In the Swiss Study on Air Pollution and Lung Disease in Adults (SAPALDIA), a reduction of particulate matter smaller than 10 μm in diameter (PM10) resulted in an attenuation of age-related decline of two lung function measures, namely forced expiratory volume in the first second (FEV1), as well as forced expiratory flow between 25 and 75% of the forced vital capacity (FEF25–75) (Downs et al., 2007).