Improved characterization of ozone air pollution through health impact assessments and applied spatial statistics

Tropospheric ozone is a criteria air pollutant associated with adverse health effects, including respiratory related mortality and morbidities. It is regulated under the Clean Air Act and the U.S. Environmental Protection Agency charged with proposing acceptable standards to protect the public's health. Exposure assessment is a critical tool that allows us to estimate the concentrations of pollutants interacting with the general population. By better understanding factors that affect ozone concentration variability and promoting the application of state of the art spatial methods for optimal mapping (spatial prediction) of ozone, we can improve our understanding of ozone's impact on health.;This research follows a paradigm with three primary Aims. Aim 1 performs a health impact assessment to quantitatively determine the reduction in morbidities and mortalities from meeting current regulatory ozone standards, as well as more stringent proposed standards. This will inform the population level impacts of ozone exposure across the U.S. and within certain metropolitan areas. Our Aim 2 focuses on the concept of understanding variability in ozone concentrations. An exploration of the environmental factors that impact ozone concentration variability was undertaken, along with a comprehensive comparison of statistical methodologies for optimal ozone mapping. Current literature has unfortunately popularized less statistically optimal methods for which this research aim will hope to highlight. Finally, building off of Aim 2 we further improve ozone exposure assessment by combining both monitoring data and output from the air quality models, Community Multiscale Air Quality (CMAQ), in spatial methods for understanding ozone concentration variability and optimal ozone mapping.;Our results show that ozone air pollution currently places a substantial burden on the public health of the United States. If all locations met the current ozone regulatory standard, there would be significant numbers of avoided premature mortalities and morbidities. If the ozone standard were lowered to 70 or 60ppb, as recommended by the Clean Air Scientific Advisory Committee (CASAC), nearly 8,000 respiratory related mortalities could be avoided. Additionally, these health benefits are not uniformly distributed across the nation, as some cities (NYC and Los Angeles) benefit substantially more than others. This analysis provides sound evidence for a policy promoting a reduced regulatory standard for ozone.;To better understand the variability in ozone air pollution, it was revealed that some environmental variables (e.g. temperature and elevation) are significantly associated with increased ozone concentrations. Ozone also varies spatially (i.e. exhibits spatial dependence) and included environmental factors, such as temperature and elevation, do not fully account for this spatial variation. Overlooking this fact was demonstrated to have detrimental effects on the more simplistic statistical methods for assessing exposure, namely the popular land use regression approach. The more state of the art spatial methods, including kriging, were proposed as a preferred alternative, providing proper inference in the presence of spatial variation as well as outperforming all other methods considered for mapping ozone. The combination of air monitoring data with CMAQ model output further improved the kriging based approach for ozone exposure assessment. This improvement was especially beneficial in regions of sparse air monitors, where incorporating CMAQ allowed us to spatially predict significantly better than without it.;This study highlights the importance of improved exposure assessment for ozone air pollution. Optimally understanding variability in ozone concentration can improve our understanding of the exposure-response relationship in regards to ozone related health effects. This is especially critical for areas that are underserved by air monitors, as generating accurate predictions in those areas has been uncertain. The information provided could not only better inform our understanding of ozone concentrations, but also inform regulatory policies about geographic disparities and potential reductions in regional ozone exposures.