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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.

From: Cardiovascular effects in patrol officers are associated with fine particulate matter from brake wear and engine emissions

Model characteristics Model A     Model B   
Number of exposure variables included 13     9   
Total variance explained 62.3%     68.9%   
Correlation with PM2.5Mass (R2) 0.73     0.63   
Correlation with PM2.5Lightscatter (R2) 0.71     0.52   
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
  1. a) Slope in μg/m3 per 1 SD change in the exposure factor score