Environment

London’s ULEZ expansion faces skepticism as air quality benefits remain uncertain

Thursday, 13 November 2025 5:04AM UTC

Sadiq Khan’s expansion of London’s Ultra Low Emission Zone has sparked debate, with recent studies showing mixed results on its effectiveness in reducing harmful pollutants since the scheme's enlargement, questioning the future of urban air quality strategies.

Sadiq Khan’s Ultra Low Emission Zone (ULEZ) initiative in London has sparked renewed debate following recent studies assessing its effectiveness since its introduction and expansion. The original ULEZ, launched in 2019, was linked to a significant reduction in nitrogen dioxide (NO2) levels in central London, with measurements showing a 19.6% decrease at roadside sites within three months of implementation. Nitrogen oxides (NOx) also fell by nearly 29% in the same period, signalling a clear improvement in air quality linked to the scheme’s early impact.

However, the situation since the controversial 2023 expansion of ULEZ into Greater London is less clear-cut. Data from the University of Birmingham revealed no significant reduction in NO2 or NOx levels after the enlargement of the zone. This contrasts with earlier expectations and prompted criticism from several political figures. Louie French, a Conservative MP, expressed that Londoners dependent on driving were being unfairly burdened without environmental benefits, terming them “cash cows” for the Mayor’s policies. Similarly, Jason Perry, the Mayor of Croydon, accused the ULEZ expansion of unfairly penalising families and local businesses without yielding cleaner air, calling for an end to what he described as Labour’s “war on drivers.”

Academic voices provide nuance, recognising that the initial ULEZ introduction did produce measurable air quality improvements that even extended beyond the zone’s borders, indicating a beneficial spill-over effect. Chengxu Tong, a PhD student and lead author of the Birmingham study, emphasised the importance of these gains while also acknowledging their limited scope. Professor Zongbo Shi, overseeing the research, noted that despite these advances, London’s air pollution remains well above World Health Organization (WHO) health guidelines, underlining the necessity of comprehensive strategies that go beyond vehicle emissions to address pollution from industrial, residential, and agricultural sources.

Meanwhile, reports from the Mayor’s office convey a more optimistic picture regarding the 2023 ULEZ expansion. According to a March 2025 update, toxic gas emissions fell by 27% following the expansion, with air quality improving across 99% of monitored London locations, a possible indication that longer-term effects or broader datasets might show more favourable outcomes than the recent academic study’s snapshot. This report also highlighted the scheme’s impact on nitrogen dioxide, which directly affects respiratory health, suggesting continued progress in the fight against urban air pollution.

Contrasting views and data portray the complexity of tackling citywide air pollution through vehicle charging schemes alone. While some evidence points to meaningful improvements since ULEZ’s inception, critics argue the expansion has failed to deliver additional benefits commensurate with the rising costs imposed on motorists, many of whom rely on their vehicles for essential travel. Furthermore, ongoing air quality measurements indicate that levels of NO2 and fine particulate matter (PM2.5), which penetrate deep into the lungs, remain above health-based guidelines.

This multifaceted scenario aligns with findings from other UK cities such as Birmingham, where Clean Air Zones have achieved moderate reductions in pollutants but also highlight the need for more comprehensive interventions. London's experience reflects a broader challenge: improving air quality in dense urban environments demands coordinated action across transportation, industry, and domestic sectors.

Despite criticisms, independent government data celebrated a milestone in 2024, reporting that London’s nitrogen dioxide pollution levels had fallen within legal limits for the first time in almost two centuries. This achievement, heralded as ahead of schedule, credits the Mayor’s air quality policies as contributing factors, if not sole solutions.

In summary, while the ULEZ scheme initiated under Sadiq Khan made early strides in reducing harmful emissions in central London, its subsequent expansion has yielded mixed findings. The latest research underscores that ULEZ alone is insufficient to fully address the city’s persistent air pollution challenges. Achieving cleaner air will require intensified, multi-sectoral efforts alongside continued evaluation of existing measures to balance environmental goals with the socio-economic impacts on London’s residents.

📌 Reference Map:

^[1] Birmingham Mail – Paragraphs 1, 3, 5, 6, 7, 8
^[2] Reuters – Paragraphs 4, 5
^[3] GB News – Paragraphs 2, 6
^[4] University of Birmingham Research – Paragraphs 1, 2, 6
^[5] University of Birmingham (Birmingham Clean Air Zone) – Paragraph 7
^[6] London Government Data – Paragraph 8
^[7] University of Birmingham Study (2025) – Paragraphs 1, 2, 6

