Geoscience Reference
In-Depth Information
A key component of smogs are airborne
particulates. Particulate matter (PM) refers to
any form of air pollution that is present in the
atmosphere in either a solid or a liquid state.
While the reaction of VOCs with sunlight produces
some of the PM we associate with smogs, atmos-
pheric particulates have a range of different
sources. PM also includes the soot and black
smoke that is produced from the burning of
coal, the sulphuric acid suspensions that are associ-
ated with acid rain and various organic com-
pounds. Particulate air pollution is often referred
to as aerosols, although technically an aerosol
is particulate matter and the gases in which it is
suspended. Regardless of their precise name or
form, PM has a series of common impacts. In
terms of human health, atmospheric particulates
have been associated with a range of conditions
including heightened levels of asthma, acute
respiratory infections, cardiopulmonary disease
and cancers of the lungs and trachea (see Cohen
et al, 2005). Such health problems are caused
by the fact that a significant portion of the PM
that is produced by air polluting activities is so
small in size that it can penetrate the nose and
throat of humans (where larger sized particles are
normally caught) and enter throats and lungs.
In a recent study for the World Health Organiza-
tion, Cohen et al (2005) estimate that particulate
air pollution is responsible for approximately 0.8
million premature deaths and 6.4 million years of
life lost, per year.
Beyond human health, PM also has a significant
impact on local climates. The particulates in
smokes and smogs can act as a 'parasol of pollu-
tion', which prevents the sun's rays penetrating
cities (see Pearce, 2007: 178). This parasol effect
was associated in earlier industrial times with the
rise of rickets within urban populations, which was
believed to be caused by a deficiency of vitamin C
in the population (vitamin C is naturally absorbed
into the human body through the skin's exposure
to sunlight). In today's world, however, the parasol
of pollution effect is associated with the artificial
cooling of cities that are thus protected from some
of the worst consequences of global warming. In
this sense, the particulate pollution of a city acts
as a kind of greenhouse gas effect in reverse,
preventing the sun's rays reaching the Earth's
surface and being trapped in the greenhouse. This
peculiar situation does, however, create something
of a policy paradox. As urban authorities attempt
to reduce the aerosols that are present in the
atmosphere of cities, they may be releasing the full
effects of climate change (it is estimated that
aerosol pollution may be responsible for holding
back around 0.2 degrees Celsius of warming,
a quarter of the present recorded warming) (see
Pearce, 2007: 179). The case of particulate air
pollution reveals the complex relationships that
exist between climate change and more localized
forms of atmospheric pollution. It also reveals the
ways in which localized air pollution is connected
to systemic shifts in the ways in which the Earth's
climate system works. To these ends, the pro-
duction of ground-level ozone causes smogs
and human health problems, whereas ozone in
the upper atmosphere protects the Earth from
dangerous forms of solar radiation. At a global
level, the burning of fossil fuels produces an
enhanced greenhouse effect that is contributing
towards dangerous forms of climate change. At a
more local level, the burning of the very same fossil
fuels is generating palls of pollution that threaten
human health, but shelter cities from the worst
affects of climate change. It is thus important to
remember that while the atmospheric changes
that are associated with the Anthropocene may
take local and global forms, they are all ultimately
part of an integrated atmospheric system (for an
interesting discussion of the complex relations
that connect climate change and ozone depletion
see Schiermeier, 2009).
3.3 REFLECTIONS ON THE
NATURE OF ATMOSPHERIC
SCIENCE
At the beginning of this chapter we saw the dual
role that science plays in contributing to the
