A recent study conducted along a stretch of interstate highway in St. Louis showed that city vehicles, ranging from motorcycles to diesel trucks, emit 30 to 40 milligrams of particulate for every mile traveled. A similar survey indicated that vehicles traveling on a nearby highway in rural Illinois emit 200 to 300 milligrams of particulate per mile traveled. Traffic on the rural highway averaged about 1,300 vehicles per hour. Traffic on the freeway averaged anywhere from 7,500 to 10,000 vehicles per hour. So much for fresh country air.
Road dust is more than the dirt a vehicle stirs up as it travels along a roadway.
Road dust contains matter from soil and fine particles from tailpipe emissions. It is a major contributor to vehicular air pollution. Scientists have linked upper respiratory illnesses, cardiovascular diseases such as arrhythmia, and cancer to road dust. PPVM is a measurement of the total particulate emissions that a vehicle creates for every mile traveled. When you then consider that you can multiply this daily value by the many thousands of miles vehicles travel on the roads each day, you get a clearer view of what role the automobile potentially plays in air pollution.