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We studied the independent role of air pollution and passive smoking on respiratory symptoms and group of symptoms by following 46 adult nonsmokers for 14 wk. Outcomes included the incidence of 15 symptoms. After adjustment for passive smoking, clear rhinorrhea and cough were positively related to nitrogen dioxide (NO2), particles (PM10), and black smoke (BS); whereas headache was positively related to BS. Sneezing, sore throat, and cough were independently positively related to passive smoking. After adjustment for passive smoking, the occurrence of groups of symptoms and of the "sore throat group" were related to three pollutants. The occurrence of the "possible infection group" was positively related to BS. The occurrence of every group of symptoms was independently related to passive smoking. In conclusion, the prevailing levels of air pollution and passive smoking had independent effects on symptoms and groups of symptoms.