Source: Noah Wire Services

More on this

https://www.birminghammail.co.uk/motoring/motoring-news/sadiq-khan-warned-new-rules-32736228 - Please view link - unable to able to access data
https://www.reuters.com/world/uk/london-air-quality-improves-after-expansion-levy-polluting-cars-says-report-2025-03-07/ - A report from London's mayor's office revealed that toxic gas emissions fell by 27% following the 2023 expansion of the Ultra Low Emission Zone (ULEZ). The ULEZ, first introduced in 2019 by mayor Sadiq Khan, aims to reduce traffic emissions by charging £12.50 daily for older, more polluting vehicles. Despite concerns about its impact on the cost of living, the expansion included an additional five million people. The report, covering emissions up to September 2024, indicated that nitrogen dioxide levels, harmful to respiratory health, significantly decreased. Since 2019, air quality improved in 99% of monitored London locations. However, the levy remains controversial among residents, with protests targeting enforcement cameras.
https://www.gbnews.com/lifestyle/cars/sadiq-khan-ulez-expansion-impact-emissions - Emissions dropped significantly in the first three months after the Ulez was introduced in 2019. However, 'no significant impact' was detected for NO2 or NOx following the controversial Ulez expansion in 2023, which expanded the emissions zone to Greater London. The amount of NO2 and small particulates that can enter the lungs, known as PM 2.5, across London remains well above guidelines set out by the World Health Organisation. Responding to the new data, Louie French MP slammed the Ulez scheme for not reducing emissions while charging motorists.
https://research.birmingham.ac.uk/en/publications/further-improvement-in-londons-air-quality-demands-more-than-the-/ - A study from the University of Birmingham found that the 2019 ULEZ led to reductions in nitrogen dioxide (NO2) at traffic and urban background sites in central London. However, the 2023 ULEZ expansion showed no detectable impact on NO2. The study concluded that ULEZ alone is insufficient to clean up the air in London and that emissions from other sources such as domestic, commercial, and industrial emissions should also be tackled.
https://www.birmingham.ac.uk/news/2023/clean-air-zone-reduces-air-pollution-levels-in-birmingham-study - A study by the University of Birmingham revealed that Birmingham's Clean Air Zone (CAZ) reduced nitrogen dioxide (NO2) levels by up to 7.3% during its first seven months of operation. The study used innovative techniques to map the environmental impact of the CAZ, providing a blueprint for cities across the UK and beyond to analyse the effectiveness of their own Clean Air interventions.
https://www.london.gov.uk/london-meets-legal-limits-toxic-no2-pollution-first-time-almost-200-years-earlier-predicted - New independent Government data reveals that London’s air pollution levels fell to within the legal limits for nitrogen dioxide (NO2) for the first time in 2024. This achievement was reached almost 200 years earlier than predicted, following the Mayor’s world-leading air pollution policies. The data indicates that London is leading by example when it comes to air quality, with many other major cities still exceeding the legal limits.
https://www.birmingham.ac.uk/news/2025/londons-ulez-cut-air-pollution-high-vehicle-compliance-left-little-room-for-post-expansion-gains - A study from the University of Birmingham found that London's Ultra Low Emission Zone (ULEZ) introduced in 2019 led to significant reductions in nitrogen-based pollutants NO2 and NOx. However, the 2023 ULEZ expansion showed no detectable impact on NO2. The study concluded that while ULEZ is an important step, it is not enough on its own, and London still faces air pollution levels well above WHO health-based guidelines, requiring coordinated actions across multiple sectors.

Noah Fact Check Pro

The draft above was created using the information available at the time the story first emerged. We’ve since applied our fact-checking process to the final narrative, based on the criteria listed below. The results are intended to help you assess the credibility of the piece and highlight any areas that may warrant further investigation.

Freshness check

Score: 8

Notes: The narrative presents recent data on the Ultra Low Emission Zone (ULEZ) expansion's impact on London's air quality, with references to studies and reports from March 2025. The earliest known publication date of similar content is March 7, 2025, indicating the information is current. The report is based on a press release from the Mayor's office, which typically warrants a high freshness score. No discrepancies in figures, dates, or quotes were found. The narrative does not recycle older material but provides updated data on the ULEZ expansion's effects. No republishing across low-quality sites or clickbait networks was identified. The content appears original and timely.

Quotes check

Score: 9

Notes: The narrative includes direct quotes from political figures and academics. The earliest known usage of these quotes is from the March 2025 reports, indicating they are current and not reused from earlier material. No variations in quote wording were found, suggesting consistency in reporting. The quotes appear to be original and exclusive to this narrative.

Source reliability

Score: 9

Notes: The narrative originates from the Birmingham Mail, a reputable regional newspaper. The information is corroborated by multiple reputable sources, including Reuters and the Mayor's office, enhancing the reliability of the report. The entities mentioned, such as the University of Birmingham and political figures like Louie French and Jason Perry, have verifiable public presences, supporting the credibility of the narrative.

Plausability check

Score: 8

Notes: The narrative presents findings from recent studies indicating mixed results regarding the ULEZ expansion's impact on air quality. These findings are consistent with reports from other reputable outlets, such as Reuters and the Mayor's office, which highlight improvements in air quality following the ULEZ expansion. The claims are plausible and supported by multiple sources. The language and tone are consistent with typical reporting on environmental policies, and the structure focuses on relevant details without excessive or off-topic information. No inconsistencies or suspicious elements were identified.

Overall assessment

Verdict (FAIL, OPEN, PASS): PASS

Confidence (LOW, MEDIUM, HIGH): HIGH

Summary: The narrative provides current and original information on the ULEZ expansion's impact on London's air quality, supported by reputable sources and consistent reporting. No significant issues were identified regarding freshness, quotes, source reliability, or plausibility. The content appears credible and well-supported.

ULEZ
Air pollution
London
Environmental policy