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Easter Saturday will see the fourth anniversary of the introduction of the Ultra Low Emission Zone (ULEZ) to central London, and in August 2023 the Mayor of London plans to extend it to the boundaries of Greater London. With the scheme high-polluting vehicles are charged when entering the zone. Not everybody is pleased about this, and four outer London boroughs and Surrey County Council have funded a judicial review, hoping to block the expansion. The expansion will improve health through reducing air pollution and emissions of greenhouse gases and by encouraging walking, cycling, and use of public transport. Doctors and other health professionals need to speak up in its favour. This matters most not only for London, but for the other cities in the UK and across the world introducing or planning to introduce similar ultra low emission zones.

Transport is one of the main sources of air pollution and greenhouse gases, and transport is one of the areas where the Mayor of London has authority. Despite the existing ULEZ, everywhere in London has air pollution above the safe limits determined by the World Health Organisation (WHO). Air pollution is particularly associated with asthma, other respiratory diseases, including lung cancer, and cardiovascular disease, but as the 2022 report of the chief medical officer for England highlights, it also contributes to low birth weight, developmental problems in children, diabetes, and dementia.12 The World Health Organisation estimates that air pollution causes about seven million premature deaths each year. Air pollution causes approximately 4000 deaths each year in London, with the young, the old, and the socially deprived suffering the most. Ella Kissi-Debrah, a nine-year-old girl, lived beside the South Circular in London and was the first person in the world to have air pollution on her death certificate. Her mother, Rosamund, is a global leader in campaigning against air pollution.

Sadiq Khan, the Mayor of London, has made acting on air pollution and climate change one of his priorities. A Low Emission Zone was introduced across London in 2008 and the first ULEZ was introduced in 2019. It was extended to, but not including, the North and South Circular Roads in 2021. Heavy-polluting vehicles (mostly older and heavier ones) must pay £12.50 each day to enter the ULEZ.

An evaluation of the ULEZ by the Greater London Authority published in February 2023 focuses on the year following the expansion of ULEZ.3 The report was independently peer-reviewed and shows falls in air pollution and that the vehicles in London are progressively cleaner. Compared with what they would have been without the ULEZ, nitrogen oxides (NOx) emissions from road traffic have fallen over four years by 23% across London and by 26% within the ULEZ. Emissions of fine particulate matter (PM2.5) are estimated to have reduced by 7% across London since 2019 compared to without the ULEZ, and by 19% within the ULEZ. Carbon emissions fell by 3% across London and by 4% within the ULEZ. As a result of the fall in emissions London’s air is cleaner: nitrogen dioxide (NO2) concentrations are 21% lower in inner London than they would be without the ULEZ and 46% lower in central London.

We know that these falls will have produced benefits to health, and the ULEZ will have contributed to a 30% reduction in children being admitted to hospital with asthma in inner London. Of the 500 000 Londoners with asthma more than half live in outer London. Expansion of the ULEZ will bring cleaner air to five million people.

Measuring the effects of the ULEZ is clearly difficult because, as the CMO’s report shows, air pollution from traffic has been coming down because of engineering improvements in cars and people replacing cars and switching to electric cars.1 The pandemic will also have complicated the study with falls in traffic during lockdown and people working more from home.

Nobody can be against cleaner air, but one problem with the ULEZ is that the poorest people are more likely to own older cars and have to pay the charge. But 70% of households with an income under £10k don’t own a car, and nearly half of Londoners don’t own a car. Recognising the problem, the mayor is funding a £110m scrappage scheme. Yet the poorest are the worst affected by polluted air and the most likely to benefit from it becoming cleaner. It’s also a social justice issue in that half of all the children admitted to hospital due to asthma in London are from minority ethnic backgrounds.

Some 90% of the cars in outer London are already compliant and will not have to pay the charge, but another problem with the ULEZ is that public transport options in outer London are not as good as those in central and inner London, although they are a lot better than in most of the UK. One of the aims of the ULEZ is to use the funds raised to improve public transport and encourage walking and cycling. As the mayor’s office has reported, more than a third of car trips made by Londoners could be walked in under 25 minutes and two thirds could be cycled in under 20 minutes. Getting people out of their cars and exercising produces benefits for their health that are large and yet poorly appreciated: as I often say, “Physical activity is the closest we come to a panacea.”

The four boroughs and one county council funding the judicial review are all Conservative-controlled, and it’s hard not to believe that their objection is largely political. The Mayor of London is Labour, and the Greater London Authority has more Labour members than from any other party. But this is about clean air and health, it should not be a party political dispute. As somebody born in inner London and who has lived 63 of my 71 years in inner London, and whose children and grandchildren go to schools in inner London, I am not amused by the County Council of Surrey, one of the wealthiest counties in Britain, opposing the expansion of ULEZ. Judicial reviews examine the process that led to the decision to expand the ULEZ, not whether it is the right thing to do, and there is always a chance it could succeed.

Doctors and health workers need to speak up for health in what has become an intense battle, and you should support the Ride for Their Lives around the perimeter of the ULEZ on 13-15 May.4 The ride will be led by Mark Hayden, an intensive care doctor from Great Ormond Street who has seen children dying from the effects of air pollution.


  • Competing interest: RS is the chair of the UK Health Alliance on Climate Change, which supports the expansion of the ULEZ in London and its introduction and expansion in other cities. He lives in inner London inside the current ULEZ, cycles, and has given up driving. His wife drives a Fiat 500, which is exempt from the ULEZ charge.

Richard Smith, Chair UK Health Alliance on Climate Change

Original BMJ article