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expert reaction to study looking at particulate matter emissions from petrol cars versus from diesel cars

New research published in Scientific Reports investigates whether gasoline cars produce more carbonaceous particulate matter than modern filter-equipped diesel cars.

 

Prof. Roy Harrison FRS, Professor of Environmental Health, University of Birmingham, said:

“This paper provides valuable insights into the relative contributions of petrol and diesel vehicles to airborne particles, and especially those particles formed in the atmosphere from the oxidation of organic vapours.  The authors tested a representative selection of light duty petrol and diesel cars, the only weakness being the use of the discredited New European Driving Cycle in the laboratory, rather than measuring actual on-the-road emissions.

“The study shows that new diesels fitted with particle filters make a smaller overall contribution to airborne particles than petrol vehicles, but that currently in Europe the emissions from older diesels are still the dominant contributor.  As the authors acknowledge, their work throws no new light on the emissions of oxides of nitrogen, for which the diesel is by far the major contributor.  Our recent studies in London and Paris demonstrate that the nitrogen dioxide, deriving predominantly from diesels now has a far greater impact on premature mortality than particle emissions from road traffic.  This further emphasises the need for motor manufacturers to focus their efforts on reducing oxides of nitrogen emissions from diesels.”

 

Dr Karl Ropkins, Senior Research Fellow, Institute for Transport Studies, University of Leeds, said:

“In my opinion this is a good paper – a good piece of work, good science and a noteworthy contribution.

“There has been some talk about petrol versus diesel PM emissions, but this work, more than most, highlights the importance of following the numbers rather than sounds bites.  A good diesel vehicle can be a clean vehicle, and a petrol vehicle can be a dirty vehicle.  However, perhaps the most important message to take away from this work is that the right engine and abatement technology combinations, maintained properly, can deliver significant emission benefits both in tests and on the road, regardless of fuel type.”

 

Prof. Ian Colbeck, Professor of Environmental Science, University of Essex, said:

“This research has compared the potential of exhaust gases from both petrol and diesel engines to form particles in the atmosphere.  They find that modern diesels with particulate filters produce no such particles.  However particulate filters require regeneration – which is a problem on short urban journeys – and regular maintenance.  Only a small percentage of older diesel vehicles without particulate filters are required for particle emissions to dominate those from cars.

“The research was carried out under laboratory conditions so it is not clear if real world emissions would yield similar results.

“It is important to remember that diesel vehicles also emit significant more toxic NOx than petrol engines.  NOx pollution has been implicated in the premature deaths of 23,500 citizens in the UK annually.  To improve public health it is important that UK cities follow the lead set by Paris, Madrid, Athens and Mexico City to start plans to remove diesel vehicles from city centres.”

 

* ‘Gasoline cars produce more carbonaceous particulate matter than modern filter-equipped diesel cars’ by S. M. Platt et al. in Scientific Reports Thursday 13 July 2017.

 

Declared interests

Prof. Roy Harrison: “I am an Honorary Fellow of the Faculty of Public Health and an Honorary Member of the Chartered Institute of Environmental Health, both of which campaign for cleaner air.  This University has research contracts with Jaguar Land Rover and I am a partner in a bid to Innovate UK led by JLR to develop cleaner vehicles.”

Dr Karl Ropkins: “Academic and consultant, working in vehicle emissions measurement sector.  Royal Society of Chemistry (RSC) member, RSC Chemometrics Special Interest Group Committee Member.”

None others received.

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