North America Historical PM2.5 Estimation

Accurate data concerning historical fine particulate matter (PM2.5) concentrations are needed to assess long-term changes in exposure and associated health risks. We estimated historical PM2.5 concentrations over North America from 1981-2016 for the first time by combining chemical transport modeling, satellite remote sensing, and ground-based measurements.

We constrained and evaluated our estimates with direct ground-based PM2.5 measurements when available and otherwise with historical estimates of PM2.5 from PM10 measurements or total suspended particles (TSP) measurements. The estimated PM2.5 concentrations were generally consistent with direct ground-based PM2.5measurements over their duration from 1988 onward (R2 = 0.6-0.85) and to a lesser extent with PM2.5 inferred from PM10 measurements from 1985 to 1998 (R2 =0.5-0.6). The collocated comparison of the trends of population-weighted annual average PM2.5 from our estimates and ground-based measurements was highly consistent (RMSD = 0.66 μg m-3). The population-weighted annual average PM2.5 over North America decreased from 22 ± 6.4 μg m-3 in 1981, to 12 ± 3.2 μg m-3 in 1998, and to 7.9 ± 2.1 μg m-3 in 2016, with an overall trend of -0.33 μg m-3 yr-1 (95% CI: -0.35 -0.30).

Data availability. The annual mean estimated PM2.5 for 1981-2016 across the North American dataset can be found here. Feel free to contact me if you have any questions.