On top of looming tougher pollution rules for vehicles, an environmental engineer at Washington Univesity in St. Louis now has devised a new measurement that could make both car owners and manufacturers nervous. It's called ppvm(pollutant per vehicle mile). It is a measurement of the total particulate matter emissions a vehicle makes per mile traveled.While ppvm won't appeal to the auto owner the way that mpg, rpm or mph do, it's likely to have future impact on air pollution measures and standards nationwide.