New research suggests the best way to minimize your pollution exposure on the commute to and from work is to crank the air conditioning in your vehicle.

Most Americans spend almost an hour traveling to and from work each day. And it is during the commute that people experience the majority of their daily exposure to contaminants.s

To determine how drivers and passengers might mitigate their exposure risks, scientists at Washington University in St. Louis tested what effects the car ventilation system has on passing pollutants.

Scientists tested different combinations and fan and air conditioning settings and monitored contaminant concentrations using portable sensors. A dashboard camera allowed scientists to determine how outside variables — a restaurant exhaust system or a passing diesel truck — impacted exposure.

“As aerosol scientists, we had access to state-of-the-art air monitoring equipment,” Nathan Reed, a doctoral candidate at WUSTL, said in a news release. “Once we began measuring inside and outside of the car, and started getting numbers back, we were able to confirm our hypothesis that by controlling our car’s ventilation we could mitigate some pollutant risk.”

Researchers found that using air conditioning reduced the amounts of the pollutants inside the vehicle by 20 to 34 percent. While the fan and AC both pull air from the outside, the air conditioning system sees air passed across a cold evaporator.

“This cold surface attracts the pollutant particles, and they deposit there, as opposed to diffusing it into the air you’re breathing,” Reed said.

Scientists found the AC was best at minimizing pollution exposure when following a heavy polluter like a bus or big rig.

Of course, using the AC also diminishes a car’s fuel economy, contributing to auto emissions. Scientists recommend deploying the AC only when presented with a high pollution exposure scenario. Once the truck or bus is gone, the driver should role down the windows to allow any buildup of pollutants to dissipate.

Scientists detailed their experiments in a paper published this week in the journal Atmospheric Environment.

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