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Vol. 6 No. 1 - Millennium Issue - January 2000

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).


This article has been reproduced from the archives of EnviroNews - Newsletter of ISEB India.


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