exDailySmoker

It is very important not to rely on hair growth estimates such as the oft cited .5 in/per month (1.3 cm). Individual hair growth is more complex and variable in the range of .5 - 1.5 cm/per month. A variance of 3X. Many factors contribute to variance. Gender (scalp hair in women grows faster than in men); ethnicity (caucasian hair grows faster than african hair); age (growth slows with age) length of hair (longer hair slightly faster than shorter) and even texture and scalp density.

Finally, the projected detection range (1.5 in closest to scalp) is based on the assumption that the metabolite enters the hair follicle at the base (papilla) thus requiring 7-10 days to emerge above the scalp. Some cannabis metabolite (THC-COOH) may be incorporated in that manner but the majority probably incorporates far higher on the hair follicle from sweat and sebaceous glands. That factor combined with sample collection (how close to scalp the hair is cut) could easily create a 2 week variance in the calculation.

Having been a frequent smoker you must assume that THC/COOH has been incorporated into your hair, but how much and where within the shaft requires individualized calculation that involves information generally not available to you.

LeBeau, et al (2011) The role of variations in growth rate and sample collection on interpreting results of segmental analyses of hair. Forensic Science International, Volume 210, Issue 1 , Pages 110-116, 15

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