Some Americans are worried that radiation from the damaged nuclear reactors in Japan could cause harm on the U.S. West Coast, prompting a run on potassium iodide pills. But the scientific consensus is that the fear is unfounded.
Greg Evans, a professor of chemical engineering at the University of Toronto, said there is no danger to people on the west coast of the United States and Canada.
"There's really no need to be worried about any sort of radiation release from Japan reaching across the Pacific to people on the West Coast," Evans told CNN International's Hala Gorani.
A U.S. agency director agrees. Gregory Jaczko, the head of the Nuclear Regulatory Commission, said Thursday there is little concern about harmful radiation levels in the United States as a result of the damaged Japanese plant.
The federal government's recommendation that U.S. citizens stay at least 50 miles away from the plant remains "prudent and precautionary," he told reporters at the White House.
Dr. Otis Brawley, chief medical officer for the American Cancer Society, said passengers on airplanes coming from Japan could carry small amounts of radiation on their clothing or belongings, but those people are being screened before departure and on arrival.
"I've actually had patients who've had nuclear medicine - bone scans or thallium stress tests - who actually have been detained by immigration officials because they set off the monitors at airports," Brawley said, "so I'm not worried that someone is going to get through immigration and into the United States with radiation on their clothing."
As for radiation drifting through the air across the ocean, it will be too diluted to cause harm, Brawley said. For those in the U.S., a typical day of sunbathing would probably result in more radiation exposure than the Japanese accident, he said.
Brawley also said people need not worry about contamination of Pacific fish and seafood.
"If it were to happen, there's going to be checks and balances to make sure that fish is safe and is not radioactive," he said. "It's very likely that this will not happen. I can't overstress that."
A New York Times graphic showing the hypothetical transport of a plume of radiation across the Pacific has prompted some alarm, but CNN meteorologist Angela Fritz said the graphic is easily misinterpreted.
"First, there is no current plume of radiation to be transported," she said. "What the model shows is an example of what could happen.
"The folks that ran this model did so to determine if various detection networks across the globe would even be able to pick up a radiation signal. They ran the model on Tuesday by taking a large mass of air within the model (what meteorologists call a 'parcel') and let it be carried by winds at various levels of the atmosphere.
"The result is that the parcel is spread out and dispersed all over the Pacific, and it can look alarming. In no way does this suggest that there is an actual plume of radiation heading to the West Coast. This was all done on a computer with atmospheric equations and a laundry list of assumptions that might not even be valid."
The reality is that radiation is leaking in small amounts near the surface, Fritz said.
"It would take a catastrophic meltdown to create a scenario where we would be able to detect radiation here in the U.S.," she said. "The radiation would have to be injected into the very high levels of the atmosphere for it to be transported. But even if that does happen (and we can't rule it out), the radiation that could reach the U.S. would be negligible. We've been comparing it to the amount of radiation you'd receive in a chest X-ray. Probably less."
The general population in Japan away from the stricken plant does not yet seem to be in any danger, said Dr. Ira Helfand of Physicians for Social Responsibility, so it stands to reason that people 5,700 miles away are in even less danger.
Dr. James Thrall, president of the American College of Radiology and chief of radiology at Massachusetts General Hospital, is concerned that public opinion will turn against nuclear power.
"If you look at nuclear power objectively, it actually has fewer health consequences than any energy production with fossil fuels," he said.