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

The United States is dealing with an escalating drug overdose crisis intensified by emerging threats, particularly xylazine, a veterinary sedative increasingly found as an adulterant in illicit drug supplies. To investigate the prevalence of xylazine and examine its spatial correlation with fentanyl consumption, we employed wastewater-based epidemiology to analyze 124 samples from four wastewater treatment plants serving El Paso, Texas, over 13 months (June 2023 to July 2024). Samples were analyzed for xylazine and norfentanyl (fentanyl metabolite) using liquid chromatography–tandem mass spectrometry, with population-normalized mass loads calculated for spatial comparisons. Xylazine was detected in three of four treatment plants, showing detection rates of 29.0, 12.9, 9.7, and 0% across different sewersheds. All samples tested positive for norfentanyl, confirming city-wide fentanyl use. Peak population-normalized loads reached 110 ± 40 μg/day/1000 people for xylazine and 2400 ± 300 μg/day/1000 people for norfentanyl. Statistical analysis revealed that sewersheds with higher xylazine detection rates exhibited significantly elevated 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 reveals spatially clustered distribution patterns that may inform targeted public health interventions to mitigate the growing threat of xylazine within the opioid crisis.