Chlorinated aromatic compounds occurrence

Examination of the data on occurrence of chlorinated aromatic compounds in the environment, summarised in Tables 8 and 9, makes it clear that PCB, PCT, PCN, and HCB show a marked tendency to accumulate in biological tissues, particularly the fatty tissues of higher animals, both aquatic and terrestrial. Bioconcentration factors of 3 orders of magnitude between water and fish may be deduced, with a further 1-2 orders of magnitude between whole fish, and the fat storage tissues of predators on them such as cormorant, heron and seal. Some bioconcentration is also indicated in the case of dichloro- and trichlorobenzenes, but data are not adequate for any quantitative assessment. 

Chlorinated phenolic compounds are examples of aromatics which may cause taste and odor problems in finished drinking-water [11 ]. These compounds may result from natural and domestic sources [12 ], from wood preservatives [13 ], or as by-products of chlorination in the treatment process [11 ]. A common treatment process for the occurrence of chlorinated taste and odor problems is super chlorination, which converts the odor causing mono- and di-chlorophenols to trichlorophenols [ 11 ] which do not cause odor, but are suspected carcinogens [ 5 ]. 

Altered Aromatic Metabolites. Loss of parent compound is insufficient evidence to support the occurrence of biodegradation. Frequently, the disappearance of the parent aromatic compound results in the formation of an altered aromatic metabolite. This product indicates that, although biotransformation has taken place, biodegradation has not. An example is the anaerobic O-demethylation of chlorinated guaiacols to chlorocatechols mediated by the acetogenic bacteria, Acetobacterium woodii and Eubacterium limosum (37). 

This chapter is divided into seven main sections. The first of these sections is focused on technological contaminants, namely heterocyclic amines, acrylamide, furan, chloropropanok and their fatty acid esters, polycycKc aromatic hydrocarbons, monocyclic aromatic hydrocarbons, nitroso compounds, and ethyl carbamate. Other sections deal with microbial toxins (mycotoxins and bacterial toxins), persistent organohalogen contaminants (such as polychlorinated biphenyls, dibenzodioxins and dibenzofurans), chlorinated ahphatic hydrocarbons, pesticides (persistent chlorinated hydrocarbons and modem pesticides), veterinary medicines and contaminants from packaging materials. Presented for each of these contaminants are structures, properties, occurrence and the main sources of dietary intake, mechanisms of formation, possibilities of food contamination, prevention and mitigation and health and toxicological evaluations. 

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