State environmental officials are testing air quality at a cluster of homes near an abandoned Copiague industrial site where chemical pollution first found more than eight years ago has moved south through groundwater.

The contaminant plume beneath 13 neighborhood houses contains trichloroethane, or TCA, an industrial solvent and common ingredient in spot removers and paints. Such chemicals evaporate easily and can move up through the soil as vapor, sometimes seeping into buildings. High concentrations in indoor air or prolonged exposure may affect people's health.

It's an issue at dozens of Long Island buildings near hazardous-waste sites ranging from tiny dry cleaners to the former Grumman defense plant in Bethpage. The problem, often identified years after the original pollution is found, typically is addressed with special ventilation systems.

Whether the Copiague plume poses health risks to residents is not clear. The owners of five affected homes have responded to requests for access by the state Department of Environmental Conservation, and results from those tests are pending.

State Health Department spokesman Jeffrey Hammond said the testing is "a precaution." The pollution does not threaten a nearby drinking water well to the northwest, officials said, and the neighborhood is on public water that is regularly tested for contaminants.

Still, news of the pollution has some residents on edge.

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"I'd like the contaminated property to be dug up and taken care of," said Jim Brady, who lives three blocks from the derelict warehouse. "I want it cleaned up from the core, and I want it cleaned up from under everyone's house."

The process is not always that simple - or fast.

"There's dozens of these happening in any given year," said John Swarthout, section chief for the DEC's division of environmental remediation. "Sometimes, later that year, somebody looks at it, sometimes it takes five years. It all depends on how serious it seems to be."

DEC officials said the pollution at the Copiague site is not as widespread or concentrated as solvent plumes associated with larger hazardous-waste sites.

"It's in one small neighborhood, where with Grumman it's a very large regional plume affecting several miles," Swarthout said.

Originally used for manufacturing, the building, at 1305 S. Strong Ave., later housed a wallpaper company and a car- and boat-repair business. It has been empty since 2003, the DEC said.

Suffolk health officials launched an investigation in 2001 after finding two drums of unknown substances, along with two fuel tanks and more than 50 5-gallon pails of inks and paints. The investigation was referred to DEC in 2004.

Two years later, the state turned the on-site portion of the investigation over to a realty company that bought the South Strong Avenue parcel. The owner applied to clean it up through the state brownfields program, which offers tax incentives for renovating contaminated sites.

But delays and missed deadlines led the state to suspend its agreement with Crescent Realty Group in August, "after little work was done," said DEC spokesman Bill Fonda. Newsday's efforts to reach the group's chairman, Dominick Mavellia, were unsuccessful.

Some residents say it's taken too long to clean up a problem officials have known about for nearly a decade.

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DEC officials said some delays stemmed from the owner's decision to clean up the property, which suspended the state investigation. Now, agency staff are putting together a plan to complete the on-site probe.

Last summer the state also began work to determine how far the pollution had traveled. Monitoring well samples indicate a plume of TCA some 400 feet wide has moved more than 700 feet south of the property.

The highest concentrations - 83.6 parts per billion and 172 parts per billion - were detected between 6 to 21 feet deep. The state drinking water standard is 5 parts per billion.

Officials said it's unlikely residents have ingested the chemicals because the neighborhood is on public water. Once results of the indoor vapor tests are available, state officials will decide whether to contact the three homeowners who declined to allow the testing, as well as the five who did not respond to letters and phone calls.

"My personal conclusion is that we're not going to find very much," said Jim Harrington, director of the DEC's regional remediation bureau.

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Some residents remain concerned. Philip Sosnicki of Brookside Court wonders if the pollution has anything to do with the pancreatic cancer that killed his wife three years ago, or the lung cancer afflicting his father, who lives next door.

Such questions are tough to answer. Studies are inconclusive on whether TCA exposure increases risk for cancer, although lengthy exposure to high levels may increase the risk of harm to the heart, liver and nervous system. What's more, household products in homes are more often the source of such chemicals in indoor air than contaminated vapor, according to the state Health Department.

"If it's gotten into the homes, what happens to the homes?" said Sosnicki, 55. "Who's going to make up the difference in the property value?"