Passive exposure to cocaine on a professional level: Importance of considering relevant interpretation parameters

Abstract

The aim of this study was to evaluate the extend of passive exposure in hair from professionals working in contact with cocaine seizures, considering cleaning procedures, hair segmentation and interpretation recommendations from the consensus on drug hair testing [ https://soht.org/images/pdf/Consensus_DoA_2021.pdf ] and from recent literature. In forensic casework where hair analysis is requested, forensic experts have to answer the question if the drug concentrations found are due to an active use or rather a passive contamination. In this preliminary study, the impact of (chronic) passive exposure to cocaine was evaluated by analyzing hair from subjects in contact with cocaine on a professional level (laboratory technicians and law enforcement dealing with clandestine laboratories). The level of exposure was depending on specific tasks from dismantling of clandestine laboratories (high) to treatment of large quantities of drug samples (medium) to the analysis of few grams of those samples in the laboratory (low). Head hair was collected from 7 volunteers. A total of 19 samples were collected at different time periods [number of samples ( n ): high = 4; medium: n = 9; low: n = 6]. Hair samples were cut in segments, decontaminated with our routine method using dichloromethane, water and methanol, and extracted [Ramirez Fernandez MdM, Di Fazio V, Wille SM, Kummer N, Samyn N. J Chromatogr B Analyt Technol Biomed Life Sci 2014;965:7–18.]. The last wash was also kept for analysis. An extended washing procedure was also evaluated. The samples were analysed with a routine method for cocaine, benzoylecgonine, norcocaine, cocaethylene, m-OH-benzoylecgonine, and methylecgonine. Five test subjects also provided us with a urine sample two days after the cocaine manipulation. The results for median (pg/mg) and minimum and maximum value concentrations in hair according to the level of exposure were as follows: – (A) cocaine in hair; – (B) ratio benzoylecgonine/cocaine in hair; – (C) ratio norcocaine/cocaine in hair; – (D) ratio cocaine hair/wash: – high: A (682; 36–7045); B: 0.07; (0.05–0.11); C: 0.023; (0.009–0.031); D: 2.23; (0.5–31), – medium: A (92; < LOQ(32)-489); B (0,92;0.13–5.49); C: < LOQ (< LOQ); D (9; 6.7–10,5), – low: A [56; < LOQ(32)-189]; B [0.16; 0,16–0.16 (only one value)]; C: < LOQ (< LOQ); D (1.51; 1.0–4.7). Increasing concentrations of cocaine were detected from root to tip when longhair strands were analysed, both in hair and in the washes. For subjects with high exposure, concentrations in hair above recommended cut-offs for cocaine (> 500 pg/mg) with relatively high concentrations of benzoylecgonine (up to 716 pg/mg) and norcocaine (up to 342 pg/mg) were detected. In cases with medium and low exposure, benzoylecgonine and norcocaine were negative or detected at traces level and all hair samples were negative for cocaethylene, methylecgonine, and m-OH-benzoylecgonine (LOQ 1–3 pg/mg). Regarding the analysis of the washing, recent contaminated hair samples presented the highest cocaine concentrations in the washes (> 10%). Extended washing procedures did not improve the interpretation of the results. All urine samples were all negative according European Workplace Drug testing cut-offs (100 ng/mL) proving no recent use. The obtained results show a good correlation between the level of passive exposure to cocaine and the concentrations in hair. This preliminary study demonstrates that the cut-off values for cocaine should not be applied as a sole criterion. Following other parameters are mandatory to be considered too: case context, cut-off-values, cocaine versus metabolites, hair versus washing concentrations ratios, and the presence of more specific metabolites such as cocaethylene, and hydroxy metabolites.