Recent analyses indicate that Sadiq Khan's Ultra Low Emission Zone (ULEZ), which charges drivers £12.50 per day, has not effectively improved air quality in London as claimed. Official data from local councils shows that over half of the boroughs continue to report illegal nitrogen dioxide (NO2) levels, primarily emitted from diesel vehicles. Despite a report from the Department for the Environment, Food, and Rural Affairs (Defra) stating that London met legal NO2 limits for the first time in 2024, monitoring stations in areas like Romford and the City of London recorded levels nearly double the legal threshold. Critics, including the charity Asthma + Lung UK, argue that the government is underreporting pollution levels and that local monitoring data should be prioritized. Susan Hall, leader of the City Hall Conservatives, accused Khan of selectively using data to advance his agenda. Although City Hall claims significant improvements in air quality due to ULEZ, experts emphasize that many areas still exceed legal limits, raising concerns about public health and the accuracy of air quality reporting.