Doctor of Philosophy (PhD)


Environmental Sciences

Document Type



Pesticides used in the United States must undergo registration by the United States Environmental Protection Agency (USEPA), after a multitude of analyses ranging from environmental fate to aquatic toxicological impacts to human risk exposure. Testing varies for each chemical, some requiring more testing than others. In many cases, environmental factors are restricted in the analysis of chemical behavior and organismal testing is limited to larvae. Many pesticides are formulated to breakdown in the environment by means of photolysis, hydrolysis, or oxidation, either to ensure low-persistence, limited transport, or to form the active ingredient (pro-pesticides). Environmental influences on chemical behaviors include salinity, sunlight, water, sediment, nutrients, etc. and can increase or decrease the half-life, persistence, formation and degradation of intermediate products, bioaccumulation, and toxicological effects to non-target organisms. Regulatory agencies often do not account for nontraditional aquatic toxicity testing, though research institutions will undergo extensive studies with nontraditional yet environmentally relevant scenarios. Two pesticides and one pesticide-degradation product were chosen to compare and assess the impacts sunlight, salinity, and sediment impose on the degradation, dissipation, and toxic response of three aquatic organisms (fathead minnows, inland silversides, and red swamp crayfish) in various environmental scenarios. Chemically, the pesticides appear to follow [similar] trends with external factors accounted for; toxicologically, no model or trend appears to remain consistent or observed across the chemicals analyzed. Therefore, the need for further investigations for potential impacts to aquatic organisms due to pesticide exposure is appropriate when managing registration processes.



Committee Chair

Armbrust, Kevin