O2: Cannabinoid findings in children hair – what do they really tell us?

Abstract

Introduction Hair analysis for drugs and drugs of abuse is increasingly applied in child protective cases. To estimate the potential risk to a child living in a household where drugs are consumed, not only the hair of the parents can be analyzed but also the hair of the child. In the case of hair analysis for cannabinoids the differentiation between external contamination and systemic uptake is particularly difficult, since the drug is quite often handled extensively prior to consumption (e.g. when preparing a joint) and smoke causes a further risk for an external contamination. As Δ9-tetrahydrocannabinolic acid A (THCA-A), the non-psychoactive biogenetic precursor of Δ9-tetrahydrocannabinol (THC), is not incorporated into the hair matrix through the bloodstream in relevant amounts it may act as a marker for external contamination. Methods 41 hair samples of children (age: 7 months-12 years) and 35 hair samples of drug consuming parents were analyzed for THCA-A, THC and cannabinol (CBN) applying methanolic extraction and a fully validated LC-MS/MS method. For comparison, a part of the samples was also analyzed applying alkaline hydrolysis followed by liquid/liquid extraction and GC/MS or by GC-HS-SPME. Results In all but one of the samples, the concentration of THCAA was higher than the concentration of THC and in 14 cases no THC could be detected despite the presence of THCA-A, suggesting that in almost all cases a significant external contamination had occurred. Within-family comparison showed a higher THCA-A/THC ratio in hair of children than in the hair of their consuming caregivers. Mean and median of this ratio over all hair samples as 6.7 and 4.2 with a large variation between samples. Application of the different methods clearly showed that the choice of methodology has a strong influence on the quantitative results obtained, mainly because of decarboxylation of THCA-A during sample processing, which may lead to artifactually elevated THC concentrations. Conclusion The findings suggest that the major part of the cannabinoids detected in the hair samples from these children arose from an external contamination through “passive” transfer by e.g. contaminated fingers or surfaces and not from inhalation or deposition from side stream smoke.