Hair Testing vs. Urinalysis: Any Racial Impact?
For years, hair drug testing has been the subject of disagreement. Opponents of the test claim that it is racially biased, producing positive results for Black Americans at disproportionate rates. The argument is that some hair products used by Black Americans are more likely to attract drug residue, and also, hair with more melanin can lead to false positives.
Drug tests should be accurate, and Trucking Alliance carriers found that 9 out of 10 illegal drug users actually pass the federally required urine test. And, the hair drug test identified them at the same relative percentages across all racial groups. Trucking Alliance member carriers also employed a higher percentage of minority drivers than the industry at large, so the claims of racial bias from hair testing appeared counterintuitive.
Hair vs. Urinalysis Efficacy
The Trucking Alliance supports hair drug testing for commercial truck drivers. In 2015, Congress passed a law to officially recognize hair drug testing as an effective alternative to urinalysis, and we believe it offers better accuracy without racial bias. Here’s why:
A 2023 study, funded by The Trucking Alliance and conducted by researchers at the University of Central Arkansas, was subsequently reviewed by researchers at the University of Tennessee. The study found that hair drug testing is significantly more accurate than urinalysis.
The study gathered data from seven commercial trucking companies providing over one million drug tests between 2017-2023. The test results comprised 514,615 urine samples and 498,879 hair samples. Research revealed more positive results for the following users:
- 57x more effective in testing for MDMA
- 24x more effective in testing for opioids
- 23x more effective in testing for cocaine
- 13x more effective in testing for amphetamines/methamphetamines
- 5x more effective in testing for marijuana
- 3x more effective in testing for PCP
The study also revealed that in 2023, hair testing uncovered 14 times more drug positives than urine testing. We believe this proves that hair testing detects more drug users and, therefore, should be used over urinalysis for pre-employment testing.
Hair testing and racial bias
Another study published in the Journal of Transportation Management analyzed over 151,000 paired urine and hair test results and found no evidence of racial bias in hair testing. The study confirmed that while pass/fail rates differed across ethnic groups, these differences were consistent across both urine and hair testing, indicating that factors other than hair type or ethnicity were responsible for the variations.
To further investigate racial bias in hair and urine testing, we tasked the University of Central Arkansas with studying hair tests vs. urinalysis for racial bias.
The result? The 2020 study showed no evidence that the test is discriminatory in nature. We’ll break down their research methods to show how they reached this conclusion.
The study
Researchers studied a sample population of over 73,000 commercial drivers. They received drug screen results from three commercial trucking companies from 2017-2019. They chose to focus on the three-year period and the year 2018 in isolation. These were the sample sizes:
- 2017-2019 urine tests: 73,176
- 2017-2019 hair tests: 72,023
- 2018 urine tests: 39,517
- 2018 hair tests: 38,900
Two research methods were used: the Four-Fifths Rule and chi-square (c2) analysis.
The Four-Fifths Rule
Defined in the Code of Federal Regulations, the U.S. government relies on the Four-Fifths Rule to determine whether a discriminatory impact has occurred on specific groups of people. To ensure equity, the policy states that each ethnic group affected must pass at least 80% of the rate of the ethnic group with the highest passing rate.
This method analyzed the 73,176 urine test results, and all racial groups exceeded the 79% threshold.
However, since hair tests are known to produce more accurate test results, every ethnic group failed the hair drug test at a higher percentage than the urinalysis. However, the Four-Fifths Rule revealed that all groups passed at equal rates, with no negative impact on any single ethnic group.
One of the researchers, Doug Voss, PhD, in a speech to the Drug Testing Advisory Board (DTAB) of the Substance Abuse and Mental Health Services Administration (SAMHSA), commented that “applying the Four-Fifths Rule to the urine and hair test results of this driver population clearly showed that hair testing is not racially biased against any ethnic group.”
Chi-square analysis
Chi-square analysis works a little differently. By this method, disparate impact would be determined if there were no significant differences between groups in urine test results, but significant differences in hair test results. In other words, if all racial groups passed the urine drug tests at similar rates but passed the hair drug test at significantly different rates, a disparate impact would have occurred. While the hair test revealed more positive results overall, similar results spanned across ethnic groups and at statistically comparable rates to the urine test.
Said Dr. Voss, “In conclusion, if hair testing is racially biased, these two methods that we applied to this huge sample size would have revealed different results than what we found. We could not find racially disparate impacts between urine and hair drug test results.”
Our Takeaway: Hair Drug Testing Does Not Discriminate
In light of this research, hair drug testing is neither racially biased nor biased against darker hair colors. After 10 years of delay, the Department of Transportation should implement what Congress mandated – recognize hair drug testing. Positive results can then be submitted to the Drug and Alcohol Clearinghouse, a database of all positive truck driver drug test results. Hair testing is a reliable, fair, and effective method for identifying drug users. This is one of the many ways we can work to keep unsafe drivers from operating commercial trucks, limiting the number of fatal accidents on our roads.