PCBs polychlorinated

BTEX Benzene, toluene, xylene PCB Polychlorinated biphenyl... 

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. 

PCB Polychlorinated biphenyls. Aka polychloro-biphenyls. Difficult to remediate chemical used in old-style transformers. Concentrated PCBs used to be referred to as "1268". 

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... 

P, pseudogenes PAHs, polycyclic hydrocarbons PCBs, polychlorinated biphenyls. 

PCB-1242 (Arochlor 1242) (PCB-polychlorinated biphenyls) PCB-1254 (Arochlor 1254) (PCB-polychlorinated biphenyls) PCB-1221 (Arochlor 1221) (PCB-polychlorinated biphenyls) PCB-1232 (Arochlor 1232) (PCB-polychlorinated biphenyls) PCB-1248 (Arochlor 1248) (PCB-polychlorinated biphenyls) PCB-1260 (Arochlor 1260) (PCB-polychlorinated biphenyls) PCB-1016 (Arochlor 1016) (PCB-polychlorinated biphenyls) Toxaphene... 

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... 

ALAD = delta-aminolevulinic acid dehydratase DMSA= dimercaptosuccinic acid NMDA= N-methyl- D-aspartate PCBs = polychlorinated biphenyls XRF = X-ray fluorescence... 

DBP = Dibutyl phthalate BEHP = Bis (2-ethylhexyl) phthalate PCB = Polychlorinated biphenyls ND = Not done... 

Fig. 3 Scientific studies in water. Ph pharmaceuticals Ft phthalates Fu fungicides HA acidic herbicides HCB hexachlorobenzene PCBs polychlorinated biphenyls OCs organochlorine pesticides PPs polar pesticides...

Fig. 4 Scientific studies in sediments. HBCD hexabromocyclododecane PCBs polychlorinated biphenyls OCs organochlorine pesticides PCN polychlorinated naphthalene DDTs dichloro diphenyl trichloroethane...

Fig. 5 Scientific studies in biota. DDTs dichloro diphenyl trichloroethane HCB hexachlorobenzene HCHs hexachlorocyclohexanes OCs organochlorine pesticides OPs phosphorate pesticides PCBs polychlorinated biphenyls HBCD hexabromocyclododecane...

Abbreviations PAH = polyaromatic hydrocarbon, TCDD = Tetrachlorodibenzo-p-dioxin, PCB = polychlorinated biphenyl, PBB = polybrominated biphenyl, TBTO = tributyltin oxide, DBTO = dibutyltin oxide, TPT = triphenyltin. 

NPDES = National Pollutant Discharge Elimination System NTP = National Toxicology Program OSHA = Occupational Safety and Health Administration OW = Office of Water PCB = Polychlorinated Biphenyl RfD = Reference Dose STEL = Short-term Exposure Limit TLV = Threshold Limit Value TSCA = Toxic Substances Control Act TWA = Time Weighted Average WHO = World Health Organization... 

GC-EI-MS permits the direct analysis of mixtures, e.g., to analyze synthetic byproducts an advantage that made GC-EI-MS benchtop instruments become widespread in modem synthetic laboratories. The GC-EI-MS combination is especially successful in monitoring environmental pollutants such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), polychlorinated dibenzo-dioxins (PCDDs), polychlorinated dibenzofuranes (PCDFs), or other volatile organic compounds (VOCs). 

A second reason why marine pollution is difficult to measme lies in the large number of pollutants being introduced and the myriad of pathways by which they enter the oceans. In 2006, 82,000 different chemicals were in commercial use, with approximately 1000 new ones being added annually. Most have the potential to reach the ocean. In some cases, groups of these compoimds can be measured in one analysis, such as the PCBs (polychlorinated biphenyls) and PAHs (polycyclic aromatic hydrocarbons). Nevertheless, a large number of analyses are required to measme all the pollutants that can potentially be present in seawater. 

When exposed to fire, black soot containing PCBs, polychlorinated dibenzofurans, and chlorinated dibenzo-p-dioxins is formed (NIOSH, 1997). 

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