03/27/2026
By Danielle Fretwell

The Francis College of Engineering, Department of Civil and Environmental Engineering, invites you to attend a Doctoral Dissertation defense by Varsha Niroula on: "Environmental Fate and Stability of Drugs of Abuse."

Candidate Name: Varsha Niroula
Degree: Doctoral
Defense Date: Thursday, April 9, 2026
Time: 1:30 - 3:30 p.m.
Location: Ball Hall 302

Committee:

  • Advisor: Sheree Pagsuyoin, Civil and Environmental Engineering, University of Massachusetts Lowell
  • Frederic Chain, Biological Sciences, University of Massachusetts Lowell
  • Weile Yan, Civil & Environmental Engineering, University of Massachusetts Lowell
  • Susan Glassmeyer, U.S. Environmental Protection Agency (retired)
  • Maricris Mayes, Chemistry and Biochemistry, University of Massachusetts Dartmouth
  • Sara Wiggington, Regional Government of Cape Cod

Abstract: Drugs of abuse (DAs) are ubiquitous in the environment due to their extensive medical and illicit use. These compounds are not completely removed during wastewater treatment and are eventually discharged to the environment, raising concerns about exposure risks to aquatic organisms and potential implications for public health. Ecotoxicological studies indicate that exposure to DAs even at environmentally relevant concentrations can induce adverse effects in aquatic organisms, including increased mortality, oxidative stress, and DNA damage. High drug consumption and continuous discharge into the environment necessitate a comprehensive understanding of DA degradation pathways and environmental fate to effectively assess and manage the risks they pose. 

The overarching goal of this research was to evaluate the stability and fate of DAs and their metabolites in aquatic environments. Specifically, this study aimed to: (1) establish the global occurrence patterns of DAs in freshwater systems (2) evaluate the contributions of degradation processes to the stability of DAs in riverine and marine water, and (3) evaluate the removal of DAs in simulated conventional and I/A septic drain field systems. For aim (1), a systematic review of literature was conducted covering a ten-year period (2012-2022) to establish occurrence patterns for 10 highly consumed DAs. Results indicate significant regional variability, with stimulant concentrations generally higher in North and South American rivers and opioid concentrations higher in African rivers. The most frequently detected drugs were cocaine, tramadol, and codeine; mean drug levels in rivers ranged from 9 ng/L for MDMA to 8.1 mg/L for cocaine.

For aim (2) drug degradation was evaluated in simulated river and marine microcosms, under dark and photolytic conditions. In dark conditions DAs exhibited high stability, with removal rates ranging from 12% (tramadol) to 29% (codeine). Biodegradation was the dominant degradation process in river whereas its contribution was more variable in marine systems. Improved removal up to 71% percent can be achieved under photolytic degradation, although recalcitrance was observed in some drugs like tramadol and ketamine. 

For aim (3), the removal of 39 DAs and other pharmaceuticals was evaluated in simulated conventional and I/A septic drainfield systems. Most compounds (66% of drugs) were effectively removed (>95% removal), although temporal decreases in drug removal were observed in conventional and sand-gravel systems. Persistent compounds (e.g., carbamazepine, lidocaine, sulfamethoxazole) showed incomplete removal (30-70%), indicating limitations in biodegradation and sorption processes. Overall, this study demonstrates that photolysis is the primary attenuation mechanism for DAs, with biodegradation playing a larger role in the absence of light. Matrix effects modulate individual attenuation processes (e.g., hydrolysis, sorption, abiotic degradation) rather than overall removal. Engineered systems such as septic drainfield can significantly enhance drug attenuation. These findings advance the mechanistic understanding of drug fate and support more accurate predictions of environmental persistence and associated risks. 

All interested students and faculty members are invited to attend the defense online or in person.