Particulate air pollution and socioeconomic position in rural and urban areas of the Northeastern United States.

Objectives: Although differential exposure by socioeconomic position (SEP) to hazardous waste and lead is well demonstrated, there is less evidence for particulate air pollution (PM), which is associated with risk of death and illness. This study determined the relationship of ambient PM and SEP across several spatial scales.

Methods: Geographic information system-based, spatio-temporal models were used to predict PM in the Northeastern United States. Predicted concentrations were related to census tract SEP and racial composition using generalized additive models.

Results: Lower SEP was associated with small, significant increases in PM. Annual PM(10) decreased between 0.09 and 0.93 micrograms per cubic meter and PM(2.5) between 0.02 and 0.94 micrograms per cubic meter for interquartile range increases in income. Decrements in PM with SEP increased with spatial scale, indicating that between-city spatial gradients were greater than within-city differences. The PM-SEP relation in urban tracts was not substantially modified by racial composition.

Conclusions: Lower compared with higher SEP populations were exposed to higher ambient PM in the Northeastern United States. Given the small percentage change in annual PM(2.5) and PM(10), SEP was not likely a major source of confounding in epidemiological studies of PM, especially those conducted within a single urban/metropolitan area.