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

Background The Toxicity Charge (T-charge) introduced in 2017 in central London, and Ultra-Low Emission Zone (ULEZ) which replaced it in 2019, are vehicle emission-based charging schemes introduced to reduce urban air pollution. There is growing evidence of health co-benefits of such interventions. We conducted a quasi-experimental analysis of these interventions’ impact on the health of adult residents in London. Methods We used interrupted time-series (ITS) analyses to quantify associations of the T-charge/ULEZ with changes in rates of adult (≥15 years) emergency hospital admissions (cardiovascular diseases, respiratory diseases, and all-causes excluding external) in residents of the intervention and control (London, Bristol) areas, between 6 January 2014 and 1 March 2020. We conducted ITS analyses using segmented negative binomial regression to model age/sex-standardised admission rates, adjusting for temperature, relative humidity, month, and public holidays. Findings We found post-T-charge-introduction reductions in annual trends for cardiovascular (−8.1% [95% CI:−2.2,−13.6] per year), respiratory (−6.2% [−1.5, −10.7] per year), and all-cause (−3.1% [−0.9, −5.2] per year) emergency hospital admissions in the intervention area. After adjusting for concurrent changes in a London control area, reductions remained for cardiovascular (−9.3% [−3.4, −14.9]) and all-cause (−5.1% [−2.5, −7.5]), but not respiratory admissions (−2.7% [−7.6, 2.5]). The short ULEZ period prevented firm conclusions regarding ULEZ changes distinct from the T-charge. Interpretation We found evidence of an association between introduction of the T-charge/central ULEZ in London and reduced rates of emergency hospital admissions in adults. Ongoing research is needed to assess longer-term health effects.