1. Departments of Environmental Health and Engineering and Epidemiology, Bloomberg School of Public Health, Johns Hopkins University, 615 North Wolfe Street, Baltimore, MD 21205, USA.
2. INCAP Research Center for the Prevention of Chronic Diseases, Institute of Nutrition of Central America and Panama, 01011 Guatemala City, Guatemala.
3. Division of Cancer Epidemiology and Genetics, National Cancer Institute, 9609 Medical Center Drive, Rockville, MD 20850, USA.
4. Integra Cancer Institute, 01010 Guatemala City, Guatemala.