Gulf War service. These factor-derived syndromes were not associated with taking PB or with the dose of PB. Haley and Kurt found an association between two of the three syndromes and self-reported symptoms that are consistent with adverse effects of PB. Because the study cohort was not assembled from a random sample of Gulf War veterans, this apparent association may be the result of inadvertent selection for veterans with both adverse health syndromes and adverse effects of PB. The evidence is not strong enough to conclude that an association exists between Gulf War illnesses and side effects of PB. In the second epidemiologic study (Unwin et al., 1999), all exposures studied (PB, diesel or petrochemical fumes, oil fire smoke, viewing dismembered bodies, etc.) showed an association of similar magnitude with adverse symptoms in U.K. servicemen. The lack of specificity of the association between the type of exposure and symptoms suggests that PB itself is not the cause of the symptoms. Recall bias and reporting bias5 may explain this finding. Thus, neither of these two studies provides good evidence for a specific association between PB and chronic adverse health effects.

The committee concludes that there is inadequate/insufficient evidence to determine whether an association does or does not exist between PB and long-term adverse health effects.


During the Gulf War, a number of different immunobiologics (e.g., cholera, meningitis, rabies, tetanus, and typhoid vaccines) were sent to the war theatre to protect military personnel against potential exposures to biological threats (Committee on Veterans’ Affairs, 1998). Concerns about Iraq’s offensive biological warfare capabilities led to the decision that available vaccines should be utilized as preventive measures against biological warfare agents. The military sent approximately 310,000 doses of FDA-licensed anthrax vaccine to the Gulf War theatre, and it is estimated that 150,000 U.S. troops received at least one anthrax vaccination (Christopher et al., 1997; Committee on Veterans’ Affairs, 1998). Approximately 137,850 doses of botulinum toxoid were sent to the Gulf, and it is estimated that 8,000 military personnel were vaccinated (Committee on Veterans’ Affairs, 1998). However, medical records from the Gulf War contain little or no information about who received these vaccines, how frequently the vaccines were administered, or the timing of vaccinations relative to other putative exposures (OSAGWI, 1999).


Common sources of information bias are due to the inability of study subjects to accurately recall the circumstances of the exposure (recall bias) or to the likelihood that one group more frequently reports what it remembers than another group (reporting bias).

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