vulgaris, extension of the alkyl chain to 12 carbon atoms resulted in a significant increase in toxicity to crustaceans (EC50: 0.1-1 mg dm -3 ). These results indicate that 3Br, 3Asp and 3Ala containing 1-dodecylquininium cation, which determines their potent antimicrobial properties are at least moderately toxic to multiple classes of freshwater organisms and should be thoroughly controlled as substances potentially hazardous to the aquatic environment in the case of their potential application. However, quinine-based QASs with dodecyl substituent were still less toxic than conventional QASs used in disinfectant formulations. The exact results of the acute toxicity tests toward D. magna are summarized in Table .10 (Supplementary Data).