still far below levels considered carcinogenic.
In Japan, winds have been primarily blowing out to sea since the March 11 earthquake and tsunami, which is good news for the millions of people who live in and around Tokyo. This does mean, however, that most of the radioactive material would be falling out of the air over the ocean, not far from Japan's east coast. "And that means that marine life will pick up this material—and if people eat fish, they will in turn intake this material," Marvin Resnikoff, a consultant at Radioactive Waste Management Associates, said during the press conference.
But Japan's fisheries are unlikely to become another Chernobyl milk incident (in which local cows grazed on contaminated grass produced isotope-tainted milk that has been implicated in many of the 1,800 cases of thyroid cancer documented in children from the affected area).
The Pacific Ocean is no small-town Ukrainian meadow. "The solution to pollution is dilution," Clanton says, quoting the adage and acknowledging the risk of sounding flippant. "The ocean's a big place." Even under the improbable scenario of a large fire in reactor No. 4, in which "it's likely there would be at least a momentary release of radioactive material into the atmosphere," he says, combined with strong winds that carried that material into the ocean, "there's a slight potential that you could detect it in fish later—but even that would be small."
Any ichthyic-bound isotopes would be so few that "they would be very hard to detect," Clanton says, comparing the amounts with the naturally occurring isotope potassium 40 found in bananas.
Dangers of displacement
The NRC's recommendation earlier this week that U.S. residents in Japan relocate to at least 50 miles from the Fukushima facility has caused confusion, given its relatively extreme distance compared with Japanese recommendations—and even local U.S. nuclear disaster contingency plans.
Clanton shares the sentiment of many radiation experts that given the comparatively few number of U.S. residents in the area, "why not be conservative?" For the Japanese government to move the evacuation boundary the additional 30 kilometers would mean dislocating a lot more people. Some 80,000 people within the 20-kilometer boundary have already been evacuated, and many more beyond that zone had left for fear of radiation contamination, The New York Times reported.
And on a population-wide scale, "there's probably much more [health] risk [in displacement] than of the reactor," Clanton says. "Just trying to house and feed them in an environment that's near freezing every night—that's got to be an untenable issue."