Climate change affects human health in several different ways, and one important effect is through changes in air pollution. Here I will discuss the state of science currently on how climate change affects air pollution, and the resulting effects on human health, drawing from the broad literature and highlighting studies from my lab. In particular, I will discuss: 1) The effects of air pollution on health globally, 2) How climate change affects air pollution, 3) The effects of climate change on air pollution and health globally, and 4) The co-benefits of greenhouse gas mitigation for air pollution and health, globally and in the US.

1. The Effects of Climate Change on
Human Health Through Changes in
Air Quality
J. Jason West
Department of Environmental
Sciences & Engineering
University of North Carolina,
Chapel Hill

2. Beijing – January 14, 2013
Some stations reported >500 µg m-3 24-hr avg.
PM2.5 (>20 times the WHO guideline)

4. • Air pollution is underappreciated for global health.
• Air pollution and its health impacts are changing globally, and
will change in ways interrelated with climate change.
• Air pollution science offers new possibilities: new
measurement methods measuring more chemical
components, cheap sensors that can be widely deployed,
satellites, and models.
• There is a need for the communities of air pollution science
and air pollution health effects science to work together
better.

5. Plan for today
1) How many people die each year due to
exposure to ambient air pollution?
2) How will climate change affect air
pollution and air pollution-related
deaths?
3) If we slow down climate change, what
are the benefits for air pollution and
health?

6. Meteorology
Emissions
Typical horizontal resolutions:
Global model – 5 to 0.5 degrees
Regional model (continental) – 50 to 10 km
Concentrations
Chemical
Mechanism
Modeling Global Air Pollution & Health
Health
Function
Incidence
Data
Health
Impacts

8. 8
Health impact function
∆Mort = y0 x AF x Pop
β = Concentration-
response factor
Baseline
mortality rate
Exposed
Population
- Respiratory diseases (RESP)
(inc. COPD – chronic obstructive
pulmonary disease)
- Cardiovascular diseases
(inc. IHD – ischemic heart disease,
STROKE – cerebrovascular disease)
- Lung Cancer (LC)
(≈ CPD)
∆Mort = y0 x (1-exp-βΔX) x Pop
ΔX = Change in
concentration

9. 9
Population and Baseline Mortality Rates
Total Population, persons
(Landscan 2011 at 30”x30”
gridded to 0.67°x0.5°)
Baseline Mortality Rates, deaths per year per 100,000
(GBD 2010, country level, AllAges > gridded to 0.67°x0.5°)
IHD
COPD
Stroke
LC
3,839 million
Population 25+, persons
(Landscan 2011 at 30”x30”
gridded to 0.67°x0.5°)
6,946 million

10. 12-km CMAQ
Global model
2.8º resolution

11. Bias in US Deaths from PM2.5
0
20,000
40,000
60,000
80,000
0 100 200 300 400
Deaths/Year
Grid Resolution (km)
CMAQ Model Output
(12km-grid)
Punger and West (AQAH, 2013)
30~40% lower than
12km grid estimate
11

12. 0
2
4
6
8
10
12
0 100 200 300 400 500
PWC(µg/m3)
Grid Resolution (km)
CMAQ
Satellite
Akita et al. in prep.
US Bias is different for Satellite PM2.5!

13. -20% Global Anthrop. Methane Emissions:
30,200 avoided premature deaths in 2030
due to reduced ozone
West et al., PNAS, 2006

14. Ozone from N.
American and
European emissions
causes more deaths
outside of those
regions than within
Avoided deaths (hundreds) from 20% regional ozone precursor reductions, based on
HTAP simulations, Anenberg et al. (EST, 2009)

15. 15
Global mortality burden – ACCMIP ensemble
Ozone-related mortality PM2.5-related mortality(*)
470,000 (95% CI: 140,000 - 900,000) 2.1 million (95% CI: 1.3 - 3.0 million)
(*) PM2.5 calculated as a sum of species (dark blue)
PM2.5 as reported by 4 models (dark green)
Light-colored bars - low-concentration threshold (5.8 µg m-3)
Silva et al. (ERL, 2013)

