Quantifying the impact of hemispheric air
pollution
Excessive ozone levels frequently play havoc with our children's outdoor
activities in summer. And if you suffer from asthma or if you are elderly,
you, too, will be advised to stay indoors. Rural ozone concentrations damage
ecosystems and reduce crop yields and forest growth. But who's to blame and
can anything be done about it?
Throughout the Northern Hemisphere, current emissions create pollution levels
that exceed air-quality objectives. High ozone levels damage ecosystems and
ozone episodes ("summer smog") are human health hazards. High levels
of fine particles have been associated with increases in mortality rates.
While local or regional pollution, such as car emissions or industrial emissions,
and environmental conditions are responsible for most of these exceedances,
there is now scientific evidence that air quality is also influenced by emissions,
transport and transformation processes elsewhere in the hemisphere.
Leading scientists from Europe, North America and Asia gathered in Bad Breisig
(Germany) in a workshop on 7-9 October 2002, organized by the German Federal
Environment Agency and the United States Environmental Protection Agency in
the framework of the UNECE Convention on Long-range Transboundary Air Pollution,
to discuss what observations and computer models tells us about the importance
of intercontinental transport of air pollution in the Northern Hemisphere.
They agreed that there is well-documented evidence for intercontinental and
hemispheric transport of ozone, particles and their precursors, as well as
mercury and persistent organic pollutants.
For ozone, hemispheric pollution adds to local background pollution. For
instance, when summer smog with high levels of ozone hit European cities,
a significant part may be due to sources in Asia and North America. Likewise,
European cars and trucks add to excessive ozone levels in Siberia. The current
levels of emissions from Asia, North America and Europe have increased the
hemispheric burden of ozone by at least 50% since the Industrial Revolution.
Any further increase in Northern Hemispheric emissions will make it more difficult
to reach local air-quality objectives through local or national measures alone,
such as clamping down on car use during pollution peaks or imposing catalytic
converters. The continuing build-up of methane will also contribute to this
growing hemispheric ozone burden.
For fine particles, intercontinental pollution transport can be detected
during specific pollution events, such as large forest fires and dust storms.
For instance, Chinese desert storms affect visibility in California. Forest
fires in the United States have an impact on Europe. Saharan dust ends up
all over Europe and even in Florida. The frequencies of these events are likely
to increase in response to changes in climate, land use and other forms of
human intervention. Desertification, erosion of agricultural land and biomass
accumulation in boreal forests are a particular worry.
Moreover, rising hemispheric levels of ozone and soot particles have an impact
on climate change. It is well established that ozone contributes significantly
to global warming and is of special importance to the climate in the northern
hemisphere. Recent studies indicate that soot particles (emitted for instance
from diesel engines) have also significant warming effects.
"These conclusions confirm the need to continue addressing air pollution
at an international level in the framework of the Convention on Long-range
Transboundary Air Pollution and to take an even broader hemispheric perspective
in developing cost-effective strategies to tackle the problems," says
Kaj Bärlund, UNECE Environment Director.
For more information, please contact:
Henning Wuester
United Nations Economic Commission for Europe (UNECE)
Environment and Human Settlements Division
Palais des Nations, office 323
CH - 1211 Geneva 10, Switzerland
Phone:+41(0)22 917 23 63
Fax: +41(0)22 907 06 21
E-mail: [email protected]
Web site: http://www.unece.org/env/lrtap/
Note: Fine particles are emitted
by many sources, including motor vehicles, particularly those that run on
diesel, industry and other combustion sources. Some particles are small enough
to penetrate the lungs. They are blamed for several health problems, such
as increased risk of heart and lung disease. They can also carry carcinogenic
substances and have been associated with premature deaths. Ground-level ozone,
not to be confused with stratospheric ozone that forms the ozone layer, is
a secondary pollutant caused by industrial and motor vehicle emissions and
the use of certain products such as solvents and paints. It irritates the
eyes and is known to damage lung function. It also causes leaf injury in plants,
including crops and trees, and causes mainly organic materials like paint
or rubber to disintegrate.
Ref: ECE/ENV/02/09