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

Benson, Adam Babcock Fitch (2015)

Permanent URL: https://etd.library.emory.edu/concern/etds/6w924c41d?locale=en
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Abstract

Acute Effects of Ambient SO2 Exposure on Pediatric Asthma Emergency Department Visits in Atlanta, Georgia

By Adam Benson

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

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


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