Interpretation results of hair analysis, particularly for cocaine, can be challenging due to the need to differentiate between active use or passive contamination. Our study aimed to assess the impact of varying degrees of passive cocaine exposure hair analysis results and their interpretation. Hair samples (n = 25) were categorized based on the declared cocaine exposure of volunteers: (a) high, involving handling up to several kilograms of cocaine powder from dismantling illegal distribution sites; (b) medium, where staff dealt with cocaine blocks (up to kilograms); and (c) low, with staff in contact with up to grams of cocaine for laboratory analysis. Hair samples were decontaminated using dichloromethane, water, and methanol. The samples and final wash were analyzed for cocaine, benzoylecgonine, norcocaine, cocaethylene, m-OH-benzoylecgonine, and ecgonine methyl ester using a validated UPLC-MS/MS method. Cocaine hair concentrations ranges were as follows (pg/mg): high (n = 53 segments) < LLOQ(32)-7046; medium (n = 91) < LLOQ-939; and low (n = 54) < LLOQ-292. All hair samples had concentrations below the LLOQ for cocaethylene, ecgonine methyl ester, and m-OH-benzoylecgonine. Applying the SoHT cocaine cut-off in combination with a hair/wash ratio criterion identified 97% of the samples as contaminated. This study advocates for a comprehensive approach in evaluating cocaine hair concentrations. This involves integrating the 500 pg/mg decision limit for cocaine with a criterion comparing wash and hair concentration. Additionally, confirming the presence of specific metabolites is crucial. This multifaceted method effectively distinguishes between environmental contamination and active cocaine usage. The research contributes significantly to refining cocaine exposure assessment in professional contexts.
Keywords: cocaine seizures; contamination; hair; interpretation criteria; passive exposure.
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