Many politicians and media commentators who are guilty of promoting misinformation about climate policies are also engaged in a propaganda campaign against air pollution policies, particularly the Ultra Low Emission Zone (ULEZ) in London, which is due to be expanded from 29 August 2023. Bob Ward dispels the myths around this policy, explaining its origins, the thinking behind the expansion and the links between air pollution and health.

A misinformation campaign about London’s Ultra Low Emission Zone is being led by a small but noisy group whose unscientific and unrepresentative views are being amplified by parts of the media. They are attempting to mislead the public by misrepresenting the threat from air pollution in London and the effectiveness of the ULEZ in combating this problem. Many of the proponents of this misinformation also have a track record of inaccurate claims about climate change.

The published evidence shows clearly that concentrations of air pollution have declined across London due to the ULEZ, but remain above the safe limits set by the World Health Organization.

What are the origins of the ULEZ?

The creation of the ULEZ was first announced by Boris Johnson in July 2014 when he was the Conservative Mayor of London, and was confirmed in March 2015 after a consultation. It was backed by the then Conservative Prime Minister, David Cameron, who also agreed to provide funding to help its implementation. The ULEZ was initially scheduled to take effect in Central London from 7 September 2020.

The ULEZ was intended to supplement the Low Emission Zone which was introduced in London by Labour Mayor Ken Livingstone in February 2008 to charge heavy diesel vehicles that did not meet minimum standards for emissions of particulate matter. The LEZ was expanded several times and now covers most of Greater London.

The March 2015 announcement about the creation of the ULEZ stated:

“The two pollutants of principal concern in London are particulate matter (PM10) and nitrogen dioxide (NO2). London is now compliant with PM limit values owing to the Low Emission Zone, taxi and private hire vehicle age limits, bus retrofit schemes and the natural turnover of vehicles. However, London is not forecast to meet the legal limits for NO2 until after 2030 – alongside Birmingham and Leeds – unless targeted action is taken. Since the Mayor was elected, the number of people living in areas exceeding NO2 limits has halved but there is a clear need to take further action. The Greater London Authority (GLA) and TfL [Transport for London] estimate that a reduction in road transport emissions of around 70 per cent is needed for central London to meet EU legal limits for NO2 in 2020, with the ULEZ delivering around two-thirds of this.”

The intention was to implement a charging system to provide a financial incentive to stop driving the most polluting vehicles in London. To be compliant, diesel-powered cars and small vans would need to meet the Euro 6 standard (generally vehicles registered from 1 September 2015) and the Euro 4 standard for cars and small vans with petrol engines (generally vehicles registered from 1 January 2006). The Euro 4 standard for petrol vehicles limits emissions of nitrogen oxides to no more than 80,000 microgrammes per kilometre (µg/km). The Euro 6 standard for diesel vehicles limits emissions of nitrogen oxides to no more than 80,000 µg/km, and particulate matter to no more than 5,000 µg/km.

Equivalent minimum standards would apply to other vehicles. Non-compliant vehicles could still drive in the ULEZ but they would be required to pay a daily charge of £12.50.

After his election as Mayor of London in May 2016, Sadiq Khan consulted on bringing forward the introduction of the ULEZ by a year. It came into effect on 8 April 2019 and its geographical extent was expanded on 25 October 2021 to cover the area out to the ring roads around Central London, the North Circular and the South Circular. Mayor Khan announced on 25 November 2022 that the ULEZ would be extended to the rest of Greater London on 29 August 2023.

How does air pollution harm health?

According to the World Health Organization (WHO), indoor and outdoor air pollution is associated with more than seven million premature deaths around the world each year. The WHO estimates there were 4.2 million premature deaths related to outdoor air pollution in 2019: “some 37% of outdoor air pollution-related premature deaths were due to ischaemic heart disease and stroke, 18% and 23% of deaths were due to chronic obstructive pulmonary disease [COPD] and acute lower respiratory infections respectively, and 11% of deaths were due to cancer within the respiratory tract”.

The WHO has published global air quality guidelines which set pollution limits for particulate matter (‎PM2.5 and PM10)‎, ozone, nitrogen dioxide, sulphur dioxide and carbon monoxide. The latest guidelines suggest that annual average levels of nitrogen dioxide should not exceed 10 µg/m3, with limits of 5 and 15 µg/m3 for PM2.5 and PM10 respectively. The UK’s current legal targets for air pollution are weaker than the WHO guidelines.

