"Thanks for the help, Bill! I agree with your assessment based on my own research. One question I have regarding the study you linked: does hair testing reveal EtG concentrations per time period, or is it merely an average over the 3 month detection period? In other words, if all of the subjects consuming 1 drink daily for 3 months passed the EtG test, how is that different from consuming 90 drinks in 1 day?"
HAT is different from other drug testing in that FAEE and EtG are created by different pathways and act differently in the hair. Both are inclined to migrate up the hair shaft but FAEE more so. Any drug that doesn't stay put on incorporation cannot be time estimated. The claim that hair testing can tell when a substance was used is a dubious claim at best. It's called
segmental analysis and amounts to aligning the root ends of the hair sample, cutting it into 1-cm segments that can be analyzed individually. This assumes an average hair growth rate of 1.3 cm per month and also that the drug enters via the hair papilla at the base of the follicle. Neither proposition is true. Hair growth varies from .5 to 1.5 cm between individuals and how a drug gets into the hair varies by class.
It is generally believed that FAEE is deposited in hair from the sebaceous glands and it is probably synthesized there as well. Susanna Vogliardi in her doctoral thesis (2008) provides an excellent illustration of the various avenues through which drugs are incorporated into human hair (see Figure 2). Available
here.
When testing for alcohol the focus is on the first 1-cm of the sample. That part closest to the scalp. The reason for that is that the metabolites move up the shaft, rather than staying in place, and they are unstable in hair and likely to be removed by normal hair washing, exposure to sunlight, etc. (That is the recommendation, but testing labs seldom follow recommendations)
So they will pulverize about 1-1/2 in of your hair and test it. There is no way to do segmental analysis as there are no segmental cutoffs for the reasons noted above. They are simply looking for cumulative EtG and a combination of 4-FAEEs.
All of the literature is clear in that moderate consumption does not usually create EtG and/or FAEE at detectable levels. However, moderate is defined as 2 drinks per day for a female. There are no studies on 60g per day across 5 days and I have no means of calculation. It might come down to the rate of consumption. Drinking slow across a longer period (1 drink every 1-1/2 hours) doesn't result in BAC buildup.