1. Wadsworth Center, New York State Department of Health, and Department of Environmental Health Sciences, School of Public Health, State University of New York at Albany, Empire State Plaza, P. O. Box 509, Albany, New York 12201-0509, Department of Environmental Atmospheric Science, Pukyong National University, 599-1 Daeyeon 3-dong, Nam-Gu, Busan 608-737, Korea, and Institute for Environmental Sciences, University of Shizuoka, 52-1 Yada, Shizuoka 422-8526, Japan