Inhalation toxicity cyanides

F.M. Esposito and Y. Alarie, Inhalation toxicity of carbon monoxide and hydrogen cyanide gases released during the thermal decomposition of polymers, Journal of Fire Sciences, 6, 195-242, 1988. 

Levin BG, Braun E, Paabo M, Harris RH, and Navarro M (1992) Reduction of Hydrogen Cyanide Concentrations and Acute Inhalation Toxicity from Flexible Polyurethane Foam Combustion Products by the Addition of Copper Compounds. Part IV. Effects of Combustion Conditions and Scaling on the Generation of Hydrogen Cyanide and Toxicity from Flexible Polyurethane Foam with and without Copper Compounds. NISTIR 4989. Gaithersburg, MD National Institute of Standards and Technology. 

Ballantyne, B., Acute inhalation toxicity of hydrogen cyanide vapor to the rat and rabbit. Toxic Sub. J., 13, 249-282, 1994b. 

The lethal effect of acrylonitrile increased in rats when coadministered with organic solvents (Gut et al. 1981), although the latter decreased the formation of cyanide. Metabolic cyanide formation was found to play only a minor role in the inhalation toxicity of acrylonitrile (Peter and Bolt 1985). This was in contrast to the toxicity of methylacrylonitrile, where the observed clinical symptoms suggest a metabolically formed cyanide. 

In an acute lethal toxicity study on the influence of exposnre ronte, Ballantyne (1983a) observed that the blood cyanide concentrations varied with the ronte. Concentrations in certain specific tissnes varied markedly with exposnre ronte. The blood cyanide concentration was lowest by inhalation and skin penetration. For a given exposure route, the cyanide level in blood were similar for different species. Among the most toxic cyanides, HCN was more toxic than NaCN or KCN by intramnscnlar and transocular routes. 

Blank et al. (1983) carried ont inhalation toxicity stndies of hydrogen cyanide on Spragne-Dawley rats. Exposnre at 68 ppm HCN in air 6 honrs per day for three consecutive days showed symptoms of hypoactiv-ity, breathing difficnlties, signs of hypoxia, convnlsions, and chromorhinorrhea. Death resulted in three of the five male rats after 1 day of exposure, caused by cyanosis of the extremities, moderate to severe hemorrhage of the lung, and pulmonary edema. All female rats survived. In a 4-week study, no mortality was observed at concentrations up to 58 ppm HCN. A brief exposure to 125 ppm HCN for 15 minutes, however, was fatal to 20% of the test animals. Increased urine thiocyanate levels were observed in test animals However, no adverse effects were observed in rats exposed at 29 ppm HCN 6 hour s weekday in 4-week studies. 

For some compounds such as hydrogen cyanide, the rate of detoxification and elimination prevent accumulation in the tissues until a certain inhaled threshold concentration is reached when the rate of uptake exceeds the rate of removal. Accumulation of the inhaled toxic substance then proceeds at a rate which is dependent on the difference between the inhaled concentration and the threshold concentration (i.e. the rate of uptake and a constant rate of removal). A modified Haber equation was produced by Flury and Zemik as early as 1931 which contained an elimination factor (e) to modify the original equation to (C — e)t = W... 

Dorex is very toxic (see Table 2) and must be handled with extreme care. Because it may produce severe dermatitis on moist skin, it is difficult to use in hot, humid climates inhalation of the dust or spray may irritate the mucous membranes. Whereas symptoms may include a flushed face, tachycardia, headache, vertigo, and hypotension, it does not produce the typical cyanide effect. 

Cyanohydrins are highly toxic by inhalation or ingestion, and moderately toxic through skin absorption (21). AH a-hydroxy nitriles are potential sources of hydrogen cyanide or cyanides and must be handled with considerable caution. Contact with the skin and inhalation should be rigorously avoided. Special protective clothing should be worn and any exposure should be avoided (18,20). The area should be adequately ventilated. Immediate medical attention is essential in case of cyanohydrin poisoning. 

Acrylonitrile (Vinyl cyanide) CH,CHCN Closely resembles HCN in toxic action Poisonous by inhalation, ingestion or skin absorption Emits cyanides when heated or contacted by acids or acid fumes Symptoms flushed face, irritation of eyes and nose, nausea etc. Colourless flammable liquid with mild, faintly pungent odour Elash point 0°C. Dilute water solutions also have low flash points... 

Unfortunately, most fatalities in fires occur by inhalation of toxic vapours. These can be carbon monoxide (which arises from incomplete combustion), cyanides (from nitrogen-containing polymers) and chlorides (from chloropoly-mers). These are the adverse consequences of flammable polymer combustion. They can be overcome by using breathing apparatus, face masks, etc. 

Hydrogen selenide, a possible by-product, is very toxic, being comparable with hydrogen cyanide. Its accidental inhalation in small amounts may produce a sore throat. 

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