Use of Satellite Observations for Long-Term Exposure Assessment of Global Concentrations of Fine Particulate Matter

Background: More than a decade of satellite observations offers global information about the trend and magnitude of human exposure to fine particulate matter (PM(2.5)). Objective: In this study, we developed improved global exposure estimates of ambient PM(2.5) mass and trend using PM(2.5) concentrations inferred from multiple satellite instruments. Methods: We combined three satellite-derived PM(2.5) sources to produce global PM(2.5) estimates at about 10 km × 10 km from 1998 through 2012. For each source, we related total column retrievals of aerosol optical depth to near-ground PM(2.5) using the GEOS–Chem chemical transport model to represent local aerosol optical properties and vertical profiles. We collected 210 global ground-based PM(2.5) observations from the literature to evaluate our satellite-based estimates with values measured in areas other than North America and Europe. Results: We estimated that global population-weighted ambient PM(2.5) concentrations increased 0.55 μg/m(3)/year (95% CI: 0.43, 0.67) (2.1%/year; 95% CI: 1.6, 2.6) from 1998 through 2012. Increasing PM(2.5) in some developing regions drove this global change, despite decreasing PM(2.5) in some developed regions. The estimated proportion of the population of East Asia living above the World Health Organization (WHO) Interim Target-1 of 35 μg/m(3) increased from 51% in 1998–2000 to 70% in 2010–2012. In contrast, the North American proportion above the WHO Air Quality Guideline of 10 μg/m(3) fell from 62% in 1998–2000 to 19% in 2010–2012. We found significant agreement between satellite-derived estimates and ground-based measurements outside North America and Europe (r = 0.81; n = 210; slope = 0.68). The low bias in satellite-derived estimates suggests that true global concentrations could be even greater. Conclusions: Satellite observations provide insight into global long-term changes in ambient PM(2.5) concentrations. Satellite-derived estimates and ground-based PM(2.5) observations from this study are available for public use. Citation: van Donkelaar A, Martin RV, Brauer M, Boys BL. 2015. Use of satellite observations for long-term exposure assessment of global concentrations of fine particulate matter. Environ Health Perspect 123:135–143; http://dx.doi.org/10.1289/ehp.1408646