HTAP2 multi-model estimates of premature human mortality due to intercontinental transport of air pollution and emission sectors
Authors: Liang Ciao-Kai , West J. Jason , Silva Raquel A. , Bian Huisheng , Chin Mian , Davila Yanko , Dentener Frank J. , Emmons Louisa , Flemming Johannes , Folberth Gerd , Henze Daven , Im Ulas , Jonson Jan Eiof , Keating Terry J. , Kucsera Tom , Lenzen Allen , Lin Meiyun , Lund Marianne Tronstad , Pan Xiaohua , Park Rokjin J. , Pierce R. Bradley , Sekiya Takashi , Sudo Kengo , Takemura Toshihiko 
Published: July 2018

Abstract. Ambient air pollution from ozone and fine particulate matter is associated
with premature mortality. As emissions from one continent influence air
quality over others, changes in emissions can also influence human health on
other continents. We estimate global air-pollution-related premature
mortality from exposure to PM2.5 and ozone and the avoided deaths due to
20 % anthropogenic emission reductions from six source regions, North
America (NAM), Europe (EUR), South Asia (SAS), East Asia (EAS),
Russia–Belarus–Ukraine (RBU), and the Middle East (MDE), three global emission
sectors, power and industry (PIN), ground transportation (TRN), and
residential (RES), and one global domain (GLO), using an ensemble of global
chemical transport model simulations coordinated by the second phase of the
Task Force on Hemispheric Transport of Air Pollutants (TF HTAP2), and
epidemiologically derived concentration response functions. We build on
results from previous studies of TF HTAP by using improved atmospheric
models driven by new estimates of 2010 anthropogenic emissions (excluding
methane), with more source and receptor regions, new consideration of source
sector impacts, and new epidemiological mortality functions. We estimate
290 000 (95 % confidence interval (CI): 30 000, 600 000) premature O3-related
deaths and 2.8 million (0.5 million, 4.6 million) PM2.5-related
premature deaths globally for the baseline year 2010. While 20 % emission
reductions from one region generally lead to more avoided deaths within the
source region than outside, reducing emissions from MDE and RBU can avoid
more O3-related deaths outside of these regions than within, and
reducing MDE emissions also avoids more PM2.5-related deaths outside of
MDE than within. Our findings that most avoided O3-related deaths
from emission reductions in NAM and EUR occur outside of those regions
contrast with those of previous studies, while estimates of
PM2.5-related deaths from NAM, EUR, SAS, and EAS emission reductions
agree well. In addition, EUR, MDE, and RBU have more avoided
O3-related deaths from reducing foreign emissions than from
domestic reductions. For six regional emission reductions, the total avoided
extra-regional mortality is estimated as 6000 (−3400, 15 500)
deaths per year and 25 100 (8200, 35 800) deaths per year through changes in
O3 and PM2.5, respectively. Interregional transport of air
pollutants leads to more deaths through changes in PM2.5 than in
O3, even though O3 is transported more on interregional
scales, since PM2.5 has a stronger influence on mortality. For NAM and
EUR, our estimates of avoided mortality from regional and extra-regional
emission reductions are comparable to those estimated by regional models for
these same experiments. In sectoral emission reductions, TRN emissions
account for the greatest fraction (26–53 % of global emission reduction)
of O3-related premature deaths in most regions, in agreement with
previous studies, except for EAS (58 %) and RBU (38 %) where PIN
emissions dominate. In contrast, PIN emission reductions have the greatest
fraction (38–78 % of global emission reduction) of PM2.5-related
deaths in most regions, except for SAS (45 %) where RES emission
dominates, which differs with previous studies in which RES emissions
dominate global health impacts. The spread of air pollutant concentration
changes across models contributes most to the overall uncertainty in
estimated avoided deaths, highlighting the uncertainty in results based on a
single model. Despite uncertainties, the health benefits of reduced
intercontinental air pollution transport suggest that international
cooperation may be desirable to mitigate pollution transported over long
distances.