16. 16
Global Burden: Ozone-related mortality
Respiratory mortality , deaths yr-1 (1000 km2)-1,
multi-model mean in each grid cell , 14 models
Global and regional mortality per year
Regions
Total
deaths
Deaths
per
million
people (*)
North America 34,400 121
Europe 32,800 96
Former Soviet Union 10,600 66
Middle East 16,200 68
India 118,000 212
East Asia 203,000 230
Southeast Asia 33,300 119
South America 6,970 38
Africa 17,300 73
Australia 469 29
Global 472,000 149
(*) Exposed population (age 30 and older)
Silva et al. (ERL 2013)

17. 17
Global Burden: PM2.5-related mortality
CPD+LC mortality , deaths yr-1 (1000 km2)-1,
multi-model mean in each grid cell , 6 models
Global and regional mortality per year
Regions
Total
deaths
Deaths
per
million
people (*)
North America 43,000 152
Europe 154,000 448
Former Soviet
Union
128,000 793
Middle East 88,700 371
India 397,000 715
East Asia 1,049,000 1,191
Southeast Asia 158,000 564
South America 16,800 92
Africa 77,500 327
Australia 1,250 78
Global 2,110,000 665
1
(*) Exposed population (age 30 and older)
Silva et al. (ERL 2013)

18. Global burden of disease of air pollution (2015)
Cohen et al., Lancet, 2017
Global Deaths perYear
Ambient PM2.5 pollution: 4.2 (3.7 – 4.8) million
Ambient ozone pollution: 0.25 (0.10 – 0.42) million
Household air pollution from solid fuels: 2.8 (2.2 – 3.6) million
1 in 12 deaths
globally!

20. GBD: US Deaths perYear (2015)
Ambient PM2.5 pollution: 88,000
Ambient ozone pollution: 12,000
Household air pollution from solid fuels: 0
Other US estimates
Ambient PM2.5 pollution: 66,000 (39,000 – 85,000) (Punger & West, 2013)
130,000 (Fann et al., 2012)
Ambient ozone pollution: 21,000 (6,000 – 34,000) (Punger & West, 2013)
4,700 (Fann et al., 2012)
1 in 26 US deaths!

21. 21
Ozone-related mortality (sectors zeroed-out)
Contributions of each sector to total ozone respiratory mortality,
fraction of total burden in each cell
Land Transportation
Energy Industry
Residential & Commercial
Silva et al. (EHP, 2016)
Global total: 45,600 deaths/yearGlobal total: 65,200 deaths/year
Global total: 80,900 deaths/year Global total: 53,700 deaths/year

22. 22
PM2.5-related mortality (sectors zeroed-out)
Contributions of each sector to total PM2.5 mortality (IHD+Stroke+COPD+LC),
fraction of total burden in each cell
Land Transportation
Energy Industry
Residential & Commercial
Global total: 290,000 deaths/year Global total: 323,000 deaths/year
Global total: 212,000 deaths/year Global total: 675,000 deaths/year
Silva et al. (EHP, 2016)

23. 23
Future ozone-related mortality - ACCMIP
Global Respiratory Premature Ozone Mortality: 2030, 2050 and 2100 vs. 2000 conc.
- Uncertainty for the ensemble mean is a 95% CI including uncertainty in RR and across models. -
Silva et al. (ACP, 2016)

24. 24
Future PM2.5-related mortality - ACCMIP
Global CPD+LC Premature PM2.5 Mortality: 2030, 2050 and 2100 vs. 2000 conc.
-Uncertainty for the ensemble mean is a 95% CI including uncertainty in the RR and across models. –
Silva et al. (ACP 2016)

25. 25
Future PM2.5-related mortality - ACCMIP
RCP2.6 6 models RCP8.5 6 models
deaths yr-1 (1000 km2)-1
-1000 -100 -10 -1 -0.1 -0.01 0.01 0.1 1 10 100 1000
IHD+Stroke+COPD+LC
Premature PM2.5 Mortality –
2100 (two scenarios)
IHD+Stroke+
COPD+LC
Premature
PM2.5 Mortality
Silva et al. (ACP 2016)

26. Summary schematic of air quality-climate connections
Figure 2, Fiore, Naik, Leibensperger, JAWMA, 2015
Climate  Air Pollution

27. Impact of RCP8.5 Climate Change on Global Air
Pollution Mortality: ACCMIP Models
Mean (95% CI)
(thousands deaths yr-1)
2030
3 (-30, 47)
2100
44 (-195, 237)
Mean (95% CI)
(thousand deaths . yr-1)
2030
56 (-34 , 164)
2100
215 (-76 , 595)
Silva et al. Nat Clim Ch, 2017
Million deaths yr-1OZONE
PM2.5

