AMERICAN JOURNAL OF INDUSTRIAL MEDICINE 50:293–302 (2007) DNA Adducts in Granulocytes of Hospital Workers Exposed to Ethylene Oxide Lee C. Yong, PhD, 1 Paul A. Schulte, PhD, 2 Chi-Yu Kao, PhD, 3 Roger W. Giese, PhD, 3 Mark F. Boeniger, MSc, 1 Gary H.S. Strauss, PhD, 4 Martin R. Petersen, PhD, 1 and John K. Wiencke, PhD 5 Background Ethylene oxide (EtO), an important industrial chemical intermediate and sterilant, is classified as a human carcinogen. Occupational EtO exposure in many countries is regulated at 1 ppm (8-hr TWA), but levels of EtO-DNA adducts in humans with low occupational EtO exposures have not been reported. Methods We examined the formation of N7-(2 0 -hydroxyethyl)guanine (N7-HEG), a major DNA adduct of EtO, in 58 EtO-exposed sterilizer operators and six nonexposed workers from ten hospitals. N7-HEG was quantified in granulocyte DNA (0.1–11.5 mg) by a highly sensitive and specific gas chromatography-electron capture-mass spectrometry method. Cumulative exposure to EtO (ppm-hour) was estimated during the 4-month period before the collection of blood samples. Results There was considerable inter-individual variability in the levels of N7-HEG with a range of 1.6–241.3 adducts/10 7 nucleotides. The mean levels in the nonexposed, low (32 ppm-hour), and high (>32 ppm-hour) EtO-exposure groups were 3.8, 16.3, and 20.3 adducts/10 7 nucleotides, respectively, after the adjustment for cigarette smoking and other potential confounders, but the differences were not statistically significant. Conclusions This study has demonstrated for the first time, detectable levels of N7-HEG adducts in granulocytes of hospital workers with EtO exposures at levels less than the current U.S. standard of 1 ppm (8-hr TWA). A nonsignificant increase in adduct levels with increasing EtO exposure indicates that further studies of EtO-exposed workers are needed to clarify the relationship between EtO exposure and N7-HEG adduct formation. Am. J. Ind. Med. 50:293 – 302, 2007. ß 2007 Wiley-Liss, Inc. KEY WORDS: ethylene oxide; DNA adducts; granulocytes; hospital workers; occupational exposure; N7-(2 0 -hydroxyethyl)guanine; gas chromatography-electron capture-mass spectrometry ß 2007 Wiley-Liss, Inc. *Correspondence to: Lee C.Yong, Industrywide Studies Branch, Division of Surveillance, Hazard Evaluations and Field Studies, National Institute for Occupational Safety and Health (NIOSH), 4676 Columbia Parkway, Mail Stop R-15, Cincinnati, OH 45226. E-mail: lay7@cdc.gov Accepted14 January 2007 DOI10.1002/ajim.20443. Published online in Wiley InterScience www.interscience.wiley.com 1 Division of Surveillance, Hazard Evaluations and Field Studies, National Institute for Occupational Safety and Health, CDC, Cincinnati, Ohio 2 Education and Information Division, National Institute for Occupational Safety and Health, CDC, Cincinnati, Ohio 3 Department of Pharmaceutical Sciences and Barnett Institute, Northeastern University, Boston, Massachusetts 4 Pb2Au Biomedical TechnologyAssessment & Development,Chapel Hill, North Carolina 5 Neuro and Molecular Epidemiology Laboratory, University of California, San Francisco, California The findings and conclusions in this report are those of the author(s) and do not necessa- rily represent the views of the National Institute for Occupational Safety and Health.