Table 3.

Regression analysis on the contribution of direct ambient exposure (the exposure that individuals experienced outdoors in the neighborhood) to personal exposure to VOC.^a

Compounds	Pi = α + β·Ai ε					Pi = α + β·(Ai·to,i %) + εb
	N	β1	SEc	p-value	R2	N	β1	SEc	p-value	R2
WFS
MTBE	155	1.00	0.04	<0.001	0.77	109	0.49	0.06	<0.001	0.42
Hexane	130	0.54	0.08	<0.001	0.27	95	0.33	0.06	<0.001	0.26
Chloroform	139	0.53	0.10	<0.001	0.18	96	0.17	0.07	0.018	0.06
Carbon tetrachloride	137	1.03	0.07	<0.001	0.61	94	0.06	0.03	0.019	0.06
Benzene	145	0.55	0.06	<0.001	0.40	105	0.22	0.05	<0.001	0.15
Toluene	155	0.40	0.06	<0.001	0.21	109	0.26	0.05	<0.001	0.19
Ethylbenzene	155	0.50	0.07	<0.001	0.25	108	0.22	0.05	<0.001	0.14
m & p-Xylene	155	0.60	0.07	<0.001	0.33	109	0.28	0.05	<0.001	0.21
o-Xylene	155	0.50	0.06	<0.001	0.28	108	0.23	0.05	<0.001	0.16
CDS
MTBE	133	0.82	0.07	<0.001	0.51	91	0.40	0.06	<0.001	0.35
Hexane	105	0.68	0.08	<0.001	0.39	73	0.33	0.08	<0.001	0.20
Chloroform	101	0.66	0.16	<0.001	0.15	70	0.36	0.11	0.003	0.13
Carbon tetrachloride	102	1.10	0.07	<0.001	0.71	71	0.04	0.03	0.209	0.02
Benzene	124	0.40	0.05	<0.001	0.30	86	0.20	0.05	<0.001	0.15
Toluene	132	0.62	0.10	<0.001	0.23	92	0.18	0.08	0.034	0.05
Ethylbenzene	134	0.67	0.13	<0.001	0.17	92	0.08	0.10	0.425	0.01
m & p-Xylene	134	0.61	0.12	<0.001	0.16	92	0.10	0.10	0.306	0.01
o-Xylene	134	0.65	0.12	<0.001	0.19	92	0.13	0.09	0.180	0.02

^aProc GLM in SAS is used for the regression analysis.

^bResults are based on the model logP_i = α + β·log(A_i·t_o,i %) + ε_i. Samples with t_o,i % = 0 are not included.

^cSE: standard error.