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

Xylazine is a veterinary sedative increasingly found in the U.S. illicit drug supply and is a growing public health concern due to its association with overdose events. To investigate its spatial distribution and relationship with fentanyl use, we analyzed 124 wastewater samples from four treatment plants serving the City of El Paso, Texas, over 13 months (June 2023 to July 2024) using liquid chromatography tandem mass spectrometry. Xylazine detections varied across sewersheds, with detection rates of 29.0%, 12.9%, 9.7%, and 0% and peak loads of 110±40 μg/day/1000 people. Norfentanyl (a primary fentanyl metabolite) was detected in all samples (100%), reaching peak loads of 2400±300 μg/day/1000 people. Sewersheds with higher xylazine detection exhibited significantly higher norfentanyl loads (p<0.05), suggesting a community-level association between xylazine and fentanyl use. This study provides the first evidence of xylazine in Texas wastewater and demonstrates the utility of wastewater monitoring for tracking emerging drug trends. These findings could inform resource allocation and public health planning for harm reduction services, including xylazine awareness programs.