Understanding Illicit Drug Use Trends During the Carnival Holiday in the Brazilian Capital Through Wastewater Analysis

Abstract

Cocaine and cannabis consumption during and after the 2019 Carnival holiday were assessed using the wastewater-based epidemiology (WBE) in the capital of Brazil, Brasília. The substances 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THC-COOH), cocaine (COC), benzoylecgonine (BE), and cocaethylene (COE) were monitored in composite samples (24 h) collected in the entrance of North-Wing (NW) and South-Wing (SW) wastewater treatment plants (WWTP) for 15 consecutive days, including the Carnival holiday. Aliquots (100 ml) were enriched with isotope-labeled standards, solid-phase extracted and analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Results reveal higher cocaine consumption during the Carnival (average of 2.8 ± 0.7 g/1000inh/day) compared to the subsequent period (average of 1.7 ± 0.3 g/1000inh/day). Cannabis (THC) use was also higher during the holiday (14 ± 5 g/1000inh/day) but differences were not significative (unpaired t-test, 95%) compared to the following days (11 ± 3 g/1000inh/day), where consumption remained relatively constant corroborating that cannabis overall consumption is less affected by occasional abuse. Regarding cocaine, an unusual low consumption was noticed in the weekend immediately after the Carnival Holiday, indicating lower demand or supply issues. Higher cocaine and cannabis use was observed throughout the entire sampling period in the area covered by NW-WWTP, probably due to the higher proportion of young people. This investigation brings the first data on cannabis use in Brazil by WBE and confirms this strategy as a well consolidate tool for estimating illicit drug use and abuse.

Trends and challenges in analytical chemistry for multi-analysis of illicit drugs employing wastewater-based epidemiology

“…Several studies have suggested that wastewater sampling should be performed by collection proportional to the flow, which takes into account possible fluctuations in concentrations and flows over time [ 6 , 7 , 24 ]. However, this requires the use of a flowmeter to activate an automatic sampler, which limits its application [ 36 ].…”

“…This is especially important in situations where it is not possible to analyze the samples immediately, which requires that they be stored (sometimes for weeks) under appropriate conditions [ 15 ]. Storage of raw wastewater samples at low temperature is often used to decrease microbial degradation, with temperatures of 4 ºC [ 6 , 7 , 12 , 16 , 23 , 39 , 40 ] and especially −20 ºC [ 8 , 9 , 32 , 33 , 37 , 38 , 41 , 42 ] being most reported. This strategy can be effective in maintaining short-term stability.…”

“…However, an acidic medium can lead to decreases of the concentrations of opioids [ 41 ] and favors the biotransformation of THC-COOH into 11-hydroxy-Δ 9 -tetrahydrocannabinol (THC-OH) [ 15 ], making it difficult to recover in the samples. Hence, some studies have avoided acidification [ 43 ], maintaining the pH at the value measured at the time of collection, which is usually between 7 and 8 [ 3 , 6 , 9 , 10 , 12 , 24 , 37 ].…”

“…Centrifugation and filtration with fiber filters are the two most widely used approaches to remove these compounds [ 11 , 39 , 41 , 44 ]. An alternative to the aforementioned filtration is the use of syringe filters before SPE [ 27 , 33 , 41 ] and/or before injection in the analytical instrument [ 6 , 38 , 40 , 43 , 45 ]. However, the possible loss of some IDBs during filtration processes must be considered (especially for less polar compounds, such as cannabinoids), since the compounds may be adsorbed on the material [ 16 ].…”

“…The application of WBE for drug detection allows the estimation of short- and long-term consumption levels, with the advantages of being a faster, direct (almost real-time), noninvasive, accurate, and less laborious tool, compared to the use of population surveys [ 1 , 3 , 8 , 11 ]. It is possible to investigate temporal trends of drug use by the community [ 3 , 16 ] and in educational institutions [ 17 ], the use of new psychoactive substances (NPS) [ 18 , 19 ], the influence of weekends and national holidays [ 20 ], festive events [ 6 , 20 ], seasons [ 1 , 9 ], and music events [ 12 , 21 ], and the impact of social isolation measures imposed due to crises such as the COVID-19 pandemic [ 5 , 10 , 22 – 25 ].…”