Tiered Approach for the Evaluation of Environmental Impacts of Triclosan on Aquatic Ecosystems
The synthetic broad-spectrum antibacterial agent triclosan is one of the most commonly encountered emerging micro-pollutant in the aquatic environment due to the extensive use since 1968 mainly in cosmetics and household cleaning products and the partial elimination from wastewater. Its low water solubility, high sorption coefficient to organic matter, accumulation potential in fatty tissues and its low acute toxicity determined by conventional ecotoxicological tests suggest that its risk is more related to chronic effects requiring risk assessment based on more sensitive ecotoxicological methods. In this paper the short- and midterm ecotoxicological effects of triclosan were investigated using various test systems taking into account ecological complexity and environmental relevance. Acute single-species, simplified microcosm experiments and complex multi-species microcosm experiments were conducted with the determination of sublethal physiological and behavioral endpoints including the Daphnia magna heartbeat rate and feeding activity, the Heterocypris incongruens movement parameters and the Lemna minor chlorophyll content and root length. All physiological and behavioral endpoints indicated sensitively the adverse effect of triclosan in the concentration range of 4–25.6 µg/L. In some cases, responses of selected organisms in single-species laboratory tests did not correspond to those of the higher levels of test systems. Daphnia sensitivity increased with the level of the test system for all chosen endpoints except the heartbeat rate. Considering the varying ecological complexity of the assembled test systems, according to our results the exposure time and the different combinations of exposure routes were the most decisive parameters in terms of triclosan ecotoxicity and endpoint sensitivity.