A Risk-Management Strategy for PCB-Contaminated Sediments (2001) / Chapter Skim
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Appendix G: Toxicity of PCBs
Appendix G: Toxicity of PCBs
Pages 363-427
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From page 363... ...
The limitations of these toxicity data are also discussed, followed by a discussion of how this information is used in risk assessments, including toxic equivalency factors. Toxic EFFECTS OF PCBS The toxicity of PCBs is well established from laboratory and field studies (Giesy et al.
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From page 364... ...
Tmmunotoxicity, carcinogenicity, neurotoxicity, and developmental toxicity, as well as the biochemical effects of commercial PCB mixtures, have been extensively investigated in various laboratory animals, fish, and wildlife species. The mechanisms and endpoints of PCB toxicity have been reviewed (Poland and Knutson 1982; Safe 1984; Barrett 1995; Silberhorn et al.
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From page 365... ...
, dioxin-like effects comprise a diverse spectrum of sex-, strain-, age-, and species-specific effects, including carcinogenicity, immunotoxicity, reproductive or developmental toxicity, hepatotoxicity, neurotoxicity, chloracne, and Toss of body weight. The wasting syndrome occurs at high concentrations of TCDD and is characterized by a loss of body weight and fatty tissue.
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From page 366... ...
The mechanisms of neurotoxic effects of or/ho-substituted PCBs and the behavioral effects reported in epidemiological studies have been reviewed (Mater et al. 1994; Chu et al.1996; Chishti et al.1996; Eriks son and Fredriksson 1996a,b; Morse et al.
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From page 367... ...
. Of about 50 individual PCB congeners tested in PCl2 cells, di-ortho- through tetra-orthosubstituted congeners were the most potent at affecting DA content, whereas coplanar PCB congeners were ineffective (Strain et al.
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From page 368... ...
368 Cal Ct ·_.
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From page 371... ...
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From page 372... ...
372 s .~ cat cat u, o .~ cat cat u, cat cut u' o Phi cat u, o x ,\ cat ._ Al tif)
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From page 374... ...
Few studies have examined the effects of or/ho-substituted PCBs on behavioral alterations orneurotoxic effects inwildlife. Dietary exposure of mink to 2,2',4,4',5,5'-HxCB (PCB 153)
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From page 375... ...
PCB concentrations in the brains were I.5°/O of those found in the blubber. Similarly, concentrations of total PCBs in the brains of marine mammals from Greek waters were 1-2% of those found in the blubber (GeorgakopouTou-Gregoriadou et al.
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From page 376... ...
(van den Berg et al.
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From page 377... ...
<0.000005 0.00001 0.0001 Source: Data from van den Berg et al.
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From page 378... ...
1998~. Teleost TEFs Because the toxicity of coplanar PCBs vary among vertebrate taxa, recent studies have focused on determining TEFs for coplanar PCBs in fish and bird models (Bosveld and van den Berg 1994; Brunstrom et al.
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From page 379... ...
It should be noted, however, that TEF values for fish are based primarily on acute exposure data. Long-term toxicity studies with rainbow trout exposed to Tower concentrations of TCDD indicate that many toxic responses can develop after a few weeks (Van der Weiden et al.
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From page 380... ...
1993) , egg volume in populations of common terns in The Netherlands (Bosveld and van den Berg 1994)
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From page 381... ...
Limitations of TEF Approach Interactive Effects of PCBs Despite the ability of the TEF approach to predict the potency of some mixtures of planar HAHs, it assumes that toxic responses to planar HAHs are additive and that other classes of contaminants do not modify or add to the toxicity. Those assumptions are equivocal (Giesy et al.
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From page 382... ...
might not be appropriate. In addition, PCB congeners have different potencies for various endpoints, resulting in a range of potency values from which the congener-specific TEF is derived.
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From page 383... ...
The TEF approach does not consider potential adverse effects of or/ho-substituted nonplanar PCB congeners that do not interact with the AhR, but elicit nondioxin-like effects (Seegal ~ 996~. Therefore, the use of TEQs for assessing the potential toxicity of PCBs might not address all the issues of potential adverse effects by PCBs, and the risk to humans or wildlife following exposure to complex mixtures of PCBs might be biased or underestimated (Safe 1994; Birnbaum and DeVito 1995; Seegal 1996~.
