Substantial and consistent evidence supports the conclusion that short-term exposure to ambient concentrations of ozone and fine particulate matter (PM2.5) is associated with increases in mortality and morbidity; however, the evidence for morbidity outcomes in populations under 65 is limited. This gap is due to the lack of a centralized, readily accessible database of emergency department (ED) visits and hospitalizations for populations under 65 for air pollution epidemiology. To address this gap, we leveraged the infrastructure of the Centers for Disease Control and Prevention National Environmental Public Health Tracking Program to gather data for respiratory ED visits and conducted a multi-county study.
We requested daily, county-level data aggregated by respiratory outcome, age group, and sex from thirty states. We conducted a descriptive analysis of respiratory ED visits to evaluate annual and daily rates. Then, we conducted a two-stage multi-county analysis of the association between short-term exposure to ambient ozone and PM2.5 and respiratory ED visits for each age-outcome group. Lastly, we evaluated the between county heterogeneity of the results from our two-stage analysis and explored the contribution of various county-level covariates to that heterogeneity for the association between PM2.5 and asthma among children.
Seventeen states submitted the requested data, resulting in a database of almost 50 million respiratory ED visits covering over 40% of the United States population. The median rate of ED visits per 10,000 population per year for all respiratory ED visits combined was 410 with an interquartile range of 276. We observed variation in the rates by state, county, outcome, age group, and sex. Ozone and PM2.5 were associated with respiratory ED visits among all ages with variation in magnitude by age group and outcome. State, region, and percent of population without health insurance explained 50% of the between-county heterogeneity for the association between PM2.5 and asthma among children.
Our work addresses an important gap in air pollution epidemiology for respiratory morbidity for populations under 65 and suggests that effect estimates from multi-city studies of populations over 65 may not be transportable to younger age groups.
Table of Contents
Table of Contents
Chapter 1: Introduction. 1
Project Proposal 16
Chapter 2: Environmental public health tracking of respiratory emergency department visits 38
Chapter 3: Age-specific associations between ambient air pollution concentrations and respiratory emergency department visits in the United States. 73
Chapter 4: Heterogeneity in the short-term association between fine particulate matter and asthma emergency department visits among children. 107
Chapter 5: Conclusion. 136
About this Dissertation
|Committee Chair / Thesis Advisor|
|Addressing gaps in the age-specific evidence used for United States air pollution policy ()||2018-04-04||