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111.1 1,11,111. 1u - 1111rrrrr.1W)MIMi lit Ip::.;rcc.orsI.edwcur-hrrvmis/ll l/prps,,let h\ Ihr titin incidence of mutant or abnormal cells [188]. This is not likely to occur at low doses. Thus, the data are inconclusive. Organ toxicity: Acute exposure primarily damages the lung and results in nervous system effects. chronic exposure may cause damage to the central nervous system. kidneys, and lungs. Other targets of the fumigant are the heart, nasal cavities, adrenal gland, and the testis. Fate in humans and animals: The major route of absorption of methyl bromide vapors is through the lungs [ 188]. Some of the compound is excreted through the lungs as unchanged methyl bromide, but a significant amount also undergoes metabolic decomposition [32]. The primary breakdown products are the bromide ion and methanol, which are detectable in the blood and tissues and are excreted in the urine [32]. Organic bromides (formed by reaction of bromide ion with molecular carbon centers in biomolecules) also appear in stomach fluids and mucus. In humans, methyl bromide's half-life in blood is about 12 days [32]. As a result, the toxic effects of methyl bromide can be delayed or prolonged [32]. Additionally, once in a cell, this chemical inactivates many enzyme systems, so prolonged small doses can cause severe toxicity [32]. Ecological Effects: Effects on birds: Bromomethane is most likely to be in vapor form, and unless birds are in the fumigation area, during the fumigation, they are unlikely to be exposed . Effects on aquatic organisms: Methyl bromide is moderately toxic to aquatic organisms. Acute toxicity in freshwater fish (bluegill sunfish) occurs at concentrations of 11 mg/L and in saltwater fish (tidewater silversides) at about 12 mg/L [8]. Effects on other organisms: It is not toxic to bees [ 1 ]. Environmental Fate: Breakdown in soil and groundwater: Methyl bromide quickly evaporates at temperatures ordinarily encountered in fumigating, but some may be entrapped in soil micropores following application [11]. Methyl bromide is moderately persistent in the soil environment, with a field half-life of between 30 and 60 days; a representative half-life is estimated to be about 55 days Transformation of methyl bromide into bromide increases as the amount of organic matter in the soil increases. It is soluble in water and very poorly sorbed by soils. Some leaching may occur if bromomethane is entrapped in soil micropores following fumigation; the rate of degradation for retained bromomethane in fumigated soil is 6 to 14% per day at 20 C [11]. Breakdown in water: Methyl bromide quickly evaporates at temperatures ordinarily encountered in fumigating; therefore run-off from fields into surface waters is very rare. If it does contact surface waters, the average half-life for methyl bromide under field conditions has been calculated to be 6.6 hours at 11 C [8]. Another study showed the half-life in water to be 20 days at 25 C in a neutral solution [8]. Breakdown in vegetation: The amount of bromide ion (the metabolite of methyl bromide) taken up from the soil, is proportional to the protein content of the crop. Higher levels of the bromide ion will most likely be found in high -protein plants [8]. Physical Properties: • Appearance: Methyl bromide is a colorless gas or volatile liquid which is usually odorless, but has a sweet. chloroform -like odor at high concentrations [1 ]. • Chemical Name: bromomethane [I ] of a 5 11 004:1011NI