[Image above] Credit: Ricky Romero; Flickr CC BY-NC 2.0



Your morning commute might be killing you.

And it’s not the dangerously bad drivers swerving across lanes, the traffic-induced stress of the drive, or that unhealthy on-the-go breakfast sandwich you’re eating that I’m concerned about. It’s a more silent suspect that you probably don’t even think about most of the time—the air you breathe.

The air around major roadways is rife with particulate air pollution. Those fine particulates—originating mostly from the combustion reactions going on inside your fossil-fueled engine and spewing out your exhaust—are so tiny that they easily travel deep inside your lungs.

And once within your body, those fine particulates don’t just risk your health with respiratory problems—particulates trigger a lot of inflammation, which eventually leads to cardiovascular disease and other health concerns. In fact, according to an article from Tufts University, “even a minuscule increase in fine particulates (just 10 micrograms per cubic meter of air), could cause up to an 18% bump in cardiovascular disease.”

So while you probably don’t think about it during your daily commute, the quality of the air you breathe is an incredibly important consideration for your overall health.

 It’s precisely why researchers have devised improved materials to more efficiently filter our inside air, including synthetic and glass fiber cabin air filters that can reduce particulates by 93%.

But let’s be honest—I’m guessing that most people never change the cabin air filter in their car (despite the fact that it’s incredibly easy on most makes and models!), let alone upgrade to a more efficient filter.

However, new research from Washington University (St. Louis, Mo.) suggests there is a simple fix to help help keep the air you breathe inside your car a little cleaner—and it only requires the click of a switch.

The Washington University team’s comprehensive measurements of air pollution, collected over a span of four months, show that running the AC offers clear cleaner-air benefits over running only the fan or simply leaving the windows down during daily commutes.

By comparing particulate levels inside and outside of cars during their daily commutes and corresponding those measurements to dashcam-captured traffic variables and weather conditions, the scientists discovered that simply running the AC inside your car can help keep the air inside 20–34% cleaner.

“We found a significant difference between running the fan versus running the AC,” Nathan Reed, Washington University Ph.D. candidate and second author of the research, says in a Washington University news story. “The AC is pulling outside air, running through the same filter with the same ventilation path as the fan. But there’s one difference: when the AC is operating, you have a cold evaporator that is cooling the air as it passes. This cold surface attracts the pollutant particles, and they deposit there, as opposed to diffusing it into the air you’re breathing.”

It’s that simple, the scientists say—nanoparticulates stick to the AC’s cold evaporator instead of remaining suspended in the air, reducing the concentration of particles that make their way through the filter and into the cabin air.

The scientists found that the level of protection that the AC offered varied depending on the conditions outside, with enhanced reduction of particulate levels during times when concentrations were elevated, such as when driving behind a large truck.

The team’s results also show that, not surprisingly, keeping the windows up can additionally help buffer the cabin air quality from the outside world. According to the scientists, keeping the windows up can offer 8–44% boost in protection from particles once all factors are considered.

However, once particles have found their way inside the cabin, keeping the windows closed of course keeps the particulates trapped inside—so the scientists’ best advice is to adopt a dynamic air flow strategy depending on traffic, weather, and environmental factors to minimize particulate levels inside.

“The vehicle cabin can be viewed as a buffer, protecting us from the outside air,” Anna Leavey, a research scientist in Washington University’s School of Engineering and Applied Science and first author of the research, says in the news release. “While driving with your air conditioning on and windows closed is the most protective thing that you can do, running the AC can decrease your fuel economy. That’s why adopting a dynamic behavior modification approach is recommended, in which the AC or closed windows are used when following a highly polluting vehicle, or on the freeway which tends to be more highly polluted. Once you have left the polluted environment, we recommend opening your windows to remove any pollutant build-up from your car.”

Watch this short video to hear more from the researchers themselves.

Credit: Washington University in St. Louis; YouTube

The paper, published in Atmospheric Environment, is “Comparing on-road real-time simultaneous in-cabin and outdoor particulate and gaseous concentrations for a range of ventilation scenarios” (DOI: 10.1016/j.atmosenv.2017.07.016).