Chronic toxicity and bioaccumulation of 2,5,2',5'- and 3,4,3',4'-tetrachlorobiphenyl and Aroclor 1242 in the amphipod Hyalella azteca
Borgmann, U; Norwood, WP; Ralph, KM
The addition of 100 micrograms/L of Aroclor 1242 (A1242) or 2,5,2',5'-tetrachlorobiphenyl (TeCB) during 10 week chronic toxicity tests with Hyalella azteca resulted in complete mortality. There were no effects on survival, growth, or reproduction after addition of 30 micrograms/L. Toxic effects were observed at tissue levels of between 30 and 180 micrograms/g on a wet weight basis, and tissue levels appear to be a better indicator of toxicity than levels in water. No toxic effects were observed after additions of up to 2,700 micrograms/L of the coplanar congener 3,4,3',4'-TeCB. H. azteca has the ability to avoid accumulating in excess of 140 micrograms/g 3,4,3',4'-TeCB. The amount taken up was proportional to the amount added in water up to 100 micrograms/L, but was constant at higher additions, possibly accounting for its relatively low toxicity. The low toxicity of the coplanar congener, as compared to the non-coplanar 2,5,2',5'-TeCB, is in direct contrast to the high toxicity of coplanar PCB congeners to mammals and may be associated with slower rates of aromatic hydrocarbon metabolism in amphipods. Polychlorinated biphenyl levels measured in amphipods from Lake Ontario are approximately 100-fold below levels associated with toxicity in H. azteca, but are above levels which, through biomagnification up the food chain, lead to salmonid residues in excess of 2 micrograms/g, a tolerance limit for human consumption.