Table 2.

Summary statistics for daily, site-specific air pollution and meteorological parameters at 53 AQS sites over the study period 2005–2014. An overall summary statistic (mean, SD, minimum, or maximum) of a parameter is a summary of 53 site-specific statistics. The 25th and 75th percentiles correspond to the percentiles of 53 site-specific statistics.

Parameter	Overall mean (25th, 75th percentile)	Overall SD (25th, 75th percentile)	Overall minimum (25th, 75th percentile)	Overall maximum (25th, 75th percentile)
PM
24-h avg ${\mathrm{PM}}_{2.5}$ (${\mathrm{\mu }\mathrm{g}/\mathrm{m}}^3$)	10.5 (9.6, 11.2)	5.5 (4.3, 6.1)	1.6 (1.2, 2.1)	53.5 (36.1, 63.1)
24-h avg ${\mathrm{PM}}_{10–2.5}$ (${\mathrm{\mu }\mathrm{g}/\mathrm{m}}^3$)	12.0 (7.0, 14.4)	7.0 (4.2, 8.3)	0.1 (0.0, 0.0)	76.8 (34.7, 77.0)
24-h avg EC (${\mathrm{\mu }\mathrm{g}/\mathrm{m}}^3$)	0.7 (0.5, 0.8)	0.4 (0.3, 0.6)	0.0 (0.0, 0.1)	5.4 (2.7, 6.7)
24-h avg OC (${\mathrm{\mu }\mathrm{g}/\mathrm{m}}^3$)	3.1 (2.5, 3.7)	2.3 (1.6, 2.9)	0.3 (0.1, 0.4)	34.1 (14.3, 45.7)
24-h avg nitrate (${\mathrm{\mu }\mathrm{g}/\mathrm{m}}^3$)	1.9 (1.0, 2.0)	2.4 (1.1, 2.8)	0.0 (0.0, 0.0)	37.0 (12.4, 47.1)
24-h avg sulfate (${\mathrm{\mu }\mathrm{g}/\mathrm{m}}^3$)	2.0 (1.3, 2.7)	1.8 (0.9, 2.5)	0.1 (0.0, 0.1)	24.3 (9.8, 27.8)
Gaseous pollutants
8-h max ${\mathrm{O}}_3$ (ppm)	0.04 (0.04, 0.04)	0.01 (0.01, 0.01)	0.01 (0.00, 0.01)	0.10 (0.09, 0.10)
1-h max ${\mathrm{NO}}_2$ (ppb)	22.6 (17.0, 27.5)	9.6 (7.9, 11.4)	2.9 (1.3, 4.3)	70.8 (55.0, 84.5)
1-h max ${\mathrm{NO}}_{\mathrm{x}}$ (ppb)	48.7 (32.7, 60.2)	38.1 (21.6, 50.3)	3.4 (1.6, 4.6)	323.7 (179.6, 442.1)
1-h max ${\mathrm{SO}}_2$ (ppb)	3.9 (1.8, 5.5)	3.8 (1.6, 4.8)	0.1 (0.0, 0.1)	42.8 (19.0, 50.9)
1-h max CO (ppm)	0.6 (0.5, 0.8)	0.4 (0.2, 0.5)	0.1 (0.1, 0.1)	3.1 (2.1, 3.7)
Meteorology
1-h max temperature (K)	294.1 (291.2, 296.7)	8.7 (7.9, 10.2)	269.7 (263.3, 278.0)	317.8 (314.2, 319.6)
24-h avg dew point temperature (K)	279.3 (278.1, 281.3)	7.9 (5.6, 10.0)	253.3 (249.3, 257.0)	294.7 (292.1, 297.0)

Note: AQS, Air Quality System; avg, average; CO, carbon monoxide; EC, elemental carbon; max, maximum; OC, organic carbon; PM, particulate matter; SD, standard deviation.