Aerosol Metrology Supporting Air Quality Monitoring in the United Kingdom and Europe

Regulatory measurements of particle mass concentration in air, such as PM10 and PM2.5, have been required in Europe for many years, but have been problematic as issues affecting the comparability of measurements, even when made by the reference method, have become apparent. The importance of airborne particulate matter for human health, and the complexity of the atmospheric processes affecting it, have led to many other parameters, such as particle number concentration, size distribution and composition being monitored, in some cases also as a regulatory requirement. Generally the metrological aspects have been covered by the monitoring network operators, with little involvement from National Metrology Institutes (NMIs). The United Kingdom (UK) National Physical Laboratory is unusual in being an NMI that also operates air quality networks on behalf of the government, directly involved in the full range of activities from fundamental metrology, standardisation of methods, and field operation. More recently, some of the measurement issues have started to be addressed by a group of NMIs within the European Metrology Research Programme. This paper outlines some of the key metrological problems in this area, and the current position in dealing with them from a UK and European perspective.