The Effect of Asian Dust Aerosol on Emergency Visits

Abstract

PP-31-008 Background/Aims: Recently, more attention has been given to the health effects of Asian Dust (AD) events, the phenomenon in which mineral dust originating from the Gobi and Taklamakan deserts is transported to East Asia. We examined the association between suspended particulate matter (SPM) with a diameter less than 10 μm and emergency visits on AD days and non-AD days. Methods: We obtained data on AD events and weather variables from Japan Meteorological Agency and air pollutants from National Institute for Environmental Studies. Data on emergency visits from October 1997 to March 2008 were collected from Nagasaki Emergency Visit Survey. We used a time-stratified case-crossover design to evaluate the association between each exposure and emergency visits. A case period was defined as the day of the emergency visit. As control periods, we chose the same day of the week in the same month of the same year as the case period. We calculated odds ratios of emergency visits using conditional logistic regression to obtain estimates of relative risk. We controlled for ambient temperature and relative humidity. Results: During study period, 104 AD events were observed in Nagasaki. There were 94,247 emergency visits excluding injuries from October 1997 to March 2008. The 24-mean SPM during March–May was significantly higher on the AD days (60.7 μg/m3) than non-AD days (31.4 μg/m3). We observed a significant increase in risk of emergency visits from the same day and 2-day after the AD day (4.59%, 95% confidence interval [CI]: 0.71, 8.61). A 10 μg/m3 increase in SPM concentration (mean of lag0–lag2) was associated with increase in risk on AD days (2.75%, 95% CI: −0.32, 5.92) and non-AD days (0.27%, 95% CI: −0.41, 0.96). The difference in the effects between AD days and non-AD days was not significant. Conclusion: The study suggested that the risk of emergency visits increased at AD days.