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Air Pollution in a Warming World: Making a Difficult Public Health Problem Even
More Challenging
Dan Greenbaum, PresidentHealth Effects Institute
AAAS Science and Technology ForumWashington, DCApril 30, 2009
The Air Pollution/Climate Nexus
• Attaining National Ambient Air Quality Standards (NAAQS) a significant challenge• Especially for ozone
• Climate likely to make the job even harder• And ozone itself is a significant short term
climate forcing agent
Ozone Health Effects• Known to cause inflammation in respiratory tract• Reduces ability to breathe (lung function) for
some people• Increases hospitalization for asthma, other lung
diseases• Recent systematic evidence of effects on
premature mortality• New evidence of effects of long term exposure
Ozone Effects on Mortality 95 US Cities Approximately 0.5% increase in mortality /10ppb
(Bell et al 2005)
Jerrett, et al March 2009
2008 National Ambient AQ Standards (NAAQS) for Ozone Increased Ozone Non-Attainment
1997 NAAQS: 85 Counties
2008 NAAQS: 345 Counties
EPA Administrator Jackson has indicated her intent to review and possibly further tighten this standard
A Further Challenge: Worldwide increase in background Ozone from increased
emissions, especially in developing countries
•Observed trends in background ozone levels in California (Jaffe et al., 2003)
Background ozone levels in the Northern Hemisphere (Vingarzan et al., 2004)
0
20
40
60
80
1880 2000 2100O
zone
(ppb
)
And What Might Climate Change Mean for the Ozone Challenge?
Key Projected Effect: Heat INCREASES IN SURFACE TEMPERATURES BY 2050
• Ozone is the primary component of smog• Ozone formation:
NO2 + VOCs ozone
• Warmer temperatures favor ozone formation
Ozone Formation Increases With Temperature
Heat/light
Ozone versus Temperature
R2 = 0.82
0
20
40
60
80
100
120
140
160
30 50 70 90 110Daily Maximum Temperature (oF)
Dai
ly M
axim
um 1
-hr O
zone
(ppb
)
Fresno, 2003-2005Riverside, 2003-2005
R2 = 0.60
0
20
40
60
80
100
120
140
160
180
40 50 60 70 80 90 100 110 120
Daily Maximum Temperature (oF)
Dai
ly M
axim
um 1
-hr O
zone
(ppb
)
California Ozone Standard
California Ozone Standard
Increased Ozone in a Global Climate Model: North America
ppb
Monthly means for 2000 – 2009
Derwent 2007, HEI Annual meeting
Monthly means for 2090 – 2099
The effects are likely to vary substantially across regions of the US
(US EPA 2050 Analysis of Impacts of Climate on Regional Air Quality 2009)
* Fresno
* Los Angeles
* San Francisco
* Sacramento
Riverside*
California slides courtesy of Bart Croes, ARB
Projected Episode Response to Climate days per year > 90 ppb ozone
Stagnation events related to temperatures aloft. All other factors assumed to remain stay constant while global emissions follow IPCC projections A2 and B1.
Kleeman and Cayan, “Impact of Climate Change on Meteorologyand Regional Air Quality In California”, Interim Report to CARB (2006)
Riverside
0
20
40
60
80
100
120
140
160
2000 2050 2100
YearD
ays/
Year
A2 B1
Visalia
0
20
40
60
80
100
120
140
2000 2050 2100Year
Day
s/Ye
ar
A2 B1
The Ozone Challenge
• Significant and strengthening evidence of health effects
• Air Quality Standards Moving Down• Increased Worldwide Background Ozone• Rising Temperature with Climate Change
likely to increase ozone formation in most parts of the US
Two Caveats• WHERE the effects will occur
• EPA’s analysis has suggested that the effects will vary substantially across the country depending on the levels of VOC and NOx emissions among other factors
• WHEN the effects will occur• Most analyses start showing measurable effects
in 2050 and many actions will likely be implemented to reduce VOC and NOx emissions before then
And a further challenge: ozone as a near term climate forcing agent (IPCC 2007)
What about the other pollutants?• They are also likely to be affected
• especially the particulate matter (PM) aerosol which has substantial health effects
• But they are not all as clearly affected in one direction as ozone
• And they have differing implications for radiative forcing• With some PM aerosols and gases increasing
pressure on climate, and other PM aerosols mitigating against climate change
PM2.5 versus Temperature (Two California Cities)
Fresno, 2003-2005Riverside, 2003-2005
R2 = 0.15
0
50
100
150
200
250
30 50 70 90 110Daily Maximum Temperature (oF)
Dai
ly M
axim
um 1
-hr P
M2.
5 (µ
g/m
3 )R2 = 0.02
0
20
40
60
80
100
120
140
160
180
200
50 60 70 80 90 100 110
Daily Maximum Temperature (oF)
Dai
ly M
axim
um 1
-hr P
M2.
5 (µ
g/m3 )
Projected PM2.5 Response to Climate South Coast Air Basin
2. Also increase background ozone to 60 ppb
Kleeman, ”A Preliminary Assessment of the Sensitivity of Air Quality in California to Global Change”, Climatic Change, accepted.
Base-case episode featuresSeptember 25, 1996 (125 µg/m3)Elevated temperature inversionCool nights, warm days
Sensitivity studyLimitations: No accounting of
future controls or the effect of temperature on emissions and meteorology
1. Increase temperature by +5°C, constant relative humidity
More complex near-term climate forcing among other pollutants (IPCC 2007)
Concluding Thoughts• We have substantial existing public health
challenges from ambient air pollution today• Especially for ozone and PM
• With worldwide growth in emissions and background, this challenge is increasing, even before the effects of climate are considered
• Climate is likely to significantly further exacerbate some of these problems by mid-century• Unlike CO2 however, near-term actions taken to reduce
emissions could substantially and much more immediately, mitigate against these effects
