Many people can conjure images of London during the Great Smog of 1952. Black and white photographs of double decker buses with lights on full beam, barely glinting through the thick air pollution that was caused by power stations in the heart of the city and coal fires burning in Londoners’ homes, to keep them warm through an usually cold and windless winter. The Great Smog is now estimated to have killed as many as 12,000 people from respiratory diseases and increased rates of influenza.

Mayor Sadiq Khan is currently driving a rapid transition to clean up London’s air. In 2017 Khan introduced the Toxicity Charge or ‘T-Charge’ – a daily charge for older and more polluting vehicles, to deter their use in the city centre. From April 2019, the Ultra-Low Emissions Zone (ULEZ) will replace the T-Charge in Central London, as an addition to the Congestion Charge, but instead of being implemented only during weekdays, the ULEZ will operate 24 hours a day, 365 days a year.

Under the ULEZ, diesel vehicles that do not meet the cleanest Euro 6 standard and petrol vehicles that do not meet the Euro 4 standard will have to pay the daily charge. It is expected that ULEZ will reduce harmful emissions from up to 60,000 vehicles every day, compared to the 6,500 affected by the T-Charge. From 2021, the ULEZ will expand beyond Central London to the North and South Circular roads. Ultimately, the ULEZ will lead to a 72% reduction of people living in areas of poor air quality in Central London and a 54% reduction London wide. But, there have been calls for it to be more ambitious still and stretch all the way to the M25 circular motorway around London. Progressive and relatively quick in terms of big city air quality measures, hitting climate goals will mean cities like London going still further to mass shifts away from car use to mass, electric urban public transport. Oslo, in Norway, for example, has plans for its city centre to become car free in 2019.

But, the London measures build upon progress that has already been achieved to tackle the air quality crisis. In the past decade, the Congestion Charge and increased cycling has reduced the number of vehicles on London’s roads by 25%. A study by Kings College London shows that premature deaths from exposure to one of the most dangerous pollutants – PM2.5 – decreased from 4,300 in 2008 to 3,500 in 2010. The same study estimates that reductions in pollutant levels between 2010 and 2020 will result in close to 4 million life years being saved as a result of fewer premature deaths linked to poor air quality. From 2019 the lives of Londoners will be lengthened and health improved by the launch of the ULEZ. 

Wider relevance

The Head of the World Health Organisation recently warned that “air pollution is the new tobacco”. Ninety percent of the world’s population now live in places where air pollution exceeds the WHO guidelines, and poor air quality causes more deaths than smoking – 7 million people annually – and harms billions more. The gravity of the problem also follows global patterns of poverty and injustice; whilst air quality is improving in many industrialised country cities, many cities in poorer countries are getting worse and worse. For example, of the 10 cities with the worst air quality in the world, 9 are in India. Africa’s cities are also highly polluted, but the technology is barely in place to measure it, never mind improve it – in 2015, the city of Paris had more monitoring stations than the entire continent of Africa.

The problem is, however, far from solved in industrialised countries. Poland, which was host to the international climate talks in 2018 has been described as having a love affair with coal, the most polluting of the fossil fuels. The nation is home to 33 of the 50 most polluted cities in the European Union. Illnesses linked to air pollution kill an estimated 48,000 each year and six out of ten Polish kindergartens are in areas of high pollution.

Also, within cities, it is often the poorest, and the young and old, that are most affected. This is the case in London, where some of the most polluted areas are economically disadvantaged neighbourhoods in East London. Poor air quality is also suffered differentially across racial lines. A study by Imperial College found that the worst air pollution levels in the UK are in ethnically diverse neighbourhoods, where more than 20% of the population are non-white. As well as an environmental and public health issue, poor air quality is a social justice issue.

London’s problem with air pollution is shared by cities all over the world, and as such the measures that it takes to address the crisis are also solutions that can be shared. And, as much as the air quality crisis is multifaceted, its solutions are too. The good news is that efforts to tackle air pollution – such as restricting car use, improving public transport or encouraging cycling or walking – also have knock-on benefits in terms of tackling climate change and improving public health outcomes.

Context and background

The main contributor to the air quality crisis in London has been the escalation in sales of diesel cars. In 2001, then UK Chancellor Gordon Brown introduced a tax incentive for diesel cars as a mechanism to tackle CO2 emissions. Diesel engines emit 15% less CO2 than petrol cars, and so, at the time, the promotion of diesel was seen as an important measure to address the climate change impacts of road transport. What was not factored into the then Government’s planning was that diesel also emits four times more NOx and 22 times more particulate soot than petrol cars – both key toxic ingredients of urban air pollution.

The failure of the UK Government, and many other European governments, to tax diesel appropriately has also been due to the duplicity of the car industry, in the systematic falsifying of emissions tests to play down the extent of local contaminants their engines produced. Volkswagen was rumbled in 2014 when a group of scientists at West Virginia University in the United States conducted their own road emissions tests of Volkswagen vehicles, which showed that the real-world emissions far exceeded legal limits in the US and Europe. The “Dieselgate” scandal revealed that Volkswagen had intentionally programmed their engines to activate emissions controls during laboratory emissions tests – which made it appear that the vehicles were clean but in fact could emit up to 40 times the legal limit of NOx when on the road.

