Douglas Dockery is Professor of Environmental Epidemiology and Chair of the Department of Environmental Health at the Harvard School of Public Health. He and his colleagues have studied the health effects of air pollution exposures in populations who have been followed for up to 25 years. That research has increasingly pointed to combustion-related particles as being causally linked to increased morbidity and mortality, even at the relatively low concentrations observed in developed countries today. Dockery and his colleagues have reported that episodes of particulate air pollution are consistently associated with increased daily mortality, increased hospital admissions and emergency room visits, exacerbation of asthma, increased respiratory symptoms and lower lung function. Long-term follow-up studies have shown particulate air pollution is associated with shortened life expectancy in adults and increased chronic respiratory illness and lower lung function in children. This research has led to the current debate on the role of particulate air pollution in producing adverse effect effects and to the re-evaluation of air quality standards both nationally and internationally. Dockery’s current research is attempting to more specifically identify the chemical and physical characteristics of those particles responsible for the observed adverse health effects.