Purpose: Previous epidemiological and limited clinical and mechanistic evidence supports an association between sulfur dioxide (SO2) and asthma exacerbation events in children. However, further investigations at a monitors-specific scale are needed to better understand this relationship due to insufficient monitor networks and the large spatial heterogeneity of SO2. Furthermore, little is known whether exposure to traffic-related pollutants modifies the association between SO2 and asthma exacerbation events.
Methods: A case-crossover study was conducted using emergency department visits from 2002 - 2013 for asthma or wheeze among children aged 1 to 17 within a 5 (n = 15,610), 4 (n = 8,522), and 3 (n = 6,742) kilometer radius of four ambient SO2 monitoring stations in the Metropolitan Atlanta Area. Concentrations of traffic-related near-surface particulate matter (PM2.5) were estimated using an R-LINE model to examine effect modification by traffic-related pollution. Odds ratios were calculated using conditional logistic regression for multiple-day moving averages of 1-hour maximum SO2 concentrations.
Results: There were trends of positive associations between SO2 and asthma-related emergency department visits overall (OR: 1.044, 95% CI: 1.006 - 1.084 at 4 Km, Lag 0), and in both warm and cold season analyses. Strongest associations were observed in the cold season using a 3-day moving average of SO2, and tended to increase as distance to monitor decreased (OR: 1.105, 95% CI: 1.013 - 1.204 at 4 Km, Lag 0 - 3, in the cold season). Odds ratios between cases exposed to high versus low concentrations of traffic-related pollution tended to be positive overall, and in season-specific analyses. Strongest associations were observed using 3-day moving averages of SO2- and during the warm season (OR: 1.031, 95% CI: 0.957 - 1.110 at 4 Km, Lag 0 - 3, for a 1 ppm increase in SO2 in the warm season).
Conclusions: These findings provide additional evidence supporting previously documented associations between SO2and asthma exacerbation events despite concerns due to large spatial heterogeneity of SO2 and a limited quantity of monitors. Furthermore, the association between SO2 and asthma exacerbation may be susceptible to modification by traffic-related pollutants, particularly during the warm season.
Table of Contents
CHAPTER I: LITERATURE REVIEW
MTEHODS: TIME-SERIES AND CASE-CROSSOVER DESIGN. 6
SULFUR DIOXIDE (SO2). 8
EPIDEMIOLOGY OF SO2 AND ASTHMA. 15
EFFECT MODIFICATION OF TRAFFIC ON SO2 AND ASTHMA ASSOCIATION. 19
CONTRIBUTION OF PROPOSED STUDY. 20
CHAPTER II: MANUSCRIPT
CHAPTER III: CONCLUSIONS AND RECOMMENDATIONS. 37
CHAPTER IV: REFERENCES. 39
CHAPTER V: TABLES & FIGURES
FIGURE 1: Asthma Emergency Department Cases within a 5 Km Radius of SO2 Locations in Atlanta Metropolitan Area. 46
TABLE 1: Descriptive Characteristics of Asthma Emergency Department Cases for All SO2 Monitors Combined. 47
TABLE 2: Descriptive Characteristics of Asthma Emergency Department Cases by Individual SO2 Monitor. 48
TABLE 3: Race and Ethnicity of Census Tracts Containing Individual SO2 Monitor. 49
TABLE 4: Descriptive Characteristics of Environmental Data by SO2 Monitors. 50
TABLE 5: Correlation Coefficients between Individual SO2 Monitors. 51
TABLE 6: Odds Ratios of Ambient SO2 Exposure on Asthma Emergency Department Visits by Radius, and Lag Period. 52
TABLE 7: Cold and Warm Season Odds Ratios of Ambient SO2 Exposure on Asthma Emergency Department Visits. 53
TABLE 8: Odds Ratios and 95% Confidence Intervals of Ambient SO2 by Quintile by Radius, Lag Period, and Season. 54
TABLE 9: Descriptive Characteristics of R-LINE Data by Categorization Type. 55
TABLE 10: Statistical Significance of R-LINE Interaction Terms by Categorization Type. 55
TABLE 11: Effect Modification of Traffic Flow on Association of SO2 and Asthma ED Visits Odds Ratios. 56
TABLE 12: Effect Modification by Quintile of Traffic Flow on Association of SO2 and Asthma ED Visits. 57
About this Master's Thesis
|Committee Chair / Thesis Advisor|
|Acute Effects of Ambient SO2 Exposure on Pediatric Asthma Emergency Department Visits in Atlanta, GA ()||2018-08-28 13:52:40 -0400||