TESTING HUMAN HAIR FOR DRUGS OF ABUSE .4. ENVIRONMENTAL COCAINE CONTAMINATION AND WASHING EFFECTS

Active cocaine use results in sequestration of parent drug in hair. In addition, hair has unique physicochemical properties that permit abso rption of cocaine from the environment. When hair is tested for eviden ce of cocaine, it is important to consider whether the positive test r esulted from active drug use or environmental contamination. In a seri es of laboratory experiments, it was found that exposure of 'cut' hair to cocaine vapor ('crack' smoke) and to aqueous solutions of cocaine hydrochloride resulted in significant contamination of hair samples, S imilar results were obtained with two subjects who were exposed to coc aine vapor in an unventilated room. The amount of contamination adsorb ed by hair depended upon both time and extent of exposure. Washing the hair samples with methanol removed > 70% of the cocaine contaminant a fter cocaine vapor exposure, but was less effective (< 50%) following contamination with aqueous cocaine. Shampoo treatment cycles (overnigh t soaking) progressively removed increasing amounts of cocaine from th e contaminated hair, but residual cocaine remained after 10 cycles. St udies were also performed to determine the usefulness of benzoylecgoni ne as a marker of active cocaine administration. Small amounts of benz oylecgonine (ca, 1 ng/mg) were formed in hair as a result of environme ntal contamination with cocaine. Also, it was found that benzoylecgoni ne could be adsorbed from illicit cocaine contaminated with benzoylecg onine. It was concluded that positive hair test results should be inte rpreted cautiously due to the possibility of environmental contaminati on from cocaine and related constituents.