Diesel exhaust enhances airway responsiveness in asthmatic subjects

Particulate matter (PM) pollution has been associated with negative health effects, including exacerbations of asthma following exposure to PM peaks. The aim of the present study was to investigate the effects of short-term e xposure to diesel exhaust (DE) in asthmatics, by specifically addressing th e effects on airway hyperresponsiveness, lung function and airway inflammat ion. Fourteen nonsmoking, atopic asthmatics with stable disease, on continuous t reatment with inhaled corticosteroids, were included. All were hyperrespons ive to methacholine. Each subject was exposed to DE (particles with a 50% c ut-off aerodynamic diameter of 10 mum (PM10) 300 mug(.)m(-3)) and air durin g Ih on two separate occasions. Lung function was measured before and immed iately after the exposures. Sputum induction was performed 6 h, and methach oline inhalation test 24 h, after each exposure. Exposure to DE was associated with a significant increase in the degree of hyperresponsiveness, as compared to after air, of 0.97 doubling concentrati ons at 24 h after exposure (p < 0.001). DE also induced a significant incre ase in airway resistance (p = 0.004) and in sputum levels of interleukin (I L)-6 (p = 0.048). No changes were detected in sputum levels of methyl-hista mine, eosinophil cationic protein, myeloperoxidase and IL-8. This study indicated that short-term exposure to diesel exhaust, equal to h igh ambient levels of particulate matter, is associated with adverse effect s in asthmatic airways, even in the presence of inhaled corticosteroid ther apy. The increase in airway responsiveness may provide an important link to epidemiological findings exacerbations of asthma following exposure to par ticulate matter.