Case-crossover studies of particulate air pollution and risk of death from asthma and from chronic obstructive pulmonary disease in the United States

Episodes of high air pollution in the twentieth century were associated with increases in mortality, especially cardiorespiratory mortality. Even though current levels of outdoor air pollution have been dramatically reduced compared to the levels during these episodes, they have been associated with respiratory adverse health effects. The following chapters present research conducted on particulate pollution, a widespread type of air pollution, and respiratory outcomes. Chapter 2 presents a review of asthma and COPD epidemiology, and a summary of studies that have investigated particulate air pollution and respiratory outcomes. Most of the studies presented in the literature review section found an association with increases in particulate matter and respiratory outcomes. Few studies were found that examined asthma and COPD mortality and air pollution. In this dissertation, a case-crossover study was conducted to estimate the association between asthma mortality and exposure to air pollution, mainly particulate matter less than 10 microns in aerodynamic diameter (PM10), among persons aged 5 to 34 in the U.S. from 1987 to 2000 (Chapter 3). We found that PM10 was positively associated with asthma mortality among children aged 5 to 14 years but negatively with mortality in adolescents and those that died from asthma on arrival. Increases in the asthma mortality risk were also observed with increases in ozone (O 3) levels (all-year long, spring, and summer) and in nitrogen dioxide (NO2) levels in the summer. In Chapter 4 we present the results of a second case-crossover study that was conducted to examine the association between COPD mortality and exposure to air pollution, mainly PM10, among persons older than 34 years of age in the U.S. from 1987 to 2000. Overall, our results showed positive associations of COPD mortality with PM10 , O3, sulfur dioxide, and NO2. Although further research confirming and strengthening these associations is needed, the results found in this study may be an indication of need for further review and possible implementation of stricter air quality standards.