Expanding the search for potentially hazardous vapors in homes and businesses in St. Louis Park, the Environmental Protection Agency said Wednesday that it will add about 50 properties to its study area on both sides of Hwy. 7 near Wooddale Avenue.

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The main chemicals of concern, trichloroethylene and perchloroethylene, have been used for decades as industrial degreasers, metal cleaners and dry-cleaning fluids and seeped into the groundwater under St. Louis Park. Long-term exposure to them at certain levels has been linked to cancer, liver disease and other problems, according to state health officials.

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EPA officials will go door-to-door this Saturday to explain the situation to those living in the expanded study area, and to seek their permission to take air samples. The testing involves drilling a small hole in the basement and inserting a 2-foot probe about the width of a pencil.

The initial study area contained about 270 homes and businesses, and the EPA received permission from owners to test vapors beneath 214 of the buildings. Of that number, 32 homes and eight commercial buildings were found to have enough contamination to justify more testing to check air in different rooms and for longer periods of time.