Persistent organic compounds human exposure

Tetrachloroethylene is a volatile organic compound that is widely distributed in the environment. It is released to the environment via industrial emissions, and it is released from building and consumer products. Releases are primarily to the atmosphere, but the compound is also released to surface water and land in sewage sludges and in other liquid and solid waste, where its high vapor pressure and Hemy s law constant usually result in its rapid volatilization to the atmosphere. Tetrachloroethylene has relatively low solubility in water and has medium-to-high mobility in soil, thus its residence time in surface environments is not expected to be more than a few days. However, it persists in the atmosphere for several months and may also persist in groundwater for several months or more. Because of its pervasiveness and ability to persist under eertain eonditions, the potential for human exposure may be substantial. It should be noted that the amount of tetrachloroethylene measured by chemical analysis is not necessarily the amount that is bioavailable. 

Fish with high fat contents is an important source of long-chain n-3 polyunsaturated fatty acids (PUFAs) in the human diet, in particular for docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) (EFSA, 2005). On the other side, a wide range of environmental contaminants have been reported to be accumulated in fish that can pose a potential human health hazard (Leonard, 2011). Major contaminations include the different OCPs, PAHs or the widely distributed persistent organic pollutants (POPs) with the polychlorinated biphenyls (PCBs) and the flame retardants compound class of the polybrominated diphenylethers (PBDEs). Also farmed fish can significantly contribute to dietary exposure to various contaminants due to the use of land sourced fish feed. A multi method for efficient control of fish and fish feed for various groups of contaminants from PCBs, OCPs, BFRs (brominated flame retardants) and PAHs is outlined in the following analytical procedure published by Kamila Kalachova et al. (Kalachova et al., 2013). 

Biotransformation of certain chlorinated hydrocarbon insecticides results in their conversion to metabolites which are less polar than the parent chemical. Heptachlor and aldrin are converted to the more lipophilic compounds heptachlor epoxide and dieldrin, respectively, whereas DDT is converted to DDE. The primary residue of DDT, which persists to the present day in animals and humans after exposure over a decade ago, is DDE. Following biotransformation, these compounds distribute to tissues which are higher in neutral lipid content than are the major organs of metabolism and excretion, the liver and kidney. These lipid-rich tissues are relatively, deficient in the so-called mixed-function oxidase (MFO) enzyme systems necessary for biotransformation of the halogenated hydrocarbons to more polar and thus more easily excreted compounds. As a result, these lipophilic chemicals remain unchanged in adipose tissue with only limited amounts returning to the circulation for possible metabolism and excretion. Paradoxically, aldrin and heptachlor metabolism results in an increased rather than reduced body load. This is opposite of the pattern seen for most other pesticide classes. 

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