Research Program Area: Health & Exposure
Heart and lung patients are considered at greater risk during episodes of significant oxidant pollution and, although there are no quantitative laboratory data available, are advised to curtail physical activity. In the present investigation, six male volunteers, ages 46-64 years, with clinically documented coronary artery disease and a well defined symptomatic angina pectoris threshold on physical exertion, served as subjects. Each patient was exposed on three occasions for 40 minutes to either filtered air or to ozone at concentrations of 0.20 or 0.30 parts per million, while walking on a treadmill at workloads simulating their regularly prescribed symptom limited exercise training regimen. Standard pulmonary function tests and periodic observations of exercise ventilation, respiratory metabolism, electrocardiographic changes, hemodynamic response, and clinical signs and symptoms were noted. Analysis of variance revealed that none of the patients' physiologic responses to ozone exposure were statistically significant. Furthermore, neither onset of angina pain or ischemic changes were related to ozone exposure in a dose dependent fashion. Hence, the patients not only failed to exhibit any unexpected cardiovascular strain while exposed to ozone, but also evidenced no significant pulmonary function impairment or exercise ventilatory pattern alteration as has been observed in clinically normal subjects exercising at similar ozone concentration levels. This apparent incongruity may be due to the fact that ozone toxicity is more closely related to the total amount of ozone inhaled (that is, as a function of pulmonary ventilation volume and exposure time, as well as ozone concentration). Hence, the angina patients' symptom limited exercise tolerance resulted in a lower total amount of ozone inhaled (termed effective dose) than that observed to effect ozone toxicity in clinically normal subjects, who exercised at greater intensities and for longer durations. It was concluded that the angina patients appear to be no more susceptible to ozone, toxicity effects than are clinically normal subjects at the effective doses imposed. However, had the patients exercised longer, they might well have evidenced pulmonary function impairment and/or cardiovascular strain, as would other heart disease patients with greater work capacity while exercising at their higher exercise training intensities for periods approximately one hour. Hence, caution is advised in generalizing our observations to other patient groups and conditions.
For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753
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