The daily commute may be taking more of a toll than people realize. A new study by researchers at the University of Southern California (USC) and the California Air Resources Board found that up to half of Los Angeles residents’ total exposure to harmful air pollutants occurs while people are traveling in their vehicles.
Although the average Los Angeles driver spends about six percent (1.5 hours) of his or her day on the road, that period of time accounts for 33 to 45 percent of total exposure to diesel and ultrafine particles (UFP), according to the study published this month in the journal Atmospheric Environment and available online. On freeways, diesel-fueled trucks are the source of the highest concentrations of harmful pollutants.
“If you have otherwise healthy habits and don’t smoke, driving to work is probably the most unhealthy part of your day,” says Scott Fruin, D.Env., assistant professor of environmental health at the Keck School of Medicine of USC. “Urban dwellers with long commutes are probably getting most of their UFP exposure while driving.”
High air exchange rates that occur when a vehicle is moving make roadways a major source of exposure. Ultrafine particles are of particular concern because, unlike larger particles, they can penetrate cell walls and disperse throughout the body, Fruin says. Particulate matter has been linked to cardiovascular disease, but the ultrafine fraction on roadways appears to be more toxic than larger sizes.
Driving with the windows closed and recirculating air settings can modestly reduce the particle pollution exposures but does not reduce most gaseous pollutants. Driving at speeds lower than 20 miles-per-hour can also reduce exposure, but none of these measures are as effective as simply cutting back on driving time, he says.
“Shortening your commute and spending less time in the car will significantly reduce your total body burden of harmful pollutants,” Fruin says.
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