. 2012 Oct 19;121(1):66–72. doi: 10.1289/ehp.1104812

Table 2.

Descriptive statistics on daily environmental variables over the study.

Variable	Suburban period		Urban period 1		Urban period 2		IQR^a
Variable	Mean ± SD	Percent of PM_2.5	Mean ± SD	Percent of PM_2.5	Mean ± SD	Percent of PM_2.5	IQR^a
PM10 (μg/m3)	135.4 ± 64.1		111.3 ± 75.0		129.4 ± 87.2		66.0
PM2.5–10 (μg/m3)	56.1 ± 47.5		36.3 ± 29.3		69.5 ± 62.8		42.3
PM2.5 (μg/m3)	82.0 ± 46.6		78.1 ± 72.5		59.9 ± 40.3		51.2
Carbonaceous fractions
OC (μg/m3)	10.2 ± 5.5	15.5	12.6 ± 9.0	20.6	10.6 ± 3.9	24.0	3.7
EC (μg/m3)	2.0 ± 1.2	2.88	3.3 ± 2.6	4.65	1.7 ± 0.9	3.64	1.5
POC (μg/m3)	4.4 ± 2.3	6.26	8.2 ± 6.3	11.4	6.0 ± 3.1	13.2	4.1
SOC (μg/m3)	5.9 ± 4.9	9.30	4.4 ± 3.3	9.20	4.6 ± 2.4	10.8	1.9
POM (μg/m3)	16.4 ± 8.8	24.9	20.1 ± 14.4	32.9	16.9 ± 6.2	38.4	5.9
Ions
SO42– (μg/m3)	16.8 ± 15.0	18.4	12.0 ± 14.2	13.0	8.9 ± 9.0	13.1	10.0
NO3– (μg/m3)	2.9 ± 2.8	2.98	3.5 ± 4.7	3.21	2.1 ± 2.8	2.57	2.6
Cl– (μg/m3)	1.0 ± 1.1	1.18	1.5 ± 1.8	1.73	0.9 ± 1.2	1.40	1.2
F– (ng/m3)	31.9 ± 32.3	0.052	57.9 ± 48.2	0.107	51.7 ± 47.1	0.099	57.0
Transition metals
Fe (μg/m3)	0.8 ± 0.4	1.21	0.7 ± 0.4	1.16	0.8 ± 0.9	1.30	0.5
Zn (μg/m3)	0.4 ± 0.3	0.52	0.4 ± 0.4	0.50	0.4 ± 0.3	0.62	0.3
Mn (ng/m3)	65.9 ± 45.0	0.116	60.4 ± 30.6	0.110	48.3 ± 26.9	0.096	35.5
Ti (ng/m3)	48.5 ± 33.3	0.071	38.0 ± 24.2	0.068	52.6 ± 79.8	0.093	29.5
Cu (ng/m3)	30.1 ± 24.3	0.038	37.5 ± 35.4	0.049	26.3 ± 22.9	0.042	26.9
Cr (ng/m3)	18.5 ± 22.5	0.036	8.9 ± 5.6	0.019	8.5 ± 6.7	0.021	5.1
Ni (ng/m3)	3.7 ± 2.2	0.006	3.4 ± 3.5	0.006	3.3 ± 2.5	0.007	2.1
Cd (ng/m3)	2.6 ± 2.8	0.003	3.2 ± 3.4	0.004	2.4 ± 2.7	0.004	2.5
V (ng/m3)	3.1 ± 1.8	0.004	1.6 ± 1.1	0.003	1.7 ± 1.9	0.003	1.3
Mo (ng/m3)	1.9 ± 2.1	0.004	1.3 ± 0.8	0.002	0.8 ± 0.7	0.002	0.9
Crustal metals
K (μg/m3)	1.1 ± 0.9	1.32	1.4 ± 0.9	2.59	1.0 ± 0.9	1.71	1.0
Ca (μg/m3)	1.1 ± 0.8	1.64	0.8 ± 0.4	1.61	1.0 ± 0.7	1.79	0.7
Al (μg/m3)	1.0 ± 0.8	1.46	0.5 ± 0.2	0.97	0.8 ± 1.6	1.23	0.5
Na (μg/m3)	0.6 ± 0.6	0.82	0.8 ± 0.5	1.60	0.6 ± 0.4	1.46	0.4
Mg (ng/m3)	292.4 ± 249.1	0.43	194.2 ± 98.9	0.37	318.4 ± 341.6	0.57	148.3
Ba (ng/m3)	14.0 ± 8.2	0.021	17.2 ± 10.0	0.033	14.6 ± 12.4	0.027	11.8
Sr (ng/m3)	9.5 ± 6.4	0.015	6.0 ± 3.1	0.011	6.6 ± 5.0	0.012	4.8
Other metals/metalloid elements
Pb (ng/m3)	127.7 ± 89.6	0.158	125.0 ± 122.5	0.153	119.2 ± 111.7	0.181	127.7
As (ng/m3)	16.0 ± 19.9	0.018	17.1 ± 24.0	0.018	32.6 ± 35.2	0.058	19.5
Sn (ng/m3)	7.3 ± 5.7	0.009	9.2 ± 9.5	0.012	6.8 ± 5.8	0.011	6.8
Sb (ng/m3)	6.6 ± 5.6	0.008	8.6 ± 7.6	0.011	6.0 ± 4.9	0.010	6.1
Se (ng/m3)	7.3 ± 5.9	0.009	5.4 ± 4.6	0.008	3.9 ± 3.4	0.006	4.4
CO (ppm)	0.90 ± 0.33		1.67 ± 0.60		1.47 ± 0.45		0.74
NOx (ppb)	41.6 ± 18.1		70.7 ± 39.4		48.3 ± 17.7		35.1
NO2 (ppb)	24.1 ± 8.0		38.0 ± 14.8		31.7 ± 11.8		14.2
NO (ppb)	17.4 ± 12.4		32.8 ± 29.3		16.5 ± 10.9		26.8
Temperature (°C)	23.8 ± 5.3		17.3 ± 6.5		22.4 ± 4.5		—
Relative humidity (%)	47.5 ± 15.9		55.7 ± 15.7		37.9 ± 14.5		—
Abbreviations: Al, aluminum; As, arsenic; Ba, Barium; Ca, calcium; Cd, cadmium; Cl–, chloride; CO, carbon monoxide; Cr, chromium; Cu, copper; EC, elemental carbon; F–, fluoride; Fe, iron; K, potassium; Mg, magnesium; Mn, manganese; Mo, molybdenum; Na, sodium; Ni, nickel; NO, nitric oxide; NO3–, nitrate; NOx, nitrogen oxides; OC, organic carbon; Pb, lead; POC, primary organic carbon; POM, particulate organic matter; Sb, antimony; Se, selenium; Sn, stannum; SO42–, sulfate; SOC, secondary organic carbon; Sr, strontium; Ti, titanium; V, vanadium; Zn, zinc. aIQR values of air pollutant concentrations during the preceding 1 day before the BP measurement.