Probing the Fate, Ecotoxicity of Acesulfame and its Transformation Products in the Aquatic Environment

Acesulfame is an artificial sweetener which has been widely used as a substitute for sugar. The sweetener, molecularly designed to be a low-calorie dietary ingredient, is highly stable to human metabolic processes. The problem is that excreted acesulfame passes through sewage treatment unchanged into the environment. Thus it has become one of the most important and persistent “emerging contaminants” which is not covered by current environmental regulations. Of all sweeteners, acesulfame of domestic sewage origin has the highest occurrence in environments worldwide. Indeed, the alarmingly high levels of acesulfame in finished drinking waters has upscaled acesulfame contamination to a global water crisis. In contrast to the extensive data documenting acesulfame’s occurrence, there is limited data on its environmental impact. While some efforts have been made to break down acesulfame in order to enhance sewage treatment and removal processes, knowledge of the biochemical behavior and ecological effects of the resulting degradation products remain largely unknown. Initial observations from our preliminary study strongly suggest that degrading acesulfame produces even more toxic and stable products, potentially creating even worse pollution. Thus, analyzing the degradation process and determining the ecotoxicity profiles of products of acesulfame degradation are of pivotal importance to designing water treatment processes that produce clean, safe drinking water.

The present work first aims to assess the degradation of acesulfame induced by UV-irradiation with a titanium oxide catalyst, which is currently one of the most commonly used processes in advanced oxidative wastewater treatment. Identities of individual transformation intermediates and products will be confirmed by comprehensive structural characterizations. Based on these identities, mechanism and transformation pathways will be established.

The second aim of this project is to evaluate the ecotoxicological impact of acesulfame degradates. Toxic effects after short-term and prolonged exposure to crustaceans and aquatic vertebrates will be measured in a variety of biological models using freshwater fleas, seawater shrimps and zebrafish embryos. Results will be integrated with findings on the transformation and fate of acesulfame as it is degraded. The entire set of toxicity data will constitute a database for comprehensive environmental risk assessment and should spark novel insights that can guide further research toward improving waste treatment and, ultimately, our environment.