Disodium methyl arsenate (DSMA) is the organoarsenic compound with the formula CH3AsO3Na2. It is a colorless, water-soluble solid derived from methanearsonic acid. It is used as a herbicide. Tradenames include Metharsinat, Arrhenal, Disomear, Metharsan, Stenosine, Tonarsan, Tonarsin, Arsinyl, Arsynal, and Diarsen.
The EPA states that all forms of arsenic are a serious risk to human health and the United States' Agency for Toxic Substances and Disease Registry ranked arsenic as number 1 in its 2001 Priority List of Hazardous Substances at Superfund sites.[1] Arsenic is classified as a Group-A carcinogen.[1] The EPA states[2] that:
The EPA also states that, while contaminated soil poses a serious risk to health, arsenic frequently mobilizes from soils and other sources, ending up in water where it is even more of a toxicity issue.[1]