Glossary

Glossary describing terms used within the OzoneWeb (ground level ozone map viewer) application

Air emission #: Discharge of pollutants into the atmosphere from stationary sources such as smokestacks, and other vents, and from surface areas of commercial or industrial facilities and mobile sources, for example, motor vehicles, locomotives and aircrafts.
Air quality measurement station #: Facility to measure systematically concentrations of pollutants in ambient air. Synonym: air quality monitoring station.
Air quality monitoring station #: Facility to measure systematically concentrations of pollutants in ambient air. Synonym: Air quality measurement station.
Alert threshold #: The EU has defined an Alert threshold of 240 µg ozone per m3 air. Any exceedance of this threshold should be reported by the Member State in which it occurs to the European Commission. The threshold reflects a 'level beyond which there is a risk to human health from brief exposure for the general population'. When the threshold is exceeded, national authorities are required to inform the public and give advice. See also Information threshold.
Ambient air #: The air occurring at a particular time and place outside of structures. Often used interchangeably with "outdoor air".
Carbon dioxide #: Gas naturally produced by animals during respiration and through decay of biomass, and used by plants during photosynthesis. Although it only constitutes 0.04 percent of the atmosphere, it is one of the most important greenhouse gases. The combustion of fossil fuels is increasing carbon dioxide concentrations in the atmosphere, which is believed to be contributing to global warming.
CO2 #: Abbreviation for carbon dioxide: gas naturally produced by animals during respiration and through decay of biomass, and used by plants during photosynthesis. Although it only constitutes 0.04 percent of the atmosphere, it is one of the most important greenhouse gases. The combustion of fossil fuels is increasing carbon dioxide concentrations in the atmosphere, which is believed to be contributing to global warming.
Carbon monoxide #: Colourless, odourless, tasteless, non-corrosive, highly poisonous gas of about the same density as that of air. Very flammable, burning in air with bright blue flame. Although each molecule of CO has one carbon atom and one oxygen atom, it has a shape similar to that of an oxygen molecule (two atoms of oxygen), which is important with regard to its lethality. (Source: PHYMAC)
CO #: Abbreviation for carbon monoxide. Colourless, odourless, tasteless, non-corrosive, highly poisonous gas of about the same density as that of air. Very flammable, burning in air with bright blue flame. Although each molecule of CO has one carbon atom and one oxygen atom, it has a shape similar to that of an oxygen molecule (two atoms of oxygen), which is important with regard to its lethality. (Source: PHYMAC)
Exceedance #: An event (characterised by duration and degree of exceedance) where the concentration of a pollutant is greater than, or equal to, the appropriate air quality standard.
Ground-level concentration #: The concentration in air of a pollutant to which a human being is normally exposed, i.e. between the ground and a height of some 2 metres above it.
Ground-level ozone #: The ozone in the air near the Earth's surface. Also known as ambient or tropospheric ozone. See also ozone, troposphere and ambient air.
Inflammation #: The response of the immune system to irritation or injury of body tissues. Signs and symptoms are pain, heat, redness, swelling and loss of function. For instance, lung inflammation can lead to reduced lung function.
Information threshold #: The EU has defined an Information threshold of 180 µg ozone per m3 air. Any exceedance of this threshold should be reported by the Member State in which it occurs to the European Commission. The threshold reflects a 'level beyond which there is a risk to human health from brief exposure for particularly sensitive sections of the population'. When the threshold is exceeded, national authorities are required to inform the public. See also Alert threshold.
Interpolation #: A mathematical method of constructing new data points from a discrete set of known data points. When a number of data points has been obtained - by sampling or experiment - one can construct a calculation (interpolation) that closely fits these data points.
Life-year #: One year of a non-specified person's life. Can be used to describe loss of life expectancy. For example, 'thousands of life-years are lost annually in Europe as a result of air pollution'
Life-expectancy #: The number of years that a person can expect to live on average, based on estimation of data on death rates of the population. Life expectancy depends on age. For example, at birth a person may be expected to live for 75 years, but if the person survives to 75, he or she may be expected to live for another 10 years.
Lung capacity #: The volume of air the lungs can hold. Lung capacity depends on a person's age, weight, sex and the degree of physical activity. The total lung capacity of an average-sized adult male is about five litres.
Lung function #: The main function of the lungs is the process of gas exchange called respiration (or breathing). In respiration, oxygen from incoming air enters the blood, and carbon dioxide, a waste gas from the metabolism, leaves the blood. A reduced lung function means that the ability of lungs to exchange gases is reduced.
Mortality #: The death rate; the ratio of the number of deaths per year to a given population.
Nitrogen oxides #: Nitrogen oxides refers to nitric oxide gas (NO) and nitrogen dioxide gas (NO2) and many other gaseous oxides containing nitrogen. The main source of these gases in urban areas are motor vehicle exhaust and indoor gas stoves and kerosene heaters. The brown haze sometimes seen over cities is mainly nitrogen oxides. These gases are also partly responsible for the generation of ozone, which is produced when nitrogen oxides react with other chemicals in the presence of sunlight. Exposure to high levels of nitrogen dioxide can interfere with the ability of blood to carry oxygen, leading to dizziness and shortness of breath. Prolonged exposure can lead to respiratory failure.
Non-methane volatile organic compounds #: Organic chemical compounds, excluding methane, that under normal conditions can vaporise and enter the atmosphere. NMVOCs include such compounds as benzene, xylene, propane and butane. NMVOCs are mainly emitted from transportation, industrial processes and use of organic solvents. See also VOCs.
