Unsaturated Halogenated Hydrocarbons

This article contains details on eleven unsaturated halogenated hydrocarbons. These compounds are used as fumigants, pesticides, and chemical intermediates. This chapter follows the outline determined for compounds and includes physical and chemical properties, odor and warning properties, exposure assessment in air and workplace, Toxic effects includes data on the human experience, epidemiology studies, community methods for monitoring, and the standards, regulations and guidelines are discussed. Dichloroacetylene is a highly toxic, spontaneously combustible, undesired, and noncommercial product of the dehydrochlorination of trichloroethylene. It has resulted from exposure of trichloroethylene vapor to Hopcalite in a closed environmental system (submarine) and soda lime in closed circuit (rebreathing) anesthesia machines and from exposure of trichloroethylene liquid to caustic in degreaser tanks. It may also be an undesired by-product during chemical processes such as production of vinylidine chloride. Because of its recognized toxicity, allyl chloride has generally been handled carefully during its manufacture. Eye irritation resulting from overexposure to the vapors has been the most frequent complaint. Although hexachlorobutadiene (HCBD) has been used as a pesticide in other countries, exposure in the United States has mostly been as an unwanted by-product of certain processes associated with chlorination of hydrocarbons. It is reported to have some use as a chemical intermediate. In the United States it was also used for recovering chlorine-containing products and as a fluid for gyroscopes. Old reviews of the toxicity of β-chloroprene are available, but surprisingly few new references were found since the Third Revised Edition of this publication. What is available tends to support the conclusions of that edition. At high concentrations β-chloroprene has an anesthetic action, but this is not as important as eye and respiratory tract irritation and liver injury, which result from excessive exposures. Hair loss has also been reported in humans and animals exposed to β-chloroprene. Because vinyl chloride is a gas, the only significant route of toxic industrial exposure is inhalation. Ingesting low levels for a long period of time has also produced adverse effects, including cancer in animals. If vinyl chloride is confined on the skin in a liquid, some might be expected to be absorbed, but the relative amount is small. The likelihood of acute toxic effects is not nearly as significant as are liver injury, angiosarcoma of the liver, liver and biliary cancer, and possibly acroosteolysis. It appears that metabolism of vinyl chloride is necessary before many of its toxic effects occur. Numerous reviews, bibliographies, and key references are available, and many regulations apply to handling vinyl chloride. Trichloroethylene has been in commercial use for almost 60 years. TCE has been used as a solvent because of its powerful ability to dissolve fats, greases, and waxes. It has been widely used in the dry-cleaning industry and as a metal degreaser and in the electronic components industry where workers have been observed using it as a cleaning solvent without any protective equipment, thus allowing uncontrolled skin contact and inhalation exposures. The only significant sources of TCE are the result of its industrial uses. Perchloroethylene is used as an industrial solvent, particularly in dry cleaning and degreasing. It has been used as an anthelmintic in humans and animals. It also finds limited use as a chemical intermediate. The major response to perchloroethylene at high concentrations is CNS depression. It is not, however, sufficiently effective to be considered a useful anesthetic. Keywords: 1,3-Dichloropropene; 1,2-Dichloroethylene; Dichloroacetylene; Allyl chloride; Hexachlorobutadiene; beta-Chloroprene; Vinylidene chloride; Vinyl chloride; PVC; Vinyl bromide; Trichlorethylene; Tetrachloroethylene