Methyl bromide

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  1. A fumigant used for soil treatment, to control pests in postharvest storage, for killing pests on fruits, vegetables, and grain going into export trade, for plant quarantine treatment, and for fumigation of buildings. Because methyl bromide contributes to depletion of stratospheric ozone, it is subject to phase out requirements of the 1987 Montreal Protocol on Ozone Depleting Substances and of the Clean Air Act (CAA). The Montreal Protocol and Vienna Adjustments require a complete phase out in industrialized countries by the year 2010, and a future freeze in developing country use. A 1998 amendment (P.L. 105-178, Title VI) conformed the Clean Air Act phase out date with that of the Montreal Protocol. All methyl bromide regulations so far exempt quarantine and pre-shipment treatment of agricultural commodities; however, this exemption is being reevaluated after completion of additional scientific assessments. Methyl bromide is regulated as a pesticide under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), as a hazardous substance under the Resource Conservation and Recovery Act (RCRA), and is subject to reporting requirements under the Emergency Planning and Community Right to Know Act (EPCRA).
  2. CH3Br, this halocarbon is released, to a degree, naturally from the oceans, but is more commonly released from its anthropogenic use as a soil fumigant or pesticide. Methyl bromide is persistent enough to reach the stratosphere where it photochemically decomposes to yield atomic bromine (radical) and proceeds to destroy stratospheric ozone in the same manner as the atomic chlorine radical. On an atom-for-atom basis, stratospheric bromine is more efficient at destroying ozone than is chlorine because the HBr reservoir species is more photochemically active than HCl; however, there is much less of hydrogen bromide in the stratosphere. [Baird, Colin. Environmental Chemistry. (1999) W.H. Freeman, New York.] Source: Atmospheric Chemistry Glossary

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