Crude and adjusted geometric means ratios (GMR) with 95% CIs for the associations between traffic characteristics and PM10 levels and exhaled NO
| Exposure variable (increment) | All | Without school 5* | ||
| Crude GMR (95% CI) | Adjusted GMR (95% CI)† | Adjusted GMR (95% CI)‡ | Adjusted GMR (95% CI)† | |
| Traffic characteristic | ||||
| Total traffic (142372–48964 vehicles/24 h) | 0.90 (0.57 to 1.41) | 1.19 (0.81 to 1.74) | 1.01 (0.65 to 1.55) | 1.26 (0.89 to 1.79) |
| Car traffic (125287–42354 vehicles/24 h) | 0.94 (0.61 to 1.44) | 1.19 (0.83 to 1.68) | 1.00 (0.66 to 1.51) | 1.25 (0.91 to 1.73) |
| Truck traffic (17085–4845 vehicles/24 h) | 0.72 (0.46 to 1.10) | 0.97 (0.62 to 1.50) | 1.02 (0.68 to 1.54) | 0.97 (0.63 to 1.49) |
| Distance of school from motorway (322–50 m, log-transformed) | 1.10 (0.93 to 1.30) | 1.19 (0.77 to 1.83) | 1.36 (0.96 to 1.94) | 0.97 (0.53 to 1.80) |
| Distance of home from motorway (997–32 m, log-transformed) | 0.99 (0.56 to 1.72) | 1.10 (0.93 to 1.31) | 1.09 (0.92 to 1.30) | 1.06 (0.89 to 1.27) |
| PM10 on day of exhaled NO measurements (60.1–16.3 μg/m3) | 1.96 (1.33 to 2.88) | 2.24 (1.37 to 3.65) | 2.01 (1.34 to 3.01) | 1.21 (0.46 to 3.19) |
| PM10 on day before exhaled NO measurements (58.0–16.3 μg/m3) | 2.08 (1.49 to 2.92) | 2.16 (1.48 to 3.16) | 1.98 (1.54 to 2.56) | 1.54 (0.73 to 3.25) |
| PM10 2 days before exhaled NO measurements (77.2–16.3 μg/m3) | 2.06 (1.44 to 2.94) | 2.27 (1.58 to 3.27) | 2.19 (1.95 to 2.47) | 1.99 (0.66 to 6.03) |
| PM10 3 days before exhaled NO measurements (100.4–16.3 μg/m3) | 17.8 (1.10 to 2.87) | 1.96 (1.13 to 3.40) | 2.05 (1.47 to 2.87) | 0.83 (0.33 to 2.08) |
↵* During the study period, a pollution peak occurred, which was associated with large PM10 emissions from traditional Easter fires. The analysis was carried out to evaluate to what extent the results were driven by the PM10 peak which may have especially affected the exhaled NO measurements in school 5, which were performed 4 days after the Easter fires.
↵† All effects were adjusted for individual confounders (sex, age, non-Dutch nationality, parental asthma and/or hay fever, parental education, current parental smoking at home, current pet ownership, use of natural gas for cooking, presence of mould stains in the home) and downwind location of the school (yes/no). Effects of traffic characteristics were additionally adjusted for outdoor PM10 on the day of exhaled NO measurements; effects of PM10 were additionally adjusted for total traffic and distance of the school from the motorway.
↵‡ Adjusted for all covariates listed above and additionally adjusted for indoor NO.
PM10, particulate matter with a 50% cut-off aerodynamic diameter of 10 μm.