Expert Reaction: Diesel and petrol car ban

Posted on 26 July 2017

Professor Alastair Lewis, from the University of York's National Centre for Atmospheric Science, reacts to a new government report that suggests any new diesel and petrol cars could be banned from 2040.

Professor Lewis said: “Although air quality in the UK is clearly much better than some other parts of the world, the economic case to continue to improve it is overwhelming, even though technically this becomes more and more challenging.

“The costs to the economy, through lost productivity and costs to the NHS are measured in the billions of pounds per year, and could well increase further with an ageing population.

“Given the rate of improvement in battery and electric vehicle technology over the last ten years by 2040 small combustion engines in private cars could well have disappeared without any government intervention. Nonetheless this new announcement of a ban is highly symbolic since it signals to both the public and to manufacturers that there is no turning back from electrification. It will go down as significant milestone in the history of air pollution in the UK.

Roadside exposure

“Eliminating petrol and diesel engines from cities will have the most beneficial impact on reducing roadside exposure to NO₂ and fine particulate matter (PM), but the policy will not in isolation completely ensure good air quality for everyone.

“Electric vehicles have no direct tailpipe emissions but they are still a source of PM from brake and tyre wear and through agitating road dust. There still remain many other urban sources of pollution not only from transport, but also heating, construction, domestic emissions, and external sources of pollution that drift into cities from outside, most notably from the agricultural sector. Some other urban sources of pollution are even on an upwards trend, most notably from wood burning stoves.

“If we look forward five to 10 years it is highly likely that the current NO₂ problems in urban centres will have noticeably diminished, but it may leave us with PM and ozone as the two stubborn pollutants that prove hardest to reduce to the levels recommended by the World Health Organisation.

Complex chemistry

“Controlling NO₂ is relatively straightforward – if a molecule is removed from the tailpipe the amount in air responds proportionately. For PM and ozone much more complex chemistry occurs in the atmosphere, where controls on emissions do not always give one-to-one improvements in air quality.

“For some particles and for ozone very large reductions in their precursor emissions can be needed to generate sometimes only modest improvements in air quality.”

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