Environmental Scientist, California Environmental Protection Agency
Protect people and the environment from exposure to soil fumigant chemicals.
Metam sodium, metam potassium, and dazomet are considered viable alternative soil fumigants to methyl bromide (MeBr) for controlling weeds, plant diseases, insects, and nematodes in soil prior to planting fruits and vegetables in California. Unlike Mebr, they do not appear to affect the stratospheric ozone layer. Metam sodium, metam potassium, and dazomet degrade rapidly to methyl isothiocyanate (MITC), the primary bioactive agent, as well as to methylisocyanate, carbon disulfide, hydrogen sulfide, and methylamine depending on soil pH and other environmental conditions. In agricultural applications, they are used as a pre-plant treatment applied directly to the soil before a crop is planted using drench, drip, flood, power mulcher and rotary tiller, rod bar, shank injection, spray blade with soil cap, and sprinkler fumigation methods. These agents are not applied directly to desired crops. In California, metam sodium, metam potassium, and dazomet products are designated as restricted materials that require a permit to apply.
Metam sodium, metam potassium, and dazomet have been designated as toxicity category I for dermal irritation and toxicity category III for acute oral toxicity and eye irritation. These agents may be corrosive, damaging to the skin, and/or induce an allergic reaction in some individuals. They may be fatal if swallowed, absorbed through the skin, or inhaled, and may cause irritation to the eyes, nose, and/or throat.
Because of the low cost and effectiveness in controlling soil pests, the use of these products increased about two-fold from 1992 to 2003. Metam sodium accounts for the majority of that increase. During this same time period, several illnesses (777) related to MITC-generating pesticides occurred. This evaluation provides information on illnesses related to the agricultural use of MITC-generating soil fumigants and the possible risk factors to people and the environment associated with their use patterns. The goal of Department of Pesticide Regulation is to protect people and the environment from exposure to soil fumigant chemicals. It may be accomplished by: (1) Following Good Agricultural Practices that help to reduce pesticide emission from the soil fumigant application sites and (2) Practicing Recommended Mitigation or Permit Condition that help to keep the fumigants into the ground and to save people and the environment from pesticide exposure.