PCBs , contaminants from aroclor

Concentrations of total PCBs — measured as Aroclors 1248, 1254, and 1260 — in adult freshwater fishes in the United States from noncontaminated sites declined between 1976 and 1984 (Table 24.9), and more than 90% of all analyzed samples contained measurable quantities of PCBs during this period (Schmitt et al. 1990). Total PCB concentrations in domestic freshwater fishes in 1986/87 from contaminated sites were as high as 124,000 pg/kg FW (USEPA 1992a). In general, total PCB concentrations in domestic freshwater fishes sampled between 1976 and 1984 were... 

Polychlorinated biphenyls (PCBs) were manufactured by catalytic chlorination of biphenyl to produce complex mixtures, each containing 60-90 different PCB molecular species or congeners (see Chaps. 1 and 4). In the United States, PCB mixtures were manufactured by Monsanto under the trade name Aroclor and were widely used as dielectric fluids in capacitors and transformers from 1929 to 1978. PCBs are widespread contaminants of aquatic sediments and continue to be a focus of environmental concern because they tend to accumulate in biota and are potentially toxic. The following sections show the most effective bioremediation techniques applied to various PCB contaminated environments ... 

Bedard et al. [245] reported that PCB dechlorination was stimulated by adding 2,5,3, 4 -tetrachlorobiphenyl (25-3 4 -CB) to slurries (incubated under methanogenic conditions) of sediments contaminated with Aroclor 1260 from Woods Pond (MA). The 25-3 4 -CB was converted stoichio-metrically to 25 - 3 -CB and stimulated a selective para-dechlorination which decreased the penta- through heptachlorobiphenyls containing 234-, 245-, or 2345-chlorophenyl groups by up to 83% in 12 weeks. 

The first results from the use of PLS were reported by Dunn fit al (6) who estimated the composition of PCB contaminated waste oil in terms of Aroclor mixtures. Stalling gt al (13), who reported on the characterization of PCB mixtures and the use of three-dimensional plots derived from principal components, demonstrated that the fractional composition of TCDD and other PCDD residues were related to their geographical origins. These two reports (6,13) described the application of an advanced chemometric tool in residue studies and illustrated the... 

It has become clear over the past ten years that the 1980s demonstration of anaerobic microbial dechlorination of PCBs is probably the most important discovery in the field of PCB biotransformations since Ahmed and Focht first demonstrated in 1973 that PCBs were biodegradable. Many new anaerobic microbial activities have been enriched and characterized from anaerobic fresh water and marine environments and heavily polluted industrial sediments. These anaerobic cultures are capable ofdechlorinating PCBs, thereby transforming highly chlorinated Aroclors to lower-chlorinated mixtures. This natural attenuation process is an important contributor to PCB degradation and detoxification in the environment and can form the basis for intrinsic remediation of many PCB-contaminated sites. 

Pentachlorinated biphenyls and hexachlorinated biphenyls are the major PCB groups typically found in P. viridis. PCBs are sold commercially as technical mixtures, called Aroclors, each with a specific pattern of chlorination. Patterns have been determined for Aroclor mixtures 1221, 1232, 1242, 1248, 1254, 1260 and 1262 (Frame et al., 1996). Principal component analysis (PCA) was performed to compare the relative PCB congener profile of mussel tissues analysed in 2002 and the commercial Aroclor mixtures (Fig. 15.14). The closest match in the PCB data for P. viridis samples collected in Singapore from our study is the common Aroclor 1254. The slight discrepancy is due to the presence of PCB-149 in mussel tissue and a greater prominence of PCB-110 and -118 in Aroclor 1254. PCA analysis revealed that samples from the west Straits of Johore (Wl, W2 and W3) contain more penta-CBs and less hexa-CBs than samples from the east Straits (E6, E7 and E8). The sample collected in the south of Singapore (S4) has an intermediary pattern of PCB contamination. A similar match has been observed in marine crabs and fishes... 

Similar results were observed in analogous rat exposures [278], in which animals exposed to the racemic PCB technical formulation Aroclor 1254 were enriched in El-PCB 95 on Chirasil-Dex and (+)-PCB 149 in adipose, liver, and skin. Enantiomer reversal, such as (—)-PCB 149 enrichment in blood, was also found. However, only E2-PCB 95 on Chirasil-Dex was enriched in rats exposed to extract with racemic PCB 95 from a soil contaminated with Chlorophen, another formulation, suggesting that differences in congener distributions and concentrations affect enantioselective toxicokinetics. 

Sediments downstream from highly contaminated sites may also be affected by PCB residues. Maximum total PCB concentrations of 5,700,000 and 36,000 ng/g were detected in sediments from the St. Lawrence River and Raquette River, respectively these sites are within the boundaries of Akwesasne, New York, a Native American community downstream from a Superfund site (ATSDR 1995). Vanier et al. (1996) measured PCB concentrations at three sites along the St. Lawrence River exposed to high potential PCB contamination, including two in urban Montreal, Quebec. PCB concentrations in the top 10 cm of the sediment were 3,800-16,000 ng/g dry weight Aroclor 1254 equivalent. In the most contaminated site, located in an industrial area, PCB inputs appear to have been relatively constant since about 1982. Di-and tri-chlorinated congeners make up more than 70% of the profile in the more concentrated area and less elsewhere along the river. 

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