Energy consumption results in emissions of pollutants. Local pollution, characteristic of urban areas or caused by emissions from an industrial plant (factory, cement works, refinery, etc.), is converted into regional pollution through accumulation of pollutants in the atmosphere.
Pollution becomes global when it concerns the entire planet, a situation we are facing with the greenhouse gas effect.
Local pollution in an urban environment is due mainly to transport. The main pollutants discharged by automotive vehicles are carbon monoxide, unburnt hydrocarbons, nitrogen oxides and particulates.
High contents of nitrogen oxides and unburnt hydrocarbons in the atmosphere favour photochemical reactions which occur in the presence of high solar radiation, and therefore mainly in summer. These reactions result in the formation of ozone and other oxidising compounds (hydrogen peroxide, aldehydes, peroxyacetylnitrate or PAN). The ozone which therefore forms in the lower atmospheric layers (tropospheric ozone) is irritating and noxious to breathe. It has an adverse effect on health, especially on the respiratory system, as well as on the environment since it attacks vegetation, thereby acting as a pollution indicator, unlike the ozone present in the higher atmospheric layers (stratospheric ozone) which protects against excessive ultraviolet radiation and which must be preserved.
The fine particulates emitted in particular by diesel engine vehicles represent a source of pollution which is especially serious in urban areas. Particulates with diameters less than 10 mm (PM10) are taken into account when analysing atmospheric pollution. Particulates with diameters less than 2.5 mm (PM2 5) seem to be the most dangerous. The finest particulates, with diameters between 0.01 mm and 0.1 mm, penetrate deeply into the respiratory tracts, into the pulmonary alveoli, from where they are only eliminated very slowly provided that exposure to the pollution is not permanent, causing pulmonary and cardiac risks. Pollutants adsorbed on the particulates also penetrate into the organism via this pathway.
In addition, some aromatic organic compounds (benzene), polycyclic compounds (PAHs) and aldehydes (e.g. formaldehyde) emitted by automobiles are potentially carcinogenic. In the industrialised countries (USA, European countries, Japan), significant progress has been made in the reduction of pollutant emissions, through the introduction of increasingly stringent standards for new vehicles.
Pollution of large urban centres nevertheless remains difficult to control due to the constant rise in the number of vehicles, despite the technical advances made. This is especially true in the developing countries.
Significant pollution remains at regional level, due in particular to the presence of sulphur in the fossil fuels (coal, heavy fuel oil). Emissions of sulphur and nitrogen oxides contribute atmospheric pollution, leading to acid rain which is harmful for forests and lakes. The atmosphere is also polluted by soot and tar emitted by vehicles or industrial facilities, carbon monoxide resulting from incomplete combustion, unburnt hydrocarbons and volatile organic compounds (VOCs) from the evaporation or incomplete combustion of fuels.
In Asia, industrial pollution caused by development of the economy produces, between April and October, a vast brown cloud consisting of sulphur-containing aerosols mixed with carbon monoxide, ozone, nitrogen oxides, soot and dust. This cloud reduces solar radiation and rain by 20% to 40%.
Progress is also underway in this area, both as regards the technical solutions and applicable regulations. The Gothenburg protocol, approved by the United Nations in 1999, plans a 75% reduction in sulphur dioxide (SO2) emissions and a 49% reduction in nitrogen oxide (NOx) emissions compared with the 1990 levels .
Amongst the problems encountered, sea pollution related to the transport of crude oil receives high media coverage. The consequences of oil spills caused by the accidental sinking of tankers are highly visible, but represent only a relatively small fraction of all hydrocarbon spills at sea. The number of oil spills is in fact steadily decreasing.
The number of accidental oil spills at sea has been divided by 10 over the last 30 years, whilst since 1980 maritime oil traffic has increased by 80%. In addition, the accelerated introduction of double hull tankers has reduced even further the risk of oil slicks. In contrast, deliberate discharges due in particular to tank cleaning, which are difficult to observe and punish, continue and represent a major source of oil pollution at sea.
The risks for the environment are not restricted to fossil fuels. The development of nuclear energy also raises a certain number of problems. The risks involved are not easy to estimate, since they are generally related to accidental phenomena rather than to normal operation. Consequently, the level of danger for the environment and the public is a subject of heated debate. It is related to the management of radioactive waste and to accidental leakage of toxic products throughout the production chain.
A constant effort is therefore required to protect the environment. The actions required to fight against climate change must not detract from the measures to be taken to protect the environment at a local level.
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