BACKGROUND: Air pollution is associated with morbidity and premature mortality. Satellite remote sensing provides globally consistent decadal-scale observations of ambient nitrogen dioxide (NO2) pollution. OBJECTIVE: We determined global population-weighted annual mean NO2 concentrations from 1996 through 2012. METHODS: We used observations of NO2 tropospheric column densities from three satellite instruments in combination with chemical transport modeling to produce a global 17-year record of ground-level NO2 at 0. 1° × 0. 1° resolution. We calculated linear trends in population-weighted annual mean NO2 (PWMNO2) concentrations in different regions around the world. RESULTS: We found that PWMNO2 in high-income North America (Canada and the United States) decreased more steeply than in any other region, having declined at a rate of –4. 7%/year 95% confidence interval (CI): –5. 3, –4. 1. PWMNO2 decreased in western Europe at a rate of –2. 5%/year (95% CI: –3. 0, –2. 1). The highest PWMNO2 occurred in high-income Asia Pacific (predominantly Japan and South Korea) in 1996, with a subsequent decrease of –2. 1%/year (95% CI: –2. 7, –1. 5). In contrast, PWMNO2 almost tripled in East Asia (China, North Korea, and Taiwan) at a rate of 6. 7%/year (95% CI: 6. 0, 7. 3). The satellite-derived estimates of trends in ground-level NO2 were consistent with regional trends inferred from data obtained from ground-station monitoring networks in North America (within 0. 7%/year) and Europe (within 0. 3%/year). Our rankings of regional average NO2 and long-term trends differed from the satellite-derived estimates of fine particulate matter reported elsewhere, demonstrating the utility of both indicators to describe changing pollutant mixtures. CONCLUSIONS: Long-term trends in satellite-derived ambient NO2 provide new information about changing global exposure to ambient air pollution. Our estimates are publicly available at http: //fizz. phys. dal. ca/~atmos/martin/? pageᵢd=232.
Geddes et al. (Fri,) studied this question.