摘要:Acknowledgements should have been as follows: Acknowledgements: The authors would like to thank Professor A.J.Bailer, Miami University and NIOSH, for reviewing this manuscript and helpful comments In addition, the authors would like to thank Dr. S.B.Koh and K.S. Kim for their comments and also all collegues for their contribution to health examinations. This study was supported by a faculty research grant of Yonsei University College of Medicine for 2005(6-2005-0122).