Comparative toxicity of 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin to seven freshwater fish species during early life‐stage development

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Abstract
The toxic effects of 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin (TCDD) to fathead minnow (Pimephales promelas), channel catfish (Ictalurus punctatus), lake herring (Coregonus artedii), medaka (Oryzias latipes), white sucker (Catastomus commersoni), northern pike (Esox lucius), and zebrafish (Danio danio) were observed during early life‐stage development after waterborne exposure of fertilized eggs. Species sensitivity based on TCDD‐Cegg (TCDD concentration in eggs) was determined by effects observed over a 32‐d period for all species except lake herring in which a 100‐d period was used. Signs of TCDD toxicity, including edema, hemorrhaging, and craniofacial malformations were essentially identical to those observed in salmonids following TCDD egg exposure and preceded or accompanied mortality most often during the period from hatch through swim‐up. The no‐observed‐effect concentrations and lowest‐observed‐effect concentrations, based on significant decreases in survival and growth as compared to the controls, ranged from 175 and 270 pg/g for lake herring to 424 and 2,000 pg/g for zebrafish, respectively. Shapes of concentration–response curves, expressed as TCDD‐Cegg versus percent mortality, were similar for all species and were consistently steep suggesting that the mechanism of action of TCDD is the same among these species. The LCegg50s (concentrations in eggs causing 50% lethality to fish at test termination) ranged from 539 pg/g for the fathead minnow to 2,610 pg/g for zebrafish. Comparisons of LCegg50s indicate that the tested species were approximately 8 to 38 times less sensitive to TCDD than lake trout, the most sensitive species evaluated to date. When LCegg50s are normalized to the fraction lipid in eggs (LCegg,l50s), the risk to early life stage survival for the species tested ranges from 16‐ to 180‐fold less than for lake trout.

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