New analysis from Imperial researchers has found that measures to cut air pollution from vehicles in central London are associated with a fall in hospital admissions.
The Ultra Low Emissions Zone (ULEZ) was introduced in central London in 2019 and aimed at reducing air pollution in the capital through a daily levy on vehicles which fail to meet emissions standards. It replaced the toxicity charge (T-charge), a similar scheme which began in 2017 to target the most polluting vehicles.
Since its introduction, ULEZ has been expanded to the North and South Circular in 2021 and rolled out to all of Greater London in 2023. While there is evidence the schemes have increased the proportion of ULEZ-compliant vehicles in London and improved air quality, the impacts on health are less well established.
To measure the potential impact of these schemes on health, researchers at Imperial College London analysed data on hospital admissions from before and after the start of the ULEZ and T-charge in central London. The study did not focus on the ULEZ expansions, and was limited to the period between January 2014 to March 2020 (covering pre- vs post-implementation of the schemes, but stopping before the COVID-19 pandemic – which significantly altered air pollution patterns).
Their analysis focused specifically on emergency admissions of adults due to cardiovascular disease and respiratory disease, as well as all-causes. These are outcomes known to be worsened by air pollution within a relatively short time of exposure to it.
The study found that since their introduction, the London schemes were linked to 8.1 % reductions in yearly trends for cardiovascular disease, 6.2% for respiratory disease and 3.1% for all cause related hospital admissions in the intervention area.
The team also included a control area in outer London as a comparison area affected by wider trends, but without ULEZ and T-charge schemes in place. After adjusting for concurrent changes in the control area, reductions remained for cardiovascular (9.3% reduction in yearly trend) and all-cause (5.1% reduction in yearly trend), but results for respiratory admissions were inconclusive (2.7% reduction in yearly trend, but not statistically significant).
Associate Professor Daniela Fecht, from Imperial's School of Public Health and senior author of the study, said: "Our results highlight that the central London ULEZ and toxicity charge are broadly linked to positive impacts on health – with a reduction in emergency hospital admissions for cardiovascular disease and all-causes.
"While we need to take caution in how scientific findings for such a complex issue may be interpreted, these results are broadly supportive of the potential for similar interventions in other cities to have positive impacts on health.
Dr Rosemary Chamberlain, Honorary Research Associate within Imperial's School of Public Health and first author of the study, said: "We need more research to better understand the findings for respiratory disease, which were inconclusive – we need to know whether this is an anomaly, or whether potential positive changes were not picked up as we focused on hospital admissions, and did not include primary care visits, where most respiratory conditions are managed."
Dr Bethan Davies, Clinical Associate Professor in Epidemiology at Imperial's School of Public Health, added: "It's crucial that future studies focus on the potential impacts of such schemes on child health, as we know children can be more susceptible to the effects of air pollution. We are currently working towards this aim and are conducting additional analysis that explore the effect in children, and the effect of the ULEZ expansions in 2021 and 2023."
The team highlights a number of limitations to the study, including the limited time period – ending the study period before the start of the COVID-19 pandemic (due to significant changes to vehicle traffic patterns linked with lockdowns, changing work and travel patterns etc.).
The research was supported by funding from the Medical Research Council (MRC), MRC Centre for Environment and Health, the National Institute for Health and Care Research (NIHR) Health Protection Research Unit in Chemical and Radiation Threats and Hazards.
The work was also supported by the NIHR Imperial Biomedical Research Centre, a translational research partnership between Imperial College Healthcare NHS Trust and Imperial College London.
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'Association of vehicle emission charging zones with adult emergency hospital admissions: an interrupted time series analysis of the toxicity charge and Ultra Low Emission Zone in London, UK' by Rosemary C. Chamberlain, John Hodsoll, Chang Cai, et al. is published in Environment International. DOI: https://doi.org/10.1016/j.envint.2026.110324
