Artificial sweeteners and drinking water treatment: a chemical and toxicological study of acesulfame under chlorination

The artificial sweetener acesulfame is widely used in considerable amount in various foodstuffs and consumers products as a substitute for natural sugar. As a result of its outstanding molecular stability, acesulfame passes through domestic sewage treatment processes and readily enters the environment. As acesulfame persists and accumulates in aquatic compartments, it is regarded as one of the most important “emerging contaminants”, currently still unregulated. Compared to other sweeteners, acesulfame has the highest occurrence in environmental compartments worldwide. More alarmingly, the intrusive presence of acesulfame in raw drinking water resources and eventually in finished potable water has escalated acesulfame contamination into a global water issue. Despite its considerable persistence, acesulfame in drinking water is substantially degraded by powerful chemical disinfection treatment such as ozonation and chlorination, with removal efficiencies of up to 60% and 85%, respectively. These figures trigger mounting concern over the health implications of the disinfection by-products (DBPs) of acesulfame, as previous experience and reports on environmental degradation indicate probable formation of toxic products. At this stage, knowledge of the transformation fate and related biological impact of DBPs from chlorination remain largely unknown. Initial observation from our preliminary degradation study revealed a progressive change of molecular profile and formation of chlorine-substituted by-products, which was found to be substantially mutagenic by toxicity testing. Novel research that can decipher the chemical mechanism and verify the toxicity of acesulfame disinfection are therefore of pivotal importance.

A primary objective of the present study is to trace the chemical transformation pathway of acesulfame undergoing chlorination treatment, which is the most widely adopted disinfection process in standard drinking water production today. Chemical structures and identities of individual acesulfame DBPs will be confirmed by comprehensive instrumental characterizations. Chemical data obtained will be used to establish the chlorine-induced degradation mechanism. All of this information will be valuable in facilitating safer, more effective engineering in drinking water treatment.

Biological testing will be carried out to thoroughly evaluate the impact of acesulfame DBPs on drinking water safety. Key parameters of acute toxicity and DNA damage will be quantified in mammalian cell assays to provide information relevant to human health. Finally, the presence of acesulfame DBPs will be screened in the water produced at treatment plants and in household water to reveal the urgency of the issue. The compilation of chemical and toxicological data in this study, complementing existing eco-environmental data, will not only consolidate the scientific foundation for comprehensive risk assessment on acesulfame, but also shed light on prospective engineering of better disinfection for a more sustainable supply of this vital resource.