Methylarsonic acid, monosodium salt is an organoarsenic compound formed from the methylation of inorganic arsenic by living organisms. Methylarsonate is used as a contact herbicide in either the monosodium or disodium salt form. It goes by the trade names Weed-E-Rad, Ansar 170 H.C., Ansar 529 H.C., DiTac and others. Methylarsonate is considered only slightly toxic, having an oral LD50 of 2200 mg/Kg for rats. The inhalation risk is greater with LD50 Rats >20 mg. Long term studies with people exposed to organoarsenicals has shown an increased risk of skin cancer (Spiewak, 2001), lung cancer and some liver cancers, although some recent studies have shown some arsenic containing compounds (specifically Arsine trioxide) may have anticarcinogenic properties (Wang, 2001). In mammals, Methylarsonate is also an intermediate in the detoxification of inorganic arsenic. In the arsenate detoxification I pathway, arsenite reacts with S-adenosyl-L-methionine to produce methylarsonate and S-adenosyl-L-homocysteine. Arsenite methyltransferase catalyzes this reaction. Methylarsonate then reacts with 2 glutathione molecules to produce glutathione disulfide and methylarsonite. This reaction is catalyzed by methylarsonate reductase. Methylarsonate is an organic arsenic compound with adverse effects similar to those of arsenic trioxide. Methylarsonate was formerly included in some vitamin and mineral preparations. It was once used to treat tuberculosis, chorea, and other affections in which the cacodylates were used.