Polychlorinated Biphenyls PCBs

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. 

PCBs have been in extremely wide use in numerous industrial applications from the 1930s. The US EPA estimated that roughly 600,000 tons of PCBs were purchased by US industry from the time they were first manufactured in 1929-1930 and the mid-1970s when this production was restricted in many developed countries due to environmental concerns. Globally, more than one million tons were produced and these compounds are still under production in many Asian countries and worldwide (Table 2). 

The hydrogen atoms on the biphenyl nucleus are replaced by from one to ten chlorines, for a total of 209 possible congeners. We omit here the explanation of the PCBs classification. We can say only that the congeners are numbered by a scheme 

The commercial formulations of PCBs are made by controlled chlorination of biphenyl. Each formulation contains various percentages of many of the 209 individual congeners, and there are significant variations among individual production lots. Hazardous waste samples may contain mixtures of two or more commercial formulations. 

PCBs are extremely stable to heat, chemical, and biological decomposition. They are excellent insulating and cooling fluids, extensively used for many years in manufacture of transformers and capacitors. PCBs are also used in hydraulic fluids, lubricating oils, paints, adhesive resins, inks, fire retardants, wax extenders, and numerous other products. The chemical and physical properties of PCBs make the remediation of polluted sites difficult. They resist degradation and absorb into soils and colloidal materials in water. Some persist with half-lives of 8-15 years in the environmental compartments. This stability contributes to their dispersion in the environment and long-range air pollution. Because they are lipophilic, these species are stored in fatty tissues and accumulate in the food webs (see Section 2.2). 

CZE 01 Jan 1999 The chemical is severely restricted. Production, import, export and distribution of the preparations containing more than 0.005% by weight of the substance is banned (with exception of mono-and dichlorinated biphenyls). The production and import ofthe substance for research, scientific and analytic purposes in quantity less than 100 g per year from one producer or importer is permitted. 

The chemical is banned. General prohibition of PCB. The use and import of any preparation with a PCB content of more than 0.005% is prohibited. 

IPCS ENVIRONMENTAL HEALTH CRITERIA. 2.. 1976 lARC MONOGRAPH, 18,43.1978 lARC MONOGRAPH. SUPPL.4,217,1982 IPCS ENVIRONMENTAL HEALTH CRITERIA. 140,. 1992 IPCS HEALTH AND SAFETY GUIDE, 68, 1992 

Well known trademarks are Arochlor 1254 and Clophen A 50, with the last two digits indicating chlorine contents of 54% and 50%, respectively, on a weight basis. The higher the chlorine content, the greater is the relative amount of heavily chlorinated and bioresistant congeners in the mixture. 

Among important previous applications of PCB mixtures are hydraulic fluids, insulation dielectrics in transformers and condensers, plasticizers in plastics, outdoor paints and printer s ink and different sealing and construction products for building and mounting purposes. 

The PCBs as environmental contaminants were first detected in Baltic Sea seals and herring in the 1960s (Jensen, 1966). Heavy bioaccumulation and biomagnification can result in very high concentrations in the fatty tissues of top predators, especially in aquatic food webs. The PCBs are also subject to long-distance air distribution and today they have contaminated the biosphere worldwide (Skaare et al., 2002). 

The PCBs are very efficiently bioaccumulated and biomagnified in food webs in particular, congeners with more than five chlorines are very persistent, with slow or practically absent metabolism. The substances are stored in adipose and fatty tissues and the only effective way for organisms to get rid of the heavier PCBs is through lipid-rich secretions such as mammalian milk, egg yolk, etc. (Skaare et al., 2002). This will, of course, result in serious exposure of embryos and offspring of the following generation. 

The acute toxicity exerted by PCBs is generally low. The most prominent effect is the pronounced induction of the MFO system in different tissues, with increased de novo synthesis and increased levels in several cytP450 isozymes. The PCBs in the environment occur as a mixture of congeners and every congener exerts specific toxicity, with some PCBs exerting exclusive effects. One such effect is the capability for planar PCBs to bind to and stimulate the cytoplasmatic aryl hydrocarbon receptor in the cell, the same receptor that is stimulated by the highly toxic polychlorinated dibenzodioxins (PCDDs) (see below). 

