Toxicity of Chlorine Compounds

Polychlorobiphenyls are responsible for many fish advisories (which advise fishermen not to eat too much fish 

Henschler has reviewed the toxicity of organochlorine compounds.32 Many are carcinogens (e.g., vinyl chloride, which is associated with liver and biliary tract cancers and angiosarcomas).33 One of the most toxic is 2,3,7,8-tetra-chlorodibenzo p dioxin (3.3). 

Some chloroacnegens, such as 3.4, are so potent that drug companies hesitate to work with them.46 The widespread use of triclosan (3.5) as a bactericide in personal care products needs to be reduced now that several strains of bacteria resistant to it have been isolated.47 Soap and water alone will suffice in many of these applications. The use of dichlobenil (3.6) to kill roots penetrating underground pipes might be eliminated by designing tighter pipe joints.48 

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The toxicity of chlorinated compounds is connected with the chlorine content. The decrease of toxicity of chlorophenols with decreasing number of chloro substituents, expressed as EC50, using the Microtox method [291], is shown in Table 21a. [290], cf. also Refs. [292,293],... 

D. Henschler, Angew. Chem. Int. Ed. Engl 1994 33, 1920 toxicity of chlorine compounds. 

In a series of papers (175) comparing chlorination and o2oni2ation, reactive and acid dyes were readily destroyed, but direct and disperse dyes reacted more slowly o2one was more effective in some instances. Although chlorination is cheaper than o2oni2ation, the possible formation of chlorinated compounds such as dioxin and its environmental impact caimotbe overlooked (see Chlorocarbonsandchlorohydrocarbons, TOXIC AROMATICS). 

The toxicity of chlorine residuals to aquatic life has been well documented. Studies indicate that at chlorine concentrations in excess of 0.01 mg/1, serious hazard to marine and estuarine life exists. This has led to the dechlorination of wastewaters before they are discharged into surface water bodies. In addition to being toxic to aquatic life, residuals of chlorine can produce halogenated organic compounds that are potentially toxic to man. Trihalomelhanes (chloroform and bromoform), which are carcinogens, are produced by chlorination. 

The disposal and destruction of chlorinated compounds is a subject of great importance. In fact, in 1993, some environmental groups had proposed the need for a chlorine-free economy. The cost of complete elimination of chlorinated compounds is quite staggering with the latest estimate as high as 160 billion/year.46 The most common method to destroy chlorocarbons is by high-temperature thermal oxidation (incineration).47 The toxic chlorinated compounds seem to be completely destroyed at high temperatures however, there is concern about the formation of toxic by-products such as dioxins and furans.48... 

Palau-Casellas, A. and Hutchinson, T.H. Acute toxicity of chlorinated organic compounds to the embryos and larvae of the marine worm Fiatynersis rfumen/ii (Polychaete Nereidae), Environ. Toxicol Water Qual, 13(2) 149-155, 1998. 

Bercz JP, Jones L, Gamer L, et al. 1982. Subchronic toxicity of chlorine dioxide and related compounds in drinking water in the nonhuman primate. Environ Health Perspect 46 47-55. 

The elemental halogens — fluorine, chlorine, bromine, and iodine — are all toxic. Both fluorine and chlorine are highly corrosive gases that are very damaging to exposed tissue. These elements are chemically and toxicologically similar to many of their compounds, such as the interhalogen compounds, discussed in Chapter 11. The toxicities of halogen compounds are discussed in the next two sections. 

Kimbrough RD. 1972. Toxicity of chlorinated hydrocarbons and related compounds. A review including chlorinated dibenzodioxins and chlorinated dibenzofurans. Arch Environ Health 25 125-131. 

SYN CHLORINATED HC AROMATIC SAFETY PROFILE In most instances, it is difficult to predict the toxicity of these compounds. However, in the case of most... 

Sabljic, A. (1983). Quantitative Structure-Toxicity Relationship of Chlorinated Compounds A Molecular Connectivity Investigation. Bull.Environ.Contam.ToxicoL, 30,80-83. 

The chlorinated hydrocarbons were among the first synthetic insecticide compounds to be used but have fallen into disfavor because of their persistence in the environment. Typical examples of chlorinated hydrocarbon insecticides are DDT, lindane, and to-xaphene. The toxicity of these compounds in small animals is characterized by severe CNS effects, including ataxia and convulsions. Small animals usually get poisoned by being accidentally sprayed or by... 

Examples of chlorinated compounds in the environment abound. Dichlorodiphe-nyltrichloroethane (DDT) is the most common example cited. Whether the use of DDT to control malaria is offset by its other impacts on the environment, e.g., the reproductive cycle of birds and other animals, is moot. (The chemical pyrethrum, described as a toxic, nonvolatile kerosene-type hydrocarbon, is an insecticide that was first derived from the flowers of a species of chrysanthemum and has emerged as a possible substitute for DDT. DDT and similar chemicals have since been synthesized, obviating the need for native sources from mountainous central Africa.)... 

Describe the general structural formulas of PCDD and PCDF congeners. Stress the role of chlorine substitution in toxicity of these compounds. 

In static renewal tests with embryos and larvae of seven species of fish and amphibians, the toxicity of PCB compounds (i.e.. Capacitor 21, Aroclor 1016, i roclor 1242, Aroclor 1254) was found to increase with percent chlorination 20). The more chlorinated PCBs also exhibit longer environmental half-life (757). The combination of high toxicity and persistence in aquatic ecosystems renders these compounds especially hazardous. Despite curtailment of production in the United States, PCBs still in use or disposed of in recent years continue to pose a problem to water quality. These compounds not only exhibit high toxicity to eggs, embryos, and larvae of aquatic species, but also affect sex hormones and the endocrine mechanisms which regulate reproduction in fish 82). 

Sabljic, A. (1983) Quantitative structure-toxicity relationships of chlorinated compounds a molecular connectivity investigation. Bull. Environ. Contam. Toxicol., 30, 80-3. 

In the literature, the PCDD and PCDF results are given as Toxicity Equivalent Quantities (TEQs). Between the 210 PCDD and PCDF congeners, the most toxic molecules are those whose positions 2,3,7,8 are chlorinated. The compounds that meet these conditions number a total of 17, 10 fiuans and 7 dioxins. Since the individual toxicity of these compounds is different, the real toxicity of a mixture was assessed bearing in mind the relative toxicity of the isomers with respect to the most toxic isomer, the 2,3,7,8-TCDD a toxicity equivalence factor (TEF) equal to the unit was assigned to the 2,3,7,8-TCDD. For the toxic assessment, the 17 toxic isomers were normaUzed by multiplying their measiued concentrations by the appropriate TEFs. The sum of these products yields the total TEQs, which express these analyte concentrations as a single munber, equivalent to that of a toxicity derived exclusively from 2,3,7,8-TCDD. 

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