Hair testing reveals widespread drug mixing at dance festivals

Hair toxicological analysis enables the verification of long-term drug use monitoring and supports epidemiological studies. In recreational contexts, multi-analyte methods are crucial for accurately characterizing consumption patterns. The present work aimed to develop and validate an LC-MS/MS method for the analysis of 47 drugs of abuse and related compounds in hair samples. A 20 mg hair aliquot was incubated with methanol at 40 °C for 16 h. The supernatant was dried and injected into the LC-MS/MS system. The monitored substances were amphetamines, cocaine and related compounds, cannabinoids, opioids, hallucinogens, synthetic cathinones, synthetic phenethylamines, and synthetic cannabinoids. The method was validated in accordance with international recommendations and subsequently applied to 81 hair samples collected at Brazilian electronic dance music festivals. The method had limits of detection of 0.5-5 pg/mg and limits of quantification of 5-50 pg/mg. All compounds showed suitable linearity (R² > 0.9903). The precision assays showed CV% from 1.3% to 19.0%, while accuracy varied from 80.1% to 119.8%. All analyzed samples presented at least one of the target compounds. The most prevalent substances were MDA (85.2%), benzoylecgonine (84.0%), cocaine (84.0%), MDMA (72.8%), and Δ9-tetrahydrocannabinol (56.8%). This study presented a validated multi-analyte method for the analysis of drugs of abuse and related compounds in hair. Application of the method to a cohort of electronic dance music festival attendees revealed widespread polysubstance exposure, with a notable predominance of MDA. The findings support the role of toxicological analysis as a valuable tool for toxicosurveillance.