TABLE 1—

Descriptive Statistics for American Indian (AI)- and Non–AI-Populated Counties Overall and Among Those With Monitors: United States, 2000–2018

Characteristic	All Counties		Counties With Monitorsa
AI	Non-AI	AI	Non-AI
All counties
No. of counties	199	2909	71	766
% AI population, mean (SD)	18.2 (19.9)	0.6 (0.6)	16.0 (15.1)	0.7 (0.8)
Modeled PM2.5 concentration, µg/m3, mean (SD)	6.3 (2.1)	8.4 (2.2)	6.0 (2.2)	8.6 (2.5)
Measured PM2.5 concentration,b µg/m3, mean (SD)	. . .	. . .	7.0 (2.7)	9.6 (2.8)
Population density, per mi2, mean (SD)	41 (116)	276 (1790)	69 (180)	787 (3400)
Median annual household income,$\times$$1000, mean (SD)	40.4 (7.6)	44.4 (11.6)	42.0 (7.2)	49.1 (12.6)
ADI,d 25th, 75th percentiles	60.5, 83.3	56.7, 79.4	50.9, 77.3	44.5, 70.9
Rural countiesc
No. of counties	163	1785	51	245
% AI population, mean (SD)	19.7 (20.7)	0.6 (0.8)	18.5 (16.3)	0.9 (1.0)
Modeled PM2.5 concentration, µg/m3, mean (SD)	6.2 (2.0)	8.0 (2.3)	5.8 (2.1)	7.2 (2.5)
Measured PM2.5 concentrationb, µg/m3, mean (SD)	. . .	. . .	6.5 (2.9)	8.3 (3.1)
Population density, per mi2, mean (SD)	19 (24)	45 (99)	25 (28)	51 (51)
Median annual household income,$\times$ $1000, mean (SD)	39.1 (7.3)	40.0 (8.1)	40.3 (7.1)	42.5 (9.6)
ADI, 25th, 75th percentilesd	64.1, 84.2	65.7, 82.5	49.5, 78.1	52.7, 78.0

Note. ADI = Area Deprivation Index; PM_2.5 = fine particulate matter.

^aCounties with at least 1 year with monitored PM_2.5 data over the study period.

^bMeasured PM_2.5 concentrations were only assessed in counties with monitors. Analyses involving measured PM_2.5 included only counties with monitors during the study period, whereas modeled PM_2.5 analyses included all counties.

^cMicropolitan and noncore counties defined by the Centers for Disease Control and Prevention National Center for Health Statistics (i.e., nonmetropolitan counties).

^dHigher values indicate higher levels of neighborhood disadvantage.