Effect of Air Pollution on Emergency Room Visits for Asthma: a Time Series Analysis

Ju, Young Su; Cho, Soo Hun

Abstract

OBJECTIVES
To evaluate the hypothesis that increasing ambient levels of ozone or particulate matter are associated with increased emergency room visits for asthma and to quantify the strength of association, if any, between these.
METHODS
Daily counts of emergency room visits for asthma, air quality, and weather data were collected from hospitals with over 200 beds and from monitoring stations in Seoul, Korea from 1994 through 1997. Daily counts of emergency room visits for asthma attack were analyzed using a general additive Poisson model, with adjustment for the effects of secular trend, seasonal variation, Sunday and holiday, temperature, and humidity, according to levels of ozone and particulate matter.
RESULTS
The association between daily counts of emergency room visits for asthma attack and ozone levels was statistically significant in summer(from June to August), and the RR by unit increment of 100 ppb ozone was 1.30(95% CI = 1.11-1.52) without lag time. With restriction of the period from April to September in 1996, the RR was 1.37(95% CI = 1.06-1.76), and from June to August in 1995, the RR was 1.62(95% CI = 1.12-2.35). In the data for children(5?14 yr), the RR was 2.57(95% CI = 1.31-5.05) with restriction of the period from April to September in 1997. There was no significant association between TSP levels and asthma attacks, but a slight association was seen between PM10 levels and asthma attacks in a very restricted period.
CONCLUSION
There was a statistically significant association between ambient levels of ozone and daily counts of emergency room visits for asthma attack. Therefore, we must make efforts to effectively minimize air pollution, in order to protect public health.