Long-range transported Asian Dust and emergency ambulance dispatches

Asian Dust (AD) particles transported from source areas contribute to sharp increases in coarse particles in Japan. We examined the association of exposure to AD events with emergency ambulance dispatches in Nagasaki city. We also examined whether AD transported at different altitude routes from source areas influenced dispatch rates. Using lidar (light detection and ranging), we determined moderate AD days (0.066/km < dust extinction coefficient <= 0.105/km) and heavy AD days (0.105/km < dust extinction coefficient). We applied a time-stratified case-crossover analysis to estimate the association between AD days and emergency ambulance dispatches. There were 9,070 dispatches from March to May during 2003-2007. The heavy AD events at cumulative lag0-3 were associated with an increase in emergency dispatches due to all causes by 12.1% (95% confidence interval (CI), 2.3, 22.9) and an increase for those due to cardiovascular diseases by 20.8% (95% CI: 3.5, 40.9). We categorized 31 AD days based on backward trajectory analyses into AD days with lower altitude routes and those with higher altitude routes. We observed a greater increase in emergency ambulance dispatches on AD days with lower altitude routes compared with those on AD days with higher altitude routes although the difference was not significant (p for interaction 0.49). These results have shown that exposure to high AD particle levels could increase emergency ambulance dispatches due to illnesses such as cardiovascular stress, and that AD traveling through different routes may have different health effects.