Associations of daily pediatric asthma emergency department visits with air pollution in Newark, NJ: utilizing time-series and case-crossover study designs

Abstract

Objective: Asthma is one of the most common chronic diseases affecting children. This study assesses the associations of ozone and fine particulate matter (PM_2.5) with pediatric emergency department visits in the urban environment of Newark, NJ. Two study designs were utilized and evaluated for usability. Methods: We obtained daily emergency department visits among children aged 3–17 years with a primary diagnosis of asthma during April to September for 2004–2007. Both a time-stratified case-crossover study design with bi-directional control sampling and a time-series study design were utilized. Lagged effects (1-d through 5-d lag, 3-d average, and 5-d average) of ozone and PM_2.5 were explored and a dose–response analysis comparing the bottom 5th percentile of 3-d average lag ozone with each 5 percentile increase was performed. Results: Associations of interquartile range increase in same-day ozone were similar between the time-series and case-crossover study designs (RR = 1.08, 95% CI 1.04–1.12) and (OR = 1.10, 95% CI 1.06–1.14), respectively. Similar associations were seen for 1-day lag and 3-day average lag ozone levels. PM_2.5 was not associated with the outcome in either study design. Dose–response assessment indicated a statistically significant and increasing association around 50–55 ppb consistent for both study designs. Conclusions: Ozone was statistically positively associated with pediatric asthma ED visits in Newark, NJ. Our results were generally comparable across the time-series and case-crossover study designs, indicating both are useful to assess local air pollution impacts.

• Epidemiology
• ozone
• PM_2.5
• threshold
• urban

Acknowledgements

The authors thank Dr. Leonard Bielory for providing pollen data funded in part through US EPA STAR Program RD83454701: Climate Change and Allergic Airway Disease. They also thank Dr. David Robinson, the New Jersey State Climatologist at Rutgers University, for providing meteorological data.

Declaration of interest

The authors report that they have no conflicts of interest. The authors alone are responsible for the content and writing of the paper. This study was supported in part by an appointment to the Applied Epidemiology Fellowship Program administered by the Council of State and Territorial Epidemiologists (CSTE) and funded by the Centers for Disease Control and Prevention (CDC) Cooperative Agreement Number 5U38HM000414.