A potentially toxic substance linked to paint pigment and recently found in Chicago air poses new challenges for environmental regulators.

University of Iowa researchers recently reported finding high concentrations of PCB 11 in air samples taken throughout Chicago between November 2006 and November 2007.

They reported their findings in the September 24 online issue of the journal Environmental Science and Technology.

Although other PCBs have been found in Chicago air, this is the first time PCB 11 has been detected in the air, says Keri Hornbuckle, who led the study.

“This compound is ubiquitous in air throughout the city of Chicago,” says Hornbuckle, professor of civil and environmental engineering at the University of Iowa and a researcher at IIHR-Hydroscience and Engineering.

The study was funded by the National Institute for Environmental Health Sciences.

The health effects of PCB 11 are not known, and research on the issue is just beginning, says Hornbuckle.

Most PCBs, or polychlorinated byphenols, were produced in large quantities between the 1930s and the 1970s. Due to their cooling and insulating properties, they were widely used in industrial and commercial products. 

Production of PCBs was banned in 1979. The U.S. Environmental Protection Agency considers them probable human carcinogens, and studies have linked them to adverse effects on the immune, reproductive, endocrine and nervous systems.

Researchers theorize PCB 11 is a byproduct of consumer paint production.

Pinpointing the source will be a priority, Hornbuckle says.

“The remediation problem is very important and yet difficult,” she says. “You want to be as precise as possible about tracking the source, but it’s hard because they’re widely dispersed.”

PCBs break down very slowly in the environment, and are still common in industrial cities like Chicago, but concentrations of PCBs declined sharply after production was banned.

However, this downward historical trend may not hold true for PCB 11, according to Hornbuckle.

The study also raises questions about human exposure.

Because PCB 11s are lighter  than other PCBs, exposure from airborne particles could prove to be more of a risk.

“It’s also possible that consumption of paint chips could be a direct exposure route for children,” says Hornbuckle.

Hornbuckle and her colleagues concluded that it’s difficult to link regions of high concentration with specific facilities, complicating prospects for regulation of emissions.

The more than 50 Chicago facilities that the study identified as paint and pigment producers are spread across the city.

“The concentrations we found could be from historical use of this chemical in paint or somewhere else,” says Hornbuckle. “It could be that it’s slowly getting released little bit by little bit.”

For the study, researchers took air samples from devices attached to two medical clinic vans provided by the Mobile C.A.R.E. Foundation of Chicago (Comprehensive Care for Chicagoland’s Children with Asthma.) The vans visited 45 sites throughout the city.

Todd Nettesheim, an environmental engineer with the EPA’s Great Lakes National Program Office, cautions that PCB 11s may have very different properties than the PCBs that the agency has been attempting to clean up for decades in the Great Lakes.

Due to their lower molecular weight, PCB 11s may not accumulate as much as other PCBs, which concentrate in fatty tissue of fish and have resulted in consumption advisories for the Great Lakes, says Nettesheim.

And they may not be as toxic.

“The case for PCB 11s may be very different from the case for PCBs,” says Nettesheim. “We can’t make correlations at this point.”