Innovative approaches to monitor illicit drug use and novel psychoactive substances in Tunisia using wastewater-based epidemiology

Numerous studies have confirmed the presence of organic compounds in wastewater, including residues of drugs of abuse and novel psychoactive substances at trace concentrations. This research investigated the presence of these emerging micropollutants in influent wastewaters from five Tunisian Wastewater Treatment Plants. Composite samples of influent wastewater (collected over 24 hours) were gathered continuously for 7 days in November 2021. A well-optimized multi-residue liquid chromatography tandem mass spectrometry method was employed to identify and quantify 11 drug of abuse compounds or their metabolites. Among the sewage plants studied, cannabis and ecstasy were the most frequently detected substances. In this study, a novel wastewater-based epidemiology approach was introduced to estimate illicit drug usage, enabling the calculation and assessment of collective illicit drug consumption at a community level. The average cannabis consumption in the examined cities ranged from 1.6 to 31.93 g/day/1000 inhabitants. Ecstasy consumption ranged from 0.1 to 7.26 g/day/1000 inhabitants. Furthermore, a qualitative study on novel psychoactive substances was carried out, assessing 32 different substances in wastewater samples. Out of these 32 substances tested at all sampling sites, 16 were tentatively identified. These identified novel psychoactive substances represented a broad spectrum of categories, including synthetic opioids, synthetic cathinones, amphetamine derivatives, and synthetic cannabinoids.