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 U.S. Department of Energy said minuscule amounts of the radioactive isotopes iodine-131, iodine-132, tellurium-132 and cesium-137 had reached a Sacramento, Calif., monitoring station tied to the CTBTO, but the readings were far below levels that could pose any health risks.
A detector at the Pacific Northwest National Laboratory in Washington state earlier this week also detected trace amounts of xenon-133 — a gas produced during nuclear fission — the DOE said.
The doses that a person normally receives from rocks, bricks, the sun and other natural background sources are 100,000 times the dose rates detected at either location, the DOE and the U.S. Environmental Protection Agency said in a joint statement.
In Alaska, Dr. Bernd Jilly, director of state public health laboratories, also said monitoring had shown no readings of above-normal levels of radiation.