ABSTRACT
High-solubility alkyl sulfate (HSAS) is a new anionic surfactant for use in consumer product applications that provides enhanced water solubility and improved water hardness tolerance. A comprehensive model stream ecosystem investigation was conducted to assess ecological and toxicological effects of HSAS on stream invertebrates. Model streams were dosed with HSAS for a period of 56 days following 56 days of colonization in a single-pass, flow-through system. Exposures were control and 9.1, 24.1, 64.0, 165.8, and 426.5 microg/L based on specific analytical detection methods. Benthic abundance on gravel substrates, drift, and insect emergence were assessed. Several taxonomically unrelated taxa were found sensitive to HSAS and formed the basis of toxicological conclusions. Abundance or biomass of a limpet (Ferrissea), a bivalve (Corbicula), flatworms (Turbellaria), and a mayfly (Stenonema) was reduced at concentrations ranging from 165.8 to 426.5 microg/L. Principal response curve analysis, a constrained form of principal components analysis, demonstrated consistency with univariate analyses and identified similar populations as being sensitive to HSAS. Comparison with historical studies from the same testing site, streams, and experimental design, but with structurally related alkyl sulfate and alkyl ethoxysulfate anionic surfactants, revealed several similar trends in response profiles at the population level for both tolerant and sensitive species. Based on the comprehensive nature of the study, strength of data trends, and demonstrated sensitivity of the aquatic communities contained in the experimental system, the no-observed-effect concentration for HSAS was concluded to be 64.0 microg/L. An application factor of 1 is justified for deriving a predicted no-effect concentration) for HSAS in aquatic systems.
