. Author manuscript; available in PMC: 2007 Oct 1.

Published in final edited form as: Environ Sci Technol. 2006 Jul 1;40(13):4226–4232. doi: 10.1021/es052477m

Table 2.

Regression Results for Elemental Carbon¹

Equation 1: log(PersonalEC) = β₁₀ + β₁₁log(WorkAreaEC) + β₁₂(Smoking) + ε_ijk
Work Area	0.99 (0.04)^**
Smoking	0.17 (0.06)^**
Constant	0.05 (0.03)
Equation R²	0.64
Equation 2: log(WorkAreaEC) = β₂₀ + β₂₁(Terminal Size) + β₂₂(P&D) + β₂₃(Shop)+ β₂₄(Ventilation)+ β₂₅log(YardEC) + β₂₆(Job)+ γ_ijk
Terminal Size	0.01 (0.002)^**
P&D Drivers	0.002 (0.001)^*
Mechanics	0.002 (0.001)
Ventilation	−0.09 (0.01)^**
Yard Background	0.71 (0.05)^**
Job	2.11 (0.09)^**
Constant	−0.21 (0.08)^**
Equation R²	0.64
Equation 3: log(YardEC)= β₃₀ + β₃₁(Relative Humidity) + β₃₂(Temperature) + β₃₃(Windspeed) + β₃₄(Interstate) + β₃₅(Industrial) + β_3(6–9)(4 Regional Dummies) + η_ijk
Relative Humidity	−0.004 (0.002)^*
Temperature	−0.01 (0.004)^**
Windspeed	−0.11 (0.01)^**
Interstate Distance	−0.30 (0.07)^**
Industrial Land Uses	0.01 (0.001)^**
Region 1 – Midwest	0.51 (0.20)^**
Region 2 – Northeast	0.84 (0.19)^**
Region 3 – South	1.08 (0.20)^**
Region 4 – West	0.68 (0.18)^**
Constant	N/A
Equation R²	0.51

Coefficients listed with standard errors in parentheses;

^**

significant at 1% level,

significant at 5% level

All particulate concentrations are log transformations measured in μg/m³