A case-crossover analysis of Asian dust storms and mortality in the downwind areas using 14-year data in Taipei

This study aims to assess the association between Asian dust storms (ADS) and daily mortality in Taipei, Taiwan. A time-stratified case-crossover design was used to investigate the effects of ADS on mortality. Odds ratios (ORs) of total non-accidental (ICD-9 <800), cardiovascular (ICD-9 390-459, 785), and respiratory deaths (ICD-9 460-519, 786) were estimated for residents in Taipei metropolis over a 14-year study period between 1994 and 2007 by conditional logistic regression. Air pollution levels and temperature data were recorded by a network of 16 monitoring stations spreading around Taipei. Compared with reference days, particulate matter with aerodynamic diameter less than 10 and 2.5μm (PM(10) and PM(2.5)) increased statistically significantly by 24.2μg/m(3) and 7.9μg/m(3) per dust day, respectively. There were also statistically significant increases in sulfur dioxide (SO(2)) and ozone (O(3)) but decreases in temperature during ADS. Excess deaths were increased significantly for residents of all ages for total non-accidental deaths, with OR=1.019 (95% CI 1.003-1.035), and also for residents above 65years old, with OR=1.025 (95% CI 1.006-1.044) for total non-accidental deaths and OR=1.045 (95% CI 1.0011-1.081) for cardiovascular deaths, respectively but not for respiratory deaths during ADS. Such increases in mortality remained statistically significant in the regression models with either SO(2) or O(3). This study found that acute exposure to long-range transported Asian dust can increase the number of non-accidental and cardiovascular deaths for people of all ages and the elderly population aged above 65 on the dust storm days in Taipei, Taiwan. Further studies are still needed to find out whether mass concentrations alone or specific components in PM are responsible for excess cardiovascular deaths by ADS.