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 by researchers at the University of Southern California (USC). On freeways, diesel-fuelled 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. High air exchange rates that occur when a vehicle is moving make roadways a major source of exposure. Particulate matter has been linked to cardiovascular disease, but the ultrafine fraction on roadways appears to be more toxic than larger sizes.
Researchers measured exposure by outfitting an electric vehicle with nine, fast-response air pollution instruments. A video recorded surrounding traffic and driving conditions on freeways and arterial roads throughout the Los Angeles region. Measurements were collected during a three-month period. Results showed that the two main sources of pollution were diesel-fuelled trucks on freeways and hard accelerations on surface streets. Surprisingly, overall congestion was only a factor on arterial roads and, even then, the highest concentrations of pollutants occurred only when vehicles were accelerating from a stop, Fruin says.
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.
MEDICA.de; Source: University of Southern California Health Sciences