Metam sodium is an organosulfur compound with the formula . The compound is a sodium salt of a dithiocarbamate. The compound exists as a colorless dihydrate, but most commonly it is encountered as an aqueous solution.[1] It is used as a soil fumigant, pesticide, herbicide, and fungicide. It is one of the most widely used pesticides in the United States, with approximately 60 million pounds used in 2001.[2]
Metam sodium is prepared by combining methylamine, carbon disulfide, and sodium hydroxide:[1]
It also arises from the reaction of methyl isothiocyanate and sodium thiolate.
Upon exposure to the environment, metam sodium decomposes to methyl isothiocyanate and other sulfur compounds.[3]
Metam sodium is nonpersistent in the environment since it decomposes rather quickly to toxic methyl isothiocyanate and carbon disulfide.[4] In 1991 a tank car with 19,000 gallons of a metam sodium based pesticide spilled into Sacramento River above Lake Shasta. This killed all fish in a 41-mile stretch of the river. 20 years later the rainbow trout population had recovered.[5]