Lung lining liquid modifies PM(2.5) in favor of particle aggregation: a protective mechanism.

The health effects of particle inhalation including urban air pollution and tobacco smoke comprise a significant public health concern worldwide, although the mechanisms by which inhaled particles cause premature deaths remain undetermined. In this study, we assessed the physicochemical interactions of fine airborne particles (PM(2.5)) and lung lining liquid using scanning electron microscopy, atomic force microscopy, and X-ray photon spectroscopy. We provide experimental evidence to show that lung lining liquid modifies the chemistry and attractive forces at the surface of PM(2.5), which leads to enhanced particle aggregation. We propose that this is an important protective mechanism that aids particle clearance in the lung.