Fine particulate air pollution and life expectancies in the United States: The role of influential observations

Figures & data

Table 1. Expanded sensitivity analysis regarding potentially influential data points with estimated regression coefficients (and SE, P values, and R ² values) of change in life expectancy on change in PM_{2. 5} (10 µg/m³) for selected data sets and regression models

Counties Used	Clustering	Robust Regression/Exclusions of Outliers and Influential Observations	Covariates	PM2.5 Coefficient (SE)	P Value	R ^2
All 211 counties	No		None	0.72 (0.21)	0.001	0.05
	Yes		None	0.72 (0.29)*	0.016	0.05
	No		Model 4	0.61 (0.16)	0.001	0.53
	Yes		Model 4	0.61 (0.20)*	0.004	0.53
	No	M robust	Model 4	0.60 (0.16)	0.001	0.46
	No	S robust	Model 4	0.62 (0.16)	0.001	0.58
	No	MM robust	Model 4	0.61 (0.16)	0.001	0.44
All counties, excluding 46 (Topeka)	No		None	0.65 (0.21)	0.003	0.04
	Yes		None	0.65 (0.29)	0.029	0.04
	No		Model 4	0.57 (0.16)	0.001	0.52
	Yes		Model 4	0.57 (0.20)	0.007	0.52
	No	M robust	Model 4	0.56 (0.16)	0.001	0.46
	No	S robust	Model 4	0.59 (0.16)	0.001	0.58
	No	MM robust	Model 4	0.57 (0.16)	0.001	0.44
51 largest counties in each metro area	No		None	0.71 (0.39)	0.076	0.06
	No		Model 7	0.95 (0.23)*	0.001	0.74
	No	M robust	Model 7	0.98 (0.23)	0.001	0.66
	No	S robust	Model 7	0.99 (0.26)	0.001	0.74
	No	MM robust	Model 7	1.00 (0.24)	0.001	0.61
Largest counties, excluding 46 (Topeka)	No		None	0.44 (0.39)	0.269	0.03
	No		Model 7	0.81 (0.23)	0.001	0.72
	No	M robust	Model 7	0.86 (0.23)	0.001	0.65
	No	S robust	Model 7	0.90 (0.25)	0.001	0.74
	No	MM robust	Model 7	0.89 (0.24)	0.001	0.61
51 Largest counties excluding outliers and influential observations	No	No exclusions	Model 6	1.01 (0.25)*	0.001	0.76
	No	RSTUDENT > 2 (exclude 20)	Model 6	1.03 (0.23)	0.001	0.78
	No	DFBETA > 0.28 (exclude  15, 46, 47)	Model 6	0.90 (0.28)	0.003	0.76
	No	Both above (exclude  20, 15, 46, 47)	Model 6	0.96 (0.25)	0.001	0.79
Notes: Models 4, 6, and 7 refer to the models reported in the NEJM paper (Models 4 and 7 included as covariates change in income, change in population, change in black population, and the proxy smoking variables, change in lung cancer mortality rate and change in chronic obstructive pulmonary disease [COPD] mortality rate; Model 6 included all available variables for socioeconomic, demographic, and both proxy smoking variables). The four regressions marked by * are exactly the same as reported in Table 2 of the original paper. R ^2 is the coefficient of determination.

Figure 1. Changes in life expectancy (A) and residual changes in life expectancy after controlling from available socioeconomic, demographic, and proxy smoking variables (B) for the 1980s–1990s, plotted against reductions in PM_2.5 concentrations for 1980–2000 for the most populated central counties in each of the 51 metropolitan areas. The numbers indicate the metropolitan areas as defined in the original paper (Pope et al., 2009). R ² values are the coefficients of determination for each of the fitted curves as illustrated.

Pope , C.A. , Ezzati , M. and Dockery , D.W. 2009 . Fine particulate air pollution and life expectancy in the United States . N. Engl. J. Med. , 360 : 376 – 386 . doi: 10.1056/NEJMsa0805646

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