The U.S. Environmental Protection Agency identified radioactive iodine-131 as the isotope that so far has reached Hawaii from the Japanese nuclear crisis.
The EPA said radiation levels here were higher than those on the West Coast but still "thousands of times" below that which would pose a health threat.
The readings were in units known as picocuries per cubic meter.
It’s a scale that measures radioactivity like flashes from cameras in the audience at a rock concert. The rate and intensity of the flashes and the size of the arena determine exposure.
On Oahu the EPA said it detected 0.759 units on March 20, 1.35 units on March 21 and 0.182 units on Wednesday.
The EPA characterized those levels as "trace amounts."
"The iodine result is consistent with March 21 preliminary monitor results in Hawaii of a detection of a minuscule level of an isotope consistent with the Japanese nuclear incident," the EPA said in an email to the Star-Advertiser on Sunday. "The levels are slightly higher than what was found earlier this week on the west coast, but still thousands of times below levels of concern."
The reported yesterday that three of the Fukushima nuclear power complex’s six reactors are believed to have partially melted down and that plutonium a heavy element less likely to spread far was found in soil outside the nuclear facility.
Trace amounts of radiation have registered in the U.S. as far as the East Coast.
For comparison, the EPA said previous iodine-131 amounts detected in San Francisco measured 0.0682 units and 0.0134 units in Seattle.
According to the agency, the threshold for shelter and evacuation to be considered for iodine-131 begins when people are subjected to 37 million units in one hour or 385,000 units for 96 hours.
Radioactive iodine, cesium and tellurium were confirmed in California and Washington. California also registered xenon.
The EPA said the radiation levels in California and Washington were "hundreds of thousands to millions of times below levels of concern."
Jeff Eckerd, acting program manager of the Hawaii Health Department’s indoor and radiological health branch, previously said he expected to see the same isotopes here.
"I think the numbers are going to be low (in Hawaii), and it will even get significantly lower because iodine-131, tellurium-132 and xenon are relatively short-lived I mean hours to days," Eckerd said last week. "It will decay out rather quickly."
Cesium has a longer life, and Eckerd said the Health Department probably would be tracking trace amounts of radioactivity in Hawaii "for months if not longer."