An international study that was published on Monday, July 17 in the journal Scientific Reports showed that modern diesel cars release fewer carbonaceous particulate matter (PM) into the air than vehicles which use gasoline engines. The study, which was conducted by researchers in Norway and Switzerland with the help from colleagues in France, Italy, and the United States, compared the carbonaceous PM emitted by vehicles that are powered by diesel engine with the carbonaceous PM released by gasoline-powered cars.
Carbonaceous PM comprises primary organic aerosol (POA), secondary organic aerosol (SOA), and black carbon, all of which can cause lung cancer.
Recently, newly-manufactured diesel vehicles in Europe and North America were mandated to have diesel particle filters (DPFs) installed in them.
According to the study that was conducted in the laboratory at the Paul Scherrer Institute near Zurich in Switzerland, “Gasoline cars emitted 10 times more carbonaceous PM at 22 degrees Celsius and 62 times more at -7 degrees Celsius compared to diesel cars. The increase in emissions at lower temperatures is related to a more pronounced cold-start effect.”
This refers to when a gasoline engine is not yet warmed up and its catalytic converter is not yet on.
“These results challenge the existing paradigm that diesel cars are associated, in general, with far higher PM emission rates, reflecting the effectiveness of engine add-ons like DPFs to stem pollution,” the study added.
Patrick Hayes, a chemist at the University of Montreal who worked on the study, said government regulators should look at shifting the blame on gasoline-powered vehicles as the source of pollution rather than cars that are powered by diesel engines.
“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 added.
The new study based its observations and conclusions on the results of the field work that Hayes did over four weeks in a parking lot of the California Institute of Technology in Pasadena in 2010. Hayes analyzed air pollution that came from vehicles that trudged along traffic-heavy Los Angeles streets.
At present, Hayes is conducting a similar investigation in Canada’s Far North, which is “the final resting place of atmospheric pollution”. (Related: BHF researchers to unravel effects of traffic pollution on heart health.)
Diesel vehicle patrons on the rise
Diesel engines are experiencing a rise in numbers, especially in cars, sport utility vehicles, hybrids, and trucks in every state except California, the District of Columbia, and Massachusetts, data from the non-profit organization Diesel Technology Forum showed.
According to U.S. News & World Report, diesels enjoy a lead over gas engines in torque, are longer-lasting, and require fewer repairs. And when it comes to fuel prices, even though diesel fuel prices are high compared with the price of regular gas, they are nevertheless lower as compared with premium gas, the Energy Information Administration said.
Texas, California, and Florida have the highest total numbers of diesel vehicles in the United States. The fastest-growth states for diesel vehicles were in New England: Vermont, with an increase of 35.6 percent in 2016 as compared with the previous year, followed by Maine, and then New Hampshire. North Carolina has the largest year-over-year growth for all diesel vehicles, up nine percent, followed by Georgia, and then Utah.
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