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From page 384... ...
Exposure of experimental animals to weathered PCBs might provide more realistic estimates for the risk assessment of or/ho-substituted PCB congeners. A few studies have examined behavioral alterations in rats following exposure to contaminated fish from the Great Lakes (Hertzler 1990; Daly 1993~.
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From page 385... ...
The use of different dose regimens in toxicity studies adds further uncertainty to the derived TEF value and eventually to the riskassessment process. TOXICITY REFERENCE VALUES A toxicity reference value (TRY)
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From page 386... ...
(EPA 1997) uses three UFs: intertaxon variability extrapolation, where values range from ~ to 5; exposure duration extrapolation, where values range from 0.75 to 15; and toxicological endpoint extrapolation, where values range from ~ to 15.
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From page 387... ...
Freshwater salmonid species, particularly lake trout and rainbow trout, are the most sensitive of fish species. The adverse effects of PCBs on fish have been studied by t~vo primary experimental methods: ~ 1 )
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From page 388... ...
With the use of that data set, effect levels were determined for marine fish species in which critical life stages were evaluated for effects, and tissue concentrations were measured (Table G-4~. Studies were evaluated for comparability to the potential species of interest, strength ofthe cause-effect linkage, exposures to critical life stages (embryos, fry, andjuveniles)
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From page 389... ...
389 · _ au so Ct o Cq Ct V: Ct AIL o ._ o ~ ._ ~ Cal ,.
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From page 390... ...
Thus, consideration of these limitations should be made to understand the uncertainty associated with estimation of risk based on TRVs from laboratory exposure to technical PCB mixtures. Total PCB Data Considerable field data and limited laboratory data are available in which the concentrations of total PCBs in fish have been
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From page 391... ...
The information includes both dietary and tissue-residue-based effect levels of PCBs. Some toxic effects of PCE]
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From page 392... ...
Values for LOAEL, NOAEL, and ECso that are useful for derivation of TRVs have been estimated for certain PCB congeners from in ova studies. Additionally, for many bird species, the most sensitive dose metric or effects predictor for PCBs and other dioxin-like chemicals is PCB concen~ations in eggs rather than adult tissue (Giesy et al.
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From page 393... ...
Some ofthe dietary avian toxicological studies Tom the 1970s are still the most useful for deriving PCB reference doses. Alternatively, a tissue-residue-based approach can be used in which observed effects are compared with a known dose to the egg or tissue residues of total PCBs (from a congener-specific analysis)
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From page 394... ...
1974 Note: All studies are laboratory studies. Abbreviations: NOAEL, no-observed-adverse-effect-level; LOAEL, lowest-observedadverse-effect level.
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From page 395... ...
1975 aLD64: The dose that is lethal to 64% of a test population. non-ortho PCB congeners ~ 26, g I, 77, and ~ 69 are Wpically the most potent compounds, and the mono-ortho PCBs 66, 70, 105, 1 l8, 122, 156, 157, and 167 and di-ortho PCBs 128, 13S, 170, ancl lSO can also incluce EROD activ~ty (Kennedy et al.
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From page 396... ...
1989 Forster's tern (field) Reproductive 7000 19,000 Bosveld and success van den Berg 1994 Caspian terns (field)
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From page 400... ...
. 1nJectlon Egg injection Egg .
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From page 401... ...
(field) success 1994a Common Hatching TEQ Tissue <1 Bosveld and tern success harden Berg (laboratory)
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From page 402... ...
(1996~. Effect Embryo mortality and teratogenesis in chickens, decreased productivity and teratogenesis for wood ducks Decreased embryonic grown, edema in herons Embryotoxicity in Forester's tern Embryo mortality in pheasants Decreased hatching success for chickens Decreased hatching success for terns, cormorants, doves, eagles TABLE ~14 Biomagnification Factors Tom Alewife to Heron (scull Fans' for Diox~n-like Compounds Compound 2, 3, 7, 8-TCDD Total PCBs 2,3,3',4,4'-Penta-CB(105)
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From page 403... ...
