External Contamination of Hair with Cocaine: Evaluation of External Cocaine Contamination and Development of Performance-Testing Materials

Abstract

The National Laboratory Certification Program undertook an evaluation of the dynamics of external contamination of hair with cocaine (COC) while developing performance testing materials for Federal Drug-Free Workplace Programs. This characterization was necessary to develop performance materials that could evaluate the efficacy of hair testing industry's decontamination procedures. Hair locks (blonde to dark brown/black) from five different individuals were contaminated with cocaine HCl. Hair locks were then treated with a synthetic sweat solution and hygienic treatments to model real-life conditions. Hair locks were shampooed daily (Monday through Friday) for 10 weeks, and samples of the hair locks were analyzed for COC, benzoylecgonine (BE), cocaethylene (CE), and norcocaine (NCOC). Three commercial analytical laboratories analyzed samples under three protocols: no decontamination procedure, individual laboratory decontamination, or decontamination by an extended buffer procedure at RTI International. Results indicated substantial and persistent association of all four compounds with all hair types. Hair that was not decontaminated had significantly greater quantities of COC and BE than did hair that was decontaminated. The only hair samples below detection limits for all four compounds were those decontaminated 1 h after contamination. Additionally, BE/COC ratios increased significantly over the 10-week study (regardless of decontamination treatment). From 21 days postcontamination until the end of the study, the mean BE/COC ratio for all hair types exceeded 0.05, the proposed Federal Mandatory Guidelines requirement. The largest variability in results was observed for samples decontaminated by participant laboratories. This suggests that current laboratory decontamination strategies will increase variability of performance testing sample results. None of the decontamination strategies used in the study were effective at removing all contamination, and some of the contaminated hair in this study would have been reported as positive for cocaine use based on the proposed Federal Mandatory Guidelines.

Morphological changes in human head hair subjected to various drug testing decontamination strategies

“…All of the hair types observed in this study were also used in a model drug contamination study in which hair samples were externally contaminated with cocaine, subjected to model hygienic treatment and then subjected to laboratory decontamination procedures including an aqueous buffer decontamination and a methanolic decontamination [17]. Hair samples subjected to aqueous phosphate buffer decontamination had lower concentrations of cocaine remaining than those hair samples subjected to methanolic decontamination protocols.…”

Hair testing is taking root

“…The participating laboratories employed different wash procedures, some extensive, but they failed to decontaminate the hair. 64 Standardized decontamination wash procedures that will effectively remove any trace of external contamination without actively removing the drugs incorporated into the hair are not currently available and, as such, the possible role of external contamination must be considered when interpreting hair testing findings.…”

“…The majority of published hair testing methods are for drugs of abuse, including opiates, 42,60,69 cocaine, 64,87,98 amphetamines 66,67,75,84 and cannabinoids, 58,85,86,99 employing GC-MS or LC-MS-MS. Although new methods have been reported using specialist analytical instrumentation including quadruple time-of-flight and matrix-assisted laser desorption/ionization time of flight, 97,100 standard instrumentation and method parameters (temperature programme, ions selected for monitoring, collision energies, etc.)…”

External post mortem artefact: a key issue in hair result interpretation

“…Approaches for preventing evidentiary false-positives due to external contamination of the hair specimens have been described since 1992 [2]. These criteria do not endorse a general acceptance [3,4]. Excluding laboratory mistakes, a false positive post mortem hair result can be observed in case of contamination from environmental pollution (external contamination) or after drug incorporation into the hair from the individual body fluids, such as sweat or putrefactive fluid (post mortem artefact).…”

“…As it can be observed from the scientific literature [2][3][4][5][6][7][8], several approaches have been proposed to get round the contamination scenario. All are dealing with living subjects and none have been developed for post mortem specimens, collected under very bad conditions.…”