International Journal of Chronic Diseases

Review Article

Association between Traffic Related Air Pollution and the Development of Asthma Phenotypes in Children: A Systematic Review

Table 2

Effect of TRAP and childhood asthma phenotypes in included studies.
Study reference and settingTraffic related pollutantTransient asthma/wheezingPersistent asthma/wheezingLate-onset asthma/wheezing
Brauer et al., 2006 (Total n = 4146; Pollutant Exposure n = 2588) [19]PM2.5OR: 1.16, 95 (CI: 1.00 - 1.34 per 4.4 g/m3 increase of PM2.5OR: 1.19 (95% CI: 0.96 - 1.48) per 3.3 µg/m3 increase of PM2.5None
NO2OR: 1.13 (95 CI: 1.00 - 1.28) per 10.6 g/m3 increase of NO2OR: 1.13 (95% CI: 0.99 - 1.29) per 10.4 µg/m3 increase of NO2None
Gehring et al., 2010 (n = 3863; NO2 n = 2668) [14]PM2.5OR: 1.29 (95 CI: 1.04 - 1.62) per 3.2 g/m3 increase of PM2.5OR: 1.37, 95% CI: 0.99 - 1.91 per 3.2 µg/m3 increase of PM2.5OR: 1.18, 95 CI: 1.01 - 1.37 per 3.2 g/m3 increase of PM2.5
NO2OR: 1.17 (95% CI: 0.97 - 1.41) per 10.4 µg/m3 increase of NO2OR: 1.30 95% (CI: 0.99 - 1.72) per 10.4 µg/m3 increase of NO2OR: 1.13 95% (CI: 0.99 - 1.35) per 10.4 µg/m3 increase of NO2
Nordling et al., 2007 (n = 3515) [20]PM10OR: 0.90 (95% CI: 0.45 - 1.81) per 6 µg/m3 increase of PM2.5OR: 1.64 (95% CI: 0.90 - 3.00) per 3 µg/m3 increase of OR: 0.94 (95% CI: 0.42 - 2.11) per 6 µg/m3 increase of PM2.5
OR: 0.82 (95% CI: 0.48 - 1.40) per 44 µg/m3 increase of OR: 1.60, 95 (CI: 1.09 - 2.36) per 44 g/m3 increase of OR: 0.87, 95% (CI: 0.47 - 1.60) per 44 µg/m3 increase of
Oftedal et al., 2009 (n= 2871, NO2 n = 2329) [21]NO2NoneNoneOR: 1.05 (95% CI: 0.64 - 1.72) per 27.3 µg/m3 increase of NO2
Pennington et al., 2018 (Total n = 24 608; prenatal exposure n = 6795; year of life n = 7755) [22]CONonePrenatal exposure absolute risk increase: 3.5 (95 CI: 1.5, 6.2) per 2.7-fold increase CO None
Age 1 exposure absolute risk increase: 3.9 (95 CI: 1.5, 6.2) per 2.7-fold increase CO 
PM2.5NonePrenatal exposure absolute risk increase: 4.4 (95 CI: 2.3, 6.4) per 2.7-fold increase PM2.5None
Age 1 exposure absolute risk increase: 4.5 (95 CI: 2.3, 6.6) per 2.7-fold increase CO 
NonePrenatal exposure absolute risk increase: 3.8 (95 CI: 1.7, 5.9) per 2.7-fold increase  None
Age 1 exposure absolute risk increase: 4.0 (95 CI: 1.8, 6.1) per 2.7-fold increase
Rancière et al., 2017 (n = 3840, n = 698) [23]OR: 1.03, 95% CI: 0.91 - 1.17 per 26 µg/m3 increase of NO2 equivalentOR: 1.27, 95 CI: (1.09 - 1.47) per 26 g/m3 increase of NO2 equivalentOR: 1.19, (95% CI: 0.89 - 1.33) per 26 µg/m3 increase of NO2 equivalent
Sbihi et al., 2017 (n = 68 195, NO2 n = 68 024) [4]NO21 vs 0 OR: 1.10 (95 CI: 1.0 - 1.3) 1 vs 0 OR: 1.42 (95 CI: 1.1 - 1.8)  1 vs 0 OR: 1.18 (95 CI: 1.0 - 1.4)  
2 vs 0 OR: 1.04 (95% CI: 0.9 - 1.2)2 vs 0 OR: 1.20 (95 CI: 1.0 - 1.5)2 vs 0 OR: 1.29 (95 CI: 1.1 - 1.5).  
(3 vs 0 OR: 1.10 (95 CI: 1.0 - 1.3)3 vs 0 OR: 1.05 (95% CI: 0.9 - 1.2)3 vs 0 OR: 1.00 (95% CI: 0.8 - 1.2).
 PM2.51 vs 0 OR: 1.15 (95 CI: 1.0 - 1.3)  1 vs 0 OR: 1.17 (95 CI: 1.0 - 1.4)  1 vs 0 OR: 1.13, 95 CI: 1.0 - 1.3  
 2 vs 0 OR: 1.21 (95 CI: 1.1 - 1.4)  2 vs 0 OR: 1.0 (95% CI: 0.8 - 1.2)2 vs 0 OR: 1.25, 95 CI: 1.1 - 1.5 
 3 vs 0 OR: 1.05 (95% CI: 0.9 - 1.2)3 vs 0 OR: 0.86 (95% CI: 0.7 - 1.1) 3 vs 0 OR: 0.97, 95% CI: 0.8 - 1.1)
Results in boldface indicate significant results at the 95% confidence level.
Reported ORs compared higher exposure quartiles (groups 1, 2, and 3) to the lowest exposure quartile (reference group = 0). NO2 exposure ranged from 15 to 53.7 µg/m3; PM2.5 exposure ranged from 3.2 to 7.6 µg/m3.