Several studies (Huang 1986; Pollini et al. 1986, 1989; Van Peenen et al. 1985) have been conducted in the petroleum industry to identify and assess potential cardiovascular risk factors. However, the studies did not look specifically at whether exposure to petroleum products or fuels was associated with an increased risk of cardiovascular disease. Instead, they attempted to identify behavioral risk factors and potential screening tools that could form the basis of behavior-modification programs and health risk assessments among petroleum industry-workers.
In contrast, cohort mortality studies of petroleum-refinery workers (such as Christie et al. 1987; Dagg et al. 1992; Hanis et al. 1985; Kaplan 1986; Rushton and Alderson 1981; Tsai et al. 1992; Wong et al. 2001a, 2001b) have examined mortality due to cardiovascular and cerebrovascular diseases. The researches typically used job titles to assess exposure and this can lead to misclassification of exposures. The studies found no increased risk of cardiovascular or cerebrovascular diseases among petroleum-industry workers compared with the general population. In fact, in many studies, mortality was lower than expected. For example, in Wong et al. (2001b), ischemic heart disease had a standard mortality ratio (SMR) of 0.88, 95% confidence interval (CI) 0.77–0.99; chronic endocardial disease and other myocardial insufficiencies had an SMR of 0.08, 95% CI 0.00–0.46; and all other heart disease had an SMR of 0.64, 95% CI 0.43–0.92. As discussed previously, the “healthy-worker effect” probably contributed to those findings.
The committee is unable to draw a conclusion of association given the lack of studies that specifically examined the relationship between exposure to fuels and cardiovascular diseases and the large confounding role of hypertension, high blood pressure, smoking, diet and exercise—which are not often controlled for in cohort mortality studies—in the etiology of those diseases.
The literature on combustion product exposure and cardiovascular disease is large and complex and the there have been recent publications that provide background for this burgeoning area of research (for example, Brook et al. 2004). However, a substantial portion of the literature concerns occupational cohorts in specific occupations (for example, vehicle drivers and tunnel workers) whose exposure is of uncertain relevance to the exposures in the Persian Gulf; such studies are nonetheless considered in this review. Another, larger group of studies, regarding acute exposure to particulate air pollution and cardiovascular events (morbidity and mortality), were not considered relevant to this review; these studies, typically time-series or case-crossover analyses, provide information on events that occurred within days of exposure and so are not relevant to Gulf War exposure and onset of cardiovascular effects long after return from the Gulf War. One useful background reference would be the recently published statement on air pollution and cardiovascular diseases from the American Heart Association.
A common difficulty in assessing the literature for this review is the lack of specificity of diagnoses reported in published articles. For example many articles treat “cardiopulmonary mortality” as one outcome. That provides some information on effects, but it is difficult to translate such a highly heterogeneous outcome into specific diagnoses to support conclusions on specific health outcomes.
This section covers the effect of exposure to combustion products on long-term cardiovascular outcomes, including ischemic heart disease, myocardial infarction, and