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Table 2 Pearson’s correlation coefficients for square root of daily PB-PAH exposures and key predictor variables

From: Modeling personal particle-bound polycyclic aromatic hydrocarbon (pb-pah) exposure in human subjects in Southern California

  PB-PAH SQRTa Indoor time (%) In-vehicle time (%) Weekday (1/0) Daytime (%) Time in rush hour (%) GPS speed (km/h) Elevation (m) Length-weighted AADT within 500 m (vehicles/day) Traffic density within 300 m (vehicles per day*km/km2) Ambient temperature (°C) Ambient wind speed (m/s) Ambient humidity (%)
N 180 180 180 180 180 180 180 180 180 180 180 180 180
Mean 3.0 90.7 4.6 0.73 55.2 22.2 2.3 38.1 35796.5 163362.7 21.1 4.2 63.0
Standard deviation 1.3 7.9 5.1 0.44 18.2 7.0 2.7 80.6 30026.1 211034.8 3.2 1.7 12.4
PB-PAH SQRTa 1.00             
Indoor time (%) −0.55*** 1.00            
In-vehicle time (%) 0.69*** −0.81*** 1.00           
Weekday (1/0) 0.16* −0.07 0.04 1.0          
Daytime (%) 0.28*** −0.22** 0.21** −0.13 1.00         
Time in rush hour (%) 0.07 −0.04 0.03 0.04 0.13 1.00        
GPS speed (km/h) 0.60*** −0.74*** 0.93*** −0.06 0.25*** 0.01 1.00       
Elevation (m) −0.08 −0.09 0.07 −0.12 −0.03 −0.06 0.16* 1.00      
Length-weighted AADT within 500 m (vehicles/day) 0.27*** 0.06 −0.02 0.08 0.32*** 0.03 −0.06 −0.10 1.00     
Traffic density within 300 m (vehicles per day*km/km2) 0.19* 0.11 −0.07 0.06 0.31*** 0.04 −0.08 −0.09 0.94*** 1.00    
Ambient temperature (°C) 0.09 0.06 0.09 −0.02 0.26*** −0.14 0.13 −0.04 0.09 0.07 1.00   
Ambient wind speed (m/s) 0.14 −0.32*** 0.17 −0.06 0.53*** 0.15* 0.20** 0.07 0.06 0.05 0.07 1.00  
Ambient humidity (%) −0.11 0.02 −0.09 0.06 −0.37*** 0.06 −0.13 0.02 −0.05 −0.01 −0.72*** −0.12 1.00
  1. a Square-root transformed PB-PAH concentration.
  2. *p-value <0.05; **p-value < 0.01; ***p-value < 0.001.