1. Department of International Health, Rollins School of Public Health of Emory University, 1518 Clifton Road, N.E., Atlanta, Georgia 30322
2. Department of Public Health, University of Liverpool, Whelan Building, Quadrangle, Liverpool L69 3GB, U.K.
3. Harvard School of Public Health, Department of Environmental Health, 665 Huntington Avenue, Boston, Massachusetts 02115
4. Environmental Health Sciences, School of Public Health, University of California, Berkeley, California 94720-7360
5. University of San Carlos, Guatemala City, Guatemala