Nine polychlorinated dibenzo-p-dioxins (PCDDs) and 2,3,7,8-tetrachlorodibenzofuran (TCDF) were tested in the Japanese medaka embryo bioassay. Individual embryos were exposed to varying nominal concentrations of a PCDD or 2,3,7,8-TCDF under static conditions. The LC50 with 95% confidence intervals for survival to 3 days post-hatch were as follows: 2,3,7,8-TCDD, 13 (10-17) nanograms (ng)/liter (L) (parts per trillion); 2,3,7,8-TCDF, 16 (12-22) ng/L; 1,2,3,7,8-PeCDD, 27 (23-31) ng/L and 1,2,3,4,7,8-HCDD, 2900 (718-11717) ng/L. Both 1,2,7,8-TCDD and 2,3,7-TriCDD caused a concentration dependent increase in visible lesions from 50 to 50000 ng/L. In the 1,2,7,8-TCDD exposed embryos, lethality was observed only at the highest concentration tested (50000 ng/L). For 2,3,7-TriCDD, there was no concentration related increase in lethality from 50 to 50000 ng/L. At 50000 ng/L, 1,3,6,8-TCDD, 2,8-DCDD and 2,3-DCDD did not cause any visible toxicity. The octachlorodibenzo-p-dioxin congener did not cause any visible toxicity at 10000 ng/L. The toxic PCDDs and 2,3,7,8-TCDF caused the same sequela of lesions in the developing Japanese medaka, suggesting that they may act through a common mechanism. These results demonstrate that 2,3,7,8-TCDF and PCDDs with the four lateral positions chlorine substituted and at least one other position non-substituted are toxic to the Japanese medaka embryo. The structure activity relationship observed here is similar to that observed in guinea pigs, mice and trout eleutheroembryos.
All Science Journal Classification (ASJC) codes
- Environmental Engineering
- Environmental Chemistry
- Health, Toxicology and Mutagenesis