If narcotics police officers or other persons handling drug material at work are suspected of consuming drugs, hair analysis may be used to prove or refute such suspicion. However, it is known for many drugs that differentiation of actual drug use from external contamination can be challenging or sometimes impossible. The aim of this study was to evaluate the extent of external contamination caused by handling of synthetic cannabinoid containing drug material under realistic conditions in a forensic laboratory.

Hair of laboratory workers was systematically analyzed for synthetic cannabinoids with a validated LC-MS/MS method after a big seizure of legal high products had to be analyzed in our laboratory. Hair samples were taken two days after the last exposure and again one week later. In addition, hair samples of laboratory staff not directly in contact with the drug material and close relatives of exposed subjects were analyzed to check for cross contamination.

All samples of persons who were in direct contact with drug material were tested positive for at least one of the synthetic cannabinoids (JWH-018, JWH-073, JWH-081, JWH-122, JWH-210, JWH-307, JWH-368, AM-2201, AM-2201 indazole derivative, AM- 2232, MAM-2201, RCS-4, XLR-11, 5F-PB-22, RCS-4 ortho isomer). Concentrations ranged from trace amounts up to a maximum of 170pg/mg (JWH-210) and roughly reflected duration and intensity of exposition. There was no significant decline in concentrations from sample 1 to sample 2 (one week later). Unexpectedly, also subjects without direct contact to drug material showed measurable hair concentrations. In one case, a hair sample (21cm) was taken 10 weeks after the last exposition with plant material. In this case, relevant concentrations of 5F-PB-22 were detected with an increase of concentrations from distal to proximal segments (7.9 – 20pg/mg).

Depending on duration and intensity of exposition, relevant concentrations of synthetic cannabinoids may be found in hair samples of persons exposed to these drugs at work. Unexpectedly, even cross contamination from an exposed person to a close relative may occur and lead to (false) positive hair findings. Concentrations caused by contamination are in the typical range found in known users of these drugs and could lead to wrong conclusions. In contrast, detection of metabolites could strongly suggest an actual consumption. However, we did not detect such metabolites so far even in samples of known consumers of synthetic cannabinoids showing extremely high concentrations of the unchanged compounds. Therefore, body fluids have to be analyzed to unambiguously prove use of these drugs.