Date of Award

5-2012

Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

First Advisor

Brian P. Leaderer

Abstract

Asthma is an inflammatory disease of the airways characterized by shortness of breath, chest tightness, wheezing and cough. It is one of the most common chronic diseases in children in developed countries, and the prevalence of pediatric asthma has been increasing in recent decades. Both indoor and outdoor air pollution have been identified as risk factors for asthma incidence, prevalence and severity. One of the major gaseous air pollutants, nitrogen dioxide (NO2), is generally related to combustion processes and research has been done to assess its role in asthma outcomes. Unfortunately, studies investigating the relationships between NO2, asthma and respiratory symptoms have remained inconsistent. A major issue that arises in studies of N02 exposure is that most do not account for the high degree of spatial variability that is present in ambient NO2 levels, especially in urban areas. This dissertation research sought to address some of the issues identified in the current literature by: assessing the state of research on traffic-related pollution and asthma in children with a systematic review; employing an exposure assessment method that uses a combination of local measurements and modeling to address the concern of spatial variability in NO2 exposure levels; and using data from a large prospective cohort study of asthmatic children (STAR) to investigate the effects of school-level exposures to N02 on asthma severity. The systematic review it highlights the need for future large sample, prospective cohort studies with longer follow-up periods to investigate further the associations between traffic and asthma in children. Using a combined measurement and modeling approach, this study found a statistically significantly increased risk of worse asthma severity from ambient NO2 exposures at school for children with indoor home N02 exposures above 6 ppb compared to children with low home exposures (OR 1.31 (1.02, 1.69)). These children were more likely to be self-reported minorities with relatively low socioeconomic profiles. There was no association found between asthma severity and length of time spent or mode of transportation used in travel to school for the children in STAR. This study sought to enhance the current literature on school air pollution exposures and pediatric asthma by estimating ambient NO2 levels at schools and investigating the association between school-related N02, including exposures during transport, and asthma severity. Overall results indicated an increased risk of more severe asthma with concurrently high home and school N02 levels, with little effects on asthma severity from exposures during school-related transport.

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