Biodegradation tests were conducted for three groups of quaternary ammonium salts (QAS) that differed in hydrophobic chain length or in hydrophilic properties. The degradation rate was influenced by the hydrocarbon chain length, the presence of aromatic or cyclic rings, and the occurrence of sulphur and oxygen atoms in the alkyl substituent. All tested QAS variants were biodegradable in an aquatic environment. The half life of the different QAS under these conditions ranged from 0.5 to 1.6 days and depended on the properties of the compound. Biodegradation intermediate products were identified by nuclear magnetic resonance spectrometry (H-1 NMR and C-13 NMR). Both the initial preparations and their biodegradation products were not genotoxic. (C) 2011 Elsevier B.V. All rights reserved.