Saturated Methyl Halogenated Aliphatic Hydrocarbons

It is impossible to generalize on the saturated methyl halogenated aliphatic hydrocarbons discussed in this chapter. Physical properties and toxicological manifestations differ over a broad range depending on the particular halogen and the number of halogen atoms involved. As mentioned in the previous edition, the usefulness of these compounds has been significantly reduced because of the concern over stratospheric ozone depletion. On the other hand, toxicological interest in these compounds has increased because of concern over their production in chlorinated water systems. The USEPA (National Center for Environmental Assessment) and others are actively investigating the possible relationship between chlorination of drinking water sources and human cancer through many avenues, including sophisticated epidemiologic tools. Many of the compounds have been shown to produce cancer in animals, but their potency for humans is still under consideration, and the complex interactions with regard to human health are challenging. The other area of biochemistry that is of relevance to some of these materials is in regard to lipid peroxidation and its role in disease and in extrapolation from animal species to humans. As in the previous editions, this review relies extensively on information provided in earlier editions. Several online databases were utilized in searching for the most recent information in preparing the chapter. These included NTP (National Toxicology Program), IRIS (Integrated Risk Information Service), and the ATSDR (Agency for Toxic Substances and Disease Registry) websites. Most recent information was sought through MEDLINE, and, when possible, the original articles were reviewed. Debatably, IRIS was considered to be the last word with regard to cancer. Many of the compounds have been recently reviewed by the ATSDR and are reported in their toxicological profiles. Recent reviews were utilized in preparing this chapter. In addition, the Pocket Guide to Chemical Hazards and the ACGIH's TLV's and Other Occupational Exposure Values-1999 were utilized. Keywords: Methyl chloride; Refrigerant; Methyl bromide; Fire extinguishing agents; Methyl iodide; Methylene chloride; Cyanosis; Chloroform; Bromoform; Lacrimator; Iodoform; Carbon tetrachloride; Tetrabromomethane