Automotive particulate matter
Particulate matter (PM) in the air continues to be the focus of increased attention due to the concern of potential health effects. Accordingly, under the EU Air Quality Framework Directive an air quality standard has been defined with respect to PM10 (particulate with an aerodynamic diameter less than or equal to 10 nm) with a review planned in 2003. There is concern that automotive tailpipe emissions, as one of the many emitting sources, may make a substantial contribution to ambient particulate concentrations especially within urban areas. Legislation is in place to measure and control the mass of automotive particulate emitted at the tailpipe and tighter limits have been progressively introduced over the years. While there is evidence that adverse health effects are associated with current ambient PM concentrations, it is, as yet, uncertain which feature of the particulate matter, be it chemical or physical, has themost relevance for health studies. Thus, attention has concentrated on the number-based size distribution of the ambient particles.