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Mutagen X (MX), or 3-chloro-4-(dichloromethyl)-5-hydroxy-5H-furan-2-one, is a byproduct of the disinfection of water by chlorination. MX is produced by reaction of chlorine with natural humic acids.

Mutagen X
Skeletal formula of mutagen X
Space-filling model of the mutagen X molecule
IUPAC name
Other names
Mutagen X
3D model (JSmol)
EC Number 253-575-7
Molar mass 217.43 g/mol
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

MX is found in chlorinated drinking water all over the world and is an environmental carcinogen that is known to cause several types of cancer in rats when present in large enough concentrations.[1] It is listed by the International Agency for Research on Cancer as a group 2B carcinogen meaning it is "possibly carcinogenic to humans". Although the concentration of MX in drinking water is typically 100- to 1000-fold lower than other common byproducts of water chlorination such as trihalomethanes, MX might play a role in the increased cancer risks that have been associated with the consumption of chlorinated water because of its potency in inducing DNA damage.[2]


  1. ^ Yuan, Jing; Liu, Hui; Zhou, Li-Hong; Zou, Ya-Lin; Lu, Wen-Qing (2006). "Oxidative stress and DNA damage induced by a drinking-water chlorination disinfection byproduct 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX) in mice". Mutation Research. 609 (2): 129–136. doi:10.1016/j.mrgentox.2006.05.011. PMID 16952480.
  2. ^ McDonald, Thomas A.; Komulainen, Hannu (2005). "Carcinogenicity of the chlorination disinfection by-product MX". Journal of Environmental Science and Health, Part C. C23 (2): 163–214. doi:10.1080/10590500500234988. PMID 16291527.

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