would have reviewed studies of Gulf War veterans. However, many of the Gulf War veteran studies were hampered by poor measures of exposure to the putative agents, used questionnaires to identify illnesses and exposure to the agents of concern, or did not include outcomes measured with actual clinical examinations or laboratory tests. The committee therefore based its conclusions primarily on evidence from studies of people exposed to the putative agents in occupational or clinical settings rather than from studies of Persian Gulf veterans. The committee found the evidence from occupational studies sufficient for drawing conclusions about associations between the putative agents and health outcomes, but the lack of adequate data on the veterans themselves complicated its consideration of the second part of the charge—determination of increased risk in Gulf War veterans.

To estimate the magnitude of risk of a particular health outcome among Gulf War veterans, the committee would need to compare the rates of health effects or disease in veterans exposed to the putative agents with the rates in those who were not exposed. That would require information about the specific agents to which individual veterans were exposed and about their doses. However, there is a paucity of data regarding the agents and doses to which individual Gulf War veterans were exposed. Furthermore, to answer questions about increased risk of illnesses in Gulf War veterans, it would be important to know the degree to which any other differences between exposed and nonexposed veterans could influence the rates of health outcomes or diseases; such information in the Gulf War veteran population is lacking. Because of the lack of various kinds of data on veterans, the committee could not extrapolate from the exposures in the studies that it reviewed to the exposures of Gulf War veterans. Therefore, it could not determine the likelihood of increased risk of adverse health outcomes among Gulf War veterans due to exposure to the agents examined in this report.

Existence of a Plausible Biologic Mechanism or Other Evidence of a Causal Relationship

Toxicologic data form the basis of the committee’s response to the third part of its charge—to determine whether there is a plausible biologic mechanism or other evidence of a causal relationship between exposure to a particular agent and a health effect. That information is summarized in general terms in Chapter 3. Specific toxicologic findings related to each health outcome are also given in the chapters that review the epidemiologic literature (Chapters 49).


Chapter 2 discusses the considerations that guided the committee’s review and evaluation of the scientific evidence and the criteria that it established to draw conclusions of association. Chapter 3 provides background information on fuels and combustion products, discusses how the veterans might have been exposed to those agents, and provides an overview of their toxicology. In Chapters 4 through 8 the committee presents its review of epidemiologic studies that identify health outcomes related to exposure to the putative agents and provide conclusions about those associations. Specifically, Chapter 4 discusses cancer; Chapter 5 examines respiratory outcomes; Chapter 6 presents the committee’s findings with respect to cardiovascular outcomes; Chapter 7 reviews reproductive and developmental outcomes, including childhood cancers; and Chapter 8 presents remaining health outcomes, such as neurologic and dermatologic findings. Finally, Chapter 9 is organized differently from the previous five chapters in that all the health outcomes related to exposure to missile propellants—hydrazines and red fuming nitric acid—are presented.

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