Modern diesel cars emit less pollution generally than cars that run on gasoline, says a new six-nation study published today in Scientific Reports whose groundwork was laid in part by an American chemist now working at Université de Montréal.
And since diesel is so much cleaner than before, environmental regulators should increasingly shift their focus to dirtier gasoline-powered cars and other sources of air pollution, says the UdeM scientist, Patrick Hayes.
“Diesel has a bad reputation because you can see the pollution, but it’s actually the invisible pollution that comes from gasoline in cars that’s worse,” said Hayes, 36, an assistant professor at UdeM.
“The next step should be to focus on gasoline or removing old diesel vehicles from the road. Modern diesel vehicles have adopted new standards and are now very clean, so attention needs to now turn to regulating on-road and off-road gasoline engines more. That’s really the next target.”
The study, led by researchers in Switzerland and Norway with help from Hayes and colleagues in Italy, France and the U.S., looked at carbonaceous particulate matter (PM) emitted from the tailpipes of cars.
Carbonaceous PM is made up of black carbon, primary organic aerosol (POA) and, especially, secondary organic aerosol (SOA), which is known to contain harmful reactive oxygen species and can damage lung tissue.
In recent years, newer diesel cars in Europe and North America have been required to be equipped with diesel particle filters (DPFs), which significantly cut down on the pollution they emit.
In the lab (at the Paul Scherrer Institute, near Zurich in Switzerland), “gasoline cars emitted on average 10 times more carbonaceous PM at 22°C and 62 times more at -7°C compared to diesel cars,” the researchers noted in their study.
“The increase in emissions at lower temperatures is related to a more pronounced cold-start effect,” when a gasoline engine is less efficient because it’s not yet warned up and its…