Cyanide released from toxicity

Grogan J, DeVito SC, Pearlman RS, et al. Modeling cyanide release from nitriles prediction of cytochrome P450 mediated acute nitrile toxicity. Chem Res Toxicol 1992 5(4) 548-552. 

The LD50 value in mice from intravenous administration of tabun has been reported as 0.287 mg/kg (Tripathi and Dewey 1989). Gupta and coworkers (1987) investigated acute toxicity of tabun and its biochemical consequences in the brain of rats. An acute nonlethal dose of 200 pg/kg was injected subcutaneously. Within 0.5-1 hour, the toxicity was maximal it persisted for 6 hours, accompanied by a sharp decline in acetylcholinesterase activity. The prolonged inhibition of this enzyme in muscle and brain may be due to storage aud delayed release of tabun from nonenzymic sites. In addition, cyanide released from a tabun molecule could cause further delay in recovery from its toxic effects. Atropine and its combination with various compounds may offer protection against tabun (see Sections 39.2 and 39.3). 

Grogan, J., DeVito, S.C. Pearlman, R.S. Korzekwa, K.R. Modeling Cyanide Release From Nitriles Prediction of Cytochrome P450 Mediated Acute Nitrile Toxicity. Chem. Res, in Tex. 1992.5, pp. 548-552. 

Cyanides are dangerously toxic materials that can cause instantaneous death. They occur in a number of industrial situations but are commonly associated with plating operations, and sludges and baths from such sources. Cyanide is extremely soluble and many cyanide compounds, when mixed with acid, release deadly hydrogen cyanide gas. Cyanide is sometimes formed during the combustion of various nitrile, cyanohydrin, and methacrylate compounds. Cyanides (CN ) are commonly treated by chlorine oxidation to the less toxic cyanate (CNO ) form, then acid hydrolyzed to COj and N. Obviously, care should be taken that the cyanide oxidation is complete prior to acid hydrolysis of the cyanate. 

The National Institute of Environmental Health Sciences is funding research at the University of Nevada at Reno on the chemical environmental problems associated with mining of gold and silver in the desert environment of the western United States. Cyanide will be the focus of an environmental chemistry project which is intended to provide essential site and chemical characterization information to concurrent biomedical projects. This research will provide information on releases of cyanide to the environment from precious metal mining and help to determine the threat to human health (i.e., potential for human exposures to cyanide) from toxic mining waste. 

Strong acids and strong bases are corrosive substances that exhibit extremes of pH. They are destructive to materials and flesh. Strong acids can react with cyanide and sulfide compounds to release highly toxic hydrogen cyanide (HCN) or hydrogen sulfide (H2S) gases, respectively. Bases liberate noxious ammonia gas (NH3) from solid ammonium compounds. 

Cyanogenic glycosides, which are widely distributed in higher plants, are a bound form of toxic hydrogen cyanide, which is released from the glucoside following enzyme hydrolysis.214... 

The important part of cyanide is the same, whether it is derived from salts, prussic acid, hydrogen cyanide, or released from kernels. It is written by chemists as CN , which means that it is the cyanide ion. When cyanide is absorbed into the body from the stomach, some will exist in this form in the blood and be transported to the liver, where it can be detoxified by an enzyme that converts it into something less toxic, thiocyanate. This is then excreted into the urine. Humans and other animals have probably evolved this mechanism to protect them from the various cyanide-containing plants that occur naturally If the amount taken is too much for the system, the victim suffers poisoning which can be lethal. 

WARNING Synthetic work involving cyanides requires great caution because of the extreme toxicity of gaseous HCN. This is readily released from any alkali-metal cyanide or labile metal-cyano complex by even very weak acids, including salts that are acidic due to hydrolysis. 

Materials that become more hazardous when contacted with water comprise another important class of incompatible materials. For example, carbonyl sulphide (COS) and calcium sulphide (CaS) both release toxic H2S on contact with water. Dry powders of sodium or potassium cyanide release toxic HCN in the presence of moisture. Care must be taken to prevent such materials from coming into contact with water during processing and storage. The 1985 Bhopal accident was started by a runaway reaction involving a water-sensitive chemical. 

Cyanides are commonly treated by chemical or biological oxidation. Of lesser importance is the precipitation of cyanide ion as complex iron cyanide, or by the direct atmospheric release of hydrogen cyanide by acidification and aeration. The oxidation methods, however, have found widest acceptance chemical oxidation is preferred for all but the more dilute cyanides free from other toxics, which may be diluted or treated biologically. Biological treatment of cyanides offers the possibility... 

These two methods involve the potential release of toxic HCN during the reaction and a cleaner as well as a safer method is to use acetone cyanohydrin 128 as a cyanide transfer reagent. The enzyme from the Brazilian rubber tree Hevea brasiliensis, called a hydroxynitrile lyase, catalyses cyanohydrin formation from aliphatic as well as aromatic aldehydes.40... 

Most nitriles are moderate to highly toxic substances. The toxic action is attributed to the presence of the cyanide (—CN) group. Acrylonitrile and acetone cyanohydrin are extremely toxic, as they decompose to hydrogen cyanide in the body. The cyanide released inhibits enzymes that cause respiration in tissue. This prevents tissue cells from using oxygen. 

In the case of SAN and ABS copolymer, the problem of monomer remnants can be more critical, because in addition to remnants of styrene, there may also be remnants of acrylonitrile monomer in the system. These are found to release from their combustion mostly the toxic gases carbon monoxide and hydrogen cyanide [11]. 

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