ACUTE RESPIRATORY EFFECTS OF PARTICULATE AIR-POLLUTION

Evidence from the selected epidemiologic studies presented in this review suggests a coherence of effects across a range of related health outcomes and a consistency of effects across independent studies with different investigators in different settings. This compilation also provides insights into the relative magnitude of effects being observed in various studies (Table 6). Total mortality is observed to increase by approximately 1% per 10 μg/m3 increase in PM10. Somewhat stronger associations are observed for cardiovascular mortality (approximately 1.4% per 10 μg/m3 PM10), and considerably stronger associations are observed for respiratory mortality (approximately 3.4% per 10 μg/m3 PM10). No acute effects are detected with cancer and other nonpulmonary and noncardiovascular causes of mortality. These relative differences in cause-specific mortality are plausible, given the respiratory route of particle exposures. If respiratory mortality is associated with particulate pollution, then health care visits for respiratory illness would also be expected to be associated with particulate pollution. Respiratory hospital admissions and emergency department visits increase by approximately 0.8% and 1.0% per 10 μg/m3 PM10 respectively. Emergency department visits for asthmatics (3.4% increase per 10 μg/m3 PM10) and hospital admissions for asthmatic attacks (1.9% increase per 10 μg/m3 PM10) are more strongly associated. Asthmatic subjects also report substantial increases in asthma attacks (an approximate 3% increase per 10 μg/m3 PM10) and in bronchodilator use (an approximate 3% increase per 10 μg/m3 PM10). Less severe measures of respiratory health also are associated with particle exposures. Lower respiratory symptom reporting increases by approximately 3.0% per 10 μg/m3 PM10 and cough by 2.5% per 10 μg/m3 PM10. Weaker effects are observed with upper respiratory symptoms (approximately 0.7% per 10 μg/m3 PM10). While lung function provides accurate objective measures, the observed mean effects are fairly modest: approximately 0.15% decrease for FEV1 or FEV.75 and 0.08% decrease for peak flow per 10 mg/m3 PM10. Despite the relatively small size of these lung-function effect estimates, they consistently achieve statistical significance. Moreover, mean changes in lung function may not reflect substantial changes in sensitive individuals. In this review, changes in health measures are reported for only small changes in daily particulate pollution: 10 μg/m3 increase in PM10 concentrations. Because daily concentrations of PM10 in some US cities average over 50 μg/m3 and often exceed 100 or 150 μg/m3, the effects of particulate pollution can be substantial for realistic acute exposures. For example, a 1% effect estimate per each 10 μg/m3 increase would produce a 5% increase in the health measure for a 50 μg/m3 increase in PM10 concentrations, and a 3% effect estimate would produce a 16% increase. Thus the estimated increase in attacks of asthma (3.0% per 10 μg/m3 PM10) would be 16% for a 50 μg/m3 increase in PM10 concentrations.