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. Author manuscript; available in PMC: 2014 Nov 25.
Published in final edited form as: Environ Res. 2013 Sep 10;126:192–203. doi: 10.1016/j.envres.2013.08.005

Table 4.

Results of linear mixed-effect models for personal exposure to gasoline-related VOCs.

Variable Group/unit Benzene
 Toluene
 Ethylbenzene
 m,p-Xylene
 o-Xylene
 MTBE
 Styrene
β SE β SE β SE β SE β SE β SE β SE
Intercept 2.21 0.41 3.74 0.37 1.41 0.42 2.23 0.37 0.78 0.29 1.82 0.32 1.09 0.33
Visit 1 −0.03 0.07 0.12 0.09 −0.14 0.08 −0.08 0.08 −0.07 0.07 0.06 0.10 0.07 0.08
2 Reference Reference Reference Reference Reference Reference Reference
City Los Angeles 0.83 0.12 0.08 0.11 0.37 0.14 0.29 0.14 −0.06 0.13 0.35 0.16 0.23 0.11
Elizabeth 0.37 0.14 0.06 0.13 −0.16 0.18 −0.25 0.19 −0.17 0.17 0.07 0.20 −0.11 0.10
Houston Reference Reference Reference Reference Reference Reference Reference
Attached garage No 0.19 0.09 0.72 0.25 0.36 0.12 0.36 0.12 0.35 0.11 0.36 0.12 −0.42 0.25
Cooking No 0.22 0.09 0.17 0.08 0.15 0.09 0.20 0.08
Education Less than HS 0.15 0.12
High school −0.08 0.10
> College Reference
Ethnicity White −0.13 0.15 −0.23 0.16 −0.21 0.14
Mexican 0.19 0.19 0.07 0.19 0.12 0.17
Hispanic 0.30 0.19 0.27 0.20 0.35 0.18
Other Reference Reference Reference
Heating fuel Electricity 0.20 0.18
Gas 0.42 0.16
Oil and wood Reference
Indoor temperature °C 0.04 0.01
Inverse wind speed knot−1 4.20 0.53 3.16 0.69 2.84 0.71 2.54 0.62 5.86 0.84
Log-transformed AER h−1 0.30 0.05 0.17 0.06 0.21 0.06 0.14 0.05 −0.09 0.07
Number of floors 0.15 0.04 0.20 0.06
Number of rooms 0.10 0.03 0.09 0.02
Open doors or windows No 0.22 0.10 0.20 0.09
Pumping gas No 0.16 0.08 0.24 0.11 0.22 0.11 0.28 0.10 0.34 0.13
Renovation in the past year No 0.30 0.10
Time spent in home min 0.0002 0.0001 −0.0002 0.0001 0.0003 0.0001
Unemployed No 0.23 0.12
Using air cleaning devices No −0.27 0.18 0.42 0.18 0.38 0.16 −0.35 0.20
Using nail polish remover No −0.29 0.17 0.39 0.16 0.33 0.17
Wore powder, spray or perfume No 0.41 0.12

n = 400 to 530 depending on models.

AER, air exchange rate; HS, high school; MTBE, methyl tert-butyl ether.

For dichotomous variables, the reference group is “Yes”.

p-Value < 0.05 shown in bold type.