Toxic chemical polychlorinated biphenyl

Masuda Y, Yoshimura H Chemical analysis and toxicity of polychlorinated biphenyls and dibenzofurans in relation to Yusho. f Toxicol Sci 7(3) 161-175, 1982... 

In earlier editions of the Eniyclopedia there have been articles covering the properties, manufacture, capacities, etc, of polychlorinated biphenyls (PCBs), chlorinated naphthalenes, benzene hexachloride, and chlorinated derivatives of cyclopentadiene. These materials are no longer in commercial use because of their toxicity. However, they stiU impact on the chemical industry because of residual environmental problems. Their toxicity and environmental impact are discussed (see Cm.OROCARBONSANDCm.OROHYDROCARBONS, TOXIC aromatics). 

Until the 1970s the chemical used as the impregnating and dielectric medium for capacitor units was PCB (polychlorinated biphenyl) liquid. It was found to be toxic and unsafe for humans as well as contamination of the environment. For this reason, it is no longer used. The latest trend is to use a non-PCB, non-toxic, phenyl xylyl ethane (PXE-oil), which is a synthetic dielectric liquid of extremely low loss for insulation and impregnation of the capacitor elements or to use mixed polypropylene or allpolypropylene (PP) liquids as the dielectric. A non-oil dielectric, such as epoxy resin, is also used. 

PCBS (polychlorinated biphenyls) Toxic synthetic chemicals with excellent heat resistance and low electrical conductivity properties. Now little used but considerable quantities remain in old electrical equipment. Produces dioxins and polychlorinated dibenzo-furans when burned below 1200°C. PCBs are toxic and bio-accumulative. 

Bedard DL, JE Quensen III (1995) Microbial reductive dechlorination of polychlorinated biphenyls. In Microbial transformation and Degradation of Toxic Organic Chemicals (Eds LY Yonng, CE Cemiglia), pp. 127-216. Wiley-Liss, New York. 

Chemicals degraded by WRF include pesticides such as organochlorines DDT and its very toxic metabolite DDE [8, 9] and organophosphate pesticides such as chlorpyrifos, fonofos and terbufos [10] polychlorinated biphenyls (PCBs) of different degrees of chlorine substitution [11-13], some even to mineralization [14, 15] diverse polycyclic aromatic hydrocarbons (PAHs) in liquid media and from contaminated soils or in complex mixtures such as creosote [16-18] components of munition wastes including TNT and its metabolites DNT [19-23], nitroglycerin [24] and RDX [25]. 

In addition to the chemicals included on the other lists, the CDC also included heavy metals such as arsenic, lead, and mercury volatile solvents such as benzene, chloroform, and bromoform decomposition products such as dioxins and furans polychlorinated biphenyls (PCBs) flammable industrial gases and liquids such as gasoline and propane explosives and oxidizers and all persistent and nonpersistent pesticides. Agents included in this volume are limited to those that are most likely to pose an acute toxicity hazard. 

Tuteliyan, V. A., Lashneva, N. V. (1988). Polychlorinated Biphenyls. Scientific Review of Soviet Literature on Toxicity and Danger of Chemical Substances. Moscow Center of International Projects of State Committee on Science and Technique Publishing House, Vol. 107, 62 pp. 

The water insoluble, highly chemically and thermally stable PCBs used as insulating fluids for transformers and capacitors, in paints, copy paper, etc., are extremely toxic, persistent in the environment and bioaccumulating. PCBs are currently destroyed by incineration of concentrates at high temperatures or chemically with sodium metals or organosodium. Both processes are costly. The cathodic reduction/elimination of the chlorine from polychlorinated biphenyl... 

Polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans and ortho-unsubstituted polychlorinated biphenyls (non-ortho polychlorobiphenyls) are three structurally and toxicologically related families of anthropogenic chemical compounds that have in recent years been shown to have the potential to cause serious environmental contamination due to their extreme toxicity [77-82], These substances are trace-level components or byproducts in several large-volume and widely used synthetic chemicals, principally polychlorobiphenyls and... 

