Fish bioassays of linear alkylate sulfonates (LAS) and intermediate biodegradation products

Linear alkylate sulfonates (LAS) are relatively toxic to fish when tested under static conditions by standard bioassay techniques, the median tolerance limit (TL m ) being around 3 mg/liter and 0.6 mg/liter for the C 12 and C 14 homologs, respectively. However, these materials are so readily degraded by bacterial attack that bluegill fingerlings live with no trouble in effluents from laboratory continuous flow activated sludge units being fed 100 mg/liter or more of either product. No effects on the fish were noticeable in exposures of 96 hr or more, except for slight alterations in the microscopic appearance of the gill tissue. Thus, the removal of the LAS by biodegradation is paralleled by the removal of toxicity and there is no indication that toxic intermediates accumulate during the biodegradation process. This conclusion is substantiated by the observation of a much lower degree of toxicity (TL m 75 mg/liter) for sulfophenylundecanoic acid disodium salt (mixed isomers), synthesized as a model of an intermediate degradation product. Characterization, gas chromatography and methylene blue analysis of this product are also discussed.