Table 1.

Descriptive statistics for air pollution, meteorological variables, and daily mortality in 135 U.S. cities, 1999–2010.

Variable	Mean	25% Percentile	75% Percentile
Temperature ($\mathrm{°}\mathrm{F}$)	57	45	72
${\mathrm{PM}}_{2.5}$ (${\mathrm{\mu }\mathrm{g}/\mathrm{m}}^3$)	12.8	7.5	16.1
Wind Speed (m/s)	6.7	4.4	8.6
Sea level Pressure (mmHg)	1,017	1,013	1,021
${\text{NO}}_2$ (ppb)*	15.3	9.5	19.8
Daily Deaths (# per day)	22.8	8.0	27.0
Height of PBL (m)	854	572	1,041

Note: All values are daily averages.

^*${\text{NO}}_2$ was available only in 105 cities.