Transcript Aerosols: Impacts and Policy - Environmental Science and

Aerosols: Impacts and Policy
Kyla Drushka - 17 November, 2006
Health effects of aerosols
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Short- and long-term exposure to fine particulate air pollution
increases the risk of lung cancer and chronic lung disease, as well
as coronary heart disease, pneumonia, and other cancers.1
Particulate matter with a diameter of less than 10 microns is the
most damaging air pollutant in terms of health.2
In developed countries, industry and automobile pollution are the
primary causes of aerosols, and those who work outdoors face
the highest risks; in the developing world, urban air pollution and
indoor coal/biomass fires present the greatest risks.
1. Pope, 2002.
2. World Bank, 1997.
Health effects of aerosols: China
From Sinton et al., 2004.
Health effects of aerosols: China
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Indoor coal/biomass burning for cooking and heating is a common
practice in developing countries.
Small-scale, inexpensive stoves do not burn fuels cleanly and
emit many pollutants and fine aerosol particles; there is
disproportionate exposure for women and children.1
Sandstorms, an increasing problem due to desertification and
overuse of land, also contribute to harmful aerosols.
Air pollution in China is blamed for >400,000 deaths a year and
health damages from air pollution are valued at up to 5% of
China's GDP.2
In developing countries, indoor air pollution is the most lethal killer
after malnutrition, unsafe sex and lack of safe water and
sanitation.1
1. World Health Organization, 2005.
2. World Bank, 1997.
Policy to address health effects: China
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Pilot programs to give rural Chinese efficient stoves have been met with success:
households with improved stoves are negatively correlated with respiratory
disease.1
China's most recent five-year plan for the economy devotes ~1.3% of the GDP to
its environmental goals.
According to the Chinese government, coal use has decreased from 76% in 1990
to 67% in 2000 - but unless alternatives are developed quickly, China's rapid
industrial growth will force coal use to increase again.
China has launched a well-funded research program to evaluate the origin and
impact of intense dust storms that plague the country. They have also relocated
some farmers in order to try to combat desertification.
1. Sinton et al., 2004.
Policy to address
aerosol effects: USA
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The 1987 PM10 standards decreased
the atmospheric concentration of
aerosols.
From 1950 to 1990, average surface
solar radiation decreased; from 1985 to
2000, it increased.1
Implications: cleaner air is good for our
health, but increases the effects of
global warming.
1. Wild et al., 2004.
Impact of new clean-air policies
Pre-1990
Increase = 8
Decrease = 24
Post-1990
Increase = 26
Decrease = 6
1. Wild et al., 2004.
1. More effective clean air regulations
2. Political transition in Eastern Europe
3. Recently, recovery from Pinatubo
Spin-down of the hydrological cycle?1
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“Indirect effect” feedbacks:
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Increase in droplet concentration...
cooling due to incr. in reflected radiation
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decrease in drop size
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decrease in precip.
increase in cloudiness, residence time
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dry conditions = more dust/smoke
increase in reflection of solar radiation
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Annual mean aerosol optical depth (AOD) estimated by
a four-dimensional assimilation model that uses satellitederived AOD for the oceans to constrain the model
AODs. The AOD here represents the sum of natural and
anthropogenic aerosol.
A decrease in surface solar radiation could cause a decrease in evaporation and thus
precipitation, leading to a spin-down of the hydrological cycle.
1. Ramanathan et al., 2001.
Changing rain patterns1
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In China and India, there has been moderate cooling in recent
decades, compared to warming in most of the rest of the world.
There has also been increased summer floods in Southern
China and droughts in Northern China.
Menon et al. (2002) ran a climate model to evaluate possible
aerosol contributions to these trends.
Results: Absorbing aerosols, especially black carbon, can
affect regional climate, and the flood/drought trends may be
related to an increase in aerosols.
1. Menon et al., 2002.
Can aerosols help reduce global warming?1
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The warming effects of CO2 could be mitigated by injecting SO2 into the
stratosphere.
Example: eruption of Mt. Pinatubo in 1991 injected ~10Tg of S into the
stratosphere; the next year saw an average global T decrease of ~0.5°C
Why the stratosphere? Because it is highly stratified, sub-micrometer particles
have a long (1-2 year) residence time, compared to particles in the troposphere.
How? (balloons?) How much? (1-2 Tg/year) How much would it cost? ($25-50
billion/year) How much would it help? What might the side-effects be? (ozone
degradation, whitening of the sky, ??????)
Crutzen stresses that this would be a last resort, should future attempts to reduce
GHG prove as ineffective as current attempts - but it would be effective quickly
(within ~6 months)
1. Crutzen, 2006.
Conclusions
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Cooling due to aerosols is a short-term effect due to the short residence time of
aerosols.
Warming due to GHG is long-term because of their long residence time
(cumulative effect).
The reduction of aerosols through clean air policy may result in a global
temperature increase higher than predicted.
References
Menon et al. (2002), Climate effects of black carbon aerosols in China and India, Science, 297(5590), 22502253.
Pope III, (2002), Lung cancer, cardiopulmonary mortality, and long-term exposure to fine particulate air
pollution, JAMA 287(9), 1132-.
Ramanathan et al. (2001), Aerosols, climate, and the hydrological cycle, Science, 294(5549), 2119-2124.
Sinton et al. (2004), An assessment of programs to promote improved household stoves in China, Energy for
Sustainable Development 8(3), 33-52.
Smith (2005), Indoor air pollution: Update on the impacts of household solid fuels, in Environment Matters,
The World Bank Group, Annual Review July 2004– June 2005.
Wild et al. (2004), From dimming to brightening: decadal changes in solar radiation at Earth’s surface,
Science 308, May 6.
World Bank (1997), Clear Water, Blue Skies: China’s Environment in the New Century, Washington DC:
World Bank.
World Health Organization (2005), Indoor air pollution and health. Accessed online 11/15/2006,
http://www.who.int/mediacentre/factsheets/fs292/en/index.html.