Methyl Bromide
Methyl bromide, a potent alkylating agent, is an odorless, colorless, extremely toxic gas used as a fumigant in soil, perishable foods, cargo containers, and buildings. It is also used in the chemical industry. Fields or buildings to be fumigated are evacuated and covered with a giant tarp, and the gas is introduced. After 12–24 hours, the tarp is removed, and the area is ventilated and then tested for residual methyl bromide before reoccupation. Methyl bromide is a major source of ozone-destroying bromine in the stratosphere, and most production and use were scheduled to be phased out by 2005 in developed countries and by 2015 in developing countries; however, it is still being used in the United States owing to EPA critical use exemptions.
Mechanism of toxicity
Methyl bromide is a potent, nonspecific alkylating agent with a special affinity for sulfhydryl and amino groups. Limited data indicate that toxicity is the result of direct alkylation of cellular components (eg, glutathione, proteins, or DNA) or formation of toxic metabolites from methylated glutathione. Animal data clearly indicate that its toxicity does not result from the bromide ion.
Pharmacokinetics. Inhaled methyl bromide is distributed rapidly to all tissues and metabolized. In sublethal animal studies, approximately 50% is eliminated as exhaled carbon dioxide, 25% is excreted in urine and feces, and 25% is bound to tissues as a methyl group. The elimination half-life of the bromide ion is 9–15 days.
Toxic dose.
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