Prescribed moorland burning in Great Britain exposes 2.3 million people to PM2.5 levels exceeding the WHO 24 h guideline limit

Prescribed fire is used across the uplands of Great Britain (GB) for vegetation management. Several estimates of the extent of prescribed burning across GB exist but the impact on air quality has never been quantified. We combined satellite-derived annual burn area estimates with satellite fire hotspot data and daily meteorological data to quantify daily emissions from moorland burning between 2017 and 2022. We estimate that moorland burning produces 0.7–1.6 kT year−1 of primary fine particulate matter (PM2.5), comparable to 5% of the primary PM2.5 emissions from domestic combustion or 30% of the primary PM2.5 emissions from road transport. PM2.5 emissions from moorland burning are largest in Yorkshire and Humber, North East England, East Scotland and North Scotland. We used a regional air quality model to simulate the impact of prescribed moorland burning on UK PM2.5 air quality. We simulated the period between October 2017 and April 2018 when wildfires accounted for less than 5% of area burned and moorland burning emissions were dominated by prescribed moorland burning. Prescribed moorland burning increased daily PM2.5 concentrations across large regions of GB by up to 2%–16%. On days where burning occurred, on average, more than 2.32 million people were exposed to at least a 5% increase in PM2.5 concentrations. On days with the most burning, 2.69 million people were exposed to at least a 15% increase in PM2.5 concentration. Across the burn season the entire population (100%) in Yorkshire and Humber, North East England, and East Scotland experienced at least one day with a 5% increase in PM2.5 concentrations due to prescribed moorland burning. While 24%–61% of the population across all four key burning regions experienced at least one day with a 15% increase in PM2.5 concentrations. Increases in PM2.5 concentrations due to prescribed moorland burning led to 2.3 million people being exposed above the WHO threshold (equivalent to 19% of the population in the affected regions). Prescribed moorland burning represents a substantial source of PM2.5 with an important impact on PM2.5 concentrations and population exposure.