Updated 03/30/11 – 4:40 p.m.

WARRENVILLE, Ill. (WBBM/CBS) — Low levels of radiation from Japan have been detected in the Chicago area, in Will and DuPage counties.

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At the Argonne National Laboratory in Darien, recent air samples revealed trace amounts of radioiodine-131, a radioactive isotope associated with the damaged nuclear plants in Japan. Trace levels of the isotope were also found on March 22 at the Dresden nuclear power plant in Morris.

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Before the disaster in Japan, Argonne collected air samples on a weekly basis to make sure the lab is in compliance with FDA regulations on radiation. After the nuclear emergency in Japan sent radiation wafting across the Pacific Ocean, environmental associate Jenny Gomez has been collecting them daily.

In the past few days small levels of radiation have been detected at Argonne.

“I was quite surprised that we saw something, because I’ve been here for almost five years now and there’s never anything here,” Gomez said.

But as CBS 2’s Roseanne Tellez reports, scientists at Argonne were not surprised.

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“I think last week what we see, a little spike, a very tiny one. But it’s a telltale sign that they’re coming from Japan, because in this region, the lab doesn’t release iodine 131 in particular,” Argonne environmental engineer S.Y. Chen said.

He said the radiation levels detected were much lower than a typical chest X-ray, at 0.1 milisieverts. To put that number in perspective, Japan’s radiation level hit 50 milisieverts before evacuations began.

Asked if people in the Chicago area could be in danger if there’s more radiation leakage in Japan,” Chen said. “At this time, we continue to monitor the (radiation levels). We’ll continue to monitor very carefully.”

This isn’t the first time the area has received radiation from overseas. Officials at Argonne said the same thing happened after the nuclear disaster at Chernobyl in 1986, but the trace amounts didn’t cause any harm.

Still officials at Argonne and government agencies that test air regularly have been stepping up testing until the emergency in Japan is over.

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Meanwhile, the State of Illinois is conducting a comprehensive review of all six nuclear power plants in the state, examining issues related to plant maintenance.