Thus, when hying to characterize risk to avian species for dioxin-like compounds, the most sensitive endpoint is developmental toxicity. The biological effects of Aroclor mixtures, individual PCB congeners, TCDF, and TCDD equivalents have been assessed with egg-injection expenments.
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From page 404... ...
. The main advantages ofthese studies, especially those conducted in the last 10 years, are that the total weathered PCBs (often by PCB congener analysis as either total PCBs or TEQs)
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From page 405... ...
for the field studies, there are potential co-contaminants that might confound the interpretation of effect levels. (In many cases, co-contaminant data are available from these studies.)
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From page 406... ...
Uncertainties This discussion of uncertainty is designed to assist in the understanding ofthe relative degree of confidence in the toxicity benchmarks and available data. An uncertainty analysis is required for ecological risk assessments under EPA guidance and should be performed for the quantitative and qualitative parameters that
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From page 407... ...
is sufficient to characterize potential risk to invertebrates. Individual PCB congener data or total PCB data can then be used, if necessary, as input to dietary food-chain models for biota that consume invertebrates.
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From page 408... ...
Individual PCB congener data or total PCB data can then be used, if necessary, as input to dietary food chain models for biota that consume invertebrates. Fish It is recommended that an estimate of tissue residues of total PCBs (from a congener-specific analysis)
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From page 409... ...
The main advantages of these studies, especially those conducted in the last 10 years, are that the total weathered PCBs (often by PCB congener analysis as either total PCBs or TEQs) in the tissue of w~I`dlife species was measured and that these concentrations were related to ecologically relevant endpoints.
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From page 410... ...
van den Berg.
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From page 411... ...
1985. Toxic interaction of specific polychlorinated biphenyls and 2,3,7,8-tetrachlorodibenzo-pdioxin: increased incidence of cleft palate in mice.
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From page 412... ...
1989. Toxicity of coplanar polychlorinated biphenyls to avian embryos.
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From page 413... ...
1998. Canadian Tissue Residue Guidelines for Polychlorinated Biphenyls for the Protection of Wildlife Consumers of Biota.
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From page 414... ...
1980. Reproductive success and nest attentiveness of mallard ducks fed Aroclor 1254.
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From page 415... ...
1996b. Developmental neurotoxicity of four orthosubstituted polychlorinated biphenyls in the neonatal mouse.
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From page 416... ...
-dioxin (TCDD) on early life stages of rainbow trout ~ Salmo gairdneri, Richardson)
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From page 417... ...
1996. Toxic equivalency factors of polybrominated dibenzo-p-dioxin, dibenzofuran, biphenyl, and polyhalogenated diphenyl ether congeners based on rainbow trout early life stage mortality.
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From page 418... ...
2000. Toxicity reference values for the toxic effects of polychlorinated biphenyls to aquatic mammals.
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From page 419... ...
1997. The selective dietar5r accumulation of planer polychlorinated biphenyls in the otter (Lu~a lutra)
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From page 420... ...
1995. The ecotoxicologyofcoplanarpolychlorinated biphenyls.
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From page 421... ...
1995. Development oftoxic equivalency Lactors for PCB congeners and the assessment of TCDD and PCB mixtures in rainbow trout.
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From page 422... ...
1995. Toxic equivalency factors do not predict the acute toxicities of dioxins in rats.
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From page 423... ...
1984. Polychlorinated biphenyls (PCBs)
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From page 424... ...
1991. Neurotoxicity of Polychlorinated biphenyls: structure-activity relationship of individual congeners.
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From page 425... ...
Van den Berg, J.H. Koeman, and A
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From page 426... ...
1991. Potencies of polychlorinated dibenzo-p-d~oxin, dibenzofuran and biphenyl congeners, relative to 2,3,7,8-tetrachlorodibenzo-pdioxin for producing early life stage mortality in rainbow trout (Oncorhynchus mykiss)
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From page 427... ...
1990. Utilization of cultured chick embryo hepatocytes as in vitro bioassays for polychlorinated biphenyls (PCBs)
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