Human beings need good air quality for health and well-being. Air is a mixture of nitrogen (78 percent), oxygen (21 percent), carbon dioxide and some. It also contains varying quantities of water vapour. In addition, the air contains numerous harmful substances: natural pollutants such as dust and volcanic ash, and pollutants that are produced by human activities.
Pollution in the outdoor air
Chemical compounds present in the atmosphere are considered to be ambient air pollutants when they occur in unnaturally high concentrations. They have the potential to cause harm to the environment and human health. Common air pollutants include sulphur dioxide (SO2), nitrogen oxides (NOx), carbon monoxide (CO), lead, particulate matter (PM10 and PM 2.5) and volatile organic compounds (VOCs).
Hazardous air pollutants include metals and metalloids such as cadmium, mercury and arsenic; some mineral fibres such as asbestos and glass micro-fibres; inorganic gases, such as fluorides, chlorine, cyanide and phosgene; and organic compounds such as aldehydes, aromatic and polycyclic aromatic hydrocarbons (PAHs) and dioxins.
With increasing urbanisation throughout the world, levels of air pollution are also rising. Europe is a highly urbanised continent, with around 70 percent of inhabitants living in urban areas. Traffic, fuel combustion and industrial production cause airborne emissions and elevated concentrations of pollutants. This pollution gives rise to a range of problems such as public health risks, the accelerated deterioration of building materials, damage to historical monuments and harm to vegetation within and around cities.