28. Impact of RCP8.5 Climate Change on Global Air
Pollution Mortality: ACCMIP Models
Silva et al. Nat Clim Ch, 2017

29. Impact of RCP8.5 Climate Change on Global Air
Pollution Mortality: ACCMIP Models
Silva et al. Nat Clim Ch, 2017

30. EPA project with Columbia Univ (Arlene Fiore, PI):
Large multi-chemistry-climate-model ensembles and high-res
downscaling, evaluated with observations
CM3 model [e.g., Donner et al., 2011]
2 CMIP5/IPCC AR5 Chemistry-climate models
• 3-member ensembles for 2006-2100 RCP4.5, RCP8.5; RCP8.5_WMGG
(climate change from WMGHGs but PM + precursor emissions held at 2005)
• 400 years from “2000 Control” to examine climate variability
 Select targeted years in ~6 U.S. regions for downscaling with CMAQ
[e.g., Neale et al., 2012]
• 40-member large ensemble with monthly PM2.5 components archived
• ~15-member medium ensembles with daily PM2.5 components archived
• 400 years from “2000 Control” to examine climate variability
 Provide statistical context for GFDL-CMAQ simulations + climate variability
Targeted high-resolution downscaling with CMAQ
• CONUS, multiple selected years (mid-century)
• Examine sensitivities (vulnerability) to meteorologically-sensitive emissions
 Combine fine-scale information with statistical power of large ensemble

31. Co-benefits of GHG Mitigation for Air
Quality
Sources &
Policies
Air
pollutants
GHGs
Air
pollution
Climate
Change
Objective: Analyze global co-benefits for air
quality and human health to 2100 via
both mechanisms.
1) Immediate and Local
2) Long-Term and Global
Human
Health

32. Approach
• Use the GCAM reference for emissions rather than
RCP8.5, for consistency with RCP4.5.
• Simulations conducted in MOZART-4.
- 2° x 2.5° horizontal resolution.
- 5 meteorology years for each case.
- Fixed methane concentrations.
- Compares well with ACCMIP RCP4.5.
Years Emissions
GCAM
Meteorology
GFDL AM3
Name
2000 2000 2000 2000
2030,
2050,
2100
GCAM
Reference
RCP8.5 REF
RCP4.5 RCP4.5 RCP4.5
GCAM
Reference
RCP4.5 eREFm45

33. Co-benefits – PM2.5 Concentration
Global population-weighted, annual average PM2.5
West et al. NCC 2013

34. Co-benefits – Global Premature Mortality
PM2.5 co-benefits
(CPD + lung cancer mortality)
2030: 0.4±0.2 million yr-1
2050: 1.1±0.5
2100: 1.5±0.6
Ozone co-benefits
(respiratory mortality)
2030: 0.09±0.06
2050: 0.2±0.1
2100: 0.7±0.5
Projection of global
population and
baseline mortality
rates from
International Futures.
West et al. NCC 2013

35. Co-benefits – Valuation of Avoided Mortality
Red: High valuation (2030 global mean $3.6 million)
Blue: Low valuation (2030 global mean $1.2 million)
Green: Median and range of global C price (13 models)
West et al. NCC 2013

36. Downscaling Co-benefits to USA (2050)
Zhang et al. ACP, 2016
PM2.5 (annual avg.)
US mean = 0.47 µg/m3
Ozone (May-Oct MDA8)
US mean = 3.55 ppbv
RCP4.5 - REF
(b)(a)

37. Downscaling Co-benefits to USA (2050)
Zhang et al. ACP, 2016
Domestic
Ozone
Most PM2.5 co-
benefits from
domestic
reductions.
Most ozone
co-benefits
from foreign
and methane
reductions.
PM2.5
0.35 µg/m3
0.12 µg/m3
Foreign
0.86 ppb
2.69 ppb

38. Domestic vs. Foreign Co-benefits: PM2.5
Zhang et al. ERL submitted
Domestic Foreign
 Domestic GHG mitigation accounts for 85% of the total avoided
PM2.5 mortality.

39. Domestic vs. Foreign Co-benefits: O3
Zhang et al. ERL, submitted
Domestic Foreign
 Foreign countries’ GHG mitigation accounts for 62% of the total
avoided deaths of O3.

