TOXIC AROMATICS

Chlorinated biphenyls, chlorinated naphthalenes, benzene hexachloride, [608-73-17, and chlorinated derivatives of cyclopentadiene are no longer in commercial use because of their toxicity. However, they still impact on the chemical industry because of residual environmental problems. This article discusses the toxicity and environmental impact of these materials. 

Environmental problems associated with PCBs are the result of a number of factors. Several open uses of PCBs have resulted in thein direct introduction into the environment, eg, organic diluents careless PCB disposal practices have resulted in significant releases into aquatic and marine ecosystems higher chlorinated PCBs are very stable in thein persistence in different environmental matrices and by a variety of processes (Fig. 1) PCBs are transported throughout the global ecosystem and preferentiaHy bioconcentrate in higher trophic levels of the food chain. 

PCBs have been identified in ambient air samples from diverse locations (15—17,18). In one study of the atmospheric levels of several halogenated 

Kirk-Othmer Encyclopedia of Chemical Technology (4th Edition) 

The identification of PCB residues in fish, wildlife, and human tissues has been reported since the 1970s (9—13,20—26). The results of these analytical studies led to the ultimate ban on further use and production of these compounds. The precise composition of PCB extracts from biota samples is highly variable and depends, in part, on the specific analyte and the commercial PCB preparations associated with a contaminated area (14). PCBs found in a composite human milk sample from Michigan (26) were highly complex, and the congener composition and their relative concentrations did not resemble any of the commercial PCB preparations. This fact raises obvious problems with regard to the ha2ard assessment of PCB mixtures (27). 

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Cm.OROCARBONSANDCm.OROHYDROCARBONS - TOXIC AROMATICS] (Vol 6) Chlorinated butyl rubber... 

CPBOROCARBONSANDCPBOROHYDROCARBONS - TOXIC AROMATICS] (Vol 6) -drinkingwater [ANALYTICALTBTHODS - HYPHENATED INSTHUTBNTS] (Vol 2) -from photochemical technology [PHOTOCHEMICALTECHNOLOGY - SURVEY] (Vol 18)... 

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