title: Applicability of the TCDD-TEQ approach to predict sublethal embryotoxicity in Fundulus heteroclitus.
abstract: The 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) toxic equivalent quantity (TCDD-TEQ) approach was used successfully to predict lethal embryotoxicity in salmonids, but its applicability to sublethal effects of mixtures of organohalogenated compounds in other fish species is poorly known. The sublethal toxicity of two dioxin-like compounds (DLCs), 3,3',4,4'-tetrachlorobiphenyl (PCB77) and 2,3,4,7,8-pentachlorodibenzofuran (2,3,4,7,8-PnCDF), two non-dioxin-like (NDL) polychlorinated biphenyls (PCBs), 2,2',5,5'-tetrachlorobiphenyl (PCB52) and 2,3,3',4',6-pentachlorobiphenyl (PCB110), and of Aroclor 1254, a complex commercial mixture of PCBs, was assessed in Fundulus heteroclitus embryos exposed by intravitelline injection. At 16 days post-fertilization, the two DLCs and Aroclor 1254 altered prey capture ability in addition to inducing classical aryl hydrocarbon receptor-mediated responses: ethoxyresorufin-O-deethylase (EROD) induction, craniofacial deformities and reduction in body length. None of these responses was induced by the two NDL PCBs, at doses up to 5400 ng g(-1)wet weight. Dose-response curves for prey capture ability for the 2 DLCs tested were not parallel to that of TCDD, violating a fundamental assumption for relative potency (ReP) estimation. Dose-response curves for EROD induction were parallel for 2,3,4,7,8-PnCDF and TCDD, but the ReP of 2,3,4,7,8-PnCDF for F. heteroclitus was 5-fold higher than the World Health Organization (WHO) fish toxic equivalent factor (TEF) based on embryolethality in salmonids. The chemically derived TCDD-TEQs of Aroclor 1254, calculated using 3,3',4,4',5-pentachlorobiphenyl (PCB126) concentrations and it ReP for F. heteroclitus, overestimated its potency to induce EROD activity possibly due to antagonistic interactions among PCBs. This study highlights the limitations of using TEFs based on salmonid toxicity data alone for risk assessment to other fish species. There is a need to assess the variability of RePs of DLCs in different species for a variety of endpoints and to better understand interactions between DLCs and other toxic chemicals.
authors.affiliation: Institut des Sciences de la Mer, Université du Québec à Rimouski, 310 Allée des Ursulines, Rimouski, Québec G5L 3A1, Canada; Fisheries and Oceans Canada, Maurice Lamontagne Institute, P.O. Box 1000, Mont-Joli, Québec G5H 3Z4, Canada. Electronic address: rigaud.cyril@gmail.com.
authors.forename: Cyril
authors.initials: C
authors.lastname: Rigaud
authors.affiliation: Fisheries and Oceans Canada, Maurice Lamontagne Institute, P.O. Box 1000, Mont-Joli, Québec G5H 3Z4, Canada. Electronic address: catherine.couillard@dfo-mpo.gc.ca.
authors.forename: Catherine M
authors.initials: CM
authors.lastname: Couillard
authors.affiliation: Institut des Sciences de la Mer, Université du Québec à Rimouski, 310 Allée des Ursulines, Rimouski, Québec G5L 3A1, Canada.
authors.forename: Jocelyne
authors.initials: J
authors.lastname: Pellerin
authors.affiliation: Fisheries and Oceans Canada, Maurice Lamontagne Institute, P.O. Box 1000, Mont-Joli, Québec G5H 3Z4, Canada.
authors.forename: Benoît
authors.initials: B
authors.lastname: Légaré
authors.affiliation: Queen's University, 99 University Avenue, Kingston, Ontario K7L 3N6, Canada.
authors.forename: Peter V
authors.initials: PV
authors.lastname: Hodson
mesh_terms: D000818:Animals; D049628:Body Size / Q000187:drug effects; D020111:Chlorodiphenyl (54% Chlorine) / Q000737:chemistry / Q000633:toxicity; D019363:Cytochrome P-450 CYP1A1 / Q000235:genetics; D004625:Embryo, Nonmammalian / Q000187:drug effects; D005260:Female; D023781:Fundulidae / Q000196:embryology / Q000235:genetics / Q000502:physiology*; D005786:Gene Expression Regulation / Q000187:drug effects; D008297:Male; D009043:Motor Activity / Q000187:drug effects; D000072317:Polychlorinated Dibenzodioxins / Q000633:toxicity*; D011235:Predatory Behavior / Q000187:drug effects*; D012044:Regression Analysis; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D000072317:Polychlorinated Dibenzodioxins; D014874:Water Pollutants, Chemical; D020111:Chlorodiphenyl (54% Chlorine); D019363:Cytochrome P-450 CYP1A1
keywords: Aroclor 1254; Behavior; Fundulus heteroclitus; Furan; PCB; TEF