Rush-Hour Pollution Is a Bigger Problem Than We Thought

Air pollution inside your car during rush hour may be twice as high as previously thought. B137/Wikimedia Commons

It’s a familiar workday ritual. You hop into your car and brave rush-hour-clogged highways for work, then turn around and do it all over again to go home. You already know exhaust fumes aren’t good for you. But new research suggests commuters may be exposed to even more pollution than scientists imagined.

A recent study of rush-hour drivers in Atlanta discovered that the amount of certain health-harming particulate matter inside their cars was twice as high as previously thought.

“We found that people are likely getting a double whammy of exposure in terms of health during rush-hour commutes,” says study author Michael Bergin in a news article from Duke University, where he is a professor of civil and environmental engineering. “If these chemicals are as bad for people as many researchers believe, then commuters should seriously be rethinking their driving habits.”

Killer commuting

Most rush-hour research up to this point has measured traffic pollution using outdoor roadside sensors. But this can miss variations in exhaust emissions related to changes in traffic congestion and other environmental conditions, such as sunlight that heats roads and causes pollution to rise higher in the air. Also, because the composition of exhaust can change rapidly once emitted from cars, drivers may be breathing in something considerably different than what’s detected by outside air monitors.

The new study — conducted by eight researchers from Duke University, Emory University and the Georgia Institute of Technology and published in the journal Atmospheric Environment — was an attempt to get a better picture of what commuters actually inhale while driving.

daily commuting wreaks health havoc
Daily commuting is not only stressful, but it also exposes you to high levels of particulate matter that wreak havoc on your health. Open Grid Scheduler/Grid Engine/flickr

Roby Greenwald, an Emory University research assistant professor at the time, created a sampling device that mimics human lungs by drawing in air at a similar rate. The device was strapped into the passenger seats of more than 30 cars and measured pollution levels as each vehicle completed 60-plus rush-hour commutes to and from downtown Atlanta.

Routes and driving conditions varied by vehicle: Some participants inched along clogged freeways and others stuck to city streets or back roadways. Whatever the driving conditions, researchers found that the amount of fine particulate matter, called PM 2.5, was often two times higher inside commuters’ cars than previously found along roadways.

Particulate problems

PM 2.5 is composed of super-fine particles produced by combustion and is a key component of the hazy smog that hangs over many cities. Individually, these tiny specks of organic compounds, metals and other chemicals are visible only through an electron microscope. But small doesn’t necessarily mean inconsequential. These mini particles are able to easily infiltrate the lungs and bloodstream where they can pack a deadly health punch in the form of oxidative stress.

Breathing in PM 2.5 prompts the creation of unstable molecules called free radicals, which oxidize cells, similar to an apple turning brown when exposed to air. While free radicals also are created during normal metabolism, exposure to particulate matter causes the body to produce significantly more.

smog contains PM 2.5
The smog that hangs over many cities during peak-traffic times is composed primarily of ozone and particulate matter, including deadly PM 2.5. biofriendly/flickr

Numerous studies have shown that oxidative stress caused by free-radical overload is one culprit behind a plethora of diseases, including cancer, heart failure, depression, chronic fatigue syndrome and Alzheimer’s disease.

“There’s still a lot of debate about what types of pollution are cause for the biggest concern and what makes them so dangerous,” Bergin says. “But the bottom line is that driving during rush hour is even worse than we thought.”

Incidentally, oxidative stress is just one health impact of commuting.

Gridlock game plan

Unless you work at home, live close enough to walk or bike to your job, or have public transportation nearby, your rush-hour regimen isn’t going away anytime soon.

“My two cents is that this is really an urban planning failure,” says Greenwald, who is now an assistant professor of environmental health at Georgia State University. “In the case of Atlanta, the poor air quality on the highways is due to the fact that 6 million people live in the metro area, and most of them have little choice but to get into an automobile to go to work or school or the store or wherever. Auto-centric transportation plans do not scale well to cities of this size, and this is one more example of how traffic negatively affects your health.”

If you live in a crowded urban area or can’t avoid daily congestion, there are a few ways to minimize your in-car fume exposure, according to new research. Tips include closing car windows and turning on the A/C.