Table 1.

Characteristics of the study population by three different air pollution measures.

Descriptive characteristics	Total study sample^a (n=3381)	Highest quartile of annual average PM_2.5 (n=842)		800 m or less from Industrial site (n=470)		400 m or less from primary or secondary road (n=1076)
Descriptive characteristics	N	%	p- trend	%	p- trend	%	p- trend
Gender			0.90		0.57		0.80
Male	1480	24.8		13.5		38.6
Female	1901	25.0		14.2		39.0
Age (in years)			0.04		< 0.0001		0.004
21–39	1104	26.8		17.8		42.2
40–59	1503	25.1		13.3		38.6
60–72	774	21.7		9.4		34.6
Education			< 0.0001		0.01		< 0.0001
H.S./GED or less	992	21.5		16.8		45.1
Some college	1309	23.5		14.8		41.3
Bachelors or	1073	29.5		12.1		33.4
higher
Income			0.02		< 0.0001		< 0.0012
< $25,000	764	21.1		19.2		43.3
$25,000 - $49,000	800	24.1		12.7		41.4
$50,000 - $99,000	1102	27.5		11.5		36.8
> $99,000	579	25.9		9.5		27.6
Smoking Status			0.24		< 0.0001		0.0017
Current	555	21.1		22.0		44.7
Former	825	23.2		10.5		35.4
Never	1535	24.6		11.9		37.7
Smoking in Home			0.74		< 0.0001		< 0.0001
Yes	541	23.7		21.0		45.6
No	2534	23.0		12.0		36.8
BMI			0.002		0.23		0.25
< 25	1264	28.2		13.4		39.5
25–30	936	23.6		12.8		36.6
> 30	1181	22.4		15.2		40.0
Physical Activity			0.40		< 0.0001		0.0002
< 600 Met Min/ week	902	25.9		18.3		44.0
> =600 Met min/week	2479	24.5		12.3		37.0
Pet Owner			0.02		0.61		0.08
Yes	1906	23.3		13.7		37.2
No	1475	26.9		14.4		40.5
Mold in home			0.16		0.19		0.003
Yes	503	25.0		15.7		44.4
No	2652	22.2		13.5		37.5
Indoor chemical use			0.04		0.16		0.10
Yes	818	20.7		15.1		40.9
No	2369	24.1		13.2		37.7
Location			< 0.0001		< 0.0001		< 0.0001
Urban	2139	32.7		20.1		43.0
Rural	1241	11.5		3.1		31.8
Residence Duration			0.24		< 0.0001		0.003
< =5 years	1234	24.5		17.6		41.3
> 5 years	1305	25.3		10.0		36.2
Allergies			0.44		0.42		0.34
Yes	1080	25.7		14.5		40.0
No	2301	24.5		13.5		38.3
Asthma			0.32		0.0015		0.001
Yes	502	26.7		19.8		47.5
No	2879	24.6		13.2		37.9
Wheezing			0.15		< 0.0001		0.0002
Yes	657	22.7		19.8		45.2
No	2712	25.4		12.5		37.4

p-trend: statistical significance by Chi-square test.

Abbreviations: GRE - General Education Development test; BMI - body mass index.

Total study sample size varies due to missing data on outcomes and confounders. See Methods sections for details.