Methyl Isothiocyanate Residential Community Air Assessment for South Franklin County, Washington

Metam sodium (metam; sodium methyl-dithiocarba-mate) by weight is the most widely used soil fumigant, and the third most used pesticide in the United States (57–62 million lb/year) (USEPA, 2005a). Metam is applied preplant to a wide variety of crops, with potatoes, tomatoes, tobacco, and strawberries receiv-ing more than 1 million pounds annually. Metam rapidly hydrolyzes upon contact with soil moisture to methyl isothiocyanate (MITC), the bio-logically active ingredient. The high vapor pressure of MITC (2.5–2.8 kPa at 20C) can lead to substantial surface emission and subsequent off-target air mass movement if metam is not properly applied to the soi