Degradation of 17alpha-ethinylestradiol in wastewater treatment systems

Abstract

The existence and persistence of estrogenic chemicals in aquatic environments is a problem that may affect public and ecosystem wellness. For this reason, it is of major concern, and being investigated by those in the field of environmental chemistry. Estrogenic compounds are known to cause endocrine disruption in wildlife and humans, including 17α-ethinylestradiol (ethinylestradiol), a widely used pharmaceutical. This compound enters the environment, primarily through discharges from wastewater treatment plants without being effectively degraded. Additionally, it is believed that some of the degradation products of ethinylestradiol formed during wastewater treatment have greater endocrine disrupting potential than the parent compound. The goal of the research presented in this thesis was to confirm the degradation of ethinylestradiol into metabolites during wastewater treatment, and to further characterize these degradation products. It is believed that these degradation products may have more estrogenic activity than ethinylestradiol, which has the potential to act as endocrine disruptors in wildlife. Because these degradation products are currently unidentified, monitoring their presence and influence in the environment is not possible. Initially, 14 C-ethinylestradiol was incubated in nitrifying activated sludge obtained from a local wastewater treatment plant, to obtain preliminary information on the extent of degradation in order to allow us to trace the parent and degradation products based on their radioactivity. It was confirmed that ethinylestradiol is degraded by nitrifying activated sludge and that degradation products are formed in the aqueous phase. Experiments were then conducted to observe the degradation of ethinylestradiol by Nitrosomonas europaea , a nitrifying bacteria, in a pure culture to minimize matrix interferences. Degradation of ethinylestradiol was again observed, and the formation of several potential metabolites was observed with molecular masses of 224, 314, 341A, 341B, and 386. These were characterized by mass spectrometric methods such as liquid chromatography mass spectrometry (LC-MS) for degradation and deuterium exchange experiments, ion-trap mass spectrometry (IT-MS) for derivatization and MS 3 experiments, liquid chromatography triple quadrupole mass spectrometry (LC-QqQ-MS) for fragmentation of samples in conjunction with liquid chromatographic separation, and liquid chromatography triple quadrupole time of flight (LC-QqToF-MS) to obtain possible elemental composition for metabolites. Possible structures were proposed for the metabolite M-314, however there is not yet enough data to confirm this structure or propose structures for the other metabolites. The results of this research are being used to optimize and refine current and future experiments planned to elucidate the structures of metabolites formed by the treatment of ethinylestradiol.