Freons and Halons
Freons (fluorocarbons and chlorofluorocarbons [CFCs]) historically have been widely used as aerosol propellants, in refrigeration units, in the manufacture of plastics, in foam blowing, and as degreasing agents. Under provisions of the Montreal Protocol of 1987, the use of CFCs is being phased out to avoid further depletion of stratospheric ozone. Nevertheless, freons remain in older refrigeration and air conditioning systems, and illicit importation of freons occurs. Most freons are gases at room temperature, but some are liquids (freons 11, 21, 113, and 114) and may be ingested. Specialized fire extinguishers contain closely related compounds known as halons, which contain bromine, fluorine, and chlorine.
Mechanism of toxicity
Freons are mild CNS depressants and asphyxiants that displace oxygen from the ambient environment. Freons are well absorbed by inhalation or ingestion and are usually rapidly excreted in the breath within 15–60 minutes.
Like chlorinated hydrocarbons, freons may potentiate cardiac arrhythmias by sensitizing the myocardium to the effects of catecholamines.
Direct freezing of the skin, with frostbite, may occur if the skin is exposed to rapidly expanding gas as it escapes from a pressurized tank.
Freons and halons are mild irritants and may produce more potent irritant gases and vapors (eg, phosgene, hydrochloric acid, hydrofluoric acid, and carbonyl fluoride) when heated to high temperatures, as may happen in a fire or if a refrigeration line is cut by a welding torch or electric arc.
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