cerebrovascular disease. It is divided into studies of Gulf War veterans, air-pollution studies, and occupational studies. Each subsection begins with primary studies that had strong methods and exposure information, and then takes up support studies that are not as methodologically robust. If the support studies’ findings are consistent with those of the primary studies, they add weight to the primary evidence.
In February 1991, retreating Iraqi forces set fire to more than 600 oil wells. Fires burned over a 10-month period, until November 1991, exposing thousands of US troops to combustion products. The two studies summarized below (Smith et al. 2002; Proctor et al, 1998) were the only well-designed Gulf War studies that examined cardiovascular effects expressly in relation to combustion-product exposure. The study of Smith et al (2002), the stronger of the two studies by virtue of its objectively documented exposures did not find a relationship; that finding is consistent with several studies of Gulf War veterans that are not reported here because they did not examine specific exposures in relation to symptoms. Another study (Kang et al. 2000), a large and representative, population-based study of 15,000 Gulf War veterans, did not find greater self-reporting of coronary heart disease among Gulf War veterans than among controls Similarly, mortality studies of Gulf War veterans have not found excess cardiovascular disease deaths.
Smith et al. (2002) examined hospitalization patterns of all active-duty personnel who were deployed to the Gulf War in 1991–1999 (n=405,142) and who were in the Persian Gulf during the oil-well fires. For each active-duty veteran (hospitalized and nonhospitalized alike), the study assigned an oil-smoke exposure by using National Oceanic and Atmospheric Administration modeling (Draxler et al. 1994; McQueen and Draxler 1994). Six exposure categories were created on the basis of average daily exposure and duration of exposure. The largest category of exposure to particulate matter (137,000 personnel) was 1–260 μg/m3 for 1–25 days; this was similar in dose but of much shorter duration than the exposure of those in the American Cancer Society (ACS) cohort (see below and Chapter 5). The study examined hospitalizations in relation to exposure. Hospitalizations were for any cause, for major diagnoses in International Classification of Diseases, 9th Edition-Clinical Modification, and for nine specific diagnoses potentially related to oil-well fires.2 A subject who had been hospitalized with one of the specific diagnoses before the war was excluded from further analysis. The study examined only hospitalizations in Department of Defence (DOD) hospitals because of the availability of data. It found decreased risk of ischemic heart disease among exposed than among nonexposed veterans (relative risk [RR] 0.82, 95% CI 0.68–0.99). One limitation of the study is that hospitalizations were captured only for DOD hospitals, which care for active-duty personnel or veterans with medical benefits. The authors pointed out, however that rates of service attrition were comparable across all exposure categories, including absence of exposure to smoke from oil-well fires.
Proctor et al. (1998) examined self-reported exposures in relation to the symptom experience of two cohorts of Gulf War veterans from Massachusetts (Ft. Devens) and New
Asthma; ischemic heart disease; emphysema, acute bronchitis, chronic bronchitis, bronchitis not specified as acute or chronic; malignant neoplasms of the respiratory and intrathoracic organs; malignant neoplasms of the oral pharynx, nasopharynx, and hypopharynx; and pneumoconiosis due to silica or silicates, pneumoconiosis due to inorganic dust, and unspecified pneumoconiosis; pneumopathy due to inhalation of the other dust; respiratory conditions due to chemical fumes and vapors; and other diseases of the respiratory system.