Schema depicting how human hair appears in a scanning electron microscope
Hair analysis may refer to the chemical analysis of a hair sample, but can also refer to microscopic analysis or comparison. Chemical hair analysis may be considered for retrospective purposes when blood and urine are no longer expected to contain a particular contaminant, typically a year or less. Its most widely accepted use is in the fields of forensic toxicology and, increasingly, environmental toxicology. Several alternative medicine fields also use various hair analyses for environmental toxicology but these uses are controversial, evolving and not standardized.
Hair analysis can refer to the forensic technique of assessing a number of different characteristics of hairs, usually consisting of hairs from "known" sources and those recovered during forensic examinations or "questioned" hairs in order to determine whether they have a common source; for example, comparing hair found at the scene of the crime with hair samples taken from a suspect. Typically, examinations of this type are conducted using stereo-microscope(s) for initial preparation, and a comparison microscope for detailed analysis (comparison).
Use in forensic toxicology
Hair analysis is also used for the detection of many therapeutic drugs and recreational drugs, including cocaine, heroin, benzodiazepines and amphetamines. In this context, it has been reliably used to determine compliance with therapeutic drug regimes or to check the accuracy of a witness statement that an illicit drug has not been taken. Hair testing is an increasingly common method of assessment in substance misuse, particularly in legal proceedings, or in any situation where a subject may have decided not to tell the entire truth about his or her substance-using history.
In December 1995 the Society of Hair Testing was founded to promote the research in hair testing technologies in forensic, clinical and occupational sciences, to develop the international proficiency tests, to organize meetings and workshops and to encourage the scientific cooperation and exchanges among members. The Board of the Society of Hair Testing agreed upon the latest version of a Consensus in Sevilla, Spain, in 2004.
Hair samples are increasingly being used to detect the presence of illegal drugs both by the state and also by private employers who test their employees. The advantages of hair analysis include the non-invasiveness, low cost and the ability to measure a large number of, potentially interacting, toxic and biologically essential elements. The judicial admissibility of the test is guided by the Daubert standard. A precedent of national reference has been United States v. Medina, 749 F.Supp. 59 (E.D.N.Y.1990).
Use in environmental toxicology
Analysis of hair samples has many advantages as a preliminary screening method for the presence of toxic substances deleterious to health after exposures in air, dust, sediment, soil and water, food and toxins in the environment. The advantages of hair analysis include the non-invasiveness, low cost and the ability to measure a large number of, potentially interacting, toxic and biologically essential elements. Hence, head hair analysis is now increasingly being used as a preliminary test to see whether individuals have absorbed poisons linked to behavioral or health problems.
Use in detection of long term elemental effects
There appears to be genuine validity to the use of hair analysis in the measurement of lifelong, or long-term heavy metal burden, if not the measurement of general elemental analysis. Several interesting studies including the analysis of Ludwig van Beethoven's hair have been conducted in conjunction with the National Institutes of Health, and Centers for Disease Control and Prevention to name a few.
A 1999 study on hair concentrations of calcium, iron, and zinc in pregnant women and effects of supplementation, it was concluded that "From the analyses, it was clear that hair concentrations of Ca, Fe, and Zn could reflect the effects of supplementation... Finally, it could be concluded that mineral element deficiencies might be convalesced by adequate compensations of mineral element nutrients."
Use in occupational, environmental and alternative medicine
Hair analysis has been used in occupational, environmental and some branches of alternative medicine as a method of investigation to assist screening and/or diagnosis. The hair is sampled, processed and analyzed, studying the levels of mineral and metals in the hair sample. Using the results, as part of a proper examination or test protocol, practitioners screen for toxic exposure and heavy metal poisoning. Some advocates claim that they can also diagnose mineral deficiencies and that people with autism have unusual hair mineral contents. These uses are often controversial, and the American Medical Association states, "The AMA opposes chemical analysis of the hair as a determinant of the need for medical therapy and supports informing the American public and appropriate governmental agencies of this unproven practice and its potential for health care fraud." A recent review of scientific literature by Dr Kempson highlighted analysis of metals/minerals in hair can be applied in large population studies for researching epidemiology and groups of chronically exposed populations, however any attempt to provide a diagnosis based on hair for an individual is not possible. An exception to this can be in advanced analyses for acute poisoning.
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