Some have raised the question whether nuclear radiation from Japan could be transmitted by upper level winds across the Pacific and reach the U.S. West Coast or Alaska. The answer is possibly, but not in sufficient quantities to pose a meaningful risk to public health according to experts.

Numerous credible sources have reached this same conclusion.

Let me share a few of them...

Cliff Mass, professor of atmospheric science at the University of Washington, wrote yesterday:

there is no serious radiation threat to us here in the Northwest.

even if they [wind trajectories] were heading straight for us..there is little to fear.

From virtually a point source, the radiation would mix through huge volumes of the atmosphere due to horizontal and vertical mixing. Since it would take days to reach us, there would be time for larger particles to settle out and precipitation would wash some out as well. Even for Chernobyl, where the core exploded while the reactor was powered up and where there was no containment, serious radiation only extended roughly 1000-1500 km away.

(Six-day forecast of a hypothetical plume of radioactive air emitted last night in Tokyo at a 50 meter altitude in the atmosphere. Top panel shows the trajectory or path of the radiation across the ocean, whereas the bottom panel shows how radiation would be lifted vertically. Image created using NOAA’s Hysplit Trajectory Model.)

The U.S. government assessment of the situation is consistent with these scientists’. An ABC News story from this morning writes:

...the U.S. Nuclear Regulatory Commission (NRC) said it is unlikely that harmful levels of radiation leaking from Japanese reactors will reach any part of the U.S., including Hawaii, Alaska, and various territories in the Pacific, considering the vast distances between Japan and those areas.

The story also refers to the opinion of Dr. James Thrall, radiologist-in-chief at Massachusetts General Hospital in Boston and president of the American College of Radiology, who said the chances of consequential radiation exposure from Japan anywhere in the U.S. are “essentially zero.”

So we have atmospheric scientists, the government and a leading medical official on the same page that U.S. residents have little cause to worry about nuclear radiation based on the current circumstances.

Some more reading on the issues:

US West Coast: on frontline from nuclear cloud?

So far, very low risk of West Coast contamination from Japanese nuclear accident, experts say

False Radiation Rumors Run Rampant

Radiation’s Effect Depends on Amount