Table 1.

Estimated mean percent change in daily mortality associated with a unit increase in pollutant concentration on the previous day, single-pollutant model analyses.

Pollutant	dfa	Mean	90% CI	95% CI	No. of cities
PM10		50		0.40		0.33, 0.51		0.30, 0.53		102
		100		0.39		0.30, 0.48		0.28, 0.49
O3		50		0.08		–0.11, 0.34		–0.16, 0.38		98
		100		0.40		0.29, 0.53		0.27, 0.56
SO2		50		1.60		1.14, 1.91		0.93, 1.94		85
		100		1.46		1.17, 1.70		1.07, 1.74
NO2		50		1.01		0.91, 1.13		0.89, 1.16		72
		100		1.03		0.92, 1.14		0.91, 1.18
CO		50		1.47		1.18, 1.71		1.15, 1.75		95
		100		1.30		1.09, 1.53		1.05, 1.58
Units are 10 µg/m3 for PM10; 10 ppb for NO2, O3, and SO2; and 1 ppm for CO. Temperature and relative humidity on the previous day are controlled using 6 df natural splines. Time trends are controlled using either 50 df or 100 df natural splines. Day of week is controlled as a categorical variable. The last column shows the number of cities available for analyses. aDegrees of freedom for natural splines of time trends.