Comparison of geostatistical interpolation and remote sensing techniques for estimating long-term exposure to ambient PM_2.5 concentrations across the continental United States

Background: A better understanding of the adverse health effects of chronic exposure to fine particulate matter (PM_2.5) requires accurate estimates of PM_2.5 variation at fine spatial scales. Remote sensing has emerged as an important means of estimating PM_2.5 exposures, but relatively few studies have compared remote-sensing estimates to those derived from monitor-based data. Objective: We evaluated and compared the predictive capabilities of remote sensing and geostatistical interpolation. Methods: We developed a space-time geostatistical kriging model to predict PM_2.5 over the continental United States and compared resulting predictions to estimates derived from satellite retrievals. Results: The kriging estimate was more accurate for locations that were about 100 km from a monitoring station, whereas the remote sensing estimate was more accurate for locations that were > 100 km from a monitoring station. Based on this finding, we developed a hybrid map that combines the kriging and satellite-based PM_2.5 estimates. Conclusions: We found that for most of the populated areas of the continental United States, geostatistical interpolation produced more accurate estimates than remote sensing. The differences between the estimates resulting from the two methods, however, were relatively small. In areas with extensive monitoring networks, the interpolation may provide more accurate estimates, but in the many areas of the world without such monitoring, remote sensing can provide useful exposure estimates that perform nearly as well.