Particulate matter (PM) is the term used to describe condensed phase (solid or liquid) particles suspended in the atmosphere. Their potential for causing health problems is directly linked to the size of the particles. A growing body of research has pointed towards the smaller particles, in particular PM less than 2.5 ?m in diameter (PM2.5), as a metric more closely associated with adverse health effects than other metrics such as PM10 (particles with a diameter less than 10 ?m).
This report, prepared by the Air Quality Expert Group (AQEG) for Defra and the Devolved Administrations gives an overview of the evidence base for PM2.5 in the UK.
The report challenges the robustness of the evidence for making future policy decisions in respect of PM2.5 in the UK context. There is an analysis of the evidence concerning key relevant aspects including PM2.5 measurement and the composition and current concentrations of PM2.5 across the UK, as well as source emissions and receptor modelling for PM2.5.
Finally, AQEG evaluates the methods for modelling PM2.5 and what can be said about future concentrations.