By Fredrik Dahl
VIENNA (Reuters) - Miniscule amounts of radioactive particles believed to have come from Japan's crippled Fukushima nuclear power plant have been detected as far away as Iceland, diplomatic sources said on Tuesday.
They stressed the tiny traces of iodine -- measured by a network of international monitoring stations as they spread eastwards from Japan across the Pacific, North America and to the Atlantic -- were far too low to cause any harm to humans.
The Comprehensive Test Ban Treaty Organization (CTBTO), a Vienna-based U.N. body for monitoring possible breaches of the atom bomb test ban, has 63 stations worldwide for observing such particles, including one in the Icelandic capital Reykjavik.
They can pick up very small amounts of radioactive particles, in this case iodine isotopes.
"They measure extremely small amounts," one Vienna-based diplomat said. "It has nothing to do with any health risks."
Another source said several CTBTO stations had so far detected particles believes to originate from the Fukushima nuclear complex, which emitted some radioactivity in the days after it was hit by a huge earthquake and tsunami.
"Reykjavik is the first in Europe," the source added.
Experts and diplomats had earlier predicted that very small amounts of radioactive particles were expected to reach Europe.
NO "HEALTH RISK WHATSOEVER"
The U.S. Energy Department and the Environmental Protection Agency late last week confirmed "miniscule" amounts of radiation that appeared to have come from Japan's damaged reactors were detected in California, where the CTBTO also has a station.
The agencies also said between March 16 and 17 trace amounts of radiation that may have come from Japan were detected in Washington state. They said the radiation amounted to one-millionth of the dose rate that a person normally receives from natural sources such as rocks, bricks and the sun.
Austria's Central Institute for Meteorology and Geodynamics said on its website on Monday that levels of radiation which posed no "health risk whatsoever" had been observed also in Alaska and western Canada.
France's nuclear safety authority ASN said that tiny amounts were set to reach the country on Wednesday.
"Very slightly contaminated air, with levels in the order of 1,000 to 10,000 times below those measured after the Chernobyl accident, should reach France on Wednesday with no consequences for human health," it said in a statement.
While only tiny traces of radioactivity have been detected in countries outside Japan, the U.N. nuclear watchdog said on Monday "high levels of contamination" have been measured around the Fukushima plant itself.
At the site on Tuesday, smoke and steam rose from two of the most threatening reactors at Japan's quake-crippled nuclear plant on Tuesday, suggesting the battle to avert a disastrous meltdown and stop the spread of radiation was far from won.
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.
The CTBTO continuously provides data to its member states, but does not make the details public.
(Additional reporting by Alister Doyle in Oslo; Editing by Ralph Boulton)