Quote Originally Posted by mauijim66
Hey drbill! Thanks for the info.. I guess what i'm really curious about is this:
We all know that (roughly) your body is clear of thc metabolites in about a month after the last use. (or maybe by then there are too few to reach the threshold of detectibility for a urinalysis test.
Either way, isn't the hair folicle 'tagged' by the metabolites while they are in the system? In other word, wouldn't new hair growth be 'clean' if it sprouts up, say, a month after the smoker's last toke? And if not then, when? A shorter period of time? Longer? Much longer?
Whats an example of a penetrating emulsifying agent, btw?
You can have THC and THCA in your system and not in circulation. The best information to date (Smeal) indicates that THC (meaning both metabolites) enter the hair by indirect deposition into hair from surrounding scalp tissue. THC is found in the sebaceous glands imbedded in your scalp and is also stored in the basilar levels of the epidermis. THC is deposited in urine via circulation and may never reach the level of detection due to the erratic nature of release from fatty tissue (a little here, a little there). In urine you are looking at a cutoff of 50 ng (billionth). In hair testing the cutoff can be as low as 0.05 pg (trillionth) and it doesn't take much to reach that threshhold. So if the THC is releases from the epidermis it could very well enter the hair while never returning to circulation.

Smeal (2007) Mechanism of cannabinoid incorporation in hair, phd dissertation, Pharmacology & Toxicology, Univ of Utah.

Also, Marilyn A. Huestis (2007) Human Cannabinoid Pharmacokinetics. Chem Biodivers. 2007 August; 4(8): 1770–1804. Sec 3.5