Department of Preventive Medicine, College of Medicine, Ewha Womans University, Korea.
*Department of Occupational & Enviornmetal Medicine, In-Ha University. Korean Industrial Health Association, Korea.
**Korean Industrial Health Association, Korea.
Copyright © 1999. Ewha Womans University School of Medicine
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.