Update in Environmental and Occupational Medicine 2005

Although air pollution consists of a heterogeneous mixture of gases and particles, most recent research has been devoted to the adverse effects of particulate matter (PM). PM consists of primary particles, such as diesel soot or other combustion-derived particles,whichare emitteddirectly into the atmosphere, and secondary particles, which are created in the atmosphere through complex physicochemical transformation of gases (1, 2). Airborne PM is generally defined on the basis of the size distribution of the particles. Thus, PM10 andPM2.5 stand for PMwithmedian aerodynamic diameters less than 10 m and 2.5 m, respectively. Ultrafine particles (UFPs) have a diameter less than 100 nm (0.1 m). These particles demonstrate very high deposition in human alveoli (3).