Asian Dust and Daily Emergency Ambulance Calls Among Elderly People in Japan An Analysis of Its Double Role as a Direct Cause and as an Effect Modifier

Objective: To evaluate the direct health effects of Asian dust on ambulance calls and its role as an effect modifier on the effects of anthropogenic air pollution in Japan. Methods: The subjects were 51,945 elderly residents who visited hospital emergency departments from 2006 to 2010. We evaluated the impact of Asian dust by time-series analyses and the excess risk from suspended particulate matter (SPM) stratified by Asian-dust exposure. Results: Asian dust was associated with daily ambulance calls due to all-cause, cardiovascular, and respiratory disease independently of SPM, for example, the relative risk per interquartile increase in Asian dust (3-day lag) was 1.021 (1.002 to 1.039) for cardiovascular disease. Furthermore, Asian dust modified the effects of SPM on cardiovascular and respiratory diseases. Conclusions: Asian dust had adverse effects and modified the effect of SPM.