Acetaldehyde (AA) derived from alcoholic beverages is a confirmed carcinogen for esophageal and head and neck cancers. AA forms various DNA adducts and is thought to play a crucial role in carcinogenesis. Transient DNA adducts are usually repaired, but the stability of AA-derived DNA adducts has not been elucidated. We investigated the stability of N-2-ethylidene-2'-deoxyguanosine (N-2-ethylidene-dG), a major AA-derived DNA adduct, in cultured cells. First, to determine the optimal concentration of AA for detecting N-2-ethylidene-dG in cell culture, a dose-response study was performed using HL60 cells of the human promyelocytic leukemia cell line. An AA concentration, >= 0.01% (1.8 mM) was required to detect N-2-ethylidene-dG in vitro. We next examined the stability of N-2-ethylidene-dG. After a 1 or 2 h exposure to 0.01% of AA in a tightly sealed bottle, N-2-ethylidene-dG content was measured by sensitive liquid chromatography tandem mass spectrometry immediately, 24 h, and 48 h after exposure. After the 1 h exposure, the mean (+/- SD) N-2-ethylidene-dG contents were 12.1 +/- 1.28, 8.20 +/- 0.64, and 6.70 +/- 0.52 adducts per 10(7) bases at each postexposure time. After the 2 h exposure, N-2-ethylidene-dG content increased to 21.4 +/- 7.50, 10.5 +/- 3.61, and 9.83 +/- 3.90 adducts per 10(7) bases at each postexposure time. The half-life of this adduct was calculated as similar to 35 h in independent experiments. These results indicate that AA exposure from daily alcohol consumption may cause DNA damage and may increase the risk of alcohol-related carcinogenesis. (C) 2012 Elsevier Inc. All rights reserved.