Anyone walking along Capital Boulevard or Six Forks Road during morning rush hour is likely to get a lungful of engine exhaust, but they won’t be as bad off as the people in the passing cars.
That’s one of the takeaways from a study of the exposure of drivers to pollution done by scientists at Duke University, Emory University and the Georgia Institute of Technology. In their study published this summer, the researchers say they found that the levels of soot and chemicals detected inside cars during rush hour in Atlanta were twice as high as those measured by roadside detectors.
“The near-road sensors are literally along the side of the road, so they are very close (like, one lane over from the slow lane),” said Heidi Vreeland, a doctoral student at Duke and the lead author of the study. “They show significantly lower concentrations, highlighting a dramatic decrease in pollution just a ‘lane’ away.”
The study, in the journal Atmospheric Environment, is the latest by scientists seeking to gauge the effect of air pollution on people inside cars, trucks and buses. In one of the earliest studies, researchers in California in 1997 found that the exposure to some air and toxic compounds was as much as 10 times higher inside vehicles than in the ambient air at nearby monitoring stations.
Since then, other scientists have refined the research, asking, for example, whether the pollution in your car is higher at red lights or in traffic jams than when the car is moving (it is, up to 40 percent higher, according to a study at the University of Surrey in England last year). Scientists in New York have now equipped cyclists with sensors that measure pollution levels and their breathing to determine their exposure in city traffic.
Researchers at N.C. State University have published studies in recent years that found that pedestrians and passengers on buses had higher exposure to particulate matter – tiny bits of soot – that spiked when trucks passed, but that people in cars were exposed to more carbon monoxide, a common ingredient of engine exhaust. Chris Frey, a professor of environmental engineering and one of the authors of the studies, says they found that those riding in cars can have lower exposures to pollution than pedestrians if their windows and vents are closed and air is recirculated.
In the study led by Vreeland, researchers sampled inside cars using devices that draw in air at a similar rate to human lungs. The devices were strapped into the passenger seat of more than 30 cars during morning rush hour in downtown Atlanta, and the contents of the filters were compared with those at roadside monitors.
The researchers found that devices in the cars detected up to twice as much particulate matter as well as chemicals that cause what’s known as “oxidative stress,” a condition thought to be involved in the development of numerous diseases and health problems, including asthma, heart disease, cancer and Parkinson’s disease.
Drivers and their passengers get a more powerful dose of these pollutants, either through vents or open windows, because they’re closer to the source, says Michael Bergin, a professor of civil and environmental engineering at Duke and a co-author of the study.
“Generally it is because the tailpipe emissions dilute very fast,” Bergin wrote in an email. “Even in going a few meters from right on the road to the side of the road the dilution results in substantially lower concentrations.”
The pollution that gets in to cars is worse in the morning, before the warmth of the sun begins to stir up the air. Before then, traffic pollution tends to sit along the ground and is especially thick, Vreeland said.
The most obvious way to reduce your exposure to pollution in the car is to drive less. Beyond that, here are some other strategies:
1. Avoid driving during heavy traffic hours. The fewer vehicles on the road, the fewer sources of polluted air to breathe.
2. Keep your vehicle’s cabin air filter clean. Find out where it is and check it once a year, if you can get to it. The location varies from vehicle to vehicle, but checking and changing the filter is often a do-it-yourself job.
3. If traffic is light, drive with the vents open and/or your windows down, to let in fresh air. If you’re in traffic, roll up the windows and close your vents, to recirculate that clean air and keep the dirty air out.