The applicability of using these interdisciplinary approaches, which include incorporation of various physical and chemical properties of the pollutants, QSARs/QSPRs and multicomponent joint action modeling are discussed and evaluated using a group of toxic and carcinogenic pollutants, i. e., polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs). 

For many, familiarity with the TSCA generally stems from its specific reference to polychlorinated biphenyls, which raise a vivid, deadly characterization of the harm caused by them. But the TSCA is not a statute that deals with a single chemical or chemical mixture or product. In fact, under the TSCA, the EPA is authorized to institute testing programs for various chemical substances that may enter the enviromnent. Under the TSCA s broad authorization, data on the production and use of various chemical substances and mixtures may be obtained to protect public health and the environment from the effects of harmful chemicals. In actuality, the TSCA supplements the appropriate sections dealing with toxic substances in other federal stamtes, such as the Clean Water Act (Section 307) and the Occupational Safety and Health Act (Section 6). 

The data needed to meet these objectives are generated on a annual basis by collecting and chemically analyzing adipose tissue specimens for selected toxic substances, mainly organochlorine compounds and polychlorinated biphenyls (PCBs). The 20 compounds... 

XZ/N VI RON MENTAL APPLICATIONS OF CHEMOMETRics are of interest because of the concern about the effects of chemicals on humans. The symposium upon which this book is based served as an important milestone in a process we, the editors, initiated in 1982. As members of the Environmental Protection Agency s Office of Toxic Substances (OTS), we have responsibilities for the acquisition and analysis of human and environmental exposure data in support of the Toxic Substances Control Act. OTS exposure studies invariably are complex and range from evaluating human body burden data (polychlorinated biphenyls in adipose tissue, for example) to documenting airborne asbestos levels in schools. 

The POCs include, but are certainly not limited to the polychlorinated biphenyls (PCBs) and the organochlorine pesticides, including those in current use, restricted use and historic use brominated flame retardants including polybrominated diphenyl ethers PAHs and the sometimes more toxic transformation products of these chemicals. Table 1 summarizes information on some of the POCs more commonly detected in alpine environments. 

It should be realized that with the exception of a few groups of chemicals (such as some organophosphorous and carbamate pesticides as well as some polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and polychlorinated biphenyls (PCBs), precise mechanistic information on their toxic effects are scarce. In realizing that the exact molecular mechanism is not known for most chemicals the term mode of action is used to describe toxicides that appear to be similar albeit the mechanism is not known in detail, see also Section 4.2.6. For several groups of endocrine disrupters this terminology seems appropriate. 

For halogenated aromatic hydrocarbons like polychlorinated biphenyls (PCBs), polychlorinated dibenzofurans (PCDFs), and polychlorinated dibenzo-p-dioxins (PCDDs) the binding to the aryl hydrocarbon (Ah) receptor regulates their toxicity [89]. The Ah receptor controls the induction of one of the cytochrome P450 enzymes in the liver. Toxic responses such as thymic atrophy, iveight loss, immu-notoxicity and acute lethality are associated ivith the relative affinity of PCBs, PCDFs and PCDDs for the Ah receptor [89]. The quantitative structure-activity relationship (QSAR) models predicting the affinity of the halogenated aromatic hydrocarbons ivith the Ah receptor describe the electron acceptor capability as well as the hydrophobicity and polarizability of the chemicals [89[. 

Biopiles have some potential limitations. For example, certain chemicals such as polychlorinated biphenyls and other hydrocarbons are resistant to biodegradation. In addition, high concentrations of toxic metals, such as lead, copper, and mercury, may limit treatment using biopiles. 

Carvone is a chemical component of the spearmint plant that has been shown to enhance the growth and ability of Arthrobacter bacteria to degrade polychlorinated biphenyl (PCB). Until this discovery the only known method of strmnlating the bioremediation of PCBs was addition of biphenyl to the soil however, biphenyl is itself a toxic snbstance. 

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