The objective of this research was to analyze the correlation between the proportion of asthma visits to all healthcare visits at the OHSU Emergency Department and the air pollution levels for the period between July 18th, 1999 and July 17th, 2000. The analysis was accomplished using a robust air pollution model from the Oregon Department of Environmental Quality (DEQ)called the Portland Air Toxics Assessment Program (PATA). similar studies have Compared health data to modeled air pollution from single sources. This study utilizes model data derived from multiple sources for the Portland metropolitan area.