Illicit drug residues in wastewater from western Polish cities: a study of spatial and temporal variability

Wastewater-based epidemiology (WBE) approach employs chemical analysis of municipal wastewater and provides a valuable data source for monitoring community-level illicit drug consumption. This study aimed to determine illicit drug residues in wastewater samples collected in eight cities located in the Greater Poland Voivodship (western Poland) to track patterns of illicit drug use across this region. The research filled the gap in WBE studies, in which Eastern European countries have been very poorly represented. The obtained data were also compared with the results of a similar study conducted by our research team in the years 2012-2014. Determination of illicit drugs and their metabolites was performed using high-performance liquid chromatography coupled to tandem mass spectrometry. The method was validated and covered nine analytes, including amphetamine-type stimulants, cocaine and cannabis metabolites, and new psychoactive substances. Among the substances investigated, amphetamine exhibited the highest mass loads across all sampling days and cities. The conducted research confirmed the presence of new psychoactive substances in many cities of western Poland. The inter-day profiles of illicit drug residues in wastewater revealed substance-specific and city-dependent temporal patterns, with stimulant drugs and a cocaine metabolite exhibiting suggestive indications of weekend-associated increases. Most cities demonstrated an increase in the levels of drug residues in wastewater compared to levels determined 10 years ago. The current study highlights the capability of WBE to capture spatial heterogeneity and short-term and long-term fluctuations in illicit drug consumption.