Comparing illicit drug use in 19 European cities through sewage analysis

► First Europe-wide study of illicit drug use through sewage biomarker analysis. ► First application of a harmonized protocol to report and evaluate sampling, analysis and data handling. ► First inter-laboratory comparison of the analysis of illicit drugs. ► Comparable illicit drug use data for 19 European cities. ► Extrapolated total daily use of cocaine in Europe during the study period was equivalent to 356 kg/day.