Table 2– Pooled# effects of nitrogen dioxide (NO2) and particulate matter <2.5 μm in diameter (PM2.5) on natural and specific-cause mortality
Total or natural mortalityCardiovascular mortalityRespiratory mortality
Increment μg·m−3Studies nRR (95% CI)I2 %Increment μg·m−3Studies nRR (95% CI)I2 %Increment μg·m−3Studies nRR (95% CI)I2 %
NO210101.040 (1.015–1.065)911015+,§,ƒ1.152 (1.094–1.213)98107##,¶¶1.024 (1.010–1.038)0
14.61.059 (1.022–1.096)17.91.288 (1.174–1.413)151.036 (1.015–1.058)
PM2.5109¶,++1.050 (1.024–1.078)781014+,§,ƒ,¶¶1.228 (1.084–1.39)98106##,¶¶,++1.062 (1.022–1.104)11
5.81.029 (1.014–1.045)71.155 (1.058–1.259)71.043 (1.015–1.072)

  • RR: relative risk; I2: inconsistency. #: random estimates. : two studies [17, 34] were excluded as they did not give interquartile range (IQR) estimates or dispersion parameters to estimate them. +: three studies [17, 25, 34] were excluded as they did not give IQR estimates or dispersion parameters to estimate them. §: two studies [28, 33] were included twice with separate groups of males and females. ƒ: two studies from Europe [13, 32] estimated cardiopulmonary mortality as a whole; they were included in the pooled, cardiovascular mortality estimate and excluded from the respiratory mortality pooled estimate. ##: three studies [16, 17, 34] were excluded as they did not give IQRs or dispersion parameters to estimate them. ¶¶: one study from Europe [28] was included twice with separate groups of males and females. ++: one study from Canada [22] could be included as it did not present the particulate matter effect estimates.