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EVALUATION OF COARSE, FINE, AND ULTRAFINE PARTICLES AS PART OF A HEALTH EFFECTS EXPOSURE STUDY
Citation:
CASUCCIO, G. S., T. L. LERSCH, S. F. SCHLAEGLE, R. B. DEVLIN, AND B. RAY. EVALUATION OF COARSE, FINE, AND ULTRAFINE PARTICLES AS PART OF A HEALTH EFFECTS EXPOSURE STUDY. Presented at American Association for Aerosol Research International Speciality Meeting, Atlanta, GA, February 07 - 11, 2005.
Description:
Ambient PM is a complex mixture that includes bioactive and toxic compounds of natural and anthropogenic origin, several of which have been theorized to be causative or contributory to the adverse effects of PM inhalation. Numerous epidemiological studies have reported associations between exposure to ambient levels of particulate matter (PM) and various indices of cardiopulmonary morbidity and mortality. However, despite a decade of intensive study, much about the PM health effects problem is still not understood. Various physicochemical properties such as particle size and surface area have also been linked to the health effects of PM, and it has been hypothesized that toxicity of PM is related to particle size, proposing that smaller particles are relatively more potent than larger ones in producing health effects. Ultrafine particles (UF; particles less than 0.1 um) have been specifically associated with a worsening of pre-existing pulmonary diseases and have been shown to have a higher acute inflammatory potency than larger particles in animal instillation studies. The current and proposed National Ambient Air Quality Standard limits on permissible PM levels are set on a mass basis for two particle size fractions, particles between 2.5 and 10 um and for those less than 2.5 um in mean aerodynamic diameter. However, UF particles present a special problem in the regulation of ambient PM because they normally contribute relatively little to the total PM mass. Thus, it is possible that current and proposed regulation of ambient PM on a mass basis fails to adequately control levels of UF particles. In an effort to provide additional insight on this issue, the U.S. Environmental Protection Agency (EPA) has initiated an experimental assessment of the health effects of exposure to UF particles concentrated from ambient air in healthy young adult human subjects. A key component of this study is evaluation of subjects exposed to PM in a specially designed aerosol chamber. As part of this effort, it is necessary to document the size distribution and composition of the PM introduced to the chamber. A discussion on the design of the EPA particle concentrator chamber is provided along with methods used to collect and analyze coarse, fine and UF particles.