Annual average PM2.5 levels in London 2016-2023, by location and site type

Roadside concentrations of fine particulate matter (PM2.5) in central London averaged 10 micrograms per cubic meter (µg/m³) in 2023. Although this was the highest level recorded by location and site type that year, it still represented a 39 percent reduction compared to 2017 levels. Several policies have helped lower air pollution in London since 2016, such as the introduction of Ultra Low Emissions Zones (ULEZs), transitions to cleaner bus fleets, and increasing cycle networks.