Diesel is now cleaner than gas, says study

Diesel-powered vehicles emit less pollution than vehicles that run on gasoline, according to a new six-nation study published today in Scientific Reports.
By Joyce Clark | Jul 18, 2017
Diesel-powered vehicles emit less pollution than vehicles that run on gasoline, according to a new six-nation study published today in Scientific Reports. Contributing researcher Patrick Hayes, a University of Montreal scientist, suggested that environmental regulators shift their focus to gasoline-powered vehicles and other pollutant sources.
"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. "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."
Hayes worked with researchers in Switzerland, Norway, Italy, France, and the United States. They reviewed data on carbonaceous particulate matter (PM)what non-scientists know as sootcoming from the tailpipes of cars. PM is hazardous to humans and can damage lung tissue.
All gas-burning cars, diesel or non-diesel, emit some PM. But newer diesel cars are equipped with diesel particle filters that remove much of it before it has a chance to disperse into the air. Gasoline-powered cars do not filter their exhaust nearly as thoroughly, on average.
The difference showed in Hayes et al.'s study results. They found that gasoline-powered cars emitted 10 times as much PM when the outside temperature is 72 degrees Fahrenheit and 62 times as much when the temperature drops to 20 degrees.
Temperature makes a difference because of the "cold-start effect," the researchers explained, referring to when a gasoline engine starts off running less efficiently in the cold because it is not fully warmed up and the catalytic converter is not yet running.
Hayes is now conducting similar studies of PM in Canada's far north and its impacts on climate change.

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