ABC News 
Sept 22, 2011
The radioactive fallout from Japan’s Fukushima nuclear plant accident has spread as far as California waters, according to scientists from the University of California, Berkeley.
But although the level of radioactivity in the water was higher than normal, they said, it was still very low and not harmful to humans.
“The levels of fallout we have observed in San Francisco Bay area rain water pose[d] no health risk to the public,” wrote the study authors, led by Eric B. Norman of UC Berkeley’s Department of Nuclear Engineering.
The March earthquake and tsunami that rocked Japan compromised the nuclear plant, causing radioactive material to run into the surrounding waters. Researchers subsequently found some of that same material in rainwater collected from the San Francisco Bay area.