Effects of co-exposure to air pollution and allergen

The investigators are investigating the effects of combined exposures to diesel exhaust and allergens on lung function and on the immune system. After exposing individuals to either filtered air or carefully controlled levels of diesel exhaust in our exposure chamber, The investigators will use a procedure called bronchoscopy (whereby a thin, flexible tube is passed down the throat and into the lungs) to place a small amount of allergen directly in the lung. 48h later, the bronchoscopy will be repeated so that samples can be collected from the lungs. After 1mo, the entire procedure will be repeated with the alternate exposure.