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Detecting Drugs in Hair: Is it Drug Use or Environmental Contamination?

NCJ Number
Date Published
June 2024

In this paper, the authors propose a possible standardized procedure for toxicology laboratories to remove external contaminants before performing drug analysis; they also discuss extrapolation methods and their production of unintentional metabolites, including phase II metabolites, and extension of the window of drug detection from hair.


Drug tests are often required for criminal investigations, child welfare checks, and compliance with probation or parole. Because drugs remain in strands of hair for months longer than they do in the bloodstream, drug tests based on hair are more robust across time and can provide evidence of drug use in the more distant past. Although neither test can reveal the quantity of drugs consumed, they can identify the drugs present. The challenge is differentiating whether a drug is present due to drug use or environmental contamination. Two National Institute of Justice-supported toxicologists have proposed a possible solution: examining the hair for drug breakdown products (metabolites) rather than the drug itself. According to the researchers, the “detection of conjugated metabolites in hair may directly affect the current policies and procedures for hair drug testing. It could alleviate concerns over the potential for external contamination and issues with interpretation of hair drug testing results.”

Date Published: June 1, 2024