Abstract: Objective To examine the effect of particulate matter less than 2.5 μm in aerodynamic diameter(PM_2.5)on lipid peroxidation in human bronchial epithelial cells(BEAS-2B).Methods PM_2.5 was collected in Zhengzhou city of Henan province; BEAS-2B cells were exposed to the PM_2.5 at the doses of 0,12.5,and 25 μg/ml,respectively.After 4 hours,the level of reactive oxygen species(ROS)was measured with flow cytometer; the amount of malonaldehyde(MDA)and the activity of superoxide dismutase(SOD)in cell lysate were measured with MDA and SOD kit 8 hours after PM_2.5 exposure.Results The levels of ROS in BEAS-2B cells treated with PM_2.5 were 6 074.69±41.65 for the dose of 12.5 μg/ml,7 338.58±168.34 for the dose of 25 μg/ml and were higher than that in the control(5816.66±114.69);the amounts of MDA for the two PM_2.5 exposure groups(195.44±35.58 and 334.11±26.75 μmol/mg) were higher than that in the control group(71.14±4.21 μmol/mg);the activity of SOD in exposure groups(100.08±7.54,80.03±7.61 U/mg) were significantly decreased compared to that in the control group(159.91±10.59 U/mg).Conclusion PM_2.5 exposure could induce lipid peroxidation in BEAS-2B cells.