| Background: Previous studies have demonstrated an association between air pollution and asthma exacerbation. Less understood is the effect of elemental carbon (EC) on increases in pediatric asthma emergency department (ED) visits across different age groups and how these relationships change across the seasons in a metropolitan area with several industries and relatively low air pollution, as well as differences between traditional time-series analysis approaches and more complex case-crossover approaches.;Methods: Measurements of EC, ozone, sulfur dioxide, and total oxides of nitrogen were available from the St. Louis EPA Supersite for June 1, 2001 to May 31, 2003. ICD-9 information was obtained on 281,763 pediatric emergency department visits from 27 hospitals in the St. Louis, MO metropolitan area. The relationship between EC and pediatric asthma emergency department visits, controlling for season, weekend exposure, allergens, and other pollutants known to exacerbate asthma, was assessed using Poisson generalized estimating equations using a 1-day lag between exposure and ED visit and using a case-crossover approach with conditional logistic regression. The relationships between pediatric asthma emergency department visits and other gaseous air pollutants and aeroallergens were also analyzed.;Results: EC did not appear to be significantly associated with pediatric asthma ED visits in this population. Major risk factors for severe asthma exacerbation included nitrous oxides and mold in the spring, tree pollen in the spring and fall, and grass pollen in the fall and winter.;Conclusions: Ultimately, the complexity of ambient PM makes explication of one single influential factor highly unlikely. Experimental and observational studies can continue to provide indication of key exposure parameters, PM physicochemical characteristics, and PM sources associated with increased adverse health effects in order to suggest relevant and improved metrics for regulations and thus improved protection of human health.;Keywords: asthma, children, air pollution, elemental carbon. |
