Table 2 Potential effect modifiers of traffic-concentration relationship
| Â | Â | Units |
|---|---|---|
Home characteristics: | Obstructed from road | Yes/no |
| Â | Obstructed from major road | Yes/no |
Sampling period characteristics: | Percent of hours downwind from major road | Percent (%) |
|  | Average windspeed during daytime sampling hours (6am–9pm) | m/s |
| Â | Percent daytime hours with still winds (< 2 m/s) | Percent (%) |
| Â | Percent of weekend sampling days | Percent (%) |
| Â | Floor (monitor height) | (Categorical: 1, 2, 3+) |
| Â | Snow during sampling period | Yes/no |