When applied, the metam in the fumigant rapidly breaks down into the active ingredient, MITC (methyl isothiocyanate), an effective pesticide used to control a variety of pests that threaten food and non-food crops. MITC is highly volatile and will break down quickly when exposed to the atmosphere therefore reducing environmental exposure to the active ingredients of the fumigant.
Like other pesticides registered in the United Stated and elsewhere, metam fumigants must undergo rigorous testing in laboratory and various field conditions before being registered and re-registered for use. These tests provide an understanding of metam fumigants behavior in soil and water as well as determining the relative sensitivity of aquatic and terrestrial wildlife to exposure of the ingredients and break-down products of metam fumigants. It is important to note that mere detection of these byproducts does not indicate a threat to human or animal health. In fact, several environmental studies accepted by government agencies have found that the low levels of metam fumigant byproducts do not pose a risk to plant or animal health.
The U.S. EPA concluded in 2009 the following about metam fumigants:
“Once MITC volatilizes into the atmosphere, it degrades rapidly due to photolysis, thus somewhat limiting exposure to terrestrial organisms. Similarly, exposure to aquatic organisms is limited by MITC’s high potential to volatilize from surface water bodies.”
Government regulators ensure that each registered pesticide continues to meet the highest standards for safety to protect human and environmental health. Over the years, these standards have become higher as the ability to evaluate potential effects of pesticides has advanced. Pesticides like metam soil fumigants have been effectively used for more than 40 years as part of pest management strategies by growers around the world.
In 2017 the government of Canada concluded the following on metam fumigants in the environment:
“….when used according to the label directions, metam sodium and metam potassium are not expected to pose risks of concern to the environment.”