Those who object to low emission or clean-air zones often say restricting old vehicles and diesel cars in city centres will hit the poorest most. A study challenges this.

Researchers from the University of the West of England combined UK census and air pollution data with information from annual vehicle safety (MOT) inspections.

They found people from poorer areas drive shorter distances and create less air pollution compared with their wealthier counterparts. But poorer neighbourhoods have the most air pollution and this gap has widened since 2003. It is similar in the US, where black and Hispanic people suffer most from air pollution.

The UK study found restrictions on diesel vehicles would have least impact in poorer areas, since diesels are predominantly owned by wealthier people.

Restricting older vehicles would have more of an impact in poorer areas, but this effect was small: cars in the poorest areas were, on average, just over a year older than those owned by the most well-off. This was due to multi-car households in wealthier areas and the age of their second, third and in some cases, fourth cars. It seems poorer areas have least to lose and most to gain from reducing traffic pollution.