Human health: Effects of ambient air particulate matter

The clearly identifiable human health effects of ambient air pollution follow their inhalation into the respiratory tract. In eastern North America, most of the acidic air pollution is associated with sulfuric acid aerosol, which is formed in the atmosphere as ultrafine particles (d < 0.1 mum) through the oxidation of sulfur dioxide emitted during fossil fuel combustion, and which is gradually agglomerated into fine particles (0.2 < d < 1.0 mum) and also neutralized to ammonium sulfate by reaction with ammonia gas, a product of anaerobic decay at ground level. Short-term peak exposures to ambient fine particles can cause asthma exacerbations and affect the lungs ability to clear itself of inhaled particles. Long-term chronic exposures are closely associated with premature mortality, increased rates of emergency department and hospital admissions, respiratory symptoms, and lost-time from work and school.