Comparison of toxicity of congener-153 of PCB, PBB, and PBDE to Daphnia magna.

Acute and reproductive toxicity tests were performed to assess the effects of two polybrominated flame retardants, polybrominated biphenyl (PBB)-153, polybrominated diphenyl ether (PBDE)-153, and polychlorinated biphenyl (PCB)-153 on Daphnia magna. According to the 24-h acute toxicity test, up to concentration of 210 microg/L, these chemicals were not toxic to Daphnia. In the reproductive tests, we used concentrations of 12.5, 25, 50, and 100 microg/L. At the concentrations of 50 and 100 microg/L, the Daphnia started to die after the second test day, and there were no Daphnia alive on the fourth test day. The testing was continued using the concentrations of 12.5 and 25 microg/L. The reproductive tests were then repeated using only concentrations of 12.5 and 25 microg/L. The results, based on the weight per volume (w/v) concentrations, showed that of the three compounds we tested PCB-153 had the most severe effects on the Daphnia reproduction. PBDE-153 was the least toxic, although in this group, too, offspring production was significantly lower and mortality significantly higher than those in the control group. Also, it was observed that PCB-153 accumulated into the parent Daphnia nearly three times more actively than the two other chemicals we tested. These chemicals, although having very similar structures, seem to affect differently the reproduction of Daphnia. They also seem to accumulate differently into Daphnia. Thus, further research data are needed to understand the mechanisms responsible for the effects caused by these kinds of chemicals and to assess their risks accurately.