Polychlorinated biphenyls , Toxic

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. 

Kannan, N., S. Tanabe, M. Ono, and R. Tatsukawa. 1989. Critical evaluation of polychlorinated biphenyl toxicity in terrestrial and marine mammals increasing impact of non-ortho and mono-ortho coplanar polychlorinated biphenyls from land to ocean. Arch. Environ. Contam. Toxicol. 18 850-857. 

Polychlorinated biphenyls are stiU used in large quantities in electrical and condenser technology. One of the main members of this group of substances is perchlorobiphenyl (PCB). In fires involving polychlorinated biphenyls, toxic dioxins can be released. Biphenyls lead to powerful induction of the cytochrome P-450 system. Following exposure, biphenyls can be detected in adipose tissue and breast milk. Severe cases of liver damage, including fatalities, have been reported. 

Chakraborty D, Bhattacharyva A, Chatterjee J, et al. 1978. Biochemical studies on polychlorinated biphenyl toxicity in rats Manipulation by vitamin C. Int J Vitam Nutr Res 48 22-31. 

Truelove J, Grant D, Mes J, et al. 1982. Polychlorinated biphenyl toxicity in the pregnant Cynomolgus monkey A pilot study. Arch Environ Contam Toxicol 11 583-588. 

Polychlorinated biphenyls Toxicity, aquatic biota, wildlife... 

Ei ivironrr lent Absence of toxic compounds such as polychlorinated biphenyls (PCB s)... 

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). 

Polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) ai e toxic compounds of anthropogenous origin, able to accumulate in tissues of alive organisms and to cause different diseases. These compounds ai e the most dangerous for aquatic ecosystems as they easily adsorb in sludge and ai e included in food chains of biota. Humans consume PCBs and OCPs mostly with fish. 

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 and PCTs are particularly troublesome liquids because of their toxicity and persistence in the environment. They are defined as polychlorinated biphenyls, polychlorinated terphenyls, monomethyl-dibromo-diphenyl metliane, monomethyl-dichloro-diphenyl metliane or monomethyl-tetrachlorodiphenyl methane. With low electrical conductivity and heat resistance they found wide use as dielectric fluids and were formerly used as hydraulic fluids. PCBs have not been made in the UK since 1977 and whilst most new uses for the substance are banned in most countries, around two-thirds of the 1.5 million tonnes manufactured in Europe and the US prior to 1985 still remain in equipment such as transformers. PCTs have been used in the past in a restricted range of specialist industrial applications. 

Polychlorinated biphenyls (PCBs) Highly toxic organic compounds used in the electrical industry, use of w hich is now restricted. 

There is a vast range of aqueous organic pollutants with a wide toxicity profile. Some, e.g. polychlorinated biphenyls, certain herbicides, fungicides and pesticides, and organo-mercury compounds, are persistent and may bioaccumulate in the food chain. Trace contaminants such as sodium chloride, iron and phenols (especially if chlorinated) may also impart a taste to water. Typical consent levels for industrial discharges are provided in Table 13.10. 

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. 

The structural range of industrially important representatives of these groups is enormous, and includes chlorobenzenes (solvents), polychlorinated biphenyls (PCBs) (hydraulic and insulating fluids), and polybrominated biphenyls and diphenyl ethers (flame retardants). There is widespread concern over both the persistence and the potential toxicity of all these compounds, and sites that have become contaminated during their production represent a threat both to the environment and to human health. Pathways for the aerobic bacterial degradation of chlorobenzenes and chlorobiphe-nyls, and their brominated analogs have been discussed in Chapter 9, Part 1. 

Wren CD, Hunter DB, Leatherland JF, Stokes PM. 1987b. The effects of polychlorinated biphenyls and methylmercury, singly and in combination, on mink. I. Uptake and toxic responses. Arch Environ Contam Toxicol 16 441 47. 

Toxic compounds polychlorinated biphenyls, polycyclic aromatic hydrocarbons, organochlorine pesticides, chlorinated pesticides, dioxins, veterinary drug residues, hormone residues, aflatoxins, toxic compounds in shellfish. Compoimds of nutritional significance in foods vitamins, fat, lipids, carbohydrates, protein, energy-calorific value, proximates, dietary fibre, ash. Other compounds hormones in blood serum... 

Office of Prevention, Protection and Toxic Substances Phosphinothricin acetyltransferase Phenoxybenzoic acid Polychlorinated biphenyl Polymerase chain reaction Polygalacturonase Acid dissociation constant... 

In the past, mineral oil hydraulic fluids sometimes included additives such as polychlorinated biphenyls (PCBs) to improve the thermal resistance or other properties of the resulting fluids. These additives may present more toxicity risks than the primary ingredients of the hydraulic fluids. While such uses of PCBs have been discontinued, PCBs may be encountered as components of hydraulic fluids at NPL sites contaminated by hydraulic fluids (ATSDR 1993b). 

Toxic organic compounds commonly found in groundwater are presented in Table 18.4. Other toxic organic compounds (representing 1% of cases) include PCBs (polychlorinated biphenyls), 2,4-D, 2,4,5-TP (silvex), toxaphene, methoxychlor, lindane, and endrin, of which 2,4-D and silvex are commonly used for killing aquatic and land weeds. Inorganic toxic substances commonly found in... 

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]. 

Kamlet, M. J., Doherty, R. M., Carr, P. W., Mackay, D., Abraham, M. H., Taft, R. W. (1988) Linear solvation energy relationships. 44. Parameter estimation rules that allow accurate prediction of octanol/water partition coefficients and other solubility and toxicity properties of polychlorinated biphenyls and polycyclic aromatic hydrocarbons. Environ. Sci. Technol. 22, 503-509. 

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. 

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