Air pollution levels in American Indian communities in the Great Plains and Southwest: The Strong Heart Study

Differences in environmental exposures-particularly to ambient air pollution-have been consistently documented across communities in the United States (U.S.). However, relatively few studies on air pollution have focused on American Indians. In this paper, we combine demographic data from Phase IV (2001 to 2003) and Phase V (2006 to 2009) of the Strong Heart Study-the largest ongoing longitudinal epidemiologic cohort study of cardiovascular disease in American Indians-and 1 km² modeled PM_2.5 data in the Northern Plains, Southern Plains, and Southwestern United States. We analyzed data at the U.S. ZIP code level to estimate 30-day and annual residential exposures of participants to PM_2.5 and assess for regional, temporal, and seasonal variations in PM_2.5 exposure. We found significantly higher mean 30-day and annual PM_2.5 concentrations among participants in the Southwest and Southern Plains (>7.4 μg/m³ and >7.6 μg/m³, respectively) than in the Northern Plains (<6.6 μg/m³ and <6.2 μg/m³, respectively). We observed heterogeneity in participants' mean 30-day and annual PM_2.5 exposure within and across regions. Furthermore, seasonal differences in ambient PM_2.5 concentrations among participants varied by region; in the Northern Plains, we generally observed higher mean 30-day PM_2.5 exposure levels in the summertime and lower levels in the wintertime, whereas levels remained relatively constant in the Southern Plains and Southwest. These findings offer essential baseline data to advance accurate and equitable exposure assessment across tribal communities in the Northern Plains, Southern Plains, and Southwest regions.