40. US Co-benefits in 2050
• Avoided premature deaths from GHG mitigation: 16000 (CI:
11700-20300) from PM2.5, and 8000 (CI: 3600-12400) from O3.
• Avoided heat stress mortality from RCP4.5 relative to RCP8.5:
2340 (CI: 1370-3320) (Ying Li).
• Monetized co-benefits in 2050 are $49 (32-67) per ton CO2
reduced at low VSL, $148 (96-201) at high VSL.
• Foreign GHG mitigation accounts for 62% of the total avoided
deaths from O3, and 15% for PM2.5.
• Previous regional or national co‐benefits studies may
underestimate the full co‐benefits of coordinated global actions.
• U.S. can gain significantly greater co‐benefits, especially for
ozone, by collaborating with other countries to combat climate
change.
Zhang et al. ERL, submitted; Li et al in preparation

41. Thank you
Contributions from
Students: Raquel Silva, Yuqiang Zhang, Susan Anenberg,
Zac Adelman, Meridith Fry
Others: Steve Smith, Vaishali Naik, Larry Horowitz, Jared Bowden,
Jean-Francois Lamarque, Drew Shindell, ACCMIP modelers
Funding Sources:
• EPA STAR Grant #834285
• NIEHS Grant #1 R21 ES022600-01
• EPA Office of Air Quality Planning and Standards
• Portugal Foundation for Science and Technology Fellowship
• EPA STAR Fellowship
• US Department of Energy, Office of Science
• Merck Foundation
• International Council on Clean Transportation
• NOAA GFDL for computing resources
834285
UNC Climate Health and Air Quality Lab
www.unc.edu/~jjwest

42. Projecting Baseline Health
2010 from WHO GBD
Future from International Futures
(mortality rates are at country level)

43. 43
Representative Concentration Pathways (RCPs)
200
400
600
800
1000
2000 2030 2050 2100
CO2 concentration (ppmv)
100
400
700
1000
2000 2030 2050 2100
CH4 emissions (TgCH4.yr-1)
40
80
120
160
2000 2030 2050 2100
NOx emissions (TgNO2.yr-1)
10
50
90
130
2000 2030 2050 2100
Sulfur emissions (TgSO2.yr-1)
Source: RCP Database - http://tntcat.iiasa.ac.at:8787/RcpDb/dsd?Action=htmlpage&page=compare

44. 44
Respiratory
premature ozone
mortality - 2030,
2050, 2100 vs.
2000
deaths yr-1 (1000 km2)-1
-1000 -100 -10 -1 -0.1 -0.01 0.01 0.1 1 10 100 1000
RCP2.6 11 models RCP8.5 13 models
Future ozone-related mortality (II)
Respiratory
premature ozone
mortality - 2100
(two scenarios)
Silva et al. (ACPD 2016)

45. Our co-benefits approach: advantages
• First co-benefits study to use a global atmospheric
model.
– Capture effects of long-range transport and methane.
• First to estimate co-benefits by two mechanisms.
• Use consistent future scenarios built on RCP4.5:
emissions, population, economics (valuation).
• By embedding the US study within a prior global study,
we capture US co-benefits from foreign reductions.

46. Results – PM2.5 Concentration
2050
2100
Annual average PM2.5
Total change
RCP4.5 - REF
Meteorology
eREFm45 - REF
Emissions
RCP4.5 – eREFm45
West et al. NCC 2013

47. Results – Ozone Concentration
Global population-weighted,
max. 6 month average of 1 hr. daily max ozone West et al. NCC 2013

48. Results – Ozone Concentration
2050
2100
Max. 6 month average of 1 hr. daily max ozone
Total co-benefit #2 Meteorology #1 Emissions
Meteorology
eREFm45 - REF
Total change
RCP4.5 - REF
Emissions
RCP4.5 - eREFm45
West et al. NCC 2013

49. Results – Global Premature Mortality
West et al. NCC 2013

50. Co-benefits: conclusions
• Global abatement of GHG emissions brings substantial
air quality and human health co-benefits.
• Global GHG mitigation (RCP4.5 relative to REF)
causes 0.5±0.2 million avoided deaths in 2030, 1.3±0.5
in 2050, and 2.2±0.8 in 2100
• Global average monetized co-benefits are $50-380 /
ton CO2
– Greater than previous estimates
– Greater than abatement costs in 2030 and 2050.
• The direct co-benefits from air pollutant emission
reductions exceed those via slowing climate change.
West et al. NCC 2013