RENO -- Minuscule amounts of radiation from Japan's damaged nuclear plant have reached Las Vegas and Germany's Black forest, but scientists say it poses no health risk.

Extremely small amounts of the radioactive isotopes iodine-131 and zenon-133 reached a monitoring station by the city's Atomic Testing Museum this week, said Ted Hartwell, manager of the Desert Research Institute's Community Environmental Monitoring Program.

Hartwell said he's certain the isotopes came from Japan because they're not usually detected in Nevada. But he said the readings were far below levels that could pose any health risks.

"Unless you have an accident like this (in Japan) you wouldn't expect to see this. No doubt it's from Japan," Hartwell said.

Minuscule amounts of radiation from Japan have been reported elsewhere in the West, including California, Colorado, Hawaii and Washington.

In addition, air detectors in Germany's Black Forest mountains have picked up radioactive iodine blowing in from Japan 5,590 miles away, but the amount is too little to be harmful, officials said Saturday.

The instruments on Schauinsland mountain can distinguish between the much larger amount of radioactive iodine constantly emitted by the soil and rock of Germany and the nuclear power station iodine-131 from Japan.

On Friday the Japanese-originated radioactivity had been 58 microbecquerels per cubic meter of air. On Saturday this rose to 500

microbecquerels, the German federal radiation protection office said.

A spokesman in Salzgitter said this posed no health risk and was only a tiny fraction of the regular radioactivity in Germany's air. "We were expecting a slight rise," he said. "The traces are very, very tiny."

Most radiation in Germany comes from radon, a gaseous element that occurs naturally as a decay product of uranium. It is common in many areas, seeping out from the soil.