Table 3.
A linear mixed model of the estimated difference (estimate) between the mean airborne concentration during paving with warm mix asphalt (WMA) and hot mix asphalt (HMA) (WMA was set as the reference) after adjusting for the ambient air temperature.
| Contaminant | Estimate | P-value | 95% CI | Estimate of covariance parameters (95% CI) | |
|---|---|---|---|---|---|
| All WMA | Organic carbon (mg m−3) | 1.02 | <0.01 | 0.67–1.37 | 0.39 (0.21–0.71) |
| All WMA | Asphalt vapor (p.p.m.) | 0.82 | 0.02 | 0.14–1.49 | 1.14 (0.53–2.46) |
| All WMA | Respirable fraction of PMa (mg m−3) | 1.13 | <0.01 | 0.47–1.79 | 0.65 (0.31–1.34) |
| All WMA | Thoracic fraction of PM (mg m−3) | 0.89 | <0.01 | 0.34–1.45 | 0.49 (0.30–8.81) |
| All WMA | Inhalable fraction of PM (mg m−3) | 0.68 | <0.01 | 0.21–1.14 | 0.35 (0.21–0.57) |
| Additive WMA | Organic carbon (mg m−3) | 0.83 | <0.01 | 0.39–1.27 | 0.29 (0.13–0.64) |
| Additive WMA | Asphalt vapor (p.p.m.) | 0.10 | 0.38 | −0.15–35 | 0.05 (0.02–0.11) |
| FOAM WMA | Organic Carbon (mg m−3) | 0.32 | 0.02 | 0.06–0.57 | 0.05 (0.02–0.12) |
| FOAM WMA | Asphalt vapor (p.p.m.) | 0.08 | 0.85 | −0.87–1.04 | 0.84 (0.32–2.22) |
All data are ln-transformed. The estimates are shown together with the corresponding 95% confidence interval (CI), P-value, and the estimates for the random effects.
aParticulate matter.