Wastewater-based epidemiology was applied in northeastern Brazil during a dance festival, revealing that cocaine consumption doubled during the event days. The daily drug loads were 0.95 ± 0.03 to 11.4 ± 0.4 g/day for BE, 1.8 ± 0.4 to 7.6 ± 0.3 g/day for COC, 0.04 ± 0.02 to 0.19 ± 0.02 g/day for COE, and 0.08 ± 0.02 to 0.80 ± 0.02 g/day for MDMA.

Abstract

This study employed the wastewater-based epidemiology (WBE) strategy to investigate cocaine (COC) and ecstasy (MDMA) usage during Carnatal festival in Rio Grande do Norte, Brazil. Wastewater samples were collected over the four festival days (December 12–15, 2019), as well as during corresponding days before and after the event. The samples underwent filtration, acidification, solid-phase extraction (SPE) for pre-concentration, and analysis using ultra-high-performance liquid chromatography–tandem mass spectrometry (UHPLC–MS/MS) with calibration using deuterated internal standards. The measured concentration ranges in the wastewater samples were as follows: benzoylecgonine (BE, a metabolite of COC use) ranged from 760 ± 30 to 8914 ± 252 ng/L, COC (non-metabolized or directly discharged) ranged from 1182 ± 25 to 6,760 ± 95 ng/L, cocaethylene (COE, a metabolite of alcohol-COC use) ranged from 21 ± 10 to 161 ± 10 ng/L, and MDMA (ecstasy) ranged from 18 ± 5 to 613 ± 15 ng/L. Daily wastewater loads were estimated as 0.81 ± 0.03 to 11.69 ± 0.33 g/day for BE, 1.42 ± 0.03 to 8.06 ± 0.11 g/day for COC, 0.02 ± 0.01 to 0.21 ± 0.01 g/day for COE, and 0.02 ± 0.01 to 0.80 ± 0.02 g/day for MDMA. Notably, COE and MDMA were only detected above the quantification limit during the festival days. The data enable estimating that COC consumption doubled during the event days. The COC/BE ratio indicated likely drug disposals on the event’s last day and the subsequent week. The study’s findings shed light on illicit substance consumption, assisting in public health programs and combating drug trafficking efforts.