Acute Effects of Ambient SO2 Exposure on Pediatric Asthma Emergency Department Visits in Atlanta, GA Open Access

Abstract

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

INTRODUCTION. 1

MECHANISMS. 2

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

INTRODUCTION. 21

METHODS. 22

RESULTS. 26

DISCUSSION. 30

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

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School	Rollins School of Public Health
Department	Environmental Health
Degree	MSPH
Submission	Master's Thesis
Language	English
Research Field	Health Sciences, Public Health Health Sciences, Epidemiology
Keyword	SO2 Monitoring Station Acute Interaction Emergency Room R-LINE Sulfur Dioxide Child Traffic-related RLINE Emergency Department Air Pollution Case-Crossover Effect Modification Pediatric Atlanta Asthma Traffic
Committee Chair / Thesis Advisor	Strickland, Matthew J, Emory University
Committee Members	Tolbert, Paige, Emory University Annor, Francis B, Georgia Department of Public Health
Partnering Agencies	Georgia state or local health department

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