Four-year long wastewater-based monitoring of illicit drug consumption pilot project in Switzerland

The potential of wastewater analysis to complement existing epidemiological tools and help assess illicit drug consumption trends in a defined population has already been established. Consequently, Switzerland has initiated in January 2021 a 4-year long wastewater-based illicit drug consumption monitoring program. The Dromedario project explores in depth the spatial and temporal dimensions through a high-frequency stratified sampling strategy with 24h composite samples collected every 13 days, for a total of 28 samples per year with each day of the week equally represented. 10 wastewater treatment plants (WWTPs) collecting wastewater from small to large cities as well as urbanized and more rural areas are included in the project, covering approximately 2 million people (23% of Swiss population). Samples undergo solid-phase extraction and ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS) analysis to qualify and quantify 6 common illicit drugs and 6 urinary metabolites, following a validated analytical method. Obtained substance loads, together with metabolism excretion data and WWTPs contributing population, are used to back-calculate population consumption estimates. Analyses have not been fully carried out yet but preliminary results should be available for disclosure by the time of the conference. These results should offer extremely valuable knowledge on trends and variations in licit and illicit drug use as well as crucial information about market dynamics. This can in turn help relevant stakeholders, whether it be at law enforcement or public health level, to prioritise their activities and take better-informed decisions about illicit drug policies.