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Most homeowners don't worry about their houses' foundations unless their basements flood.

But Professor of Engineering Eric Suuberg and Kelly Pennell, assistant professor at the University of Massachusetts Dartmouth, are drilling holes in basement floors of homes in Somerville, Mass., to determine if residents have something else to be concerned about: subsurface vapors.

For the past five years, the researchers worked with graduate students to better understand vapor intrusion — the process by which harmful subsurface chemicals in the soil and groundwater diffuse into residential and commercial structures.

These contaminants migrate from the soil and groundwater through the concrete foundations and joints of buildings. While the chemicals are only found in low concentrations, their long-term carcinogenic effects worry researchers and policymakers alike.

Many states have begun to update their vapor intrusion guidelines and reevaluate brownfields — sites that were once used for commercial and industrial activities — that were previously thought to be clean and safe. "The vapor intrusion problem may affect about a quarter of the estimated inventory of 500,000 U.S. brownfield sites," Suuberg said in a Sept. 9 webinar.

"This isn't just a problem in Rhode Island, it's a national one and an international one," said Pennell, who recently left Brown to join UMass Dartmouth's faculty but continues to lead the research.

The problem is caused by the contamination of sites with volatile organic compounds. Two classes of these compounds account for most of the contamination — chlorinated hydrocarbons, which are contained in dry cleaning chemicals, and petroleum hydrocarbons, which are contained in gasoline, diesel and jet fuel.

But many variables affect the rate of vapor intrusion, including building foundations and the local geology, making it hard to predict which sites are at risk for contamination.

Further complicating the research, many of these chemicals are contained in household products, so some of their indoor air presence cannot be attributed to vapor intrusion, Pennell said.

About five years ago, the two professors began to use three-dimensional computer modeling to better account for these variables and site-specific conditions.

Recently, they have begun to conduct field studies of contaminated residential sites in Somerville, collecting soil vapor, indoor air and ground water samples.

Pennell said she and Suuberg are also focused on making their research practical, helping to direct site investigations and develop better regulatory guidelines.

The study is supported by Brown's Superfund Research Program, a group that studies the health and environmental effects of hazardous waste sites.




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