??? 1)Smoking??? 2) Occupational exposures- exposure to workplace dusts found in coal mining, gold mining, and the cotton textile industry and chemicals such as cadmium, isocyanates, and fumes from welding have been implicated in the development of airflow obstruction.??? 3) Air pollution??? 4) sudden airway constriction in response to inhaled irritants,??? 5) Bronchial hyperresponsiveness, is a c