[EPA w]orkers are testing the air inside 40 homes and businesses in St. Louis Park after chemical vapors were discovered in the soil under their basements, the U.S. Environmental Protection Agency said Wednesday.

Those properties were among more than 200 homes and businesses that were checked for potential risk from underground solvent contamination.

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Each of the 40 properties will be visited by a mobile lab, [EPA's "on-scene coordinator, Sonia] Vega said. Technicians are going room to room in the homes, using special hoses to pump air into the lab to see whether the vapors are present in high concentrations. They will also leave 24-hour sampling canisters in each building to test the air in the basement and first-floor levels.

The main chemicals of concern, trichloroethylene and perchloroethylene, have been used for decades as industrial degreasers, metal cleaners and dry-cleaning fluids. Long-term exposure to them at certain levels has been linked to cancer, liver problems and other adverse health effects, according to state health officials.

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The properties being tested are on both sides of Hwy. 7 near Wooddale Avenue. By last week, workers had pulled air samples from beneath the basement floors of 184 residences and 29 commercial or industrial buildings.

Vega said the vapors measured beneath the 32 homes and eight commercial buildings ranged from slightly above health guidelines to more than twice what is considered safe. The buildings with the higher vapor concentrations in their soils were clustered, Vega said, but she could not provide more details until the test results are completed and mapped.

• Jan. 28: Solvent fume testing begins in St. Louis Park
• Dec. 14: Testing for vapors has St. Louis Park on edge