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Although exposure to particulate matter with a diameter of <2.5μm (PM 2.5 ) is associated with chronic obstructive pulmonary disease (COPD), the major components of PM 2.5 in COPD pathogenesis are controversial. Here we employed the human lung epithelial cell line BEAS-2B to elucidate the association between COPD and the organic and water-soluble components of PM 2.5 . We found that the PM 2.5 organic extract was a potential major risk factor for pulmonary epithelial barrier dysfunction through the depletion of proteins from the zonula occludens. This extract induced severe oxidative stress that increased DNA damage and the production of proinflammatory cytokines by BEAS-2B cells as well as decreased α1-antitrypsin expression, suggesting a mechanism that increases the risk of COPD. These effects were mainly mediated by polycyclic aromatic hydrocarbons (PAHs) through the aryl hydrocarbon receptor pathway. PAHs with high benzo(a)pyrene (BaP)-equivalent concentrations, but not major PAH components, have an increased risk of causing COPD, suggesting that BaP-equivalent concentrations represent a PM 2.5 -induced COPD risk metric, which may contribute to provide a rationale for the remediation of air pollution., (Copyright © 2016 Elsevier B.V. All rights reserved.)