1. 3M Occupational Health and Environmental Safety Division, 374-5 Byeongjeom-dong, Hwaseong-si, Gyeonggi-do 445-360, Korea
2. Department of Environmental Health, Kyung-In Women's College, Gyeyang-gu, Incheon 407-740, Korea
3. Department of Environmental Health, Kyung-In Women's College, 101 Gyesan-gil, Gyeyang-gu, Icheon 407-740, Korea. Phone: 82-32-540-0166; Fax: 82-32-555-2615; E-mail: jch9999@korea.com
4. Department of Environmental Science and Engineering, Gwangju Institute of Science and Technology, Puk-gu, Gwangju 500-712, Korea