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Update on atmospheric pollutants emissions in the European Union, their decrease and their further evolution


Glossary over Update on atmospheric pollutants emissions in the European Union, their decrease and their further evolution

Carbon monoxide (CO)

An odorless, colorless, and highly poisonous gas.



"Dioxins" refers to a group of chlorinated organic chemicals with similar chemical structures.

In all GreenFacts publications the term "dioxins" is used to cover both polychlorinated dibenzo-dioxins (PCDDs) and polychlorinated dibenzo-furans (PCDFs). Other sources may refer to these compounds as "dioxins and furans".

Some dioxins have harmful properties, depending on the number and position of chlorine atoms. One of the most toxic dioxin is known as TCDD (2,3,7,8 tetrachlorodibenzo-p-dioxin). Some PCBs which have similar properties are considered "dioxin-like". (Source: GreenFacts)


Elemental Arsenic

The element with the symbol "As" and the atomic number 33. Its molecular weight is 74.92160 g. It can be classified as semi metallic and its colour is observed to be metallic grey. (Source: GreenFacts)


Elemental mercury

Hg. Mercury in its elemental (pure) form, that is, as a metal; hence the synonym metallic mercury. A shiny, silver-gray metal that is a liquid at room temperature. (Source: GreenFacts)


European Environmental Agency

The European Environmental Agency (EEA) is one of the 15 specialised agencies of the European Union, which handle specific technical, scientific or management tasks. Operational since 1994, the EEA is based in Copenhagen.

"Its mission is to collect, prepare and disseminate timely, targeted, relevant and reliable information on the state and trends of the environment at European level. The founding regulation of EEA stipulates that it is open to countries that do not belong to the European Union but share its concern for the environment. Iceland, Liechtenstein and Norway have been members from the start, and 12 out of 13 candidate countries have joined in 2002 (...)." (Source: EEA website )

Heavy metals

Metallic elements with high atomic weights, e.g. mercury, chromium, cadmium, arsenic, and lead.

They can damage living things at low concentrations and tend to accumulate in the food chain. (Source: US EPA Drinking Water Glossary  )


Methane is a colorless, flammable, nontoxic gas with the chemical formula CH4.

This gas is formed naturally by the decomposition of organic matter. Wetlands, livestock and energy are the main sources of methane emissions to the atmosphere, where it acts as a greenhouse gas.

Methane is also a major component of natural gas. It is mainly extracted from geological deposits for fuel and industrial uses (Source: GreenFacts )

Nitrogen oxides (NOx)

NOx is the generic term for a group of highly reactive gases, all of which contain nitrogen and oxygen in varying amounts [such as nitric oxide (NO) and nitrogen dioxide (NO2)].

Many of the nitrogen oxides are colorless and odorless. However, one common pollutant, nitrogen dioxide (NO2) along with particles in the air can often be seen as a reddish-brown layer over many urban areas.

Nitrogen oxides form when fuel is burned [...]. The primary sources of NOx are motor vehicles, electric utilities, and other industrial, commercial, and residential sources that burn fuels.

In the atmosphere, nitrogen oxides can contribute to formation of photochemical ozone (smog) and have health consequences. They also lead to acid rain and contribute to global warming. (Source: US EPA NOx: What is it? Where does it come from?   )



Ozone is a form of oxygen having the molecular form of O3. It is a bluish, unstable gas with a pungent odour, found in two parts of the atmosphere: the stratosphere and the troposphere.

The ozone layer: The stratosphere contains a layer in which the concentration of ozone is greatest, the so called ozone layer. The layer extends from about 12 to 40 km. It shields the Earth from ultraviolet radiation's harmful health effects on humans and the environment. This layer is being depleted by human emissions of chlorine- and bromine-containing compounds.

Ground-level ozone: At ground level (in the troposphere), ozone is considered an air pollutant that can seriously affect the human respiratory system. It is a chemical oxidant and a major component of photochemical smog. (Source: GreenFacts)


Particulate matter

Sum of all microscopic solid and liquid particles, of human and natural origin, that remain suspended in a medium such as air for some time. These particles vary greatly in size, composition, and origin, and may be harmful.

Particulate matter may be in the form of fly ash, soot, dust, fog, fumes etc. (Source: GreenFacts)



Polychlorinated biphenyls (PCBs) are a family of 209 congeners of structurally similar organic chemicals, ranging from oily liquids to waxy solids. There are 12 PCBs that are dioxin-like and can similarly be toxic and non-toxic. One dioxin-like PCB is 3,4,4',5-Tetrachlorobiphenyl.

PCBs are synthetic and produced either as a singular congener, as a homogeneous group or as a mixture. They are non-flammable, stable, have a high boiling point and exhibit electrical insulating properties. As such, PCBs have been used as coolants and lubricants in transformers and other electrical equipment, as hydraulic fluids, and as plasticizers, pigments, dyes and carbonless copy paper ink. They are also generated and released into the environment as waste byproducts of chemical manufacturing and incineration. (Source: GreenFacts)


Persistent organic pollutants

Persistent organic pollutants (POPs) are chemical substances that persist in the environment, bioaccumulate through the food web, and pose a risk of causing adverse effects to human health and the environment. This group of priority pollutants consists of pesticides (such as DDT), industrial chemicals (such as polychlorinated biphenyls, PCBs) and unintentional by-products of industrial processes (such as dioxins and furans).

Persistent Organic Pollutants are transported across international boundaries far from their sources, even to regions where they have never been used or produced. (Source: European Commission Environment DG POPs  )

Polycyclic aromatic hydrocarbons

A group of over 100 different organic compounds composed of several benzene rings. Some of them are persistent and carcinogenic.

PAHs are commonly formed during the incomplete burning of coal, oil and gas, garbage, or other organic substances like tobacco or charbroiled meat.

Generally, tobacco smoke is by far the most important source of exposure for humans. (Source: GreenFacts)


Radiative Forcing

In the context of the IPCC assessments, radiative forcing refers to an external perturbation in the radiative energy budget of the Earth’s climate system, which may lead to changes in climate parameters.

A positive forcing (more incoming energy) tends to warm the system, while a negative forcing (more outgoing energy) tends to cool it. This is due to changes in drivers of climate change such as the concentration of carbon dioxide or the output of the Sun.

In the IPCC reports, changes in radiative forcing are relative to the year 1750. (Source: GreenFacts)


Sewage refers to waste-water from homes and industry which is collected and carried away in sewers (pipes or tunnels). When raw waste-water is cleaned in treatment plants the waste product is sewage sludge, which can be used as a fertiliser under certain conditions or deposited in landfills. (Source: GreenFacts )

Volatile organic compound

Any organic (carbon-containing) compound that evaporates readily to the atmosphere at room temperature.

VOCs contribute significantly to smog production and certain health problems.

VOCs often have odors, examples include gasoline, alcohol, and the solvents used in paints. (Source: GreenFacts)


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