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Global Air
Pollution:
Does the
World Take a Restricted View?
By: J.N.B.
Bell
In 1972,
Dennis and Donella Meadows published their controversial book, "The Limits to
Growth", which painted a highly pessimistic view of the world’s future. It
represented the outcome of a massive computer modelling exercise on a world
scale - a problematical exercise with a vengeance - which prophesied that
economic growth would be brought to a grinding halt within a frighteningly
short period of time, due to population increase, depletion of mineral
resources, failure of agriculture to increase production sufficiently, and
global pollution. At the time the book attracted enormous interest, much of it
highly critical. Thus it became viewed by some, in particular economists, as
being "Malthus with a computer", and technocentrics pointed out the ability of
human ingenuity over the centuries to find technical solutions, including
materials substitution. The publication of "Limits to Growth", was followed
shortly afterwards by the oil crisis, which was probably the beginning of real
interest by industry in the environment, albeit via the single issue of energy
conservation.
It is
salutary to look back over the 27 years which have passed since the meadows’
publication. The rate of population increase is falling in the world as a whole
and, indeed, is negative in some developed countries (which has its own serious
economic and social implications, ignored by the more extreme advocates of
population control!). While socio-economic factors result in an inequitable
distribution of food across the world’s population, overall production has
matched reasonably well the increase in numbers of people on our planet. Even
more interesting is the developments in utilisation of mineral resources. We
have seen no signs of imminent depletion of any category of mineral and,
indeed, this is demonstrated by falling world prices of both fossil fuels and
metals. The economists were right in their belief telephone messages has
resulted in tonnes of copper wire being replaced by kilograms of silica, with
an enormous increase in capacity.
So were the
so-called "prophets of doom" wrong in 1972? Since then we have seen many global
environmental issues rise on the international scale to unprecedented levels.
Destruction of the world’s habitats has reached frightening levels, with legal
or illegal removal of rainforests in particular, reflecting the fundamental
problem at the heart of global environmental issues viz. over-consumption in
the developed world and population growth in developing countries. However, the
potentially most alarming issue is the one that was most criticised by the
critics of "Limits to Growth" almost 30 years ago. This was global pollution
which was predicted to be a major contributor to the halting of economic
growth. At the time this was treated with derision by many, and I have to admit
that as a young and native environmental scientist, albeit one working on local
pollution issues, I could not conceive pollution having this role. Clearly the
Meadows had spectacular foresight in that global pollution is the issue that is
now widely identified as having the potential to cause spectacular disruption
of economies over the next century.
In 1972 the
first glimpses of global pollution problems were becoming apparent, in both
cases being in accord with our present priorities in seeing air pollutants as
being the dominating issue. This is hardly surprising as the most mobile form
of air pollution is atmospheric. Thus it has been known for a long time that
radio activity is distributed worldwide as a result of above ground nuclear
bomb testing, which effectively terminated in 1963, albeit in this case
transport occurred via the stratosphere. At the time there was a knowledge that
increases in CO, emissions resulting from release of carbon locked away in the
earth’s crust over geological time, appeared to be overwhelming the world’s
homeostatic mechanism which previously balanced out the outputs from
respiration with the inputs from photosynthesis. While the concerns at the time
suggested that the CO, increase might have major effects in terms of global
warming, other greenhouse gases were identified subsequently as representing in
total an equivalent warming potential, including methane, tropospheric O3,
N2O and chlorofluorocarbons. About the same time Rowland and Molina
hypothesised that the stratospheric O3 layer, which protects biota
at the earth’s surface against the damaging effects of ultra-violet radiation,
could be threatened by global pollution. Initially it was suggested that the
problem would arise as a result of emissions of supersonic aircraft travelling
in the stratosphere. In the event the aircraft problem became a trivial issue:
the only commercial aircraft which has flown is the Anglo-French Concorde, with
a few transatlantic flights daily by two airlines, representing a luxury for a
few wealthy passengers of the developed world. If the techno-centric
predictions of the early 1970s had come to pass, with all long distance
aircraft flying at supersonic speeds in the stratosphere, then the situation
could have been very different. As a resident of a town directly under
Concorde’s flight path from London Heathrow, I can declare a personal interest
in a different form of pollution: on a bad day this expensive (to the
taxpayer) toy will wake a baby and stop conversation in the street!
It is
interesting to review briefly developments since 1972 in terms of both
stratospheric O3 depletion and greenhouse gas problems. In the
former, there was much debate over an issue which was based entirely on
theoretical considerations. Some countries took action in the late 1970s to
remove chlorofluorocarbons from what were considered to be "non-essential"
uses, notably as aerosol propellants. And there the matter rested until in the
late 1980s the British Antarctic Survey identified a growing hole in the
stratospheric O3 layer in the Antarctic spring. This was in accord
with the earlier theoretical projections and raised enormous concern over the
potential biological effects of increased u.v. penetration to the troposphere.
The horrific implications of this problem resulted in the development of a
number of world agreements to eliminate the compounds responsible for 03
depletion. This represents a case of a remarkable international consensus,
probably due to the clear identification of realistic substitutes for the
offending substances and the relatively low economic implications of using
them.
