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Air Pollution Problems from Energy

Production and Use

The increased use of fossil energy since the industrial revolution, and especially since 1950, hasbeen the major cause of increased emissions of air pollutants and, correspondingly, many

environmental problems. Emissions due to the use of energy are major sources of sulfur dioxide,

nitrogen oxides, carbon dioxide, and soot and constitute a large contribution of methane, non-methane volatile organic compounds, and heavy metals. Depending on conversion due to

atmospheric chemical reactions, on meteorological transport, and on deposition processes, air

pollution can be transported from hundreds of kilometers (ammonia) to several thousands

kilometers (aerosols) on a truly global scale (CO2 and CFCs).

The adverse effects of emissions due to use of energy range from very local to regional andglobal. In cities, traffic can cause very high concentrations of nitrogen oxides and carbonmonoxide, but also secondary products such as ozone and aerosols, especially under conditions

of stagnant air. The adverse effects of ozone on human health at concentrations higher than 200

mgm_3 are well documented. Investigations indicate that aerosol concentrations of 50100mgm_3 are harmful and in The Netherlands (16 million inhabitants) cause the same number of

deaths as traffic accidents per year, approximately 1500. On a regional scale (1000 km), acid

deposition and photochemical smog (ozone) cause well-documented harm to vegetation and

human health. Eutrophication (too high concentrations of nutrients such as phosphate,ammonium, and nitrate) is also a regional problem, quite manifest in Western Europe. Loss of

visibility due to backscatter of light by aerosols is also largely a regional phenomenon. A truly

global problem is the changes in the radiative balance of the earth due to increasedconcentrations of greenhouse gases and aerosols.

Air Pollution Effects and Acid Deposition

Air pollution problems is difficult to define because many air pollutants (at low concentrations)

are essential nutrients for sustainable development of ecosystems. Therefore, air pollution

problems can be defined as a state of the atmosphere that leads to exposure of humans and/or

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ecosystems to such high levels or loads of specific compounds or mixtures thereof that damage is

caused. With very few exceptions, all compounds that are considered air pollutants have bothnatural and man-made origins, mainly from energy production and use. Also, air pollution effects

due to energy use is not a new phenomenon; it was forbidden in medieval times to burn coal in

London while Parliament was in session. Air pollution problems have dramatically increased in

intensity and scale due to the increased use of fossil fuel since the industrial revolution.

All reports on air pollution problems in the 19th and early 20th centuries indicated that theproblems were local, in or near the industrial centers and the major cities. Even the infamous

environmental catastrophes in the area of Liege in the 1930s and in London in the 1950s were

essentially local phenomena. In the London smog episode, stagnant air accumulated suchextremely high sulfur dioxide and sulfuric acid concentrations of approximately 1900 and 1600

mgm_3 , respectivelysome 20 times the current health limitthat 4000 inhabitants died as a

result. The main causes were the emissions from coal stoves used for heating and the fact that all

emissions were trapped in a layer of air probably only a few hundred meters high, with noexchange of air within the city.

During the second half of the 20th century, air pollution effects due to energy use and productionwere detected on regional (4500 km), continental, and even global scales. In approximately

1960, the first observed acid deposition effects were observed on regional and continental scales.

Fish populations in lakes in Scandinavia and North America declined as the lakes were acidifiedby acid deposition to such a degree that fish eggs would not hatch and no young fish were

produced. Approximately 10 years later, damage to forests, the loss of vitality of trees, also

contributed to acid deposition. Smog episodes in cities such as Los Angeles were reported during

the same period. Reactions of volatile organic compounds (VOCs) and nitrogen oxides, emittedby traffic, produced high concentrations of ozone and peroxides, which are harmful for humans

and ecosystems. During the same period, high oxidant concentrations (the complex mixture of

ozone, peroxides, and other products of the reactions of organics and nitrogen oxides) werebecoming increasingly more frequent in Europe during stagnant meteorological conditions. Also,

severe eutrophication (damage and changes to ecosystems due to the availability of large

amounts of nutrients) occurred in Europe and the United States. Deposition of ammonium and

nitrates (partly caused by fossil energy use) was shown to contribute substantially to highnutrient concentrations in soil and groundwater, leading to large-scale dying off of fish in the

United States and Europe. It also caused extremely high nitrate concentrations in groundwater,

with the result that a large part of the superficial groundwater in The Netherlands is now unfit forhuman consumption.

Since 1990, the increased concentrations of radiative active substances (compounds that alter theradiative balance of the earthgreenhouse gases, aerosols, and water in liquid form as clouds)

and the resulting climatic change have received a lot of attention. Greenhouse gases absorb long-

wave infrared radiation emitted from the earth, thereby retaining heat in the atmosphere and

increasing the total radiative flux on the surface of the earth. Aerosols and clouds reflectincoming short-wave sunlight and influence the optical properties of clouds toward more

reflection of sunlight; hence, increasing aerosol concentration leads to a decrease in the radiative

flux on the surface.

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The destruction of stratospheric ozone by chlorofluorocarbon compounds (CFCs) is one of the

few environmental problems not related to energy use. Epidemiological research hasdemonstrated the effects of aerosols on the respiratory tract (inducing asthma and bronchitis),

and a large part of the ambient aerosol is caused by emissions due to energy use and production.

Air Pollution Problems and Acid Deposition

This timing of air pollution problems could give the impression that there were sudden increasesin air pollutant concentration, but this is probably not correct, as can be demonstrated in the case

of ozone. By carefully characterizing old methodologies, it has been possible to reconstruct

ozone concentrations effects in the free troposphere (the air not directly influenced by processes

taking place on the earth surface) during the past 125 years. The ozone concentrations in Europeslowly increased at a rate of 1% or 2% per year from 10 parts per billion (ppb) to more than 50

ppb as a result of the use of fossil energy. It is well documented that the effects of ozone start at

levels of approximately 40 ppb (ppb is a mixing ratio of one molecule of ozone in 1 billion

molecules of air). Therefore, it is not surprising that the effects of ozone were detected in the

1970s because the background concentration of continental ozone was 30 ppb and additionaloxidant formation would increase the ozone concentrations locally or regionally. However, the

increase in the continental background concentrations, mainly caused by fossil fuel, had beenoccurring for a long period.

In general, effects of pollution, and those of air pollution effects, are a function of the degree oftransgression of the limits over which effects can be expected. The use and production of energy

is the major cause of most of the current environmental problems, with the exceptions of

eutrophication and stratospheric ozone loss.