According to the GAO, reports by the DoD, CIA and VA vastly underestimated the number of veterans exposed to chemical warfare agents during Gulf War I:
"It is likely that if models were more fully developed and more credible data for source term and meteorological conditions were included in them,...the hazard area would be much larger and most likely would cover most of the areas where U.S. troops and Coalition forces were deployed."
Link to .pdf of report