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Hugh Pickens writes:

Sara Novak reports that according to a recent study, “badly tuned” cars and trucks make up one quarter of the vehicles on the road, but cause 95 percent of black carbon, also known as soot, 93 percent of carbon monoxide, and 76 percent of volatile organic chemicals like benzene, toluene, ethylbenzene, and xylenes. “The most surprising thing we found was how broad the range of emissions was,” says Greg Evans. “As we looked at the exhaust coming out of individual vehicles, we saw so many variations. How you drive, hard acceleration, age of the vehicle, how the car is maintained – these are things we can influence that can all have an effect on pollution.”

Researchers at the University of Toronto looked at 100,000 cars as they drove past air sampling probes on one of Toronto’s major roads. An automated identification and integration method was applied to high time resolution air pollutant measurements of in-use vehicle emissions performed under real-world conditions at a near-road monitoring station in Toronto, Canada during four seasons, through month-long campaigns in 2013–2014. Based on carbon dioxide measurements, over 100 000 vehicle-related plumes were automatically identified and fuel-based emission factors for nitrogen oxides; carbon monoxide; particle number, black carbon; benzene, toluene, ethylbenzene, and xylenes (BTEX); and methanol were determined for each plume.

Evans and his team found that policy changes need to better target cars that are causing the majority of the air pollution. “The ultrafine particles are particularly troubling,” says Evans. “Because they are over 1,000 times smaller than the width of a human hair, they have a greater ability to penetrate deeper within the lung and travel in the body.”