Table 2 Source model characteristics Characteristics of the two models and their factors of the principal factor analysis and their associations with the two PM2.5-measures: Model A includes all components shown in Table 1, Model B excludes Ca, Cr, Se and W.
Model characteristics | Model A | Â | Â | Â | Model B | Â | Â |
|---|---|---|---|---|---|---|---|
Number of exposure variables included | 13 | Â | Â | Â | 9 | Â | Â |
Total variance explained | 62.3% | Â | Â | Â | 68.9% | Â | Â |
Correlation with PM2.5Mass (R2) | 0.73 | Â | Â | Â | 0.63 | Â | Â |
Correlation with PM2.5Lightscatter (R2) | 0.71 | Â | Â | Â | 0.52 | Â | Â |
Factor characteristics | Factor 1 "crustal" | Factor 2 "steel wear" | Factor 3 "gasoline" | Factor 4 "speed-change" | Factor 1 "road surface" | Factor 2 "gasoline" | Factor 3 "speed-change" |
Sum of squares of factor loadings | 2.48 | 2.11 | 1.82 | 1.67 | 3.01 | 1.68 | 1.51 |
Proportion of total variance | 19.1% | 16.3% | 14.0% | 12.9% | 33.5% | 18.6% | 16.8% |
Slopea of correlation with PM2.5Mass | 2.95 p = 0.0006 | 4.11 p < 0.0001 | 2.16 p = 0.003 | 4.50 p < 0.0001 | 4.74 p < 0.0001 | 3.03 p = 0.002 | 3.21 p = 0.002 |
Slopea of correlation with PM2.5Lightscatter | 0.68 p = 0.6 (n.s.) | 3.58 p = 0.01 | 3.74 p = 0.004 | 11.32 p < 0.0001 | 2.48 p = 0.15 (n.s.) | 4.03 p = 0.026 | 9.27 p < 0.0001 |