Abstract: ObjectiveTo explore the damage mechanism of lung in rats exposed to air mixed pollutants.Methods48 Wistar rats were randomly divided into control group,actual-,middle-and high-dose groups.Treated rats were exposed to PM 10 by intratracheal instillation and then were exposed to SO₂,NO₂ and CO by static inhalation 2 hours per day for 30 days.The activities and contents of enzymes in the brochoalveolar lavage fluid(BALF)and the serum were determined.ResultsThe activities of LDH(4.03,2.98,3.63 U/ml)and the levels of proteins(1.14,0.71,0.98 g/L)in BALF in rats of treated groups were higher than that of control group(1.91 U/ml,0.37 g/L).The level of MDA in BALF in rats of high-dose group averaged 2.10 mmol/ml(control group 0.95 mmol/ml)and the activities of SOD in BALF in rats of treated rats averaged 18.32,25.72,16.82 Nu/ml(control group 40.88 Nu/ml).There were significant differences compared with control group.The levels of all indexes in serum were not significant between different groups.ConclusionAir mixed pollutants may resultin oxidative damage in pulmonary tissue and may increase the membrane permeability of pulmonary cells in rats.