Investigate the following in rescue and cleanup workers exposed to the World Trade Center (WTC) disaster 17 years post-fallout: 1) allergic hypersensitivity; 2) spirometry; 3) impulse oscillometry; and 4) the reversibility of airway hyperresponsiveness and distal airways narrowing pre- and post-bronchodilator.In subjects (n = 54) referred to our clinic from the WTC Health Program for management of allergy-immunology services, environmental allergy testing, IOS, and spirometry results were retrospectively reviewed to determine the long-term impact of exposure to the WTC fallout.Rescue and cleanup workers exposed to the WTC fallout had a high incidence of allergic hypersensitivity and had evidence of permanent small airways dysfunction characterized by distal airways narrowing and airway hyperresponsiveness.Following exposure to the WTC disaster, the patients in our cohort developed allergic hypersensitivity and severe lung injury with only partial reversibility.