Michigan detects radioactive iodine in air

A Dept. of Environmental Quality sampling device in Lansing has detected a small amount of radioactive iodine-131 in the air, a likely result of the Fukushima nuclear emergency in Japan.

State environmental officials say that iodine-131 is a signature radioactive isotope for Japan‘s nuclear power plant emergency and that the level detected is low — about a quarter of the level measured here during the peak of the Chernobyl nuclear accident.

The DEQ maintains a continuously running air sampler in Lansing that processes 50 liters of air per minute for a total of 504,000 liters last week. The average human uses 7 liters of air per minute.

On Monday an analysis of last weeks sample showed a total activity of 23 picocuries or 0.85 becquerels of iodine-131.

“These are scant detection levels, even when compared to the radiation levels people are exposed-to every day,” DEQ said in a release. “For example, a typical banana contains 15 becquerels of potassium 40, a common radioactive isotope.”

Iodine-131 has a half life of 8 days and concentrates in the thyroid glands of exposed people. Cesium-137, another isotope associated with the Fukushima disaster, has a half life of 30 years and concentrates in bone.

Air samples taken in California have shown traces of cesium-137 from Japan.

Ken Yale of the DEQ’s Radiological Protection Division said that the Michigan air sample shows no cesium-137 in excess of typical background levels.

The state does not have measurements of radioactive isotopes in precipitation.

Snow is difficult to measure, Yale said, and it hasn’t rained since Tuesday when the department installed a system to monitor rain.

In Massachusetts and Pennsylvania state and Virginia officials have measured iodine-131 in rainwater at levels that exceed those established for drinking water. The U.S. Environmental Protection Agency said these levels found don’t pose a health threat with short term exposure.

In Washington state iodine-131 was found in milk this week.

Michigan monitors milk for radioactive isotopes on a weekly basis, Yale said, and results from last week should be available soon.

Radioactive pollution is expected to continue to spread throughout the northern hemisphere as the nuclear disaster continues in Japan.