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<br />moods, and cassava. Factors favoring cyanide
<br />build-up in c}•anogenic plants include high nitro-
<br />gen and ]ow phosphorus in soils (Biehl 1984); the
<br />potential for high glycoside levels is greatestinim-
<br />mature and rapidly growing plants (Egekeze and
<br />Oehme 1980). At present, more than 28 different
<br />cyanoglycosides have been measured in about
<br />1,000 species ofhigher plants (Leduc 1984). In cas-
<br />sava, for example, more than 90°'0 of the cyanide is
<br />present as linamurin, a cyanogenic glycoside, and
<br />the remainder occurs as free (nonglycoside) cya-
<br />nide (Gomez et al. 1983). Laetrile, a preparation
<br />made from apricot kernels, contains high levels oC
<br />amygdalin, a cyanogenic glycoside that can be de-
<br />graded in the gut to cyanide and benzaldehyde.
<br />Several cases of cyanide poisoning in humans have
<br />been reported tram intake of laetrile, either orally
<br />or ana]]y (Solomson 1981; Homan 1987). Cyanide
<br />formation in higher plants and microorganisms
<br />can also occur with compounds other than
<br />cyanogenic g]ycosides,such as glycine, glyoxylate
<br />plus hydroxylamine, or histidine (Solomonson
<br />1981; Vennesland et al. 1981b). In some cases,
<br />plants may contain cyanide residues resulting
<br />from Cumigation with HCN (Way 1981).
<br />Many species of plants, including some fungi,
<br />bacteria, algae, and higher plants, produce cya-
<br />nide as a metabolic product (Leduc et al. 1982;
<br />Leduc 1984). Some species ofsoi] bacteria suppress
<br />plant diseases caused by soilborne pathogens by
<br />producing metabolites with antibiotic activity.
<br />Certain strains of Pseudomonas /tuorescens, a soil
<br />bacterium, suppress black root rot of tobacco
<br />caused by the fungus Thielauiopsis basicola by ex-
<br />creting several metabolites, including HCN
<br />(Voi sard et al. 1989 ). A wide variety of bacteria and
<br />fungi can degrade cyanide compounds, and maybe
<br />useful in the treatment of cyanide wastes (Tovril]
<br />et al. 19781. For example, several species of fungi
<br />knoK•n to be pathogens of cyanogenic plants can
<br />degrade cyanide by hydration to formamide; dried
<br />mycelia of these species are now sold commercially
<br />to detoxify cyanide in industrial wastes (Iviowles
<br />1988 ).
<br />Anthropogenic sources of cyanide in the envi-
<br />ronment include industrial processes, laborato-
<br />ries, fumigation operations, cyanogenic drugs,
<br />fires, cigarette smoking, and chemical warfare op-
<br />erations ~:~:arrs and Ballant}~ne 19871. Cyanides
<br />are present in many industrial tti•astewaters, espe-
<br />cially those of electroplaters; manufacturers of
<br />paint, aluminum, and plastics; meta] finishers;
<br />metallurgists; coal gasification processes: certain
<br />mine operations; and petroleum refiners (Towill et
<br />CYANIDE 13
<br />al. 1978; Egekeze and Oehme ]980; Way 1981,
<br />1984). Electroplaters area major source. In the
<br />United States alone, electroplaters discharge
<br />about 9.7 million kg of cyanide wastes annually
<br />into the environment from 2,600 electroplating
<br />plants (Marrs and Ballantyne 1987). Paint resi-
<br />dues annually contribute an additional 141,300 kg
<br />of cyanide wastes into the environment, and paint
<br />sludges 20,400 kg (Way 1981; Marrs and Ballan-
<br />tyne• 1987). Cyanide can also origipate from natu-
<br />ral processes, such as cyanide production by
<br />bacteria, algae, and fungi, and from many terres-
<br />trial plants that release free HCN when their cel-
<br />lularstructure isdisrupted (Leduc 1981). Hospital
<br />wastewaters usually contain no detectable cya-
<br />nide, but concentrations up to 64 ttg CN-/L have
<br />been measured after alkali chlorination treatment
<br />(Tatsumoto and Hattori 1988). It s8ems that vari-
<br />ous compounds common in hospital wastewaters
<br />will produce 15-25 pg CN'/L after alkali chlorina-
<br />tion; these compounds include hyd'antoin tan an-
<br />tiepilepsy agent) and related nitrogenous
<br />compounds, such as hydantonic acid, 5,5-dipheny]
<br />hydantoin,imidazole,and 2-imidaz0lidinone(Tat-
<br />sumoto and Hattori 1966).
<br />Free hydrogen cyanide occurs only rarely in
<br />nature because of its high reactivity. The gas is
<br />sometimes found in the atmosphere, however, as a
<br />result of emissions from the petroc}lemica] indus-
<br />try, malfunctioning catal}rtic convetters on auto-
<br />mobiles, fumigation of ships and warehouses,
<br />incomplete combustion ofnitrogen-containing ma-
<br />terials,and from tobacco smoke (Towill et al. 1978;
<br />Way 1981, 1984). Hydrogen cyanide i5 known to be
<br />produced in fires involving nitrog6n-containing
<br />poh•mers and is probably the most important nar-
<br />cotic fire product other than carbon monoxide
<br />(Purser et al. 1984). Cyanide-related fire deaths
<br />and injuries, as judged by elevated blood cyanide
<br />and thioc}•anate concentrations, have been docu-
<br />mented in airplanes, jails, and high-uses (Becker
<br />1985; Ballantyne 1987b; Lundquist and Sorbo
<br />1989). In a study of fire victims in Scotland, ele-
<br />vated blood cyanide levels were found in 7850 of fa-
<br />talities, and 31`ir had blood levels considered to be
<br />toxic (Purser et al. 19841. Major factors that influ-
<br />ence HCN release include the chemiaa] nature of
<br />the material, temperature, oxygen availability,
<br />and burning time (Ballantyne 198761. Substantial
<br />quantities of free HCN and organic c}•anides are
<br />known to be produced in fire settings involving
<br />horsehair, tobacco, woo], silk, and many synthetic
<br />polymers, such as polyurethane and poly-
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