Assessment of the environmental relevance of anaerobic biodegradation of surfactants

The anaerobic biodegradation of surfactants is used as an acceptability cri terion in some environmental legislation (eco-label, risk assessment, etc.) without proper evaluation of the relevance of such a characteristic. Surfa ctants are a group of chemicals with considerable environmental importance due to their high volume consumption and widespread use as essential ingred ients in most laundry and cleaning products. Since the major part of the bi osphere is aerobic, priority has been given to the study and assessment of biodegradability under these conditions. Nevertheless there are environment al compartments which can be permanently (e.g. anaerobic digesters) or temp orarily (e. g. river sediments and soils) anaerobic and surfactants do reac h these. The majority of surfactants entering the environment will be expos ed to and degraded under aerobic conditions, and only less than 20 % will p otentially reach anaerobic environmental compartments. In all but a few cas es their presence in these will not be permanent. A systematic evaluation o f the risk to the structure and function of these compartments due to the p resence of undegraded surfactants led to the conclusion that, in contrast t o the adverse effects observed in the absence of aerobic degradation, the l ack of anaerobic biodegradation does not seem to be correlated with any app arent environmental problem for most compartments. Consequently it is concl uded that anaerobic biodegradability does not have the same environmental r elevance as aerobic. Anaerobic biodegradability should not, therefore, be u sed as a pass/fail property for the environmental acceptability of surfacta nts that are readily biodegradable under aerobic conditions.