Investigating drivers of recent reductions in PM2.5 concentrations across the UK

Exposure to particulate matter less than 2.5 micrometres in diameter (PM_2.5) is the leading environmental risk factor for the global burden of disease and is associated with tens of thousands of deaths in the UK each year. Across the UK, legal compliance and progress towards the PM_2.5 targets set out in the Environment Act, are measured using a network of fixed monitoring sites as part of the Automated Urban and Rual Network (AURN) across the country.

Over the last two decades, significant progress has been made in the reduction of PM_2.5 concentrations across the UK. However, larger than expected decreases in PM_2.5 have been observed recently across the UK. Temporal trends in PM_2.5 concentrations across UK sites all show annual reductions in concentrations since 2018 with large reductions across the early part of 2019, before UK and European COVID-19 lockdowns in 2020.

This work utilises the AURN and complementary networks that measure gas-phase PM_2.5 precursors including volatile organic compounds and ammonia as well as both inorganic and organic aerosol components. The aim is to investigate the potential drivers of recent reductions in PM_2.5 concentrations across the UK to evaluate if the reductions are due to anthropogenic or natural drivers. These drivers could include emission reductions, changes in transboundary sources and atmospheric chemical pathways, as well as the effect of local and regional weather and climate. This analysis will inform assessment of whether the observed reductions may be a transient response to changes in the economy and commodity prices, changes in weather patterns, or whether the reductions represent change that is likely to be sustained. This has implications for both progress towards reducing the health burden of air pollution and future air quality policy.