USC study shows large pollution exposure reductions possible with car ventilation setting choices
Based on a new study, environmental health researchers at the University of Southern California have advice for parents who want to reduce their child’s exposure to harmful traffic pollutants: The car ventilation choice you make can be effective in reducing exposure to on-road particle pollution. Scott Fruin, D.Env., assistant professor of preventive medicine, and Neelakshi Hudda, PhD, research associate in the environmental health department of the Keck School of Medicine of USC, recently conducted the first systematic measurements of invehicle exposure that included a full range of car types and operating conditions, and for all types of particulate pollution. “Short of driving less, putting your ventilation to ‘recirculate’ is the best way to reduce exposure to all types of vehicle-related particulate pollution,” said Fruin,
senior author on the study. “Otherwise, an hour-long commute to work or school can double your daily exposure to traffic-related particulate air pollutants.” The scientists found in addition to the benefits of recirculation settings, exposures are lower in newer cars, at slower speeds, and on arterial roads, where pollutant concentrations are lower than on freeways. According to the researchers, concentrations of particle pollutants on freeways are often five to 10 times higher than elsewhere. To put the results in perspective, measurements were turned into predictive models, then the models were applied to the national fleet of car models and ages and Los Angeles driving conditions. Drs. Fruin and Hudda found that for a typical car (seven years old, the national average), recirculation settings reduce in-vehicle particle pollution for very small particles from 80 percent (of on-road levels) to 20 percent, and from 70 percent to 30 percent for larger particles, compared to air ventilation settings which bring in outside air. (Windows were always closed in this study. Keeping windows open while driving quickly raises inside pollutant concentrations to the same levels as on-road levels.) “Until this comprehensive study, measurements have been based on only a few cars and usually only one pollutant,” Hudda said. “We showed that recirculation settings produce large exposure reductions across all car types and for all particulate pollutants.” The researchers also found that leaving the windows closed over 30-minute or longer drives with several passengers raised carbon dioxide levels in tight new cars to those of stuffy meeting rooms.