To determine the validity of DOD’s and the Department of Veterans  Affairs’ (VA) conclusions—based on epidemiological studies—that there  was no association between Khamisiyah exposure and the rates of  hospitalization or mortality, we reviewed published epidemiological  studies in which hospitalization and mortality among exposed and  nonexposed U.S. troops were analyzed. Information for Modeling

In addition to identifying the appropriate event to model, modeling  requires several components of accurate information:  the characteristics or properties of the material that was released and its  rate of release (for example, quantity and purity; the vapor pressure; the  temperature at which the material burns; particle size; and persistency and  toxicity); temporal information (for example, whether chemical agent was  initially released during daylight hours, when it might rapidly disperse into  the surface air, or at night, when a different set of breakdown and  dispersion characteristics would pertain, depending on terrain, plume  height, and rate of agent degradation);   data that drive meteorological models during the modeled period (for  example, temperature, humidity, barometric pressure, dew point, wind  velocity and direction at varying altitudes, and other related measures of  weather conditions);   data from global weather models, to simulate large-scale weather patterns,  and from regional and local weather models, to simulate the weather in  the area of the chemical agent release and throughout the area of  dispersion; and information on the potentially exposed populations, animals, crops, and  other assets that may be affected by the agent’s release. DOD’s Conclusion about U.S. Troops’ Exposure to Chemical Warfare Agents Cannot Be Adequately Supported

DOD’s conclusion about the extent of U.S. troops’ exposure to chemical  warfare agents during and immediately after the Gulf War, based upon  DOD and CIA plume model estimates, cannot be adequately supported. First,  the models DOD and the CIA selected were in house models not fully  developed for analyzing long-range dispersion of chemical warfare agents  as environmental hazards. Fourth, postwar field testing at the U.S. Army Dugway Proving Ground, in  Utah, to estimate the source term data did not realistically simulate the  actual conditions of the demolition operations at Khamisiyah or the effects  of the bombings at any of the other sites in Iraq. The MOD  estimated that the total number of British troops potentially exposed was  about 9,000 and the total number of troops as “definitely” within the path  of the plume, however, was about 3,800. DOD and VA Used Flawed Criteria for Determining Troops’ Exposure

In the two epidemiological studies, DOD and VA researchers used DOD’s  1997 plume model for determining which troops were under the path of  the plume—who were estimated to be exposed—and which troops were  not—those who were estimated to be nonexposed. DOD and VA Used an Insensitive Outcome Measure for Determining Hospitalization Rates

Hospitalization rates—the outcome measure used in the hospitalization  study—were insensitive because they failed to capture the chronic  illnesses that 1991 Persian Gulf War veterans commonly report, but that  typically do not lead to hospitalization. Studies that rely on this type of  outcome as an end point are predetermined to overlook any association  between exposure and illness. Even when models with the same source term data were used, the  results diverged.
Why GAO Did This Study

Since the end of the Gulf War in 1991, many of the approximately 700,000 U.S. veterans have experienced undiagnosed illnesses. They attribute these illnesses to exposure to chemical warfare (CW) agents in plumes--clouds released from bombing of Iraqi sites. But in 2000, the Department of Defense (DOD) estimated that of the 700,000 veterans, 101,752 troops were potentially exposed. GAO was asked to evaluate the validity of DOD, the Department of Veterans Affairs (VA), and British Ministry of Defense (MOD) conclusions about troops' exposure.

What GAO Found

DOD's and MOD's conclusion about troops' exposure to CW agents, based on DOD and CIA plume modeling, cannot be adequately supported. The models were not fully developed for analyzing long-range dispersion of CW agents as an environmental hazard. The modeling assumptions as to source term data--quantity and purity of the agent--were inaccurate because they were uncertain, incomplete, and nonvalidated. The plume heights used in the modeling were underestimated and so were the hazard area. Postwar field testing used to estimate the source term did not realistically simulate the actual conditions of bombings or demolitions. Finally, the results of all models--DOD and non-DOD models--showed wide divergences as to the plume size and path. DOD's and VA's conclusion about no association between exposure to CW agents and rates of hospitalization and mortality, based on two epidemiological studies conducted and funded by DOD and VA, also cannot be adequately supported because of study weaknesses. In both studies, flawed criteria--DOD's plume model and DOD's estimation of potentially exposed troops based on this model--were used to determine exposure. This may have resulted in large-scale misclassification. Troops under the path of the plume were classified as exposed; those not under the path, as nonexposed. But troops classified as not exposed under one DOD model could be classified as exposed under another DOD model. Under non-DOD models, however, a larger number of troops could be classified as exposed. Finally, as an outcome measure, hospitalization rate failed to capture the types of chronic illnesses that Gulf War veterans report but that typically do not lead to hospitalization.