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BACKGROUND: Asthma is one of the most common chronic diseases affecting children. Air pollution has been shown to exacerbate asthma among children. This study assesses the associations of ozone and fine particulate matter (PM2.5) 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-day through 5-day lag, 3-day average and 5-day average) of ozone and PM2.5 were explored. Effect estimates from both single and multipollutant models controlling for temperature and pollen were estimated for both study designs. A dose-response analysis comparing the bottom 5th percentile of 3-day average lag ozone with each 5 percentile increase was also 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 (RR=1.10, 95% CI 1.06-1.14), respectively. Similar associations were seen for 1-day lag and 3-day average lag ozone levels. PM2.5 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 on respiratory outcomes.