AbstractThe first comprehensive evaluation of the environmental safety of three similar cationic surfactants to aquatic life is reported. Toxicity tests were conducted that exposed freshwater and marine species, representing three trophic levels, to the dialkyl dimethyl ammonium compounds. The studies were conducted in a high‐quality laboratory water and in river waters that were used to model realistic receiving streams. Most current laboratory test methods for the assessment of chemical effects on aquatic life do not consider the physical and chemical properties of the test material in surface waters. This safety assessment shows that these considerations are important in developing realistic conclusions about the ecological safety of cationic surfactants. In tests using river water, acute and chronic toxicities and bioconcentration were considerably less than those in corresponding tests conducted in filtered laboratory waters. This reduction in toxicity and/or uptake was attributable to the aqueous insolubility of the surfactants, strong adsorption to natural solids and tendency to form chemical complexes with anionic substances. The mean ratio of the concentration of anionic to cationic surfactants in municipal sewage treatment plant effluent is 4:1. Safety margins were calculated for daphnids and fathead minnows using the ratio of the no observed effect concentration, determined from chronic toxicity tests, to mean measured surface water concentrations. Safety margins for fish and daphnids were 7 and 11, respectively, for a river having a low wastewater effluent dilution factor of 10. For a river with a higher dilution factor of 150, the values were 115 (fish) and 190 (daphnids). Projected safety margins for marine invertebrates and fish were several orders of magnitude greater than those for freshwater species. Based on available information and expected usage levels, the projected environmental impact of these surfactants on aquatic life is minima
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