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The Case Against Hair Testing
An effort to approve hair samples for drug testing in commercial truck drivers is drawing some criticism. The Drug Free Commercial Truck Driver Act of 2015 has bipartisan support, but critics say the science behind it is flawed.
Hair testing is based on the premise that certain drugs leave chemical markers in the hair. When hair samples are analyzed, those markers provide a history of drug use. Unlike urinalysis, which shows drugs that have been ingested within the last few days at most, hair testing can provide months of evidence.
It may not, however, reveal the most recent drug use. “Hair testing has a window of testing for the previous months or weeks. If you take one-and-a-half inches closest to the scalp, it will give an indication of drug use for the past 90 days,” said Dr. Kent Peterson, president of Occupational Health Strategies, Charlottesville, Va., in an interview with Fleet Owner.
“Hair testing may be used for pre-employment screening to show long-term use, but it gives no indication of current use or recent impairment.”
As it is currently written, the Drug Free act allows hair testing for pre-employment screening and random tests but not for tests required after an accident.
A bigger problem with hair testing, say critics, is that results can be affected by an individual’s hair color. “Curly haired and persons of color are more likely to test positive because they have more melanin in their hair, which binds more strongly with markers,” said Peterson.
“It’s believed that if hair testing were to be used and brought to court, it would be thrown out on that basis alone.” Peterson added that people with white hair retain almost no chemical drug markers in their hair.
Those are not the only issues with hair testing. The Substance Abuse and Mental Health Services Administration, a branch of the U.S. Department of Health and Human Services, has declined to recommend hair testing for a myriad of reasons.
In addition to the problems with timeline and hair color bias, scientists still are not sure exactly how chemical markers are deposited in hair shafts, whether the rate of hair washing can affect the presence of those markers or how environmental contamination can play a role.
They do know that the test has a low sensitivity to marijuana and a high sensitivity to cocain.
“There are no peer-reviewed articles that say hair testing works,” said Lewis Maltby, president of the National Workrights Institutes, Princeton, N.J. “The only people who say hair testing works are those selling hair testing services.”
Advocates for hair testing, including the American Trucking Associations, say that hair samples are more resistant to tampering than urine samples. They also believe that evidence of drug use over a longer period of time would increase the industry’s ability to suss out users.
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