As Japan’s nuclear plant crisis intensified after Friday’s 9.0 earthquake and tsunami, fears that radiation could cross the Pacific Ocean to the West Coast surfaced.
Pierce County Emergency Management fielded calls from some worried residents. We asked two atmospheric scientists about the situation.
Could radiation from a major meltdown of one or more nuclear reactors in Japan reach the Puget Sound, 4,800 miles away?
Yes, but the health risk would be zero, said Dan Jaffe, a University of Washington Bothell atmospheric chemist who has studied pollution patterns crossing the Pacific from Asia for 20 years.
“I can’t imagine a scenario where the radiation release would be big enough to be a health hazard,” he said.
UW meteorology professor Cliff Mass, who writes the weather blog cliffmass.blogspot.com, agreed.
On Sunday, Mass posted a graph showing that, based on an atmospheric model, wind could bring radiation from Japan to the Northwest.
“The bottom line is, it’s not unusual to have a trajectory coming from Japan and reaching us,” he said, “but there is no health risk.”
Why is there no health risk?
Japan is too far away for radiation to get here in any concentration, said Jaffe and Mass.
Airborne particles don’t flow like a river but tend to disperse quickly over distance and time. Weather and wind directions are big factors. Rain would quickly push particulates to the ocean surface.
The danger zone for the 1986 Chernobyl nuclear plant meltdown in Ukraine, the worst nuclear plant disaster in history, was about 500 miles, though radiation was detected around the world.
If Japan became another Chernobyl, which is considered unlikely, the radiation risk to the United States would still be nil, Mass added.
How long would it take for any radiation from Japan to reach the Northwest?
Computer models suggest seven to 10 days, Jaffe said. Mass’ trajectory indicated it would take nine days to reach the Puget Sound area.
What kind of computer model did Mass use?
There are a variety of such models but the one developed by the National Oceanic and Atmospheric Agency and used by Mass is the HYSPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectory) – model.
It can compute simple air parcel trajectories as well as complex dispersion and deposition simulations. It was developed after Mount St. Helens erupted and was used to plot the plume from the eruption of the volcano in Iceland last spring.
Could radiation from Japan ride the so-called “Pineapple Express” storms that hit the Northwest in the winter?
No. Pineapple Express storms have nothing do with Japan. They form in sub-tropical Pacific Ocean around Hawaii, which is south of any radiation trajectory from Japan.
What does the U.S. Nuclear Regulatory Commission say about the radiation danger from Japan?
In a statement Sunday noting that prevailing winds in Japan have taken the small radiation releases east out to sea, the commission said:
“Given the thousands of miles between the two countries, Hawaii, Alaska, the U.S. Territories and the U.S. West Coast are not expected to experience any harmful levels of radioactivity.”
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