1. a Department of Preventive Medicine and Public Health, Ajou University, 5 Paldal, Suwon, 442–749, Korea; E-mail: jangjjy@madang.ajou.ac.kr
2. b Department of Preventive Medicine and Public Health, Ajou University, 5 Paldal, Suwon, 442–749, Korea
3. c Department of Industrial Environmental and Health, Yonsei University, Wonju, Korea
4. d Department of Preventive Medicine and Public Health, Yonsei University, Seoul, Korea