Particulate matter PM2.5 concentrations in UK schools: a nationwide study into the influence of ambient PM2.5 and the resulting exposure potentials

This paper analyses the concentration of particulate matter PM2.5 from monitors deployed, by the Schools’ Air Quality Monitoring for Health and Education Initiative (SAMHE), to 490 schools across the United Kingdom throughout the academic year 2023—2024. The data shows that the PM2.5 concentration in schools is closely correlated to the ambient outdoor PM2.5 concentrations. Whilst the evidence gathered indicates that sources of PM2.5 within schools contribute to the concentrations, it is shown that outdoor sources are the dominant signature within the PM2.5 concentration measurements made indoors. Moreover, over the academic year, outdoor PM2.5 events — periods of elevated outdoor PM2.5 concentration — are shown to account for approximately 41% of the total potential dose, whilst occurring on only around 13% of schooldays. These, and other findings presented herein, have important implications for school air quality and how air quality within schools, and beyond, is managed.