The relationship between air pollution and health is being questioned at the highest levels of the US Environmental Protection Agency (EPA) today. However, it is well established in the medical literature that short-term exposure to higher levels of outdoor air pollution is associated with reduced lung function, asthma exacerbations, myocardial infarction, emergency department visits, hospital admissions, and even deaths, primarily from respiratory and cardiovascular causes, although a broader range of systemic effects also have been documented.1,2 The cumulative adverse health effects associated with long-term exposure to air pollution have been most convincingly shown by cohort studies with decades of follow-up that have found, after controlling for potentially confounding factors, a significantly higher rate of cardiopulmonary death among participants living in areas with higher outdoor fine particulate matter less than or equal to 2.5 μm in diameter (PM2.5) air pollution.3-5