Cells were treated with 5 μM, 10 μM, 20 μM arsenite for 24 h or pretreated with 10 mM NAC for 2 h and subsequently treated with 10μM arsenite. Arsenite-induced DNA damage and chromosomal breakage were determined by comet assay (a)-(d) and micronucleus assay (e), respectively. Representative images in comet assay were showed (200×) and illustrated in (a). The effects of arsenite on tail DNA (%), tail length and OTM were illustrated in (b)-(d). “*” denotes a significant difference (P<0.05) detected between treated cells and untreated cells, whereas “**” denotes a significant difference (P<0.05) detected between cells pretreated with NAC and cells treated with 10 μM arsenite.