Potential for Prevention/Public Policy
The increase in relative risk for cardiovascular disease due to air pollution for an individual is small compared with the impact of the established cardiovascular risk factors. However, because of the enormous number of people affected, even conservative risk estimates translate into a substantial increase in total mortality within the population. The impact on cardiovascular disease therefore represents a serious public health problem. The latest draft of the US EPA Air Quality Criteria for Particulate Matter has confirmed the presence of an apparent linear dose-response relationship between PM and adverse events.186 Data from all North American studies demonstrate that this curve is without a discernible threshold below which PM concentrations pose no health risk to the general population.186 At present-day levels, ≈40 000 deaths per year in Austria, France, and Switzerland combined have been attributed to PM.187 Estimates based on time-series studies suggest that ≈5000 excess deaths per year in Canada188 and 6000 cardiovascular events in the United Kingdom189 can be attributed to poor air quality. Approximately 1 in 50 myocardial infarctions were thought to be triggered by outdoor air pollution in a London, England, study.3 On a global scale, the World Health Organization has estimated that 800 000 deaths occur per year and 7.9 million disability-adjusted life-years are lost annually due to PM exposure.189a
Given the burden of epidemiological evidence, the US EPA updated the National Ambient Air Quality Standards in 1997 to specifically include PM2.5 (Table).190 The most current estimates by the EPA suggest that attainment of these standards would reduce total mortality by 23 000 deaths annually and cardiovascular hospital admissions by 42 000 per year in the United States.191 Nevertheless, 19% of all US counties with air-quality monitoring systems are presently not meeting these standards.192 This percentage is substantially greater in regions such as the industrial Midwest (41%) and southern California (60%). In light of these data, there is a clear potential to improve the national public health and to substantially reduce cardiovascular morbidity and mortality by reducing PM levels to current EPA standards. The potential cardiovascular health effect of reducing the gaseous copollutants remains less certain.