Table 1

Distribution of traffic characteristics and PM10 levels for the nine schools

School number and locationNo. of childrenTruck traffic density (vehicles/24 h)Car traffic density (vehicles/24 h)Distance of school from motorway (m)Distance of home from motorway (m), median (min–max)Outdoor PM10 (μg/m3)Indoor NO (μg/m3)
Same day* Lag 1* Lag 2* §Lag 3*
1 Sliedrecht851393463476170259 (97–800)16.0–17.316.3–21.121.1–25.225.2–53.16.3–9.6
2 Gorinchem431657168382125377 (50–958)24.3–26.117.3–26.116.3–17.316.3–21.112.3–39.3
3 Badhoevedorp561040411199874442 (42–976)33.333.436.951.583.0
4 Badhoevedorp21210404111998237404 (50–901)17.2–33.017.2–33.317.2–33.433.3–36.929.0–50.3
5 Bergen op Zoom80673843170247270 (65–906)60.158.077.2100.413.6
6 Rotterdam2717085125287168202 (70–295)24.028.647.555.011.3
7 Rotterdam14916058107467322385 (50–997)27.141.651.021.228.0
8 Roosendaal9466104235450220 (32–939)46.737.727.520.822.6
9 Sassenheim66484546150250392 (125–982)26.019.416.918.717.3
  • * Daily average. If there was more than one measurement day, minimum and maximum values are given.

  • On day of exhaled NO measurements.

  • 1 day before exhaled NO measurements.

  • § 2 days before exhaled NO measurements.

  • 3 days before exhaled NO measurements.

  • PM10, particulate matter with a 50% cut-off aerodynamic diameter of 10 μm.