Polychlorinated biphenyls neurotoxicity

Neurotoxicity can also occur as a result of indirect effects. For example, damage to hepatic, renal, circulatory, or pancreatic structures may result in secondary effects on the function and structure of the nervous system, such as encephalopathy or polyneuropathy. Secondary effects would not cause a substance to be considered neurotoxic, though at high enough doses, neurotoxicity could be evident. Thus, for the purpose of this review, a substance is defined as neurotoxic when it or its metabolites produce adverse effects as a result of direct interactions with the nervous system. It should be noted, nevertheless, that some chemicals may have multiple modes of action and affect the nervous system directly and indirectly. For example, several halogenated compounds (e.g., polychlorinated biphenyls (PCB), polybrominated diphenyl ethers (PBDE)) may interact directly with brain cells, and also affect the development of the nervous system by altering thyroid hormone homeostasis.7 8... 

Eriksson P, Fredriksson A. 1996a. Developmental neurotoxicity of four ortho-substituted polychlorinated biphenyls in the neonatal mouse. Environ Toxicol Pharmacol 1(3) 155-165. 

SeegalRE. 1995. Dopaminergic bases of polychlorinated biphenyl-induced neurotoxicity. In Chang LW, Slikker W Jr, eds. Neurotoxicology Approaches and methods. San Diego, CA Academic Press Inc., 347-357. 

Tilson HA, Kodavanti PR. 1998. The neurotoxicity of polychlorinated biphenyls. Neurotoxicology 19(4-5) 517-525. 

Winneke G, Bucholski A, Heinzow B, et al. 1998b. Developmental neurotoxicity of polychlorinated biphenyls (PCBs) cognitive and psychomotor functions in 7-month old children. Toxicol Lett 102-103 423-428. 

Polychlorinated biphenyls, PCBs, are among the most hazardous human-made substances, distributed so widely that they have been classified as global POPs. They comprise a group of 209 structurally similar compounds, so called congeners, with diverse teratogenic, reproductive, immunotoxic, neurotoxic and carcinogenic effects. 

Polychlorinated biphenyls (PCBs), the ultimate (poly)chlorinated solvents are 2 membered ring compounds that when heated to 270 produce dibenzofurans (DBFs) that are 1,000 or more times as neurotoxic.Initial evaluations were of a few PCB exposed individuals and 14 firemen exposed to DBFs who showed severe impairment measmed after a medical schools power plant transformers cooked and exploded. Most of the firemen could not pass the physical, balance and truck driving requirements to return to duty and were retired on disability. ... 

The undesirable ecological effects have also restricted the applications of polychlorinated biphenyls (PCBs), the substances which are used in the cooling of high voltage electrical transformers. The main disadvantage of the use of PCB s is their slow rate of degradation after use. Dichlorodiphenyltrichloroethane (DDT) is a very efficient insecticide, but its use is restricted due to its carcinogenic and neurotoxic effects. 

Dioxins are prominent members of the class of polychlorinated hydrocarbons that also includes diben-zofuran, biphenyls and others. Dioxins are highly toxic environmental contaminants. Like others small planar xenobiotics, some dioxins bind with high affinity to the arylhydrocarbon (Ah) receptor. Dioxins activate the receptor over a long time period, but are themselves poor substrates for the enzymes which are induced via the Ah-receptor. These properties of the dioxins and related xenobiotics may be important for the toxicity of these compounds. Dioxins like 2,3,7,8-tetrachloro-p-dibenzodioxin can cause persistent dermatosis, like chloracne and may have other neurotoxic, immunotoxic and carcinogenic effects. 

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