Many studies have documented the relationship between specific air pollutants and adverse health outcomes such as daily mortality, hospital admissions, or emergency department (ED) visits. This epidemiological evidence has been used in the regulatory process when defining air quality standards. Such standard setting in theory may be updated as more epidemiological evidence becomes available.
Recently, attention has focused on the relationship between fine particulate matter (particulate matter < 2.5 ¦Ìm; PM2.5) and adverse health outcomes, especially cardiac events. Recent findings have suggested a number of possible biological mechanisms, which mediate this relationship, and multiple epidemiological studies have investigated such relationship. Despite such research, key uncertainties still remain regarding the role PM2.5 plays in contributing to illness. Such uncertainties include the role played by the size and composition of such particles, whether a threshold exposure for the risk exists, and whether the PM2.5 is the actual risk factor, or is a proxy indicator for other pollutants that are the actual risk factor.
The St. Louis Metropolitan Area provides a significant opportunity to investigate these issues. From 2000 - 2003, St. Louis was a designated Environmental Protection Agency Super site, which resulted in the collection of exposure levels of pollutants at various high levels of resolution. This availability of exposure data for such a large number of pollutants and time period will assist in investigating the uncertainties listed above. Other pollution data is available from the EPA/AIRS/State (Missouri and Illinois) air monitoring program data. In addition, for a population center of its size, the St. Louis Metropolitan area has a high density of monitoring sites and substances, which will help with the ability for spatial resolution. Finally, the use of the St. Louis Metropolitan Area is important in that midwestern cities such as St. Louis differ from cities in other regions in terms of emissions, meteorology, and other factors.
The primary objectives are to determine if cardiac and upper respiratory illness reported at Hospital Emergency Departments (ED) in the metropolitan St. Louis area are associated with to air quality measures and specific and/or combination of air pollutants.