By varying the munber and the position of the chlorine atoms, there are 209 theoretical PCB congeners (Table 1). Most of these have been shown to be present in the PCB mixtures that have been available on the market. Recently, interest has been focused on 12 congeners (four non-ortho and ten mono-ortho) due to their similar toxicological properties to 2,3,7,8-TCDD. 

The analysis starts with screening. Antibiotics can be detected with the help of the bacteria whose growth they inhibit. Their differentiation can be further improved by means of an electrophoretic preliminary separation. 

In principle, the same isolation and separation methods and mass spectrometric techniques are used for the unambiguous identification of veterinary medicines as for pesticides (cf. 9.4.3). Enzyme immunoassays are also used (cf. 2.6.3). 

The PCBs are complex mixtures of substances which have been on the market since 1950. They are widely used, e. g., as transformer oil, hydraulic fluid, heat exchange medium, dielectric fluid in condensers, plasticizer and additive for printing ink. Formula 9.3 shows 2,2, 5,5 -tetrachlorobiphenyl (I) and 2,2, 4,5,5 -pentachlorobiphenyl (II) as examples. 

As a result of their widespread use, the PCBs also came into contact with food. Because of their persistence and solubility in fat, they accumulated like in the case of DDT (cf. 9.4.2.1). Therefore, they have been increasingly identified in fatty foods since their discovery. This and the fact that PCBs can produce highly toxic dioxins (cf. 9.10) in the combustion process led to the banning of the production and application of PCBs in 1989. In Germany, the contamination with PCB, e. g., in milk fat (mg/kg) has subsequently fallen on average 0.012 (1986), 0.007 (1992), 0.003 (2001). 

Lbrary Wiley6 Spectnjm 132276 Name 1,1 -Biphenyl, 2,4-dichloro 

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

The aim of the first example is to look for polychlorinated biphenyls (PCB) for which C-NMR spectra, measured in deuterochloroform, as well as the partition coefficients between 1-octanol and water arc known. Since it is not reliable to per-... 

The performance of SCWO for waste treatment has been demonstrated (15,16). In these studies, a broad number of refractory materials such as chlorinated solvents, polychlorinated biphenyls (PCBs), and pesticides were studied as a function of process parameters (17). The success of these early studies led to pilot studies which showed that chlorinated hydrocarbons, including 1,1,1-trichloroethane /7/-T5-6y,(9-chlorotoluene [95-49-8] and hexachlorocyclohexane, could be destroyed to greater than 99.99997, 99.998, and 99.9993%, respectively. In addition, no traces of organic material could be detected in the gaseous phase, which consisted of carbon dioxide and unreacted oxygen. The pilot unit had a capacity of 3 L/min of Hquid effluent and was operated for a maximum of 24 h. 

TSCA also addresses the problem of polychlorinated biphenyls (PCBs) and chlorinated fluorocarbons (CECs). EPA has developed regulations on the cleanup, handling, and disposal of PCBs. The manufacture and use of CECs has been banned for all but essential uses, in accordance with the Montreal Agreement, an international treaty on worldwide use of CECs. 

Common examples of compounds that are amenable to carbon adsorption are aromatics (benzene, toluene) and chlorinated organics (trichloroethylene, trichloroethane [71-55-6, 75 -(9(9-j5y, tetrachloroethylene, polychlorinated biphenyls (PCBs), DDT /T(9-77-77, pentachlorophenol [87-86-5J. Compounds that are not adsorbed effectively by carbon include ethanol [64-17-5], diethylene glycol [111-46-6], and numerous amines (butylamine [109-73-9, 13952-84-6, 75-64-9], triethanolamine [102-71-6], cyclohexylamine [108-91-8], hexamethylenediamine [108-91-8] (1). Wastewater concentrations that are suitable for carbon adsorption are generally less than 5000 mg/L. 

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). 

