DaytonDailyNews.com

TROY — The federal Environmental Protection Agency found 16 homes and one school, St. Patrick School, where levels of volatile gases were above state health standards.

"I don't think the levels we are seeing pose a health threat over the short term," Robert Frey, chief of the health assessment unit of the state Department of Health, said Wednesday.

Long-term direct, physical contact with tetrachloroethylene (PCE) — sometimes referred to as "perc" — is thought to cause cancer. PCE is used in dry cleaning and metal degreasing.

Frey said the state standards are based on research into dry-cleaning employees with long-term exposure to higher concentrations of PCE. There is no research on chronic low-concentration exposure, so "in the absence of hard data, we use these very conservative calculations, assuming exposure 24 hours a day, 365 days a year for 30 years," he said.

Calls to a St. Patrick Parish spokesman were not immediately returned.

Steve Renninger, the EPA's on-scene coordinator, said the agency would begin solving the immediate problem by this summer.

"It's very similar to radon mitigation," he said. The gases would be sucked out of the basements by a small fan and pipe to the outside.

The EPA, following Ohio EPA and city tests that found groundwater PCE contamination from two or more sources, sent out 400 letters to homeowners asking if they wanted their basements tested. Eighty-five requested tests.

The PCE becomes a vapor when exposed to water. The vapor works its way through the soil into homes through cracks in the foundation or slab.

Renninger said the EPA is still trying to determine the source of two plumes under a 40-block industrial and residential area east of the downtown Public Square.

Patrick Titterington, Troy public service and safety director, said the city would continue to cooperate with state and federal officials.