The other
major global issue - greenhouse gases and their consequences - continues to
attract enormous attention at the macro-level. Interestingly, at the personal
level in the developed world, which is responsible for the vast bulk of the
emissions, this issue appears to be viewed as one "which will not affect me". I
can only assume that this is the result of the adverse consequences not being
immediately apparent to the public, at least in their own lifetimes. But
stratospheric O3 depletion was addressed almost immediately with
enthusiasm by both public and politicians alike. Why the difference? Increased
uv penetration is certainly an issue affecting relatively small populations at
high latitudes, particularly in the southern hemisphere. But - the solutions to
the problem were relatively easy, with substitution of the offending compounds
being economically and technically feasible. In the case of greenhouse gas
emissions the issue appears to be intractable, and in spite of brave words at
international meetings such as Kyoto, I believe that the prospects are gloomy.
In the case of stratospheric O3 depletion the scientific evidence
some years ago, provided incontrovertible evidence of the problem. There is
even better long term evidence for global increases of both CO2 and
other greenhouse gases, and there are many indicators of warming taking place.
In the UK a set of these has been devised for the government and includes
factors such as nesting dates of some birds, dates of flowering of certain
plant species and the number of days that sking is possible in northern
Scotland.
Enormous
attention is paid to the likely consequences for global warming of the rapid
industrialisation of many developing nations, particularly where this depends
on a vastly increased amount of coal burn, notably in the world’s two most
populous countries - India and China. However, far less attention is paid to
the fact that the resulting increases in CO2 emissions will be
accompanied by large increases in both SO2 and nitrogen oxides (NOX),
which have been shown to cause in the developed world serious problems with
respect to human health and acidification and eutrophication of the
environment. The identification of these problems has led to the introduction
of increasingly stringent emissions controls, with predicted reductions such as
7% and 36% for SO2 in the USA and Europe, respectively. This
contracts with the situation in much of the developing world, where between
2000 and 2010 SO2 emissions are predicted to increase from 34 to 48,
6.6 to 10.9 and 12.4 to 19.1 million tonnes in China, India and the rest of
Asia, respectively. At the same time motor traffic is growing at a great pace
in many parts of the developing world, often in the form of old poorly
maintained vehicles with minimal or zero emission controls. These are
contributing toxic volatile organic compounds, NOX and particulates
to the atmosphere of cities, causing major deterioration in the air quality.
The two former compounds will interact in the presence of bright sunlight and
high temperatures to produce photochemical oxidants, the most important of
which is O3. Thus photochemical smog, once thought to be the
preserve of developed world cities, such as Los Angeles, are now recorded in
many developing country cities, where climatic conditions are often
particularly conductive to their formation, with Mexico City and Santiago being
particularly notorious examples. And the growing air pollution problems of
these countries is by no means restricted to urban and industrial areas. It has
been recognised for many years in Europe and North America and long distance
transport of pollutants results in the deposition of acid precipitation and O3
over large areas of countryside, with the latter paradoxically often being at
higher concentrations than within the cities. It is only in very recent years
that there has been the growing realisation that such widespread rural air
pollution is occurring in parts of the developing world. Thus the pH of
precipitation in parts of southwest China is now as low as 4.25 on average,
with an apparently associated forest decline, reminiscent of the situation in
northern
Europe
and Eastern North America.
The rising
air pollution levels in developing world cities have sparked off major research
programmes into their effects on human health, particularly bronchial diseases.
Indeed, many countries have developed air quality standards for a range of
pollutants towards which pollution controls can be directed in order to
minimise health effects. What has scarcely been addressed, however, is the
potential for air pollution to affect human health indirectly via reductions in
crop yield and quality, which are likely to affect the poor most severely. The
only developing country where any significant research into this subject has
been carried out is India. In this case, most research has been directed
towards
SO2
impacts in the vicinity of industrial point sources. Thus the possibility of
widespread crop reductions in rural areas arising from O3 pollution
has effectively been ignored, and, indeed, monitoring of this pollutant in such
places is almost non-existent. Research with Dr. Fiona Marshall at Imperial
College over the last 9 years has been aimed at a very preliminary attempt to
determine the importance of air pollution, particularly O3, as a
constraint on crop production in developing countries. The results are
startling and must raise grave cause for concern. Thus work in the Delta area
of Egypt has shown 20-30% loss of yield of vegetable crops, while work on the
urban fringe of Lahore and its neighbouring countryside has produced evidence
of reductions of wheat, rice and soybean yield of up to 60%. Current research
in India is aimed at elucidating the impact of the complex mix of pollutants in
cities on urban and peri-urban agriculture. This is using Delhi and Varanasi as
case-study cities, in conjunction with colleagues at the Jawaharlal Nehru
University and Banaras Hindu University, respectively. Preliminary indications
are that substantial losses in yield and quality of key summer and winter crops
are taking place, with implications for the livelihood and nutrition of the
urban poor. In general plants are damaged at lower concentrations of air
pollutants than are injurious to human health. Thus if crops are to be
protected against reduction in yield caused by growing air pollution in
developing countries, then it is necessary to develop air quality standards
appropriate to local conditions, as occurs in Europe and North America.
In this
paper we have raised the issue of air pollution in various forms representing
the most serious environmental problem for the world’s future. We have tried to
draw attention to the fact that this problem is not confined to greenhouse gas
effects and stratospheric O3 depletion, but that other pollutants of
traditional concern in the developed world are becoming widespread to the
extent that they can be viewed effectively as global in dimension: human health
may be impacted not only directly, but also indirectly, via threats to food
security.
Dr. J.N.B. Bell is Professor of Environmental Pollution at
Imperial College Silwood Park, Ascot, Berkshire SL5 7PY (UK). |
