Hair Analysis As A Test For Drug Use

Because every drug taken becomes a permanent part of the user's hair, laboratory analysis of hair can reveal the presence of a variety of drugs, including HEROIN, COCAINE, AMPHETAMINES, PHENCYCLIDINE, MARIJUANA, NICOTINE, and BARBITURATES. Hair analysis is widely accepted by courts, parole boards, police departments, and employers around the country for detecting long-term drug use. It's also increasingly used to determine maternal/fetal drug exposure and to validate self-reports of drug use.

Unlike urinalysis, which can only detect drugs ingested within the past three to four days, hair analysis can reveal the ingestion of drugs during the past ninety days (or longer). Since hair grows at a relatively constant rate of1⁄ 2 inch (1 cm) per month, segmental analysis of hair strands could localize the time of drug exposure to within as little as one particular week. Although various hair treatments—such as tinting and perming—may remove some of the evidence, detectable traces will indelibly remain in the hair.

DRUGS IN HAIR

Hair is nonliving tissue composed primarily of a sulfur-rich protein called keratin. Hair growth occurs at a rate of 0.3 to 0.4 millimeters (0.011 to 0.012 inches) per day from the follicle (a saclike organ in the skin) in cycles of active growth followed by a resting phase. For an adult, approximately 85 percent of scalp hair is in the growing stage at any time. Two sets of glands are associated with the follicle: The sebaceous glands, which excrete sebum (a waxy substance), and the apocrine glands, which excrete an oil that coats the hair. Hair color is determined by genetic programming for varying amounts of melanin, a pigment that is synthesized in hair cells called melanocytes.

The exact mechanism by which drugs enter hair is unknown. They may be deposited from the capillaries, which supply blood to the follicles, or they may be excreted in the sebum, oil, or sweat that coat the hair shafts. Drugs can also be deposited on the hair by environmental exposure (such as marijuana smoke or cocaine powder in the air).

When hair is analyzed for drug use, a sample is taken from either the head or the body. It's washed to remove dirt and any external drug deposits (the wash medium is also tested), then stripped of melanin. The actual analysis is performed by RADIOIMMUNOASSAY that detects not only traces of drugs but their metabolites, chemicals that appear only when the body has metabolized (processed) the drug. All positive samples are confirmed by gas chromatography/mass spectrometry (GC/MS). This second test has a cutoff level to eliminate specimens containing drug levels that could come from environmental exposure (inhaling second-hand marijuana smoke or eating food that contains poppy seeds).

SIGNIFICANCE OF HAIR TESTING

Once a drug is embedded in hair it appears to be stable indefinitely, although concentration diminishes somewhat over time. (Cocaine metabolite has, for example, been detected in hair from a pre-Columbian mummy more than 500 years old.) This is an obvious advantage over other methods of DRUG TESTING, such as urinalysis, which can detect drugs ingested only within the past few days. Depending on length, hair analysis can determine drug use from months to years in the past. Hair is also easily collected and stored. If more testing is required, another sample may be easily obtained.

One disadvantage of hair analysis is that it won't reveal drug use during the three to five days before testing, since hair does not grow quickly enough to show this. Hair analysis is also more expensive than urinalysis, and the results take longer to be determined. The two tests can always be used in combination, however, to give a more complete picture of the individual's past and present drug use.

IS IT FAIR?

Some groups have raised concerns that hair testing may be biased against minority subjects because coarser, darker hair tends to trap more environmental drug residue than lighter, thinner hair. Hair testing labs say that their processes, which remove melanin from samples, removes any chance of distinction or discrimination by race or ethnic group. The Society of Forensic Toxicologists disagrees, arguing that even removing the pigment from hair does not eliminate the risk of bias in analysis.

Definitive proof of drug use, however, is based not on environmental exposure to drugs, but on the metabolites incorporated into the hair shaft. These indicators can only appear when the subject's body has metabolized the drug. The results of hair analysis are widely used and accepted by courts, law enforcement bureaus, and government agencies, including Federal Reserve banks and more than 80 state programs and medical research projects.

(SEE ALSO: Industry and Workplace, Drug Use in; Military, Drug and Alcohol Abuse in the U.S.)

BIBLIOGRAPHY

HARKEY, M. R., & HENDERSON, G. L. (1989). Hair analysis for drugs of abuse. In R. C. Baselt (Ed.), Advances in analytical toxicology. Chicago: Year Book Medical Publishers.

MIECKOWSKI, T. An analysis of the racial bias controversy in the use of hair assays. In Drug testing technologies: Field applications and assessments. Boca Raton, FL: Crc Press.

MIECKOWSKI, T. Hair analysis as a drug detector. (NCJ156434). http://www.ncjrs.org/drgstest.htm

EDWARD J. CONE

REVISED BY AMY LOERCH STRYMOLO