Background: Despite the growing importance of ethyl glucuronide (EtG) in hair for detection of chronic excessive alcohol consumption, the mechanism of incorporation is not yet clear. Deposition from sweat is believed to be the main route. In order to get more information, EtG was determined in daily shaved beard hair after single higher alcohol doses.
Methods: Three volunteers drank within 5.5 h 153, 165 and 200 g ethanol followed by abstinence. Daily shaved beard hair was analysed for EtG using a validated liquid chromatography-tandem mass spectrometry method with a limit of quantification of 2 pg/mg.
Results: For all three volunteers, small concentrations of EtG were already detected 9 h after end of drinking. The concentrations increased to maxima of 182, 242 and 74 pg/mg on days 2 to 4 and then gradually decreased to limit of quantification on days 8 to 10.
Discussion: The time course of EtG is discussed based on literature data about anatomic dimensions of the hair root, physiology of hair growth, kinetics of EtG formation and elimination in blood, and in comparison to literature results about drugs in beard hair. It follows that for beard hair the predominant portion of EtG is incorporated in the upper part of the hair root between suprabulbar region and isthmus leading to a positive zone of about 3 mm (8-9 days) after a single drinking event. Deposition from sweat which is only possible into the residual hair stubble after shaving and in the infundibulum down to the sebaceous gland mouth was found to be of minor importance but could play a greater role in long hair.
Conclusion: It is concluded that EtG in hair fulfils the prerequisites for time-resolved interpretation of segmental concentrations and that a single excessive drinking can be well detected in sufficiently short hair segments. However, in the routinely investigated 3-cm proximal scalp hair segment and using the cutoff of 7 pg/mg, a negative result can be expected with high probability because of dilution by negative hair.