Geography Reference
In-Depth Information
released from soils due to acidification; they may
then enter aquatic food chains and eventually
reach humans.
Respiratory problems caused by poor air
quality are the most common diseases to which
acid precipitation contributes. McCormick (1997)
records the number of deaths caused by serious
smogs in the industrialised world pre-1965; among
the worst were those in London in 1873 and 1880,
which together caused 2500 deaths. These were
extreme events linked to industrialisation and little
or no air quality control. The old, the young and
those suffering respiratory disease were especially
vulnerable. Today, such events are characteristic of
the newly industrialising countries. Moreover,
these were extreme events with an obvious cause
and effect. In the developed world, urban air
quality may still be poor (see the example of
Noril'sk, Siberia, in the previous section) due to
gaseous rather than particulate emissions. As
McCormick points out, health problems may
ensue from regular exposure to air that is
characterised by low-level pollution. Although the
relationship between air pollution and respiratory
problems has eluded precise definition, the huge
increase in such problems, especially asthma,
reflects the at least partial influence of air quality,
although other factors may also contribute.
McCormick (p. 32) states 'the World Health
Organisation estimates that in Europe alone,
excessive levels of sulphur dioxide may be
responsible for 6000 to 13000 extra deaths every
year among people aged 65 or older, intensified
chronic respiratory problems for 89000 to 203000
people and 58000 to 99000 extra cases of diseases
in the lower respiratory organs among children.'
The potential for health problems due to the
indirect effect of acid precipitation has been
discussed by Oskarsson
et al
. (1996). They were
particularly concerned with the possible impact
of toxic elements such as lead, copper zinc,
cadmium, methylmercury and selenium. The latter
may become scarce under acidified conditions and
cause health problems because of its scarcity; the
other metals may cause problems because their
mobility is increased under acid conditions, and
consequently they enter food chains and webs in
increased proportions. In addition, acidic water
will cause increased extraction of metals such as
lead from domestic plumbing. Oskarsson
et al
.
were unable to find unequivocal relationships
between health problems due to metal
contamination and acidification, although they
identified a number of possible links. They suggest
that safety margins are small in relation to the
exposure of humans to toxic metals and that curbs
on acid precipitation are essential before damage
to human health becomes apparent.
CONCLUSION
Acid precipitation is a product of the industrial age
and represents anthropogenic perturbations to the
sulphur and nitrogen cycles. So serious have its
consequences been that they have prompted
international agreements, with the initial concerted
efforts to curb emissions of nitrous and sulphurous
gases beginning in 1985. This was one of the first
international agreements to tackle a pollution
problem, pre-dating the Montreal Protocol on
ozone by two years. The effectiveness of the 1985
and later protocols is manifest in many parts of the
industrialised world as lake and stream water quality
has improved. In some instances, fish populations
have been restored. Despite these improvements,
acid precipitation remains a significant agent of
environmental change in the Northern
Hemisphere, and further curbs on emissions,
especially nitrous emissions, are necessary. Moreover,
the problem of acidification is spreading as many
developing countries are industrialising rapidly. Acid
precipitation is thus set to become a global problem.
The chemistry of acid precipitation is
understood in relation to its production, although
once it is deposited its reactions with organic and
inorganic substances in soils and water are
complex. It influences many other biogeochemical
cycles, especially those of the heavy metals, raised
concentrations of which may cause further
ecosystem change. The most severely affected
regions are those on acid bedrock that are either
close to emission sources or that receive air masses
from industrial centres. Lakes, streams, soils, forests
