Global Estimates and Long-Term Trends of Fine Particulate Matter Concentrations (1998–2018)
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Date
2020-06-03
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Hammer, M. S., A. van Donkelaar, C. Li, A, Lyapustin, A. M. Sayer, N. C. Hsu, R. C. Levy, M. J. Garay, O. V. Kalashnikova, R. A. Kahn, M. Brauer, J. S. Apte, D. K. Henze, L. Zhang, Q. Zhang, B. Ford, J. R. Pierce, and R. V. Martin (2020), Global Estimates and Long-Term Trends of Fine Particulate Matter Concentrations (1998-2018), Environ. Sci. Technol., 54 (13), 7879–7890, https://doi.org/10.1021/acs.est.0c01764
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This work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.
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Abstract
Exposure to outdoor fine particulate matter (PM2.5) is a
leading risk factor for mortality. We develop global estimates of annual
PM2.5 concentrations and trends for 1998−2018 using advances in satellite
observations, chemical transport modeling, and ground-based monitoring.
Aerosol optical depths (AODs) from advanced satellite products including
finer resolution, increased global coverage, and improved long-term stability
are combined and related to surface PM2.5 concentrations using geophysical
relationships between surface PM2.5 and AOD simulated by the GEOSChem chemical transport model with updated algorithms. The resultant
annual mean geophysical PM2.5 estimates are highly consistent with globally
distributed ground monitors (R2 = 0.81; slope = 0.90). Geographically
weighted regression is applied to the geophysical PM2.5 estimates to predict
and account for the residual bias with PM2.5 monitors, yielding even higher
cross validated agreement (R2 = 0.90−0.92; slope = 0.90−0.97) with ground monitors and improved agreement compared to all
earlier global estimates. The consistent long-term satellite AOD and simulation enable trend assessment over a 21 year period,
identifying significant trends for eastern North America (−0.28 ± 0.03 μg/m3
/yr), Europe (−0.15 ± 0.03 μg/m3
/yr), India (1.13 ±
0.15 μg/m3
/yr), and globally (0.04 ± 0.02 μg/m3
/yr). The positive trend (2.44 ± 0.44 μg/m3
/yr) for India over 2005−2013 and
the negative trend (−3.37 ± 0.38 μg/m3
/yr) for China over 2011−2018 are remarkable, with implications for the health of billions
of people.