Doctors Say Japan Radiation Danger Outside Plant Not Large, for Now

"This disaster is different from Chernobyl, but the consequences will be very severe," said Williams. "Because of the high population density, the local effects may be as bad or worse. Disruption and displacement of the population are likely to produce the greatest health impacts, as was the case with Chernobyl."

And Dr. Janette D. Sherman, who published a book on Chernobyl, agreed.

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"It appears that a Chernobyl-style disaster is underway," said Sherman. "It took but 10 days for radionuclides from Chernobyl to spread through the northern hemisphere… Chernobyl shows clearly that there is no barrier to spread of radioactivity."

Henry Spitz, professor of nuclear and radiological engineering at the University of Cincinnati, had a more optimistic outlook, though he said things could change.

"It is unlikely that any elevated health effects will be observed resulting from the radioactive emissions that have occurred to date," said Spitz. "Unfortunately, the event at the Fukushima reactor site continues to evolve."