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<br />No usable cyanide prophylactic therapy now
<br />exists for humans, although sodium thiosulfate,
<br />hydroxocobalamin, and other compounds have
<br />been used to protect against cyanide toxicity in
<br />laboratory animals (Menge] et a I. 1989). For exam-
<br />ple, pYridoxal 5-phosphate, the active form of vita-
<br />min B,:, readily forms complexes with cyanides,
<br />and was effective in providing significant protec-
<br />tion to rats (Keniston et al. 1987). Fructose ted
<br />prior to insult lessens cyanide-induced hepato-
<br />toxicity in rats (Younes and Strubelt 1988). L-
<br />ascorbic acid and dehydroascorbic acid probably
<br />act as protectants against cyanide toxicity by way
<br />of nontoxic cyanohydrin formation (Sprince et al.
<br />19821. Carbon tetrachloride pretreatment was ef-
<br />fective in protecting mice against death from most
<br />nitrites (Willhite and Smith 1981), and pretreat-
<br />ment with p-aminopropiophenone serves to pro-
<br />tect against cyanide toxicity (D'Mello 1987).
<br />Sources and Uses
<br />Production of cyanides in the United States
<br />increased from about 136 million kg in 1963 to 316
<br />million kg in 1976 (Town! et al. 1978; Way 1981;
<br />Marrs and Ballantyne 1987). Cyanide consump-
<br />tion in North America was 64 million kg in 1988
<br />and 98 million kg in 1989; about BOLO of these
<br />amounts was used in gold mining (Knudson 1990 ).
<br />About 84 °%n of domestic HCN production is
<br />used to produce organic cyanides, also known as
<br />nitrites, including acrylonitriles, methyl metha-
<br />crylate, and adiponitrile (Towill et al. 1978).
<br />Nitrites tend to polymerize, which is the basis for
<br />their use in the manufacture of synthetic fibers,
<br />resins, plastics, dyestutis, vitamins, solvents, eias-
<br />tomers, agricultural insecticides, and high pres-
<br />sure lubricants (Willhite and Smith 19811. The
<br />widespread usefulness of HCA' is related to its
<br />strong tendency and that of its inorganic salts to
<br />form complexes with metals. For example, sodium
<br />cyanide is used in metallurgy for the extraction of
<br />gold and silver from ores and in electroplating
<br />baths because it forms stable soluble complexes.
<br />Similar behavior makes alkali cyanide solutions
<br />excellent for cleaning silverware and other pre-
<br />c;ous metals and is responsible for their general
<br />use in industry as meta] cleaners (Towill et al.
<br />1978 ). In Canada, more than 50~i~ of the gold mined
<br />is extracted from ores with the cyanidation proc-
<br />ess. This process consists of leaching gold from the
<br />ore as agold-cyanide complex, and gold being pre-
<br />
<br />CYANIDE 11
<br />cipitated with the addition of zinc dust. A variety of
<br />cyanide compounds are produced during gold
<br />cyanidation (Simovic and Snodgrass 1985). In ad-
<br />dition to their primary use in thB metals and elec-
<br />troplating industries, and in the manufacture of
<br />synthetic fibers and plastics, various cyanide com-
<br />poundshave been used directly or as an intermedi-
<br />ate to produce synthetic rubber, fumigants,
<br />rodenticides,insecticides,predatOrcontrolagents,
<br />rocket fuels, paints and paint finishes, paper, ny-
<br />lon, pharmaceuticals, photographic chemicals,
<br />mirrors, cement, perfume, bleaches, soaps and de-
<br />tergents, riot control agents, fertilyzers, and herhi-
<br />cides (Towill et al. 1978; Way 19$1; Willhite ar~d
<br />Smith 1981; Leduc 1984; Homan 1987).
<br />Hydrogen cyanide vapor, because of its high
<br />and rapid acute lethal toxicity and heady diffusion,
<br />has been used wlde]y to fumigate buildings, ships,
<br />and warehouses; to exterminate rabbits, rodents,
<br />and large predators; and in horticultural practice,
<br />to control insect pests that have developed resis-
<br />tance toother pesticides (Homan 1987; Ballantyne
<br />1988). Typically, fumigation powders containing
<br />either calcium cyanide, Ca(CN)x, Or sodium cya-
<br />nide, NaCN, are blown into burrows or scattered
<br />over the floor in greenhouses. On cgming into con-
<br />tactwith water, such powders liberate HCN vapor
<br />(Ballantyne 1988). Hydrogen cyalnide released
<br />from Ca(CN)~ is registered for usp on almonds,
<br />dried beans, citrus, cocoa beans, grains, nuts, and
<br />spices (Towill et al. 1978). Cyanide-containing
<br />compounds are used for a variety of agricultural
<br />and pesticidal agents. These compounds include
<br />cyanogen (NCCN), as an intermediate in the pro-
<br />duction of some commercial fertilizers; cyanogen
<br />chloride (CNC]), in the manufacture of triazine
<br />herbicides; cyanogen bromide (CNI}r), as a pes-
<br />ticidal fumigant; hydrogen cyanide, in the synthe-
<br />sis of methionine for animal feeds; ammonium
<br />thiocyanate (NH.SCN), as a cotton defoliant; so-
<br />dium thiocyanate (NaSCN), as a weedkiller; and
<br />calcium cyanamide (CaNCN), as a plant fertilizer,
<br />herbicide, pesticide, and defoliant of cotton and to-
<br />matoes (Homan 1987). Cyanide compounds have
<br />also been used as preservatives for raw vegetables
<br />(Towill et al. 1978).
<br />Sodium cyanide has been used ifor about 50
<br />years by the U.S. Fish and Wildlife Service against
<br />coyote in attempts to protect livestock, especiall}•
<br />sheep. The Service has made extensive use of two
<br />A'aCN ejector devices: "the coyote getter," from the
<br />]ate 1930's to 1970; and the M-44, from about 1968
<br />to the present, except for the period 1972-74, when
<br />al] uses of NaCN for predator control were can-
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