AS3MT and cancer: An association has been reported between polymorphisms in the arsenic methyltransferase gene (AS3MT) and arsenic‐related cancer risk.42 Multiple studies have demonstrated that incomplete arsenic metabolism, with higher fractions of inorganic arsenic and methyl‐arsenic acid and lower fractions of dimethyl‐arsenic acid, is a marker for increased susceptibility to arsenic‐related cancers.5, 43, 44 The methylation of arsenic is thought to be one of the primary aspects of arsenic carcinogenicity.