Chemical asphyxiates

Asphyxiant Simple asphyxiants are inert gases which deplete the oxygen supply in the breathing air to below the critical value of J8% by volume, such as gaseous fuels or nitrogen. Chemical asphyxiants, such as carbon monoxide and hydrogen cyanide, have a direct biological effect. 

Chemical asphyxiant A substance that interferes with the absorption or utilization of oxygen in the body, e.g., carbon monoxide. 

A chemical asphyxiant works by interfering with the body s ability to absorb or transport 02 to the tissues. A relevant example of a chemical asphyxiant is CO, which can be present in inert gas streams produced... 

Note that C02 acts as neither a simple asphyxiant (like N2) nor a chemical asphyxiant (like CO). The normal concentration of C02 in air is approximately 300 ppm (0.03 vol %). Table 23-19 (Air Products, Carbon Dioxide, Safetygram 18, 1998) illustrates that exposure to air diluted by 5 vol % C02 (yielding an oxygen concentration of 21 x 0.95, or approximately 20 vol %) prompts physiological effects that are more severe than those inferred from Table 23-18 for dilution by the same amount of nitrogen. 

The primary route of exposure to H2S is inhalation. Hydrogen sulfide is classified as a chemical asphyxiant. A single breath of HjS at a concentration of 1000 ppm is sufficient to kill an individual. Prolonged exposure at 250 ppm levels can cause pulmonary edema (the lungs filling with fluid), which can lead to death. However, even at low concentrations (less than 10 ppm), H2S may cause irritation of the eye and respiratoiy system (including the nose, mouth, and bronchial tubes). The effect of hydrogen sulfide can be exacerbated if the individual already suffers from such a pulmonaiy disease as asthma. 

Designated work areas should be established for handling materials with a high degree of acute toxicity (such as chemicals with corrosive effects, e.g., nitric, sulfuric, and hydrochloric acids hydrofluoric acid sodium hydroxide or chemical asphyxiants such as carbon monoxide and hydrogen sulfide). 

Tawackoli, W., Chen, G.D., Fechter, L.D. (2001). Disruption of cochlear potentials by chemical asphyxiants cyanide and carhon monoxide. Afeurotoxzco/. Teratol. 23 157-65. 

Asphyxiant A vapor or gas that can cause unconsciousness or death by suffocation (lack of oxygen). Most simple asphyxiants are harmful to the body when they become so concentrated that they reduce (displace) the available oxygen in air (normally about 21%) to dangerous levels (18% or lower). Chemical asphyxiants, like carbon monoxide (CO), reduce the blood s ability to carry oxygen or, like cyanide, interfere with the body s utilization of oxygen. 

Respiratory asphyxiant A material that prevents or reduces the available oxygen necessary for normal breathing. Divided into simple and chemical asphyxiants. 

I. Mechanism of toxicity. Cyanide is a chemical asphyxiant binding to cellular cytochrome oxidase, it blocks the aerobic utilization of oxygen. Unbound cyanide is detoxified by metabolism to thiocyanate, a much less toxic compound that is excreted in the urine. 

Cyanide is released during the metabolism of cyanogenic glycosides. The best established and probably most important toxic action of cyanide is incapacitation of the cell s mechanism for using oxygen, resulting in chemical asphyxiation (oxygen deprivation) (Nelson 2006). 

Carbon monoxide is a highly toxic, flammable, colorless, odorless gas. It is a chemical asphyxiant with a recommended threshold limit value of 100 parts per million parts of air (0.01 vol. %). The gas is slightly lighter than air (sp. gr. = 0.966). 

Chemical asphyxiates are toxic agents which enter into reactions to cause histotoxic hypoxia. These chemicals prevent the red blood cells from carrying oxygen. Some more familiar chemical asphyxiates are carbon monoxide, nitrites, hydrogen sulhde, and aniline. 

A chemical asphyxiant, such as carbon monoxide, prevents hemoglobin from adsorbing oxygen. 

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