Development of a Method for Assessing Illicit Drug Consumption during Brazilian Carnival through Wastewater-Based Epidemiology Using Gas Chromatography–Mass Spectrometry

Wastewater-based epidemiology (WBE) is a noninvasive and real-time method for assessing illicit drug consumption and the impact of events on community drug use. In this study, a WBE method combining solid-phase extraction (SPE) and gas chromatography–mass spectrometry (GC-MS) was applied to monitor assessing illicit drugs in raw wastewater samples, which were collected during the 2023 Carnival, and in a reference week in Recife (community A) and Olinda (community B) cities. The method was then validated for linearity, limit of quantification, precision, and accuracy. Population-normalized daily drug loads followed the consumption trend of cannabis > cocaine > MDMA > methamphetamine. Cannabis was the most consumed drug, with weekly consumption rates of 8575 mg–1 day–1 1000 inhabitants in community A and 16,978 mg–1 day–1 1000 inhabitants in community B, especially during the Carnival period. Methamphetamine was the least consumed, detected only during Carnival days, underscoring its recreational use. Additionally, stimulant drug use more than doubled during Carnival compared to the reference week, highlighting the significant impact of the festivities. The statistical analysis enabled distinguishing collection periods and highlighting key consumption trends. These findings provide valuable insights into drug use patterns and demonstrate the effectiveness of WBE for monitoring illicit drug consumption.