In 2015, more than a third of the cars on the road in the UK were diesel, with new registrations totalling 1.35 million – half of all new cars in 2014. The London Assembly estimates that diesel vehicles account for 40% of the capital’s air pollution. It is not just the increase in diesel cars though, but the growth in overall traffic that compounds London’s air quality problems. Traffic speed in Central London averages 8 miles an hour on weekdays, no faster than travel by horse drawn carriage in Victorian times, and the medieval road system, with narrow winding roads and tall modern buildings traps the pollution at street level. It is this combination of factors – increased diesel, greater congestion and London’s ill-equipped infrastructure – that have added up to the toxic air the capital suffers today.

Previous London administrations have also failed to tackle the issue of air quality seriously enough. As Mayor, Boris Johnson expanded cycle routes and made improvements to public transport, but also scrapped the extension of the congestion zone and put off plans for a low emissions zone.

Enabling factors

The key catalyst for the drive to tackle air pollution in London is the severe damage it is doing to Londoners’ hearts and lungs. Fine Particulate Matter (PM2.5) caused by exhaust fumes is invisible to the naked eye, and also small enough to enter our lungs and pass into the circulatory system when we breathe toxic air. PM2.5 can cause fatal heart and lung diseases and significantly worsen chronic conditions like asthma. Nitrogen dioxide (NO2), for which London has reached rates as bad as Beijing, inflames our lungs and has also been associated with higher rates of dementia.

In London in 2010, 1990 and 420 respiratory hospital admissions in the capital were associated with PM2.5 and NO2, respectively, and an additional 740 hospital emissions were associated with PM2.5. A recent University of Oxford study estimated that the health damage caused by cars and vans in London totalled £650 million a year. This growing public health emergency is undoubtedly the main driver for Sadiq Khan’s actions to tackle air pollution. Activism by Greenpeace and other environmental campaign groups in partnership with medical experts were also vital in building public pressure on the mayor to address the public health crisis.

An important factor in driving urgent action is that it is the most vulnerable – children and the elderly – that suffer the worst effects of London’s poor air quality. There is evidence of stunted lung growth in children living in heavily traffic polluted areas worldwide, which makes them more susceptible to lifelong breathing disorders, and reduces their life expectancy. The Mayor’s campaign has made a strong case for the need especially to protect children’s lungs – pointing out that at least 360 primary schools in London are in areas that exceed safe pollution levels. This focus on children’s health appears to have been an effective message in shifting attitudes.

Growing public consciousness around the dangers of diesel and air pollution is also important. This is evident from the sharp decline in sales of diesel cars – with a 40% drop, year on year, in March 2018, part of a wider annual decline in car sales over the twelve month period. Sadly, the shift away from diesel also saw a 3% rise in the average CO2 emissions of new cars. Over the course of 2018 sales of electric cars accounted for only around five of every 200 new cars registered according to the Society of Motor Manufacturers and Traders. It is also evident from the public consultations that TFL led on the Mayor’s plans for the Ultra Low Emissions Zone, which showed wide public support. TFL’s largest ever consultation, with more than 18,000 responses showed that 60% strongly supported the ULEZ, with 63% of respondents pushing for earlier implementation. In spite of progress on air quality, hitting necessary reductions in CO2 will still require a large scale, general shift onto mass, electric powered public transport beyond anything currently imagined.

Mayor Sadiq Khan is himself an asthma sufferer, and his political will has helped drive the transition so far. Since becoming mayor in 2016 he has committed £800 million for initiatives to improve air quality. Khan also ensured that the public transport sector led by example, mandating that TFL procure hybrid, electric or hydrogen buses, with all buses on the roads meeting the new minimum standard of Euro 6 by 2020.  The London Mayor has also been a vocal critic of the Government’s failure to tackle the issue of traffic air pollution nationally, pushing for a diesel scrappage scheme to help motorists swap to cleaner alternatives.

Scope and evidence

  • Globally, 7 million people die annually from air pollution. This is far more deaths than caused by HIV, tuberculosis and malaria combined. Air pollution has reached illegal levels in urban areas in the UK since 2010, resulting in around 40,000 early deaths a year. In London, it is estimated that over 9,000 people die each year due to air pollution.
  • Reductions in pollutant levels between 2010 and 2020 have already improved the situation – resulting in close to 4 million life years in London being saved. This figure is expected to improve further with the impacts of the ULEZ from 2019.
  • The expanded ULEZ is expected to affect 100,000 cars, 35,000 vans and 3,000 lorries with tighter emissions standards.
  • By 2021, 100,000 Londoners will no longer be living in areas that exceed air quality limits. Ultimately, the ULEZ will lead to a 72% reduction of people living in areas of poor air quality in Central London and a 54% reduction London wide.



Financial Times (2018) Air pollution: why London struggles to breathe

The Guardian (2018) Air pollution is the ‘new tobacco’, warns WHO head

The Guardian (2018a) Everything you should know about air pollution (2017) Mayor: Ultra-Low Emission Zone will start in 2019 to tackle toxic air (2018) Health and exposure to pollution (2018a) Mayor: Ultra-Low Emission Zone to expand up to North & South Circular 

Walton, H. et al (2015) Understanding the Health Impacts of Air Pollution in London For: Transport for London and the Greater London Authority Kings College London

Pacific Standard (2018) Silent Killer: In London, air pollution has become a matter of life and death

Transport & Environment (2015) Five facts about diesel the car industry would rather not tell you