Acute Toxicity of
LAS to Various Fish Species
THOMAS O. THATCHER, Aquatic Biologist
Cincinnati Water Research Laboratory
Federal Water Pollution Control Administration
Cincinnati, Ohio
JOSEPH F. SANTNER. In Charge
Mathematical Sciences
R. A. Taft Sanitary Engineering Center
Cincinnati, Ohio
INTRODUCTION
In 1964, a series of. short-term continuous-flow-through bioassays was conducted to compare the tolerances ot 11 species of freshwater fishes "to alkyl benzene sulfonate (ABS) detergents (1). In that study three species were obviously
more resistant than the others, and statistical tests indicated differences among
several of the other eight species. Because ABS materials were being replaced in
marketed cleansing products by more readily biodegradable linear alkylate sulfonates (LAS), a similar series of tests with LAS materials was conducted to supplement the earlier study. We hope that the results of these tests will help in the
evaluation of the effects of detergent pollution, particularly the surfactant changeover, on the fish populations in areas where detergents may be a problem.
The tests with the LAS products were conducted during 1965, and all test
conditions were similar to those of the 1964 study with ABS except that only five
species of fish, representing the complete range of sensitivity to ABS, were tested.
In addition, the present study was designed to allow for better statistical evaluation of experimental factors and results.
METHODS AND MATERIALS
Similar test systems were used for both the 1964 and the 1965 tests. The 10-
liter test chambers were situated in two seven-chamber systems, and each system
received the proper amount of toxicant and water from a continuous-flow-through
proportional dilution apparatus (2).
The water was analyzed by Standard Methods (3) and had the following characteristics: versenate hardness 50 ± 0.5 mg/1 as CaC03; methyl orange alkalinity, 40 ± 5 mg/1 as CaC03; dissolved oxygen, 6.5 ± 0.5 mg/1; pH, 7. 5 ± 0.3;
and water temperature, 23 ± 1 C. Water was mixed in 5,000-gal batches and
stored in and transported through PVC or vinyl plastic, stainless steel, or glass
containers and tubing.
The LAS stock powder was supplied by the Soap and Detergent Association
and was identified by them as "Interim Sample LAS lot No. 1-1." Its components, by percentages, were: LAS, 60.8; sodium sulfate, 36.1; free oil, 0.4;
and water, 2.7. This material represented a composite sample of the products of
several member surfactant producers and was the most recent composite sample
available for research purposes.
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