The Pulmonary Effects of Outdoor Ozone and Particle Air Pollution

Abstract

Over the past three decades, considerable progress has been made in controlling levels of several outdoor air pollutants with well-established effects on human health (e.g., sulfur dioxide, carbon monoxide, and lead). However, concern remains about the potential human health impacts of two air pollutants, ozone (O₃) and fine particulate matter (PM_2.5), for which much less progress has been made. Both O₃ and PM_2.5 derive largely from fossil fuel combustion, and both have been shown to have human health effects at levels frequently observed in outdoor air. In the case of O₃, controlled chamber experiments have shown that brief, ambient-level exposures cause acute, reversible drops in lung volumes, increases in nonspecific bronchial responsiveness, and pulmonary inflammation. Epidemiology studies have confirmed many of these findings and further have demonstrated associations with asthma exacerbations, emergency room visits, hospital admissions, and deaths. Populations most at risk include children and adults who are active outdoors, especially those with asthma. PM_2.5 is a heterogeneous mixture of suspended solid and liquid particles with widely varying diameters and compositions. The evidence for health effects of PM_2.5 derives largely from epidemiological studies that have reported associations with both acute and chronic mortality in urban areas. Other effects associated with ambient particulate matter include increases in hospitalizations and respiratory symptoms and decreases in lung function. Populations at greatest risk of PM_2.5 effects include the elderly and those with preexisting cardiopulmonary disease. Important questions remain regarding PM health effects, including the nature of the PM component(s) responsible, the biological mechanism(s) involved, and the host factors that promote greater susceptibility; these are currently areas of active research.

Key Words:

Ozone - PM_2.5 - health effects