Abstract: OBJECTIVE： According to the OECD 487 Guidelines for testing of chemicals，the in vitro mammalian cell micronucleus test was used to determine whether the electronic cigarette liquid was mutagenic or not. METHODS： The doses for the liquid were 1.25，2.50 and 5.00 μL/mL. Solvent and positive controls were included，and replicate cultures were set up per dose in the test. The CHL cells were exposed to the liquid in the presence or absence of an exogenous metabolic activation system (S9)，for 4 and 24 hours of incubation. Then，they were harvested，exposed to hypotonic solution and fixed. The cells were then stained with acridine orange and observed under fluorescence microscopy. For each dose group，2 000 binucleated cells were selected for micronucleus rate analysis. RESULTS： After incubation for 4 hours with the dose levels of 1.25，2.50 and 5.00 μL/mL，the induced micronucleus rates without S9 (4 h，-S9)were 2.50‰，1.50‰ and 1.50‰ respectively；and 1.50‰，2.00‰ and 1.00‰ respectively with S9 (4 h，+S9). After 24 hours treatment without S9 (24 h，-S9)，the rates were 1.50‰，1.00‰ and 1.00‰，respectively.. Compared with the solvent control group，there was no statistically significant difference observed (P>0.05). CONCLUSION： Under the current test conditions，electronic cigarette liquid showed no evidence of mutagenic potential in the CHL at the tested dose level of 1.25-5 mg/mL.

Key words: electronic cigarette liquid, in vitro mammalian cell micronucleus test, Chinese hamster lung cells, genotoxicity