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Effects of atmospheric pollution

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THE NOTION OF SCALE

Atmospheric pollution operated on various levels. On each level, the pollutants have different impacts. They differ in their life cycle in the atmosphere and physicochemical dynamics.

Local Level
Local pollution is mainly due to fixed sources (a mixture of residential and industrial) or mobile (exhausts fumes from road traffic). It is often ugly to look at or unpleasant to smell and the pollutants have a short life in the atmosphere. In the case of dense activity, high pollution levels can span whole agglomerations. 

Regional Level
Urban or industrial pollution can cover large distances and affect suburbs of agglomerations and even rural areas. This is especially case for what are known as “secondary” pollutants such as ozone (photochemical pollution) or fallout in the shape of acid rain. Fallout can occur tens, even hundreds of kilometres away from the place of emission.

Worldwide Level
Two main pollution phenomena have been highlighted on this scale.
-The destruction of the stratospheric ozone, or "hole” in the ozone layer.
-Global warming or climatic imbalance, due to the increase in man-made greenhouse gasses.
At this level, the origin of the emission is of little importance: all components emitted will accumulate in the atmosphere and persist for several dozens or hundreds of years and have an impact across the whole planet.

EFFECTS ON THE ENVIRONMENT

Main effects on local environment
Some components alter materials Sulphur dioxide corrodes and blackens buildings. Dust from the combustion of petrol products or industrial mine activity makes buildings dirty and the combination with moisture and micro-organisms damages them. Plants can also be damaged by some pollutants: Necrosis, impaired growth, acidification of ecosystems, diminished resistance etc. Some plants can be used to indicate the presence of pollution (lichen is sensitive to sulphur dioxide, tobacco reacts to ozone etc.): This is known as biomonitoring 
Acid rain comes from certain pollutants emitted by human activity that are said to be “acid” (SO2, NOx, HC1, HF). They fall near emission sources but also hundreds, even thousands of miles away from them, in other forms (rain, fog, snow in cold countries etc.) As they travel, these pollutants are subject to chemical transformations and it is impossible to identify the source of emission with certainty. Acid fallout has an impact on materials (damaging buildings, facades etc.) and on ecosystems (acidification of forests, watercourses etc.).


Effects on the scale of the planet

Today, our whole planet is affected by atmospheric pollution. 
The hole in the ozone layer. The "hole” in the ozone layer (weakening of stratospheric ozone) is a decrease in concentration of ozone in the stratosphere, namely above the poles, that increases the flow of UV rays to the ground. 
Ozone is naturally present in the atmosphere, at an altitude of around 25km. Here, it is qualified as “good ozone”, as opposed to the “bad ozone” in the stratosphere that we can breathe, which is considered a pollutant. "Good” stratospheric ozone filters the sun’s ultraviolet rays and therefore protects life on earth.
Since the late seventies, a regular, seasonal reduction in the stratospheric ozone layer has been observed. Fluoride components, especially chloroflorocarbons (CFC or freons) are considered to be those that cause the most damage to the ozone layer. 
These components were produced by Man to be used as propellants in aerosol cans or as refrigeration gas in refrigerators or air conditioning systems. They can also be found in some plastics or foams.
To reduce this impact, the protocol of Montreal was adopted by most industrialised countries. The international approach aims to protect the ozone layer by regulating the emission of substances that damage it.

Climate change
The greenhouse effect is a natural phenomenon which enabled life on earth to develop. Without this mechanism, the average temperature on earth would be -18°C instead of +15°C. Greenhouse effect gases trap rays emitted by earth having been warmed by the sun.
Global warming or climate change has been observed for around 150 years and is a growth in this phenomenon. The growth is attributed to the increase in concentration of gas in the atmosphere, mainly due to human activity. We reject many of these components into the atmosphere, through industry or agriculture but also through travel and energy consumption.  The main greenhouse gas is carbon dioxide, which is rejected by combustion of organic or fossil matter and by certain industrial processes. 

Other components also largely contribute to this phenomenon: 
- CH4 methane (mainly emitted by waste decomposition, agriculture and industry) 
- Nitrogen protoxide