In the UK, the impact of air pollution is estimated by the Government to be equivalent to between 28,000 and 36,000 premature deaths per year. This is an estimate because air pollution is not recorded as the cause of death on death certificates – it causes mortality by triggering disease and other health conditions (such as heart disease, stroke and COPD, as described in the WHO quote above). Details of how these impacts are calculated are provided by the Committee on the Medical Effect of Air Pollution.

Researchers at Imperial College London have estimated the health impacts of air pollution in London. They concluded: “In 2019, in Greater London, the equivalent of between 3,600 to 4,100 deaths (61,800 to 70,200 life years lost) were estimated to be attributable to human-made PM2.5 and NO2, considering that health effects exist even at very low levels. This calculation is for deaths from all causes including respiratory, lung cancer and cardiovascular deaths.”

Air pollution policy in the UK

Under current UK legislation, the annual average concentration of nitrogen dioxide must be no higher than 40 µg/m3 across a calendar year in every assessed location in each of the 43 air quality reporting zones of the UK. Additionally, an hourly average concentration over 200 µg/m3 must not be reached more than 18 times in a year.

For PM10, the annual average concentration must be no higher than 40 µg/m3 and an hourly average concentration over 50 µg/m3 must not to be exceeded more than 35 times in a calendar year.

For PM2.5, the annual average concentration must be no higher than 25 µg/m3.

In January 2023, the Department for Environment, Food and Rural Affairs (Defra) published its ‘Environmental Improvement Plan 2023’, including information about progress on improving air quality. It outlined two legal sets of long-term targets for PM2.5, created by the Environment Act 2021, to be achieved by the end of 2040:

  • a maximum Annual Mean Concentration Target (AMCT) of 10 µg/m3 or below; and
  • a reduction in population exposureby 35% compared to 2018 levels.

It noted that “the concentration target will be the most challenging to meet in the South East (because this experiences the greatest amount of pollution blown in from other countries) and in London and other urban areas (as these are where the greatest amounts of UK pollution is produced)”.

In April 2023, Defra published its ‘Air quality strategy: framework for local authority delivery’. It drew attention to interim targets for reducing air pollution from PM2.5:

  • 10 μg/m3 annual mean concentration PM2.5 nationwide by 2040, with an interim target of 12 μg/m3 by January 2028; and
  • 35% reduction in average population exposure by 2040, with an interim target of a 22% reduction by January 2028, both compared to a 2018 baseline.

Declines in air pollution in recent years but some breaches of UK and WHO limits

National statistics show that average levels of both nitrogen dioxide and particulate matter pollution across the UK have declined significantly over the past few decades. The number of days of moderate or higher levels of air pollution, at which adverse health impacts can occur, at urban sites have also declined to relatively low levels, with zero days recorded for nitrogen dioxide in 2022 and PM2.5 and PM10 together responsible for just five days.

The Environment Research Group at Imperial College London carries out monitoring of air quality in London, and publishes annual reports for the London Air Quality Network. The most recent report is for 2020, so the results are skewed by the extended period of COVID-19 lockdown, which reduced road traffic.

The results showed that of 86 sites across Greater London where enough data for nitrogen dioxide was recorded, none exceeded the legal target of not reaching an hourly average concentration over 200 μg/m3 more than 18 times in a year. However, 10 sites recorded breaches of the annual average limit of 40 μg/m3. This represented 12% of sites and compared with 35% of sites in breach in 2019 and 37% in 2018. However, the report also noted that all the 86 sites in 2020 exceeded the WHO guideline annual average limit of 10 μg/m3.

Of the 57 sites that recorded enough data for PM10, only one exceeded the UK legal thresholds, but 49 exceeded the annual average threshold set by the WHO 2021 guidelines.

Of the 13 sites that recorded enough data for PM2.5, all were within the UK legal limit but all exceeded the WHO 2021 guideline threshold.

It seems likely that concentrations of air pollution have risen since 2020 but it is not yet clear to what extent it has broken the legal limits.

A report commissioned by the Mayor of London and published in October 2021 concluded that in 2019, “communities which have higher levels of deprivation, or a higher proportion of people from a non-white ethnic background, were still more likely to be exposed to higher levels of air pollution”. Areas where the most deprived Londoners were likely to live recorded annual concentrations of nitrogen dioxide that were on average 3.8 μg/m3, or 13%, higher than the least deprived areas. PM2.5 concentrations were 0.7 μg/m3, or 6%, higher in the most deprived areas.

