COMPARATIVE TOXICITY OF 2,3,7,8-TETRACHLORODIBENZO-P-DIOXIN TO 7 FRESH-WATER FISH SPECIES DURING EARLY LIFE-STAGE DEVELOPMENT

The toxic effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) to fat head minnow (Pimephales promelas), channel catfish (Ictalurus punctatu s), lake herring (Coregonus artedii), medaka (Oryzias latipes), white sucker (Catastomus commersoni), northern pike (Esox lucius), and zebra fish (Danio danio) were observed during early life-stage development a fter waterborne exposure of fertilized eggs. Species sensitivity based on TCDD-C-egg (TCDD concentration in eggs) was determined by effects observed over a 32-d period for all species except lake herring in whi ch a 100-d period was used. Signs of TCDD toxicity, including edema, h emorrhaging, and craniofacial malformations were essentially identical to those observed in salmonids following TCDD egg exposure and preced ed or accompanied mortality most often during the period from hatch th rough swim-up. The no-observed-effect concentrations and lowest-observ ed-effect concentrations, based on significant decreases in survival a nd growth as compared to the controls, ranged from 175 and 270 pg/g fo r lake herring to 424 and 2,000 pg/g for zebrafish, respectively. Shap es of concentration-response curves, expressed as TCDD-C-egg versus pe rcent mortality, were similar for all species and were consistently st eep suggesting that the mechanism of action of TCDD is the same among these species. The LC(egg)50s (concentrations in eggs causing 50% leth ality to fish at test termination) ranged from 539 pg/g for the fathea d minnow to 2,610 pg/g for zebrafish. Comparisons of LC(egg)50s indica te that the tested species were approximately 8 to 38 times less sensi tive to TCDD than lake trout, the most sensitive species evaluated to date. When LC(egg)50s are normalized to the fraction lipid in eggs (LC (egg.l)50s), the risk to early life stage survival for the species tes ted ranges from 16- to 180-fold less than for lake trout.