German Scientists Have Debunked Hair Testing for Pot

In a monumental scientific finding published on October 7, researchers from the Institute of Forensic Medicine in Freiburg, Germany have concluded that finding cannabinoids in hair does not prove cannabis consumption. In a surprising discovery they found that THC and its metabolites do not pass from the bloodstream into hair follicles and hair in any relevant amount; any cannabinoids detected in people’s hair comes from external sources.

Researchers gave participants daily doses of either THCA (the naturally occurring form that is not psychoactive) or THC (decarboxylated THCA, which is psychoactive) daily for a month and compared levels of THC metabolites in their blood, and in their hair.

They found that only a very small level of THC metabolites get incorporated into hair follicles and hair from the blood stream, at such a small level that they consider it to be irrelevant. The Society of Hair Testing has the limit for THC detection in hair set at 50 picograms (pg, one-billionth of a gram) of THC per milligram of hair. This latest research has concluded that having even just 50 pg/mg “would require consumption of extremely high amounts of THC.” Consumption of such a high amount would inevitably lead to cross contamination from people’s hands and smoke getting THC onto hair and skin that way.

Hair testing companies tout the technique’s ability to give the screener a “timeline” of drug use. This latest research from Germany found THC metabolites in samples of hair that grew before they were ever exposed to THC. This leaves external contamination as the only way it could have gotten into that portion of the hair strand.

Since THC and its metabolites pass at such low levels from a person’s blood to their hair, and external contamination has the potential to provide large amounts of THC to a person’s skin and hair without ever having to consume it, hair testing has been officially debunked. While it may take years for courts, law enforcement agencies and companies that drug test to fully accept that hair testing has been discredited, this is the beginning of the end of hair testing for cannabis.

While these findings only apply to cannabis and not necessarily to other substances, victims of the Drug War now have ground to stand on if they wish to try to repeal and regain their employment, custody of their children, or their freedom.