Air pollution means that certain substances that are released into the air, change its natural composition. It may happen by means of natural processes, such as volcanic explosion or biological decomposition, or by anthropogenic emissions, which are produced by burning of coal and heating oils in power plants or homes, or those produced by transportation or ibbindustrial manufacture.
Together with water, food, and sunlight, air is vital for people, plants, and animals. Clean air is made up of 75 percent of nitrogen, 21 percent of oxygen, and certain noble gases. Germany alone releases into the air almost 20 million tonnes of toxic gases every year. It is mainly carbon dioxide, sulphur oxide, oxides of nitrogen, and dust particles or droplets.
Air currents spread this toxic load, which can travel great distances of many hundred kilometres. This is helped greatly by tall stacks of industrial installations.
One of the major toxic wastes is sulphur oxide, which is produced by burning of heating oil and coal. This oxide, together with carbon dioxide, are contained in harmless rain. In general, rain always contains acids. It is given by volcanic explosions that expel sulphur, as well as by the composition of the air, containing acids in the form of noble gases. Natural acid contents of the rain are not dangerous to the environment. However, this changed with the arrival of the industrialisation.
Wind carries into the air the additional oxides, which in the sunlight change into sulphates and nitrates. Acids containing nitrogen and sulphuric acid collect in the clouds, and are then deposited by rain and other types of precipitation on the surface of the earth. This rain is 500 times more acid than harmless rain.
As long as it contains neutralising chemicals (such as calcite), the soil may fight these toxic materials. However, nutrients, such as magnesium or calcium, are separated from the soil by acid rain, which damages the trees. The area in Germany most impacted by acid rain is the Middle Range. In winter, the situation worsens, because the trees are covered by acid snow, which eliminates the nutrients directly from the needles of the trees. When the snow melts, acid water seeps into the soil and damages the roots. That is how the trees are assaulted by toxic materials from the environment. When there is an additional problem, such as pests or a prolonged drought, the weakened trees die.
The example of Alps gives sense of a chain reaction causing the disease of mountain forests. This region suffers from noise and air pollution, produced by automobiles, ski lifts, skiers, and tourists. With the dying forest, the area is losing the protection of existing ravines and soil. That triggers avalanches and mud- as well as landslides, making many Alpine valleys inhabitable. Agriculture is suffering, and meadows and pastures are drying out.
With no trees, wind can develop its full potential. This, together with the loss of tree roots acting as water reservoirs, causes that the soil dries out. When the trees are dying, so are the animals and plants. The value of the landscape as a recreational area decreases, leading to the decrease of tourism and elimination of jobs. In order to solve this complex problem, measures have to be taken to protect the land.
Carbon monoxide, produced by incomplete combustion in stoves and motor vehicles, impacts negatively human health. When inhaled, it joins with the haemoglobin in the blood, blocking the entry of oxygen, and thus even at very low concentrations impairs the functioning of vital organs.
The oxides of nitrogen damage the respiratory system as well, because oxidation changes them into nitric acid. Due to the ease with which it penetrates the body, this type of respiratory system disease often affects children. Nitrogen oxides are generated by fuel combustion in furnaces and vehicles.
In transport and industrial agglomerations, in particular, the air is filled with toxic material, causing smog under certain meteorological conditions. The word "smog" is made up of "smoke" and "fog." It was used as a synonym of the famous London fog.
Today, smog occurs in virtually every larger city. It is caused by the industry, solid fuel combustion, and exhaust emissions. Smog alert is often issued during wintertime. This is due to the fact, that inversion obstructs the exchange of air. Coolor surface air is blocked by the warmer upper air layers. Inversion forms usually in the areas of high air pressure.
Gas emissions lead to the water vapour condensation, producing smog, which threatens the environment. Humid air then contains oxides of nitrogen and sulphur oxide. When droplets containing acids deposit, they damage masonry, but they are toxic to flora and people inhaling these toxic materials as well. It causes lung disease and bronchitis. Frequently, these diseases are chronic in city dwellers. Children and elderly are usually the most affected segment of the population.
During a smog alert, the use of private motor vehicles is forbidden in order to prevent the increase of the toxic materials in the air. Healthy people should also avoid being outside in the toxic air. At least, physically demanding work should not be done, because it requires deep breathing.
Chloro-fluoro-carbohydrates, used in the past as cooling and cleaning agents, or in sprays, are still being used as solvents. They survive a long time in the atmosphere. In the lower layers of the air they are almost insoluble. Reaction with ultraviolet light releases chlorine, which damages the ozone layer. After eliminating ozone, an atom of chlorine is again free and can react with the next molecule of ozone. As a result, more ultraviolet light reaches the surface of the earth through the depleted oyone layer. This weakens the human immune system and increases the risk of cancer.
While smog has only a local impact, acid rain and the increasing amounts of nitrogen reach the regional level. The effects of the destruction of the ozone layer are of global proportions.