Editing Drug test (section)

===Hair testing===
{{main article|Hair analysis}}
Hair analysis to detect addictive substances has been used by court systems in the United States, United Kingdom, Canada, and other countries worldwide. In the United States, hair testing has been accepted in court cases as forensic evidence following the Frye Rule, the Federal Rules of Evidence, and the Daubert Rule. As such, hair testing results are legally and scientifically recognized as admissible evidence.<ref>{{Cite journal |last=Huestis |first=M. A. |year=1996 |title=Judicial acceptance of hair tests for substances of abuse in the United States courts: scientific, forensic, and ethical aspects |url=https://pubmed.ncbi.nlm.nih.gov/8857568/ |journal=Therapeutic Drug Monitoring |volume=18 |issue=4 |pages=456–459 |doi=10.1097/00007691-199608000-00025 |issn=0163-4356 |pmid=8857568 |access-date=October 21, 2022 |archive-date=October 21, 2022 |archive-url=https://web.archive.org/web/20221021172711/https://pubmed.ncbi.nlm.nih.gov/8857568/ |url-status=live }}</ref> Hair testing is commonly used in the USA as pre-employment drug test. The detection time for this test is roughly 3 months, which is the time, that takes head hair to grow ca. 1.5 inches, that are collected as a specimen. Longer detection times are possible with longer hair samples.

A 2014 collaborative US study of 359 adults with moderate-risk drug use found, that a large number of participants, who reported drug use in the last 3 months,  had negative hair tests. The tests were done using an [[immunoassay]] followed by a confirmatory [[GC-MS]].
For marijuana, only about half of self-disclosed users had a positive hair test. Under-identification of drug use by hair testing (or over-reporting) was also widespread for cocaine, amphetamines, and opioids. Because such under-identification was more common among participants, who self-reported an infrequent use, the authors suggested, that the immunoassay did not have the sensitivity required for such infrequent uses.<ref name="z300">{{cite journal | last1=Gryczynski | first1=Jan | last2=Schwartz | first2=Robert P. | last3=Mitchell | first3=Shannon Gwin | last4=O’Grady | first4=Kevin E. | last5=Ondersma | first5=Steven J. | title=Hair drug testing results and self-reported drug use among primary care patients with moderate-risk illicit drug use | journal=Drug and Alcohol Dependence | volume=141 | date=2014 | pmid=24932945 | pmc=4080811 | doi=10.1016/j.drugalcdep.2014.05.001 | pages=44–50}}</ref> It is worth noting, that most earlier studies reported, that hair tests found ca. 50-fold higher prevalence of illicit drug use, than self reports.<ref name="j960">{{cite journal | last1=Delaney-Black | first1=Virginia | last2=Chiodo | first2=Lisa M. | last3=Hannigan | first3=John H. | last4=Greenwald | first4=Mark K. | last5=Janisse | first5=James | last6=Patterson | first6=Grace | last7=Huestis | first7=Marilyn A. | last8=Ager | first8=Joel | last9=Sokol | first9=Robert J. | title=Just Say "I Don't": Lack of Concordance Between Teen Report and Biological Measures of Drug Use | journal=Pediatrics | volume=126 | issue=5 | date=2010-11-01 | issn=0031-4005 | pmid=20974792 | pmc=3508771 | doi=10.1542/peds.2009-3059 | pages=887–893}}</ref>

In late 2022 the US [[Federal Motor Carrier Safety Administration]] denied a petition to recognize hair samples as an alternative (to the currently used urine samples) drug-testing method for truckers. The agency did not comment on the test validity, but rather stated, that it lacks the statutory authority to adopt new analytical methods.<ref>{{Cite web |title=FMCSA denies petition for federal recognition of hair-sample drug testing {{!}} Safety+Health |url=https://www.safetyandhealthmagazine.com/articles/23411-fmcsa-denies-petition-for-federal-recognition-of-hair-sample-drug-testing |access-date=2023-11-16 |website=www.safetyandhealthmagazine.com |language=en |archive-date=October 30, 2023 |archive-url=https://web.archive.org/web/20231030144425/https://www.safetyandhealthmagazine.com/articles/23411-fmcsa-denies-petition-for-federal-recognition-of-hair-sample-drug-testing |url-status=live }}</ref>

Although some lower courts may have accepted hair test evidence, there is no controlling judicial ruling in either the federal or any state system declaring any type of hair test as reliable.

Hair testing is now recognized in both the UK and US judicial systems. There are guidelines for hair testing that have been published by the Society of Hair Testing (a private company in France) that specify the markers to be tested for and the cutoff concentrations that need to be tested. Addictive substances that can be detected include Cannabis, Cocaine, Amphetamines and drugs new to the UK such as Mephedrone.

====Alcohol====
In contrast to other drugs consumed, alcohol is deposited directly in the hair. For this reason the investigation procedure looks for direct products of ethanol metabolism. The main part of alcohol is oxidized in the human body. This means it is released as water and carbon dioxide. One part of the alcohol reacts with fatty acids to produce esters. The sum of the concentrations of four of these fatty acid ethyl esters (FAEEs: ethyl [[myristate]], [[ethyl palmitate]], [[ethyl oleate]] and ethyl [[stearate]]) are used as indicators of the alcohol consumption. The amounts found in hair are measured in nanograms (one nanogram equals only one billionth of a gram), however with the benefit of modern technology, it is possible to detect such small amounts. In the detection of [[ethyl glucuronide]], or EtG, testing can detect amounts in picograms (one picogram equals 0.001 nanograms).

However, there is one major difference between most drugs and alcohol metabolites in the way in which they enter into the hair: on the one hand like other drugs FAEEs enter into the hair via the [[keratinocytes]], the cells responsible for hair growth. These cells form the hair in the root and then grow through the skin surface taking any substances with them. On the other hand, the [[sebaceous glands]] produce FAEEs in the scalp and these migrate together with the sebum along the hair shaft (Auwärter et al., 2001, Pragst et al., 2004). So these glands lubricate not only the part of the hair that is just growing at 0.3&nbsp;mm per day on the skin surface, but also the more mature hair growth, providing it with a protective layer of fat.

FAEEs (nanogram = one billionth of a gram) appear in hair in almost one order of magnitude lower than (the relevant order of magnitude of) EtG (picogram = one trillionth of a gram). It has been technically possible to measure FAEEs since 1993, and the first study reporting the detection of EtG in hair was done by Sachs in 1993.<ref name="Kintz">{{cite book |author=Pascal Kintz |title=Analytical and practical aspects of drug testing in hair |url=https://books.google.com/books?id=IBBq180lUEAC&pg=PA305 |date=August 30, 2006 |publisher=CRC Press |isbn=978-0-8493-6450-1 |pages=305–}}</ref>

In practice, most hair which is sent for analysis has been cosmetically treated in some way (bleached, permed etc.). It has been proven that FAEEs are not significantly affected by such treatments (Hartwig et al., 2003a). FAEE concentrations in hair from other body sites can be interpreted in a similar fashion as scalp hair (Hartwig et al., 2003b).