Keywords: 
• chlorpyrifos /
• parathion /
• carbofuran /
• propoxur /
• genotoxicity /
• synergistic effect

Abstract: The paper aims to evaluate in vitro DNA damage of PC₁₂ cells induced by pesticides chlorpyrifos, parathion, carbofuran and propoxur alone or jointly after 12-hour exposure. The concentrations of pesticides chlorpyrifos and parathion applied were 0, 50, 100, 200 and 400 μmol·L^-1, respectively. The concentrations of pesticides carbofuran and propoxur applied were 0, 25, 50, 100 and 200 μmol·L^-1, respectively. PC₁₂ cells were first exposed to these pesticides alone or jointly for 12 h. The Comet assay was then used to evaluate the degree of DNA damage via measuring the length of comet tails, DNA contents in comet tails and tail moments. The PC₁₂ cells showed typical images with tailing after being exposed for 12-hour to chlorpyrifos, carbofuran, parathion and propoxur. The tail length, tail DNA percentage and tail moments increased significantly comparing to the controls, and the difference is significant in statistics (P < 0.01); factor analysis showed that chlorpyrifos and carbofuran, parathion and propoxur interacted (P <0.01) in both low dose and high dose of combinations, and the synergistic effect was observed. Therefore, the DNA damage of PC₁₂ cell can be induced by both organophosphorus and carbamate pesticides. The extents of DNA damage induced by a joint exposure of two pesticides were more significant than that induced by an exposure of a single pesticide. Joint exposure of two pesticides demonstrates a synergistic effect.