So far, very low risk of West Coast contamination from Japanese nuclear accident, experts say, Daily Democrat (Woodland, CA), March 16, 2011:
... Nevertheless, if conditions are right, recent research has shown tiny particles can -- and regularly do -- drift from Asia to the United States.
Dust from sandstorms in China's Gobi Desert has been found in California. So has mercury burned in coal in Chinese power plants, as particles drifted across the ocean, raining down in small amounts into San Francisco Bay.
It can take six to 15 days for such particles to reach the United States, said Tony VanCuren, an atmospheric scientist with the California Air Resources Board who has studied the issue since 2001.
"We see it in the Rocky Mountains, in Alaska; it's very widespread," he said. "We've actually seen evidence of Asian dust in the Virgin Islands."...