By Fredrik Dahl and Nichola Groom
VIENNA/LOS ANGELES (Reuters) - California air quality officials said on Friday they saw no elevated radiation levels on the U.S. West Coast from Japan's nuclear power plant disaster.
"At this point we're unable to verify if there are any elevated levels," said Ralph Borrmann, a spokesman for the Bay Area Air Quality Management District in San Francisco. "We're not seeing it on our live data in California."
Radiation levels have not shown an increase at any of the monitoring stations up and down the West Coast, he added.
Earlier on Friday, diplomatic sources in Vienna said data showed tiny amounts of radioactive particles that were believed to have come from Japan's stricken Fukushima plant.
The level of radiation was far too low to cause any harm to humans, they said. One diplomat, citing information from a network of international monitoring stations, described the material as "ever so slight," consisting of only a few particles.
"They are irrelevant," the diplomat added.
Another diplomatic source also said the level was very low.
The Comprehensive Test Ban Treaty Organization, a Vienna-based independent body for monitoring possible breaches of the test ban, has more than 60 stations around the world, including one in Sacramento in California.
They can pick up very small amounts of radioactive particles such as iodine isotopes.
"Even a single radioactive atom can cause them to measure something and this is more or less what we have seen in the Sacramento station," said the first diplomat, who declined to be identified.
He said the particles were believed to originate from the Fukushima plant, which has leaked radioactivity since being damaged by last week's massive earthquake and tsunami.
The CTBTO provides data to its member states, but does not make the details public.
On Thursday, the U.S. Nuclear Regulatory Commission said radioactivity would disperse over the long distance and it did not expect any harmful amounts to reach the country.
Radiation from the Chernobyl disaster in 1986 spread around the globe and reached the west coast of the United States in 10 days, its levels measurable but minuscule.
(Additional reporting by Sylvia Westall; editing by Tim Pearce)