Increased levels of particulate air pollution (PM10) have been implicated as a causal agent in pulmonary disease exacerbation and increased deaths from respiratory and cardiovascular disorders. The exact mechanism by which PM10 drives toxicity in the lung is still unknown, but studies have focused on inhibition of macrophage function and impaired alveolar clearance mechanisms. To assess the effects of PM10 on pulmonary macrophage clearance mechanisms ex vivo, Wistar rats were instilled with 125 or 250 mu g of PM10 collected from the North Kensington, London. Control rats were instilled with sterile saline. The rats were sacrificed after 18 h and a bronchoalveolar lavage (BAL) was performed. Macrophages isolated from the BAL fluid were assessed for ability to migrate towards a positive chemoattractant (ZAS) ex vivo and to perform phagocytosis. Macrophages isolated from the PM10-exposed rats showed inhibition of potential to migrate. Macrophage phagocytic ability ex vivo was also significantly reduced by the presence of PM10 inside the cells. This study indicates that acute PM10 exposure diminishes macrophage motility and phagocytosis in a manner that could prove deleterious to particle clearance from the alveolar region of the lung. Decreased particle clearance promotes inflammation, and hence, warrants further investigation in relation to the effects of chronic PM10 exposure on macrophage clearance mechanisms and establishing the mechanisms behind decreased macrophage migration.