Fig. 1

Map Delineating Districts for VHAS sampling. Map created by Digit Lab, University of Utah (https://digit.utah.edu/).© University of Utah Department of Geography DIGIT Lab. Districts are categorized according to exposure to all ordnance dropped from U.S. and allied airplanes and helicopters in Vietnam between 1965 and 1975, as well as artillery fired from naval ships. These data come from the 1965–70 Combat Activities-Air (CACTA), the 1970–75 Southeast Asia (SEADAB), and Combat Naval Gunfire (CONGA) databases