Evidence for the positive impacts of the ULEZ on air pollution and health

There have been several studies of the impact of the ULEZ since it was introduced.

A study by researchers at Imperial College London published in the journal Environmental Research Letters in November 2021 assessed the impact of the ULEZ in the first five to eight weeks after it was introduced in April 2019. This analysis showed widespread, but relatively small, reductions, and some increases, in air pollution concentrations across the ULEZ zone. Overall, the authors found an average reduction of less than 3% in nitrogen dioxide levels, and insignificant changes in PM2.5 concentrations.

A further study, published in the Journal of Environmental Health in July 2022, found statistically significant reductions in nitrogen dioxide levels in the first 90 days after the introduction of the ULEZ at 16 sites across London, compared with the same period in 2018.

Another study, published in the journal Atmospheric Pollution Research in August 2022, examined the impact of ULEZ in its first year, finding a cut in nitrogen dioxide concentrations of about 12% inside the zone compared with the year before its implementation.

The Mayor of London published in February 2023 an assessment of the first year of the ULEZ after its expansion to the North Circular and South Circular Roads in October 2021. Among its findings were that the number of non-compliant vehicles recorded fell by almost 60%. It also estimated the impact of concentrations of air pollutants that could be attributed to the ULEZ by comparing trends within the zone with trends outside it. This analysis measured the effect on air pollution that occurred from 2017, when Sadiq Khan confirmed that he would be implementing the ULEZ . By the third quarter of 2022 (July to September), nitrogen dioxide levels were 49% lower in central London than would have been the case without the ULEZ, and concentrations across the expanded ULEZ zone were down 22%.

A review of studies published in July 2023 in The Lancet Public Health on low emission zones around the world (not including London’s ULEZ) found positive air pollution-related health outcomes, with the most consistent effect being on cardiovascular disease.

Expansion of the ULEZ and opposition

The current Mayor of London, Sadiq Khan, announced on 25 November 2022 that the ULEZ would be extended to Outer London from 29 August 2023. The expansion is forecast to “make further progress to reduce air pollution, by reducing nitrogen oxides (NOx) emissions from cars and vans in outer London by 10 and 7 percent respectively, and reducing PM2.5 car exhaust emissions in outer London by nearly 16%, benefitting five million outer London residents”.

The announcement indicated that about 85% of cars in the expansion zone in Outer London are already compliant with the ULEZ thresholds. Several measures have been introduced to help those who own non-compliant vehicles, including improvements in public transport and a scrappage scheme, originally available to those on the lowest incomes but widened in July 2023 to include anyone who owns a non-complaint vehicle in Outer London, offering up to £2,000 for cars.

The campaign against the ULEZ expansion has stepped up since the result of the by-election for a new Member of Parliament for the West London constituency of Uxbridge and South Ruislip on 20 July 2023. The by-election was precipitated by the sudden decision of its MP, former Prime Minister Boris Johnson, to leave Parliament, and before constituents cast their votes there was much speculation that the Conservatives would lose the seat because of their poor polling nationally. But Steve Tuckwell held on to the seat for the party (albeit with a much reduced majority of 495 compared with Mr Johnson’s margin of 7,210 at the 2019 General Election) and the victory was linked by many to opposition to the planned ULEZ expansion, set to happen under a Labour Mayor. The Uxbridge and South Ruislip constituency is located in Hillingdon, one of the Outer London boroughs to be included in the enlargement.

The noisy campaign against the expansion of the ULEZ scheme has included the promotion of falsehoods, too, many from individuals and media outlets that have been spreading misinformation about climate change policies.

For instance, Howard Cox, who has been selected by the Reform UK party as its candidate for the London Mayoral election in May 2024, wrote in the Daily Express on 17 June that “the levels of particulates at roadside level in London according to WHO are at normal safe background levels of concentration”. This is untrue, as the reports of the London Air Quality Network have documented – as mentioned, even in 2020, a year when traffic in London was reduced by the COVID-19 lockdown, levels of PM2.5 were exceeding the WHO 2021 guideline threshold. Mr Cox wrote on Twitter in August 2022: “I am now even more convinced man is not responsible for global warming.”

It remains to be seen how much opposition to the expansion of the ULEZ remains after it takes effect on 29 August and whether it is major factor during the London Mayoral election in May 2024. The majority of households, businesses and drivers in the expanded area will not be directly affected by the ULEZ. However, it might persist as an issue if opponents successfully conflate it with climate policies ahead of the General Election, due to take place within the next 18 months.

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