Hair analysis for THCA‐A, THC and CBN after passive in vivo exposure to marijuana smoke

Abstract

Condensation of marijuana smoke on the hair surface can be a source of an external contamination in hair analysis and may have serious consequences for the person under investigation. Δ9-tetrahydrocannabinolic acid A (THCA-A) is found in marijuana smoke and in hair analysis, but is not incorporated into the hair through the bloodstream. Therefore it might be a promising marker for external contamination of hair and could facilitate a more accurate interpretation of analytical results. In this study, three participants were exposed to the smoke of one joint every weekday over three weeks. Inhalation was excluded by an alternative breathing source. Hair samples were obtained up to seven weeks after the last exposure and analyzed for THCA-A, Δ9-tetrahydrocannabinol (THC) and cannabinol (CBN) by liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. Additionally 30 hair samples from various regions of the head were obtained seven weeks after the exposure from one participant. The obtained results show that the degree of contamination depends on the hair length, with longer hair resulting in higher THC and CBN concentrations (1300 pg/mg and 530 pg/mg at the end of the exposure period) similar to the ones typically found after daily cannabis consumption. THCA-A could be detected in relatively low concentrations. Analysis of the distribution of the contamination showed that the posterior vertex region was affected most. The relatively low THCA-A concentrations in the samples suggest that most of the THCA-A found in forensic hair samples is not caused by sidestream marijuana smoke, but by other sources.

Comparison of cannabinoid concentrations in oral fluid and whole blood between occasional and regular cannabis smokers prior to and after smoking a cannabis joint

“…Chronic use can be assessed by measuring cannabinoid concentrations in hair. However, this matrix is not always available, or can be contaminated by cannabis smoke [4] or by contact with dirty hands, thus making its interpretation quite challenging. Furthermore, in comparative studies, discrepancies were found between "positive" urine specimens and hair tested as "negative" [5,6].…”

Hair analysis of synthetic cannabinoids: does the handling of herbal mixtures affect the analyst’s hair concentration?

“…One possible explanation for these results could be direct transfer through contaminated fingers; for example, from a head massage or by sleeping on pillows accidentally contaminated by the hands of the partner. The presence of only trace amounts of cannbinoids in the hair samples of participant 2 was attributed to his short hair length (0.5 cm), because previous studies have indicated that shorter hair is less prone to external contamination [10]. Obviously, the risk of cross contamination would be much higher if the drugs were handled at home.…”

“…One household group (participants [10][11][12][13][14] included two putative donors of contamination, viz., the husband/father (participant 3) and one child/sibling (participant 1). In this household, one child/sibling (participant 14) had trace amounts (\0.5 pg/mg) of JWH-210 in the two proximal 6-cmlong segments (42 cm hair strand), and no synthetic cannabinoids were detected in the hair of the wife/ mother or the three other children/siblings.…”

“…As a consequence, the parent compounds are the usual targets in hair analysis for synthetic cannabinoids. However, similar to other drugs of abuse that are smoked and handled extensively prior to consumption, external contamination may distort the results [10,11]. In numerous cases with confirmed heavy consumption, high concentrations of parent compounds are found in the hair, but no metabolites could be detected (own unpublished data).…”

Validity of Substances of Abuse Detection in Hair by Biochips Array Technology

“…This phenomenon was also described by other scientific research groups [7,8], and can be explained by the assays' limited sensitivity to detection of cannabis in hair samples. On the opposite side, other scientific researcher's states a scientific evidence of detection of cannabis abuse by means of hair analysis should involve the sensitive detection of the THC metabolite THC carboxylic acid (THC-COOH) in a very lower detection limit, (pg) detection unit [9][10][11].…”