Polychlorinated biphenyls toxic equivalency factors

Clemons, J.H., L.E.J. Lee, C.R. Myers, D.G. Dixon, and N.C. Bols. 1996. Cytochrome P4501A1 induction by polychlorinated biphenyls (PCBs) in liver cell lines from rat and trout and the derivation of toxic equivalency factors. Canad. Jour. Fish. Aquat. Sci. 53 1177-1185. 

Safe, S. 1990. Polychlorinated biphenyls (PCBs), dibcnzo-p-dioxins PCDDs), dibenzofurans (PCDFs), and related compounds environmental and mechanistic considerations which support the development of toxic equivalency factors (TEFs). Crit. Rev. Toxicol. 21 51-88. 

Zabel, E.W., P.M. Cook, and R.E. Peterson. 1995. Toxic equivalency factors of polychlorinated dibenzo-p-dioxin, dibenzofuran and biphenyl congeners based on early life stage mortality in rainbow trout (Onco-rhynchus mykiss). Aquat. Toxicol. 31 315-328. 

S. Safe, Polychlorinated Biphenyls (PCBs), Dibenzo-p-dioxins (PCDDs), Dibenzofurans (PCDFs) and Related Compounds Environmental and Mechanistic Considerations Which Support the Development of Toxic Equivalency Factors (TEFs), C. R. C. Crit. Rev. Toxicol. 21 (1990) 51-88. 

Although this public health statement will focus on CDDs, it is important to note that CDDs are found in the environment together with other structurally related chlorinated chemicals, such as chlorinated dibenzofurans (CDFs) and polychlorinated biphenyls (PCBs). Therefore, people are generally exposed to mixtures of CDDs and other classes of toxicologically and structurally similar compounds. 2,3,7,8-TCDD is one of the most toxic and extensively studied of the CDDs and serves as a prototype for the toxicologically relevant or dioxin-like CDDs. Based on results from animal studies, scientists have learned that they can express the toxicity of dioxin-like CDDs as a fraction of the toxicity attributed to 2,3,7,8-TCDD. For example, the toxicity of dioxin-like CDDs can be half or one tenth or any fraction of that of 2,3,7,8-TCDD. Scientists call that fraction a Toxic Equivalent Factor (TEF). More information on TEFs can be found in Section 2.5. 

Ahlborg UG, Brouwer A, Fingerhut MA, et al. 1992. Impact of polychlorinated dibenzo-p-dioxins, dibenzofurans, and biphenyls on human and environmental health, with special emphasis on application of the toxic equivalency factor concept. Europ J Pharmacol 228 179-199. 

Ahlborg UG (1989), Chemosphere 19 603-608. Nordic risk assessment of PCDDs and PCDFs" Ahlborg UG, Brouwer A, Fingerhut MA, Jacobson JL, Jacobson SW, Kennedy SW, Kettrup AAF, Koeman JH, Poiger H, Rappe C, Safe SH, Seegal RF, Tuomisto J, van den Bergh M (1992), Eur. J. Pharmacol. 228 179-199.. .Impact of polychlorinated dibenzo-p-dioxins, diben-zofurans and biphenyls on human and environmental health, with special emphasis on application of the toxic equivalency factor concept"... 

EPA. 1991a. Workshop report on toxicity equivalency factors for polychlorinated biphenyl congeners. Risk Assessment Forum. Washington, DC U.S. Environmental Protection Agency. 

Harris M, Zacharewski T, Safe S. 1993. Comparative potencies of Aroclors 1232, 1242, 1248,1254, and 1260 in male Wistar rats-assessment of the toxic equivalency factor (TEF) approach for polychlorinated biphenyls (PCBs). Fundam Appl Toxicol 20(4) 456 63. 

The different Cl and CI2 compounds, summarized as halogenated hydrocarbons, are metabolized and excreted via urine or milk, or they are lost through expiration. However, the fate of these compounds depends on their specific characteristics (solubility, affinity to fat, liberation of Cl ). Polychlorinated dioxins and biphenyls are stored in fatty tissues. Among European people, typical levels of 30 ng TEQ diox-inskg fatty tissues have been estimated (TEQ = toxicity equivalence factor in comparison to 2,3,7,8-tetrachlordibenzodioxin Eorth et al. 2001). These substances are mobilized, for example at the onset of the... 

Hanberg A., Waern E, Asplund L. Haglund E. and Safe S. (1990) Swedish dioxin survey determination of 2,3,7,8-TCDD toxic equivalent factors for some polychlorinated biphenyls and naphthalenes using biological tests. Chemosphere, 20, 1161-1164. 

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