Wastewater-Based Epidemiology of Cocaine in the Brazilian Federal District: Spatial Distribution, Weekly Variation and Sample Preservation Strategies

Abstract

The distribution of consumed cocaine in the Brazilian Federal District (FD) was estimated using the wastewater-based epidemiology (WBE) approach. Sewage samples from eight wastewater treatment plants were analyzed for cocaine (COC) and benzoylecgonine (BE) using solid-phase extraction followed by liquid chromatography-mass spectrometry. The highest per capita consumption was noticed for the northern area of the Brazilian Capital (1162 mg day -1 1000 inh -1 ) being 32% higher than the average consumption rate of the investigated region. In this area, a day-to-day investigation revealed an average cocaine consumption of 1800 mg day -1 1000 inh -1 during the weekend, i.e., more than 50% higher than weekdays. An annual street-grade cocaine load of about 2 ton was estimated for the FD considering previous information on the actual purity of seized street drugs as well as consumers between 15 and 64 years old. Sample preservation strategies were also investigated in order to expand the WBE approach to other Brazilian areas. Sample acidification to pH 2.0 presented the smallest relative errors for COC (+11%) and BE (−4%) after a period of three days under typical transport conditions practiced by the Brazilian national postal service.Keywords: illicit drugs, cocaine use, WBE, sample preservation, consumption estimates IntroductionCocaine and its metabolites are commonly found in wastewater due to human urinary excretion or even through direct drug disposal (accidentally or not) in the sewer system. 1,2 Concentration of the drug residues can be assessed through analytical routines that include sample collection and preservation, followed by specific analytes separation and quantification. Benzoylecgonine (BE) and cocaine (COC) have been the most frequently investigated substances within wastewater-based epidemiology (WBE) initiatives around the world, [3][4][5][6][7] since the former is the most abundant cocaine metabolite. Also for this reason, analytical data concerning benzoylecgonine in wastewater samples has been used as a near real-time tool to estimate cocaine consumption for a given population. 8,9 Several works have explored different aspects of the WBE approach including other cocaine metabolites, 10 estimation of other consumed drugs, 10-12 influence of recreational events, [13][14][15][16] consumption dynamics in restricted facilities, [17][18][19] temporal and spatial variability, [20][21][22] stability of target chemicals, 23,24 refinement on estimates calculation, [25][26][27] innovations in sample preparation and analysis, [28][29][30] among others. In Brazil, the first work to put the WBE approach into practice was designed to assess cocaine consumption on regions served by six wastewater treatment plants (WWTP) installed in the Brazilian Federal District (FD). 31 Results revealed a consumption of 920 mg day -1 1000 inhabitants -1 . Recently, our group also showed higher cocaine consumption patterns in the FD during the FIFA World Cup weekend matches as well as significant crack-cocaine use in the FD th...

Assessing cocaine use patterns in the Brazilian Capital by wastewater-based epidemiology

“…In the region covered by the North-Wing WWTP, the average cocaine use during the weekdays (2296±353 mg day -1 1000 inhab -1 ) was 25% lower than the estimates for the weekend (3100±233 mg day -1 1000 inhab -1 ) and 36% lower than the estimates for Sunday (3566±171 mg day -1 1000 inhab -1 ). This result is similar to previous data produced in the same region in 2012, where cocaine use was 50% higher in the weekend in comparison with weekdays [28]. In the region covered by the South-Wing WWTP, cocaine use on Sunday (7385±121 mg day -1 1000 inhab -1 ) was more than three times higher than the average calculated for weekdays (1707±250 mg day -1 1000 inhab -1 ).…”

“…In [28,34]. The work carried out by Devault et al [38] also shows higher in-sewer stability of COC and BE under acidic conditions (pH 5).…”

“…In addition, it has been reported that excessive drug use, including cocaine, is common in universities in Brazil [50]. Cocaine use in the region served by the North-Wing WWTP has been the highest in the Federal District since the first estimates were obtained [28][29][30] probably as a result of this significant university population.…”

“…In order to contribute to the studies of WBE in Brazil, this work aimed to assess the levels of COC, BE and COE in sewage samples collected in two wastewater treatment plants (WWTP) of the Brazilian Capital, Brasilia. The area served by these two WWTP was previously investigated concerning the use of cocaine using the WBE approach [28][29][30]. For the first time in Brazil, we assess the levels of COE during a dayto-day investigation in order to better understand the co-consumption of cocaine and alcohol [31] and to assess the potential of WBE in the study of users in a community-scale investigation.…”

Ten Years-Snapshot of the Occurrence of Emerging Contaminants in Drinking, Surface and Ground Waters and Wastewaters from São Paulo State, Brazil

“…This could be related to the excretion metabolism of this illicit drug since 25% of the consumed crack/cocaine is excreted in urine as benzoylecgonine. 130 In addition, considering that the main source of illicit drugs to the environment is the human excretion, a variety of studies show that benzoylecgonine is more stable than cocaine under different environmental conditions such as temperature and pH. 67,121,131 Different removal efficiencies for cocaine and benzoylecgonine were observed for each conventional WWTP evaluated.…”