Occurrence, source, and ecological risk of pharmaceuticals and illicit drugs in surface water in Las Vegas, USA

Globally, pharmaceuticals and illicit drugs (PIDs) are only partially removed by conventional wastewater treatment plants. The origin, sources, and ecological risk of PIDs in Las Vegas Wash are studied scarcely. Therefore, this study aimed to provide insights into the impact of large social events [Electric Dance Carnival (EDC) and National Football League Draft (NFL Draft)] on the levels of PIDs of a unique surface water system located in Las Vegas, Nevada (USA), a contributary to the Colorado River. Thus, distribution of PIDs was evaluated at multiple locations (n = 10) along the Las Vegas Wash. The results of this study showed that the concentrations of benzoylecgonine, ketamine, 3,4-methylenedioxymethamphetamine (MDMA), and methamphetamine were 8-41 ng L-1, 14-192 ng L-1, 3.5-2118 ng L-1, and 13.7-194 ng L-1, respectively. Compared the control period, usage of drugs of abuse was significantly elevated during the EDC period. For example, the median concentration of MDMA (558 ng L-1) in surface water during the EDC festival was 46 times higher over the control period. The source of PIDs contamination was determined with principal component analysis and linear discriminant analysis (LDA). LDA provides a perspective in assessing the 2022 EDC impacts on the usage of drugs of abuse. MDMA has low to moderate median risk quotient ranging from 0.07 to 6.1, indicating ecological concerns. This study demonstrated that surface water analysis can capture changes in illicit drug use pattern during large music events.