González-Mariño I, Baz-Lomba JA, Alygizakis NA, et al. - Researchers evaluated spatial and temporal trends, over 7 years (2011–17), of population-normalized mass loads of benzoylecgonine, amphetamine, methamphetamine and 3,4-methylenedioxymethamphetamine (MDMA) in raw wastewater, as well as reported overall drug use by estimating the average number of combined doses consumed per day in each city. Also, comparison of these with existing prevalence and seizure data was done. This analysis was carried out in catchment regions of 143 wastewater treatment plants in 120 cities in 37 countries. They used liquid chromatography–tandem mass spectrometry to measure parent substances (amphetamine, methamphetamine and MDMA) and the metabolites of cocaine (benzoylecgonine) and of Δ⁹-tetrahydrocannabinol. Findings revealed that benzoylecgonine was identified at higher loads in southern and western Europe; they found amphetamine, MDMA and methamphetamine in East and North–Central Europe. In other continents, the highest levels were demonstrated by methamphetamine in the United States and Australia and by benzoylecgonine in South America. Almost real-time drug use estimates globally corresponding to prevalence and seizure data were generated in this study of wastewater to quantify drug loads.