UH Researchers Test for Airborne Metals at Elementary School

"How Much of the Pollution We Measure Can Be Attributed to Motor Vehicles?"

To better measure the airborne metals that spew from vehicle tailpipes, a University of Houston research team has installed air samplers at an elementary school near the intersection of Interstate 10 and Federal Road.

The sampling site is in a field behind the Houston Independent School District’s R.P. Harris Elementary School, on a site operated by the Texas Commission on Environmental Quality, making air quality there especially relevant to children’s health, said Shankar Chellam, professor of civil and environmental engineering at the Cullen College of Engineering.

Chellam will use the information to determine how much cars and trucks contribute to the region’s air pollution.

Houston traditionally has vied with Los Angeles for the top spot as the nation’s smoggiest city; it ranked No. 7 in 2013, according to a list compiled by the American Lung Association. The top six were in California.

While much of Houston’s air pollution is linked to petrochemical plants along the Houston Ship Channel, the chemicals and tiny particles produced by its commuting culture add to the city’s dirty air. Researchers increasingly have linked respiratory and cardiovascular diseases, allergies and even cancer to living next to heavily traveled roads.

Chellam said that makes the findings from the air samplers installed just south of Interstate 10 particularly relevant. In addition to the airborne metals, the air samplers will measure particulate emissions including re-suspended road dust and brake and tire wear.

Chellam first isolated certain metals – rhodium, palladium and platinum – from gasoline-powered vehicles during a two-month test in the Washburn Tunnel in late 2012. Because the tunnel, which runs under the Ship Channel between Galena Park and Pasadena, has been closed to heavy-duty trucks since April 2008, the test allowed him to calculate emissions solely from light-duty vehicles, he said.

Earlier research into metals content from airborne emissions has focused mainly on non-platinum elements, complicating the analysis because the elements could also be emitted by other sources. But rhodium, palladium and platinum are emitted by the three-way catalytic converters commonly used in gasoline-powered automobile emission control systems.

The Washburn Tunnel research was published in Environmental Science & Technology in December 2013. The new research will build on those findings, but Chellam said they will be more relevant to human health because they are capturing particulate air pollution at a school serving a heavily populated neighborhood.

“That is the air that is more important for human health,” he said. “The tunnel is more like a lab. It’s good to do scientific experiments, but we also want to see meaningful results.”

The samplers, located on a small strip of land within the school property and just off Interstate 10, are encased in white metal boxes, topped by intake valves. Ayse Bozlaker, a post-doctoral researcher who works with Chellam, said the air samplers are employed to collect both fine and coarse particles in the air, including those that are less than 2.5 microns across – a human hair is about 7 microns – and those that are less than 10 microns.   

Smaller particles are considered more harmful to human health, because they can be inhaled more deeply into the lungs.

Undergraduate Chris Wiggs also is working with Chellam and Bozlaker on the project.

“The main question,” Chellam said, “is how much of the pollution we measure can be directly attributed to motor vehicles? In the tunnel, it was almost 100 percent. Here, it won’t be.”

Bozlaker said the data gathered in the Washburn Tunnel will allow researchers to isolate trace elements from soil and elsewhere, ensuring they measure only the airborne metals from vehicle traffic.