Mutagen X (MX) is a chlorinated furanone that accounts for more of the mutagenic activity of drinking water than any other disinfection byproduct. DNA damages provoked by the six mutagens (furylframide, MX, 4-nitroquinoline N-oxide, sodium azide, 1-nitropyrene, and captan) used in the present study have been known to subject to the nucleotide excision repair system.