Assessment of the potential toxicity of a linear alkylbenzene sulfonate (LAS) to freshwater animal life by means of cladoceran bioassays.

The acute and chronic toxic effects of LAS on the cladocerans Daphnia similis, Ceriodaphnia dubia and Ceriodaphnia silvestrii were tested. Both types of toxicity bioassays and the methods of culture and stock maintenance of the test organisms conformed to the recommendations of ABNT (Brazilian Society of Technical Standards), which closely follow the standard methods of USEPA. The results obtained for EC(50) (48 h) were: 14.17 mg L(-1) for D. similis, 11.84 mg L(-1) for C. dubia and 13.52 mg L(-1) for C. silvestrii. In the chronic toxicity tests performed on C. dubia and C. silvestrii, there was a significant decrease in the fecundity of the exposed animals; the value of NOEC for C. dubia and C. silvestrii were 1.00 mg L(-1) and 2.50 mg L(-1), respectively. Cladoceran bioassays provided evidence that LAS concentration as low as 1.00 mg L(-1) can damage invertebrate animal life in freshwaters, concentrations that can be found in many eutrophic rivers and reservoirs.