Diesel cars are cleaner than petrol reveals new research
A new international study has found that petrol cars emit up to 62 times more lung damaging pollution in cold weather than petrol counterparts.
The team analysed carbonaceous particle matter (PM), which is made of black carbon, primary organic aerosol and is thrown into the air by vehicle exhaust pipes.
PM is also known to contain harmful reactive oxygen species which can damage lung tissue when the tiny specs are breathed in.
However, modern diesel vehicles are fitted with exhaust filters capable of removing the pollutant before it enters the air.
Catalytic converters in petrol cars are less efficient at lower temperatures
Dr Patrick Hayes, of the University of Montreal, said: “Diesel has a bad reputation because you can see the pollution but it’s actually the invisible pollution that comes from petrol in cars that is worse.
“The next step should be to focus on petrol 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 petrol engines more.
“That is really the next target.”
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In recent years, diesel vehicles have been fitted with these particle filters in an attempt to dramatically reduce the amount of pollutants they emit.
It’s actually the invisible pollution that comes from petrol in cars that is worse
Dr Patrick Hayes, of the University of Montreal
Researchers found that petrol cars emit on average 10 times more carbonaceous PM at 22 degrees Celsius and 62 times more at -7 degrees Celsius compared to diesel cars.
According to the study, the reason for the increase in emissions at lower temperatures is due to a “cold start effect” which is where a petrol car is less efficient because it has yet to warm up and its catalytic converter is not yet on.
Dr Hayes believed the since diesel cars are more cleaner than before, environmental regulators need to shift their focus to dirtier petrol cars and other sources of air pollution in the UK.
Diesel particle filters (DPFs) have been fitted to newer diesel cars in Europe and North America, which significantly reduce the emissions they emit.
Dr Hayes said: “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.”
Older diesel cars do pollute more than petrol vehicles due to the fact that they don’t have DPFs, and diesel cars in general emit far more nitrogen oxides, which cause smog and acid rain.
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For their investigation, the researchers utilised field work on air pollution that Dr Hayes carried out in California in 2010 and published in 2013 when he was a researcher at the University of Colorado.
Over four weeks in a parking lot of the California Institute of Technology, in Pasadena, Dr Hayes analysed air coming from nearby traffic-heavy Los Angeles, drawn through a tube in the roof of a modified construction trailer.
Now he’s doing something similar up in Canada’s Far North, “the final resting place of atmospheric pollution,” said Dr Hayes, a New Yorker from Albany who has lived in Montreal since 2013.
He is interested in whether the carbonaceous PM up North exacerbates climate change.