Residues of PCBs

Residues of PCBs in animal tissues include not only the original congeners themselves, but also hydroxy metabolites that bind to cellular proteins, for example, transthyretin (TTR Klasson-Wehler et al. 1992 Brouwer et al. 1990 Fans et al. 1993). Small residues are also found of methyl-sulfonyl metabolites of certain PCBs (Bakke et al. 1982, 1983). These appear to originate from the formation of glutathione conjugates of primary epoxide metabolites, thus providing further evidence of the existence of epoxide intermediates. Further biotransformation, including methylation, yields methyl-sulfonyl products that are relatively nonpolar and persistent. 

Table II. Residues of PCB in Tern and Green Bayl Eggs Collected from Lake Poygan...

In practice there is little evidence for the migration of PCBs from packaging (JFSSG, 1999a). There is considerably more evidence for the other two routes leading to PCBs in food. Indeed, historical trends can be drawn up for residues of PCBs in human fat, breast milk and fish. There has been a very gradual decline in levels of these organochlorine compounds in the environment, food and human tissues. This is entirely consistent with the persistence of these compounds. 

Indirect food additives, manufacturing of foodpackaging material Temporary tolerances for residues of PCBs as unavoidable environmental or industrial contaminants Finished animal feed for food- Yes 0.2 ppm FDA 1998b 21 CFR 509.15 FDA 1998c 21 CFR 509.30... 

The identification of PCB residues in fish, wildlife, and human tissues has been reported since the 1970s (9—13,20—26). The results of these analytical studies led to the ultimate ban on further use and production of these compounds. The precise composition of PCB extracts from biota samples is highly variable and depends, in part, on the specific analyte and the commercial PCB preparations associated with a contaminated area (14). PCBs found in a composite human milk sample from Michigan (26) were highly complex, and the congener composition and their relative concentrations did not resemble any of the commercial PCB preparations. This fact raises obvious problems with regard to the ha2ard assessment of PCB mixtures (27). 

Butler PA, Schutzmann RL. 1978. Fish, wildlife and estuaries Residues of pesticides and PCBs in estuarine fish, 1972-1976—national pesticide monitoring program. PesticMonitJ 12 51-59. 

Both PCDDs and PCDEs are refractory lipophilic pollutants formed by the interaction of chlorophenols. They enter the environment as a consequence of their presence as impurities in pesticides, following certain industrial accidents, in effluents from pulp mills, and because of the incomplete combustion of PCB residues in furnaces. Although present at very low levels in the environment, some of them (e.g., 2,3,7,8-TCDD) are highly toxic and undergo biomagnification in food chains. 

PCDDs and PCDEs, together with coplanar PCBs, can express Ah-receptor-mediated toxicity. TCDD (dioxin) is used as a reference compound in the determination of TEFs, which can be used to estimate TEQs (toxic equivalents) for residues of PHAHs found in wildlife samples. Biomarker assays for Ah-receptor-mediated toxicity have been based on the induction of P450 lAl. TEQs measured in field samples have sometimes been related to toxic effects upon individuals and associated ecological effects (e.g., reproductive success). 

Surhcial stream sediments in the San Francisco estuarine system during 1972 had high residues (350 to 1400 pg/kg DW) at several locations (Phillips and Spies 1988). However, residues were highly variable between sites (Law and Goerlitz 1974). In 1984, low to intermediate concentrations of PCBs (9 to 60 pg/kg DW) were measured at four locations in the San Francisco Bay. Overall, congener profiles resembled Aroclor 1254 and were dominated by pentachlorobiphenyl isomers (NOAA 1987). The patterns of the 11 reported congeners were variable between areas, indicating many sources of different PCB mixtures. 

When compared to other cetaceans, PCB residues in blubber of harbor porpoises (Phocoena phocoena) from the Black Sea showed a measurable sexual difference. PCB concentrations were lower in older female porpoises possibly due to lactational transfer to their calves, while in males the PCB concentrations were positively correlated with increasing age (Tanabe et al. 1997). In stellar sea lions (Eumetopias jubatus), the transfer rate of PCBs through lactation was estimated at 80% of the total body PCB burden of adult females (Lee et al. 1996). PCB concentrations in liver of the stellar sea lion from the Bering Sea increased with increasing age and correlated positively with those of blubber (Lee et al. 1996). In ringed seals (Phoca hispida) from the Russian Arctic, lactational transfer of PCBs was estimated at 25% of whole-body burden in the mature female (Nakata et al. 1998), or about one third that of stellar sea lions. In grey seals (Halichoerus... 

The upper Hudson River was massively contaminated with PCBs from an industrial plant for several decades prior to 1975. All fishing in this section in 1976 was banned because of PCB contamination. The prohibition is still in effect because, in part, of measurable PCB residues in caged fishes from this area (Table 24.9) (Jones et al. 1989). Striped bass (Morone saxatilis) collected near Troy and Albany, New York, contained higher concentrations in muscle of PCB 77 (37 pg/kg FW) and PCB 126 (8 pg/kg FW) than conspecifics from other locations in New York (Hong et al. 1992). Almost all (99%) the PCB toxicity in muscle of striped bass was attributed to PCBs 77, 105 (62 pg/kg FW), and 126 (Hong et al. 1992). 

The highest total PCB concentrations recorded in terrestrial mammalian wildlife occurred in fat and liver tissues of species collected near urban areas di-ort/jo-congeners were the major contributors to PCB tissue burdens (Table 24.12). Atmospheric transport of PCBs governed uptake in terrestrial mammalian herbivores and predators. For example, PCB residues in tissues of voles and shrews in the Scandinavian peninsula directly correlated with fallout loadings (Larsson et al. 1990). An increase in atmospheric deposition of PCBs increased PCB burdens in plants, herbivores, and predators of the herbivores. But herbivores and predators differentially metabolized PCBs, raising concentrations of highly chlorinated congeners in predators and concentrations of the more easily metabolized low-chlorinated PCBs in herbivores (Larsson et al. 1990). 

High-dose fish had 58% dead survivors had egg production reduced 77% and their livers had 33 mg total PCBs/kg DW. The two lower dose groups had 60 and 62% reduction in egg production and liver residues of 3 and 12 mg total PCBs/kg DW, respectively. Food consumption declined with increasing dose. Egg production was related to pituitary gonadotropin content and food consumption... 

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