SW-846, is used to measure emissions of semivolatile principal organic constituents. Method 0010 is designed to determine destruction and removal efficiency (DRE) of POHCs from incineration systems. The method involves a modification of the EPA Method 5 sampling train and may be used to determine particulate emission rates from stationary sources. The method is applied to semivolatile compounds, including polychlorinated biphenyls (PCBs), chlorinated dibenzodioxins and dibenzofurans, polycyclic organic matter, and other semivolatile organic compounds. 

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. 

Alkylphenols, ammonia, asbestos, chlorinated paraffins, 4-chloroaniline, cyanide, detergents, di- -butyl phthalate, polyaromatic hydrocarbons (PAHs e.g. anthracene, benzopyrene, methylcholanthrene, /i-naphthoflavone), nitrate, nitrite, petroleum oil, phenol, pentachlorophenol, 4-nitrophenol, dinitro-o-cresol, polychlorinated biphenyls (PCBs especially coplanar), polychlorinated dioxins, polybrominated naphthalenes, /i-sitosterol, sulfide, thiourea, urea, acid water, coal dust... 

Polychlorinated Biphenyl (PCB) Sources, Fire Training Areas, and Fill... 

Polychlorinated biphenyls (PCB) L S A Lubricants and hydraulic fluids Pesticides Plasticizer in paint and polymers Plasticizer (polymers) Transformer oils... 

Polychlorinated biphenyls (PCBs) zero 0.0005 Skin changes thymus gland problems immune deficiencies reproductive or nervous system difficulties increased risk of cancer Runoff from landfils discharge of waste chemicals... 

Extraction, employs a liquid solvent to remove certain compounds from another liquid using the preferential solubility of these solutes in the MSA. For instance, wash oils can be used to remove phenols mid polychlorinated biphenyls (PCBs) from die aqueous wastes of synthetic-fuel plants and chlorinated hydrocarbons from organic wastewater. 

Liver cancer can also be a consequence of exposure to hepatotoxic chemicals. Natural hepatocarcinogens include fungal aflatoxins. Synthetic hepato-carcinogens include nitrosoamines, certain chlorinated hydrocarbons, polychlorinated biphenyls (PCBs), chloroform, carbon tetrachloride, dimethyl-benzanthracene, and vinyl chloride.Table 5.15 lists the chemical compounds that induce liver cancer or cirrhosis in experimental animals or... 

TCDD is the most potent inducer of chloracne. This has been well known since the accident in Seveso, Italy, in 1976 in which large amounts of TCDD were distributed in the environment subsequent to an explosion in a factory that produced a chlorophenoxy herbicide, 2,4,5-T. TCDD is an impurity produced during the production of 2,4,5-T. The most common long-term effect of TCDD exposure was chloracne. Exposed individuals also suffered increased excretion of porphyrins, hyper-pigmentation, central nervous system effects, and liver damage and increased risk of cancer was a long-term consequence of the exposure. In addition to TCDD, polychlorinated biphenyls (PCBs), polychlorinated dibenzofurans, and polychloronaphthalens cause chloracne as well as other effects typical of TCDD. 7i... 

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

The values of n and the corresponding N which are necessary to resolve 50-90% of the constituents of a mixture of 100 compounds are listed in Table 1.5, thus making clear the limitations of one-dimensional chromatography. For example, to resolve over 80 % of the 100 compounds by GC would require a column generating 2.4 million plates, which would be approximately 500 m long for a conventional internal diameter of 250 p.m. For real mixtures, the situation is even less favourable to resolve, for example, 80 % the components of a mixture containing all possible 209 polychlorinated biphenyls (PCBS) would require over lO plates. 

In general, capillary gas chromatography provides enough resolution for most determinations in environmental analysis. Multidimensional gas chromatography has been applied to environmental analysis mainly to solve separation problems for complex groups of compounds. Important applications of GC-GC can therefore be found in the analysis of organic micropollutants, where compounds such as polychlorinated dibenzodioxins (PCDDs) (10), polychlorinated dibenzofurans (PCDFs) (10) and polychlorinated biphenyls (PCBs) (11-15), on account of their similar properties, present serious separation problems. MDGC has also been used to analyse other pollutants in environmental samples (10, 16, 17). 

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