en Environmental Health, Sciences, and Engineering Environmental Health, Sciences, and Engineering پژوهشي Original Article <span style="line-height:1;"><span style="font-size:14px;"><span style="font-family:Times New Roman;"><b>Background: </b>Wastewater analysis has emerged as a promising methodology for<b> </b>real-time monitoring of illicit drug consumption. The main objective of this article is to identify the occurrence and distribution of illicit drugs and their metabolites in the wastewater treatment plants (WWTP) of municipalities with adequate sewage coverage systems, in terms of water and sewage services, in the Hydrographic Regions of the State of Rio de Janeiro (HRRJ).<br> <b>Methods: </b>Diurnal composite samples of influent were collected from 13 wastewater treatment plants between December 27, 2022, and January 10, 2023, to detect the presence of illicit drugs, including Ecstasy, Amphetamine, Methamphetamine, Cocaine, Benzoylecgonine, and Cannabis. The excretion products were quantified using liquid chromatography coupled with mass spectrometry.<br> <b>Results: </b>The highest per capita consumption was observed for Cannabis, with a consumption rate of 432mg/day/1,000 inhabitants. Benzoylecgonine was the second most consumed drug, with a rate of 190mg/day/1,000 inhabitants, followed by Cocaine with a rate of 98mg/day/1,000 inhabitants. Amphetamine had a consumption rate of 104mg/day/1,000 inhabitants, while Methamphetamine had a rate of 42mg/day/1,000 inhabitants. 3,4-Methylene-dioxy-N-methylamphetamine had the lowest consumption rate, with a rate of 23.8mg/day/1,000 inhabitants.<br> <b>Conclusion: </b>The consumption patterns of illicit drugs were analyzed, and it was observed that stimulant drugs such as Cocaine, Ecstasy, and Amphetamines were consumed to a greater extent in municipalities located on the coast or with greater purchasing power. In contrast, Cannabis consumption was found to be more widespread across the surveyed locations, with higher consumption rates observed in regions with high traffic.</span></span></span> Wastewater-based epidemiology, Illicit drug, Addiction, Drug consumption, Public health, 63 71 http://jhehp.zums.ac.ir/browse.php?a_code=A-10-591-1&slc_lang=en&sid=1 Aldo Pacheco Ferreira aldo.ferreira@fiocruz.br 100319475328460012903 100319475328460012903 Yes Department for studies on violence and health Jorge Careli, Sergio Arouca National School of Public Health, Oswaldo Cruz Foundation, Rio de Janeiro, Brazil. Eduardo Dias Wermelinger edw@fiocruz.br 100319475328460012904 100319475328460012904 No Department of Biological Sciences, Sergio Arouca National School of Public Health, Oswaldo Cruz Foundation, Rio de Janeiro, Brazil. Maria José Cruz-Hernández mjcruzhernandez.conadic@gmail.com 100319475328460012905 100319475328460012905 No National Council Against Addictions, Mexican Ministry of Health, Mexico City, Mexico.