NMVOCs #: Abbreviation for Non-methane volatile organic compounds. Organic chemical compounds, excluding methane, that under normal conditions can vaporise and enter the atmosphere. NMVOCs include such compounds as benzene, xylene, propane and butane. NMVOCs are mainly emitted from transportation, industrial processes and use of organic solvents. See also VOCs.
Ozone #: Ozone, the triatomic form of oxygen (O3), is a gaseous atmospheric constituent. In the troposphere - at ground level - it is created both naturally and by photochemical reactions involving gases resulting from human activities (photochemical smog). In high concentrations, tropospheric ozone can be harmful to a wide range of living organisms. In the stratosphere, ozone is created by the interaction between solar ultraviolet (UV) radiation and molecular oxygen (O2). Stratospheric ozone plays a decisive role in protecting life on earth from ultraviolet radiation from the sun.
Ozone precursor #: Chemical compounds, such as carbon monoxide (CO), methane (CH4), NMVOCs and nitrogen oxide (NOx), which in the presence of solar radiation react with other chemical compounds to form ozone, mainly in the troposphere.
Ozone layer #: Very diluted atmospheric concentration of ozone found at an altitude of 10 to 50 kilometres above the earth's surface.
Ozone layer depletion #: The fragile shield of ozone is being damaged by chemicals released on earth. The main chemicals that are depleting stratospheric ozone are chlorofluorocarbons which are used in refrigerators, aerosols, and as cleaners in many industries, and halons, which are used in fire extinguishers. The damage is caused when these chemicals release highly reactive forms of chlorine and bromine. Over the past 30 years ozone levels over parts of Antarctica have dropped by almost 40 % during some months and a 'hole' in ozone concentrations is clearly visible in satellite observations.
Ozone episode #: A period of usually a few days up to 2-3 weeks with high ozone concentrations, characterised by daily exceedances of the thresholds set to protect human health. Ozone episodes occur under specific meteorological conditions characterised by large stagnant areas of high pressure. Since the formation of ozone requires sunlight, ozone episodes mainly occur during summer.
Particulate matter #: A collective name for fine solid or liquid particles added to the atmosphere by processes at the earth's surface. Particulate matter includes dust, smoke, soot, pollen and soil particles.
PM #: Abbreviation for Particulate Matter. A collective name for fine solid or liquid particles added to the atmosphere by processes at the earth's surface. Particulate matter includes dust, smoke, soot, pollen and soil particles.
PM10 #: An air pollutant consisting of small particles with an aerodynamic diameter less than or equal to a nominal 10 micrometer (about 1/7 the diameter of a single human hair). Their small size allows them to make their way to the air passages deep within the lungs where they may be deposited and result in adverse health effects. PM10 also causes visibility reduction.
Respiratory disease #: Respiratory disease is an acute or chronic illness affecting the respiratory system; includes acute respiratory infections, bronchitis, pneumonia, influenza, and chronic obstructive pulmonary diseases.
Photochemical smog #: A combination of fog and chemicals that come from automobile and factory emissions and is acted upon by the action of the sun. Nitrogen dioxide, in the presence of the sun and some hydrocarbons, is turned into nitric oxide and atomic oxygen. The atomic oxygen reacts with the oxygen molecules and other constituents of automobile exhaust fumes to form a variety of products including ozone. The ozone is harmful in itself and is also implicated in a highly complex series of continuing reactions. As long as there is ozone or nitrogen dioxide and sunlight present, other undesirable reactions will occur.
Stratosphere #: Highly stratified region of atmosphere above the troposphere extending from about 10 km (ranging from 9 km in high latitudes to 16 km in the tropics on average) to about 50 km.
Sulphur dioxide #: Heavy, pungent, colourless gas formed primarily by the combustion of fossil fuels. It is harmful to human beings and vegetation, and contributes to the acidity in precipitation.
SO2 #: Abbreviation for Sulphur dioxide. Heavy, pungent, colourless gas formed primarily by the combustion of fossil fuels. It is harmful to human beings and vegetation, and contributes to the acidity in precipitation.
Threshold #: The dose or exposure level below which a significant adverse effect is not expected.
Troposphere #: The lowest part of the atmosphere from the surface to about 10 km in altitude in mid-latitudes (ranging from 9 km in high latitudes to 16 km in the tropics on average) where clouds and 'weather' phenomena occur. In the troposphere, temperatures generally decrease with height.
Volatile organic compound #: Organic chemical compounds that under normal conditions are gaseous or can vaporise and enter the atmosphere. VOCs include such compounds as methane, benzene, xylene, propane and butane. Methane is primarily emitted from agriculture (from ruminants and cultivation), whereas non-methane VOCs (or NMVOCs) are mainly emitted from transportation, industrial processes and use of organic solvents. See also NMVOC.
VOC #: Abbreviation for Volatile organic compound. Organic chemical compounds that under normal conditions are gaseous or can vaporise and enter the atmosphere. VOCs include such compounds as methane, benzene, xylene, propane and butane. Methane is primarily emitted from agriculture (from ruminants and cultivation), whereas non-methane VOCs (or NMVOCs) are mainly emitted from transportation, industrial processes and use of organic solvents. See also NMVOC.
µg/m3 #: The concentration of an air pollutant (eg. ozone) is given in micrograms (one-millionth of a gram) per cubic meter air or µg/m3.
Respiratory system #: The system consisting of the airways (nose, mouth, throat, bronchi) the lungs and the respiratory muscles that pump the air into and out of the body. See also lung function.