Abstract: OBJECTIVE To study the local irritative response by intratracheal instillation, hemolysis and cytotoxicity of 1,2-propylene glycol(PG) in vivo and in vitro, and evaluate the inhalation safety of PG. METHODS Rats were administrated with 30% PG 200 µL by intratracheal instillation once a day, followed by 5 d to evaluate the local irritation. The hemolysis rate of 1,2-propanediol was investigated by in vitro test tube visual observation and ultraviolet spectrophotometer. The toxic effects of PG on human lung adenocarcinoma A549, human bronchial epithelial cells 16HBE and rat tracheal epithelial cells RTE were studied by MTT assay, calculated IC₅₀ value separatel. RESULTS After intratracheal administration of PG, rats showed extremely mild perivascular edema and extremely mild to mild infiltration of inflammatory cells in bronchi. The control group showed extremely mild to mild perivascular edema. The upper layer of PG solution with concentration ≥ 50% turned out to be red slightly after incubating 1 h, the color deepens as the incubation time increases. After 3 h incubation, hemolysis occurred, but no aggregation occurred. The hemolysis rate was calculated by the ultraviolet spectrophotometer method to be >5%, and hemolysis occurred. There was a dose-effect relationship between the cytotoxicity on A549, 16HBE and RTE cells with varying volume fraction of PG concentration in the range of 0.12%-10%, R² values were 0.986, 0.989, 0.993, and IC₅₀ were 2.538%, 2.015%, 1.983%, respectively. CONCLUSION PG is less likely to irritate in lung by intratracheal instillation with good pulmonary tolerance. Hemolytic reaction will be caused by PG with the concentration ≥ 50%. PG has obvious toxic effect on A549, 16HBE and RTE cells when the volume fraction reached 2%. All the above studies provide a supportive data for PG inhalation toxicity.