The increasing prevalence of crack cocaine across Europe is concerning. In contrast to benzoylecgonine (BE), the analysis of anhydroecgonine methyl ester (AEME) in influent wastewater (IWW) supports the estimation of crack cocaine use at the population level, since it is exclusively formed as a pyrolysis product during inhalation. This study aims to monitor spatiotemporal trends in the population-normalized mass loads of AEME and BE in IWW of different European communities, as a proxy for human consumption.

A validated analytical method quantified AEME and BE in IWW from different European cities. A 2024 spatial analysis compared Western and Eastern European cities, while monthly IWW composites in May 2023 covered 24 cities in Flanders (Belgium). Yearly trends were evaluated over six years (2019-2024) in Antwerp and Brussels.

Higher population-normalized mass loads of AEME and BE were observed in Belgium and the Netherlands compared to Eastern European countries. In Lithuania, Latvia and Romania, AEME concentrations were generally below the lower limit of quantification. The spatial analysis in Flanders showed that crack cocaine use was not limited to urban locations. In Belgium, the population-normalized mass loads of AEME remained stable throughout the six-year period with no clear week-weekend pattern, suggesting continuous use due to its highly addictive properties.

AEME is a reliable biomarker for estimating crack cocaine use in populations using IWW analysis. WBE is a strong and effective monitoring tool, essential to feed situational analysis and allows timely insights to support public health surveillance.