(a) WHO PM2.5 exceedance plots segmented
across three
categories by aerosol composition classes: CARB (black carbon and
organic aerosol), SNA (sulfate, nitrate, and ammonium), and DSTSS
(fine dust and sea salt). The legend describes the colors corresponding
to overlapping regions where multiple categories exceed the 5 μg
m–3 guideline. (b) Compositional representation
of population-weighted PM2.5 exposure for the modern day
emission (ModernDay, MD) scenario and the extreme
abatement (noAnthro, nA) scenario organized by continent.
The numbers on top of each bar correspond to the population-weighted
annual PM2.5 exposure for each continent (with levels that
exceed the WHO guideline in red). See Figure S9 for a version of panel a with the 2005 WHO guideline of 10 μg
m–3.