Pollutants carried by air are one of the greatest threats to human health and the health of ecological systems. Polluted air can have enormous consequences. Acidification kills life in thousands of inland lakes and waters. It also reduces growth of trees and other plants on land, contributing to forest death. Acid rain damages buildings, monuments, etc., through corrosion. The destruction of old cultural monuments are especially serious since they can not be replaced. The total costs of air pollution has been estimated in Europe and amounts to some hundreds of billion of dollars yearly.
The largest source of polluted air is burning of fossil fuels. The large scale turnover of energy, in power plants, in traffic, in countless individual homes, in industries, etc., has become one of the major sources of local, regional, and global environmental impact. Sulphur in oil and coal, turned into sulphur dioxide at combustion, gives rise to large scale acidic precipitation damaging rivers, lakes, and forests all over Europe. Combustion also causes atmospheric nitrogen to form nitrogen oxides, contributing to acidification and eutrophication. In short, these energy conversions lead to large scale changes in the chemistry of the planet.
A further source are the large industrial farms specialising in animal production, from which huge amounts of ammonia are emitted. When deposited on ecosystems, ammonium contributes to acidification and eutrophication.
Polluted air typically also contains various organic compounds that interact with other pollutants to form oxidising substances, mostly ozone. This ground level ozone is quite toxic to plants in particular, and is a serious problem for forests. Human health is threatened by these oxidants and even more so by the microscopic particles that are either emitted to the air directly, or secondarily formed from oxides of sulphur and nitrogen.
The entire range of organic pollutants, heavy metals and the inorganic acids mentioned, can be distributed by air from their sources of emission. In some cases, for instance exhaust from car traffic, pollutants have mostly a local impact. In other cases, pollutants are distributed by winds over very long distances, they are transboundary, and cause regional impacts. Acidifying and eutrophying substances belong to this category.
Yet another category of air pollutants are the radioactive substances. The nuclear industry is a source of radioactive pollution from uranium exploration and mining, to use of fuel in a reactor, and waste storage. As noted in the previous chapter, the 1986 nuclear power accident in Chernobyl in Ukraine, that badly hit Belarus and large parts of Europe with radioactive fallout, reminds us of its dangers.
This chapter examines air pollution, its sources, distribution and the damages it causes. The efforts, beginning in the 1980s, to limit air pollution have been quite successful when it comes to sulphur emissions. These have been steadily declining for 20 years. Emissions of nitrogen, however, are diminishing at a much slower rate. There is still much to be done to reach an acceptable situation. Acidified soil and water in many areas will take a long time to recover.
What is acceptable when it comes to air pollution? The limits of tolerance are expressed as critical loads and levels. These in turn are used to establish emission limits within the Convention on Long-Range Transboundary Air Pollution. Within the convention, monitoring and modelling are carried out to follow the development and study possible measures to reduce air pollution. In the end this will require drastic changes in our energy systems. An energy system based on combustion of fossil fuels is not sustainable because of the large linear flows of coal, sulphur, nitrogen, and to some degree heavy metals, and their environmental impacts.
Authors of this chapter are: