First Detection of Xylazine in Texas Wastewater and Its Association with Fentanyl Use.

The United States is dealing with the drug overdose crisis that has intensified over the past decade and compounded by the emergence of new threats particularly xylazine, a veterinary sedative increasingly found in illicit drug supplies. This study investigates the prevalence of xylazine in El Paso, Texas, a U.S.-Mexico border city where its impact remains poorly understood. We employed wastewater analysis to detect xylazine and examine its potential correlation with fentanyl use over a 14-month period (June 2023 to July 2024). Our results show that xylazine was detected in wastewater samples from three of the four treatment plants serving the city. The prevalence of xylazine was heterogeneous, with the highest detection rate of 29% observed in one sewershed. All samples on xylazine-positive days also tested positive for norfentanyl, a fentanyl metabolite, demonstrating the widespread fentanyl consumption. Notably, sewersheds with higher xylazine detection exhibited significantly higher fentanyl loads, suggesting a community-level association between the two substances use. This study provides the first evidence of xylazine in Texas wastewater and highlights the urgent need for enhanced monitoring and targeted public health interventions to mitigate the growing threat of xylazine, particularly in border communities affected by the opioid crisis.