Further improvement in London's air quality demands more than the Ultra Low Emission Zone policy
The 2019 Ultra Low Emission Zone (ULEZ1) significantly reduced nitrogen dioxide (NO2) and nitrogen oxides (NOx) in central London and had positive spillover effects, though its impact on fine particulate matter (PM2.5) was limited. However, the city-wide expansion in 2023 (ULEZ3) showed no detectable impact on air pollution, and overall NO2 and PM2.5 levels remain well above World Health Organization guidelines, indicating ULEZ alone is insufficient to achieve truly clean air.