e-Digest Statistics about: Air quality
Air quality and the main air pollutants
For most air pollutants, the main sources of emissions are from fossil-fuel combustion (electricity generation, heating and vehicles).
Sulphur dioxide (SO2) and nitrogen oxides (NOx) emissions contribute to acidification and local air pollution. Sulphur dioxide is an acid gas and can affect health and vegetation. It affects the lining of the nose, throat and airways of the lung. Nitrogen oxides are acid gases and ozone pre-cursors and can affect human health and vegetation. Nitrogen dioxide (NO2) is thought to have both acute and chronic effects on airways and lung function.
Airborne particulate matter is very diverse, including products of combustion, dust, grit, seasalt and biological particles. It has many sources , such as road traffic, construction work and chemical reactions in the atmosphere. Fine particles can be carried into the lungs and can be responsible for causing premature deaths among those with pre-existing lung and heart disease. The most commonly used measurement method is based on the size of particles and collects mainly particles 10µm (10 thousandths of a millimetre) in diameter or smaller – small enough to penetrate deep into the lungs. This material is known as PM10.
Carbon monoxide (CO) is a toxic gas emitted by combustion processes, and is also formed by the oxidation of hydrocarbons and other organic compounds. It affects the transport of oxygen by the blood.
Ground level ozone (O3) occurs naturally but levels can be increased as a result of reactions between NOx, oxygen and VOCs in the presence of sunlight. Once formed, O3 can persist for several days and can be transported long distances. It can cause irritation to the eyes and nose and very high levels can cause damage to the airway lining. Ozone can also damage vegetation.
Volatile organic compounds (VOCs) comprise a wide range of chemical compounds including hydrocarbons, oxygenates and halogen containing species. The major environmental impact of non-methane VOCs lies in their involvement in the formation of ground level ozone, but they may also cause a range of health effects. VOCs include benzene and 1,3-butadiene, which are carcinogens.
Ammonia causes nitrogen enrichment, disrupting the delicate balance of plant species in valuable ecosystems. It also contributes to the formation of fine particles through reaction with other chemicals in the atmosphere, and can potentially cause acidification.
Hydrogen chloride and hydrogen fluoride are both gases that cause acidification.
Heavy metals, including lead (Pb), have various health effects, the most important of which relate to deterioration of the immune system, the metabolic system and the nervous system. Some are known or suspected to be carcinogenic.
Persistent organic pollutants (POPs) are found in trace quantities in all areas of the environment. They do not break down readily and they accumulate in humans and plants. They have varying levels of toxicity. They include polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), dioxins and furans and pesticides.
Further Information:
- Data Tables:
- 1 Air pollutant types (including greenhouse gases) XLS
- Internet Links:
- UK Air Quality Archive
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Page last modified: 16 September 2003
Page published: 10 September 2003