Opioids, stimulants, and depressant drugs in fifteen Mexican Cities: A wastewater-based epidemiological study.

Abstract Background Monitoring drug use in Mexico is a challenge due to emerging drugs and rapid changes in consumption patterns. The temporal and geographical patterns of cocaine, methamphetamine, amphetamine, MDMA, cannabis, heroin, ketamine, and fentanyl were examined in Mexican cities using wastewater-based epidemiology (WBE). Methods 105 daily composite wastewater samples were collected from sewage treatment plants in fifteen Mexican cities. We quantified drug residues using liquid chromatography–high-resolution mass spectrometry, and estimated drug use by back-calculation of drug loads. Results We identified ten drug target residues in at least one sample across cities. Drugs with the highest median levels were cannabis, methamphetamine, and cocaine. The median range of cannabis for one week was between 147 and 20,364 mg/day/1000inhab across cities, whereas methamphetamine ranged between 5 and 3,628 mg/day/1000inhab. Cocaine was found in levels between 2 and 370 mg/day/1000inhab. The highest levels of methamphetamine and amphetamine were observed in the US border cities of Tijuana and San Luis Rio Colorado. The presence of heroin, MDMA, ketamine, and fentanyl was stronger during weekends, while cannabis, cocaine, and amphetamine were found throughout the week. Conclusion This study provides the first report of fentanyl, norfentanyl, and ketamine in wastewater in Mexico. The results indicate an increased presence of drugs on known drug traffic routes, demonstrating that WBE can help identify areas of high drug use and assist governments in developing policies to reduce drug use and harm in the communities.