Table 1– Pooled# effects of nitrogen dioxide (NO2) and particulate matter <2.5 μm in diameter (PM2.5) (per 10 μg·m−3) on natural and cause-specific mortality by region of the world
Total or natural mortalityCardiovascular mortalityRespiratory mortality
Studies nRR (95% CI)I2 %Studies nRR (95% CI)I2 %Studies nRR (95% CI)I2 %
NO2
 All countries121.041 (1.019–1.064)8918¶,+1.133 (1.088–1.180)989+,§,ƒ1.024 (1.017–1.032)0
 Asia11.020 (1.000–1.030)21.588 (0.675–3.740)9921.023 (1.010–1.036)47
 North America51.027 (0.987–1.069)9571.031 (0.999–1.065)6731.005 (0.975–1.035)0
 Europe61.066 (1.029–1.104)7291.059 (1.032–1.086)7941.029 (1.013–1.045)0
PM2.5
 All countries11##1.045 (1.007–1.088)8717¶,+,##1.196 (1.091–1.31)988+,§,ƒ,##1.050 (1.009–1.094)61
 Asia11.000 (0.980–1.020)21.380 (0.761–2.502)9921.034 (0.943–1.134)50
 North America41.047 (1.035–1.106)8361.047 (0.992–1.106)7121.046 (0.990–1.104)0
 Europe61.071 (1.021–1.124)6291.188 (1.091–1.295)4241.075 (1.009–1.146)40
  • RR: relative risk; I2: inconsistency. #: results from random-effects meta-analyses. : two studies (one from North America [33] and one from Europe [28]) were included twice with separate groups of males and females. +: four studies (one from America [23] and three from Europe [13, 32, 34]) estimated cardiopulmonary mortality as a whole; they were included in the pooled cardiovascular mortality estimate and excluded from the pooled respiratory mortality estimate. §: one study from China [14] was excluded because it estimated lung cancer together with respiratory mortality. ƒ: one study from Europe [28] was included twice with separate estimates for males and females. ##: one study from the USA [22] could be included because it did not present particulate matter effect estimates.