1. School of Public Health, University of Texas, Brownsville Regional Campus, RAHC Building, 80 Fort Brown, Brownsville, Texas 78520, Division of Environmental & Occupational Health, School of Public Health, University of Minnesota, Minneapolis, Minnesota 55455, Minnesota Pollution Control Agency, 520 Lafayette Road, St. Paul, Minnesota 55155, and School of Public Health, University of Texas, Houston Health Science Center, Houston, Texas 77030