Abstract
Many epidemiological studies have investigated health effects of particulate air pollution. This article provides a simple framework to categorize the basic study designs of most of the currently available studies of the health effects of particulate air pollution and briefly discusses the common methods of statistical analysis. Within this framework it outlines basic strengths and limitations associated with currently available epidemiological evidence. Both the strengths and limitations of the epidemiological studies stem largely from the use of people who are living in uncontrolled environments and who are exposed to complex mixtures of particulate air pollution. Inherent to these studies are at least four basic limitations, including: (1) limited information about biological mechanisms, (2) relatively meager information regarding linkages between ambient and personal exposures, (3) difficulty of disentangling independent effects or potential interactions between highly correlated risk factors, and (4) inability to fully explore the relative health impacts of various constituents of particulate pollution. Associations of cardiopulmonary health outcomes with particulate air pollution that have been observed in the epidemiological studies provide only one important part of the full picture. A more complete understanding of the health effects of particulate air pollution will require important contributions from toxicology, exposure assessment, and other disciplines. Nevertheless, the pattern of cardiopulmonary health effects associated with particulate air pollution which has been observed by the epidemiological studies is currently the strongest evidence of the potential health effects of this pollution.