Interpreting sources and endocrine active components of trace organic contaminant mixtures in Minnesota lakes

Abstract

On-site wastewater treatment systems (OWTSs) are a suspected source of widespread trace organic contaminant (TOrC) occurrence in Minnesota lakes. TOrCs are a diverse set of synthetic and natural chemicals regularly used as cleaning agents, personal care products, medicinal substances, herbicides and pesticides, and foods or flavorings. Wastewater streams are known to concentrate TOrC discharges to the environment, particularly accumulating these chemicals at outfalls from centralized wastewater treatment plants. Fish inhabiting these effluent dominated environments are also known to display intersex qualities. Concurrent evidence of this phenomenon, known as endocrine disruption, in Minnesota lake fish drives hypotheses that OWTSs, the primary form of wastewater treatment in shoreline residences, may contribute to TOrC occurrence and the endocrine activity in these water bodies. The causative agents specific to fish in this region remain poorly understood. The objective of this dissertation was to investigate OWTSs as sources of TOrCs in Minnesota lakes, and TOrCs as potential causative agents for endocrine disruption in resident fish. Three research efforts were executed to investigate these topics: examining chemical and biological signatures of OWTS proximity in Minnesota lakes (Chapter 2), prioritizing potential causative agents of endocrine disruption using liquid chromatography tandem mass spectrometry (LC-HRMS) (Chapter 3), and conducting a suspect search of OWTS-associated LC-HRMS features at an adjacent Minnesota lake (Chapter 4). In Chapter 2, traditional targeted aqueous analyses indicated higher concentrations of TOrCs at locations more proximal to residences with OWTSs. Residential proximity also corresponded to feminization of male sunfish. The particular contaminants detected at these locations are considered weak indicators of wastewater presence in environmental compartments and inactive with current metrics for endocrine activity. Unexpected features unique to sites with pronounced endocrine disruption were identified in Chapter 3; however, these components were still considered endocrine inactive by current toxicology metrics. This suggests that temporal resolution in sampling was too low for this chronic-toxicity endpoint, or current regulatory efforts underestimate the effects of these contaminants as environmental mixtures. Finally, Chapter 5 indicated that LC-HRMS analysis and passive sampling allowed for identification of a broader suite of OWTS-associated compounds in adjacent lake water, but that higher spatial resolution was required to refine lake-specific OWTS-compound interest lists. The results from this dissertation encourage further investigation of residential inputs of TOrCs to Minnesota lakes, particularly prioritizing locations with endocrine disruption, so that local regulatory agencies may effectively manage these highly valued state resources.