Freshwater crustaceans of the D. magna species are highly sensitive to the presence of a wide range of chemicals in water, including cationic surfactants. QASs of synthetic origin such as benzalkonium chloride, didecyldimethylammonium chloride or cetyltrimethylammonium bromide are characterized by acute toxicity toward D. magna at very low concentrations (EC50 <0.1 mg dm -3 ) , which qualifies them in the "super toxic" category. This forces special caution in the disposal of conventional disinfecting agents and prompts the search for active ingredients characterized by lower toxicity to aquatic animals.