Limitations of the toxic equivalency factor (TEF) approach for risk assessment of halogenated aromatic hydrocarbons
- Texas A and M Univ., College Station, TX (United States). Dept. of Veterinary Physiology and Pharmacology
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) and related halogenated aromatic hydrocarbons (HAHs) are present as complex mixtures of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and biphenyls (PCBs) in most environmental matrices. Risk management of these mixtures utilize the toxic equivalency factor (TEF) approach in which the TCDD (dioxin) or toxic equivalents of a mixture is a summation of the congener concentration (Ci) times TEF{sub i} (potency relative to TCDD) where. TEQ{sub mixture} = {Sigma}[Cil] {times} TEF{sub i}. TEQs are determined only for those HAHs which are aryl hydrocarbon (Ah) receptor agonists and this approach assumes that the toxic or biochemical effects of individual compounds in a mixture are additive. Several in vivo and in vitro laboratory and field studies with different HAH mixtures have been utilized to validate the TEF approach. For some responses, the calculated toxicities of PCDD/PCDF and PCB mixtures predict the observed toxic potencies. However, for fetal cleft palate and immunotoxicity in mice, nonadditive (antagonistic) responses are observed using complex PCB mixtures or binary mixtures containing an Ah receptor agonist with 2,2{prime},4,4{prime},5,5{prime}-hexachlorobiphenyl (PCB153). The potential interactive effects of PCBs and other dietary Ah receptor antagonist suggest that the TEF approach for risk management of HAHs requires further refinement and should be used selectively.
- OSTI ID:
- 203619
- Report Number(s):
- CONF-9511137--; ISBN 1-880611-03-1
- Country of Publication:
- United States
- Language:
- English
Similar Records
TEFs for dioxins and furans as MFO inducers in fish: Where do we compare potencies?
Potency of 3,3{prime},4,4{prime},5-pentachlorobiphenyl (PCB 126) and 2,3,7,8 tetrachlorodibenzo-p-dioxin (TCDD), to produce lake trout early life stage mortality