Table 2.

Descriptive statistics of PM_2.5 pollution indices, their units, mean ± SD levels, interquartile range (IQR), and 10th–90th percentile range for participants in 100 MSAs during 2000–2005 (derived per Thurston et al. 2011).

PM metric	Units	Mean ± SD	IQR	10th–90th percentile
As	ng/m3	1.4 ± 0.5	0.55	0.9–2.0
Ca	ng/m3	61.1 ± 35.1	43.8	29.6–100.4
Cl	ng/m3	34.6 ± 38.3	33.5	7.8–69.9
Fe	ng/m3	106.6 ± 56.2	47.8	59.1–220.9
Pb	ng/m3	5.1 ± 3.3	2.6	2.7–9.3
Mn	ng/m3	3.7 ± 5.1	2.1	1.5–6.3
Ni	ng/m3	2.0 ± 2.5	1.5	0.7–4.0
Se	ng/m3	1.4 ± 0.9	0.8	0.7–2.1
V	ng/m3	2.5 ± 2.0	2.6	0.8–6.4
Si	ng/m3	104.4 ± 55.1	42.9	61.5–157.6
Zn	ng/m3	18.0 ± 14.8	10.1	7.6–31.8
K	ng/m3	68.4 ± 18.6	21.9	48.0–93.4
Na	ng/m3	71.7 ± 48.2	33.4	35.7–141.2
EC	μg/m3	0.8 ± 0.3	0.26	0.5–1.1
OC	μg/m3	4.4 ± 0.9	0.98	3.5–5.3
S	μg/m3	1.3 ± 0.4	0.53	0.7–1.7
PM2.5	μg/m3	15.0 ± 2.7	3.01	11.3–17.6
Crustal/soil	μg/m3	0.8 ± 0.5	0.56	0.4–1.3
Metals-related	μg/m3	0.2 ± 0.2	0.18	0.0–0.3
Traffic-related	μg/m3	5.5 ± 2.2	2.40	2.9–7.6
Salt aerosols	μg/m3	0.1 ± 0.2	0.10	0.0–0.4
Oil combustion	μg/m3	1.1 ± 1.1	1.09	0.3–2.2
Steel industry	μg/m3	0.0 ± 0.1	0.00	0.0–0.1
Coal combustion	μg/m3	1.1 ± 0.9	0.64	0.3–1.9
Biomass burning	μg/m3	1.4 ± 0.7	0.54	0.9–2.0