Decrease of ethyl glucuronide concentrations in hair after exposure to chlorinated swimming pool water

The direct alcohol marker ethyl glucuronide (EtG) is widely used for the assessment of alcohol consumption behavior and abstinence monitoring by hair analysis. We investigated the influence of chlorinated swimming pool water on EtG concentrations in hair in comparison to deionized water (Milli-Q) containing no chlorine. EtG concentrations were measured with a validated online solid-phase extraction-liquid chromatography-tandem mass spectrometry (SPE-LC-MS/MS) method. EtG positive hair samples were obtained from 3 regular drinkers and incubated for 0, 2, 4, 6, 8, and 10 hours at room temperature. EtG concentrations in hair were reduced after 2 hours of incubation in chlorinated water by 20 ± 12% (range: 4-33%), in deionized water by 24 ± 5% (range: 18-29%). Incubation for 10 hours resulted in a decrease in EtG concentrations of 57 ± 6% (range: 52-65%) for chlorinated water and 47 ± 11% (range: 32-60%) for deionized water. To demonstrate washout in forensic hair samples, 20 samples from subjects with known alcohol consumption behavior were investigated additionally. The samples were divided into 2 strands and analyzed with incubation in chlorinated water for 10 hours and for comparison without any incubation. A mean decrease of 53 ± 18% (range: 26-88%) was observed. These results clearly demonstrate that washout effects are caused by water and have a significant impact on EtG concentrations in hair. For people with hair that are regularly exposed to water for a longer period (eg. swimmers), washout effects may lead to a significant decrease of EtG concentrations in hair. Concentrations may fall below threshold concentrations used for the interpretation of consumption habits (7 pg/mg for social consumption, 30 pg/mg for excessive consumption).