1. Assistant Professor, Dept. of Environmental Health, Kyungin Women’s College, 101 Kyesan-gil, Kyeyang-gu, Incheon 407-740, South Korea (corresponding author). E-mail: jch 999@korea.com
2. Professor, Dept. of Environmental Science and Engineering, Gwangju Institute of Science and Technology, 1 Oryong-dong, Puk-gu, Gwangju 500-712, South Korea.