Glossary

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1,3-Butadiene

Organic compound emitted into the atmosphere mainly from fuel combustion, for example petrol and diesel vehicles. 1,3-butadiene is also an important chemical in certain industrial processes, particularly the manufacture of synthetic rubber. 1,3-butadiene is known to cause cancer in humans.

A

Agglomeration Zone

Urban area with a population greater than 250,000. See Non-agglomeration zone.

Air Information Resource (AIR)

See UK-AIR.

Air Pollution Information System (APIS)

The Air Pollution Information System is a searchable database and information on pollutants and their impacts in habitats and species.

Air Quality Action Plan (AQAP)

Detailed description of measures, outcomes, achievement dates and implementation methods that show how a local authority intends to achieve air quality limit values.

Air Quality Information System Review (AQIS)

The Air Quality Information System Review is considering the effectiveness of the current air quality information system. It will recommend possible updates to the Daily Air Quality Index (DAQI) and broader air quality messaging channels.

Air Quality Directive

The European Union’s Directive 2008/50/EC on Ambient Air Quality and Cleaner Air for Europe is often referred to as ‘the Air Quality Directive’.

Air Quality Expert Group (AQEG)

The Air Quality Expert Group provides independent scientific advice on air quality to Defra, in particular the air pollutants contained in the Air Quality Strategy (AQS) for England, Scotland, Wales and Northern Ireland and those covered by the EU Directives on Ambient Air Quality.

Air Quality Management Areas (AQMA)

If air quality falls below required standards, a local authority must declare an Air Quality Management Area and publish a plan to improve the air quality. This area could be just one or two streets, or it could be much bigger. See Air Quality Action Plan.

Air Quality Standards Regulations

Prior to 31 January 2020, the UK was a Member State of the European Union. As such, the UK was required to incorporate – or ‘transpose’ – the provisions of EU Directives into their own national law by a specified date. The Air Quality Standards Regulations are the legislation by which the UK fulfilled this requirement.

Air Quality Strategy

The Environment Act 1995 requires the UK Government and the Devolved Administrations for Scotland and Wales to produce a National Air Quality Strategy containing standards, objectives and measures for improving ambient air quality; there is equivalent legislation in Northern Ireland.

The Air Quality Strategy sets objectives for the maximum concentrations of eight pollutants. These are at least as stringent as the limit values of the Air Quality Directive and Air Quality Standards Regulations.

Ambient Air

Outdoor air.

B

Benzene (C₆H₆)

Chemical compound that is harmful to human health. As an air pollutant, benzene can be emitted from domestic and industrial combustion processes, and road vehicles.

Benzo[a]pyrene

One of a group of compounds called polycyclic aromatic hydrocarbons that can be air pollutants. The main sources in the UK are domestic coal and wood burning, fires, and industrial processes such as coke production.

C

Carbon Monoxide (CO)

Pollutant gas released in road vehicle exhausts. When breathed in, carbon monoxide affects the blood’s ability to carry oxygen around the body.

Chief Scientific Adviser (CSA)

Most government departments have a Chief Scientific Adviser to provide scientific advice. Professor Gideon Henderson was appointed Chief Scientific Adviser at the Department of Environment, Food and Rural Affairs on 1 October 2019. He is also Director General for Science and Analysis.

Committee on the Medical Effects of Air Pollutants (COMEAP)

The Committee on the Medical Effects of Air Pollutants advises the government on all matters concerning the health effects of air pollutants.

COPERT

COPERT is the European Union’s standard vehicle emissions calculator. It uses vehicle population, mileage, speed and other data such as ambient temperature and calculates emissions and energy consumption for a specific country or region.

D

Daily Air Quality Index (DAQI)

Informs the public about the current level of air pollution and provides recommended actions and health advice. The index is numbered 1-10 and divided into four bands, low (1) to very high (10), to provide information about air pollution levels in a simple way, similar to the sun index or pollen index.

Department for the Environment, Food & Rural Affairs (Defra)

UK Government department responsible for improving and protecting the environment. The department aims to grow a green economy, sustain thriving rural communities, and support the food, farming and fishing industries.

Digital, Data & Technology (DDTS)

Teams within Defra responsible for developing and delivering digital, data and technology services.

E

Episode (Air Pollution Episode)

Period of time (usually a day or several days) when air pollution is high (and air quality is poor).

European Study of Cohorts for Air Pollution Effects (ESCAPE)

Collaboration of more than 30 European cohort studies including some 900,000 subjects aimed at quantifying health impacts of air pollution.

G

Greenhouse gas (GHG)

Gas which reflects radiation that the Earth emits and stops it from being lost into space. This makes the Earth hotter than it would be without greenhouse gases. This is called the ‘greenhouse effect’.

J

Joint Air Quality Unit (JAQU)

Joint venture between Defra and the Department for Transport (DfT) to deliver the UK Government’s NO₂ reduction strategies.

Joint Nature Conservation Committee (JNCC)

The Joint Nature Conservation Committee is a public body that advises the UK Government and Devolved Administrations on UK-wide and international nature conservation.

L

Low Emission Zone (LEZ)

Area where access by some polluting vehicles is restricted or deterred with the aim of improving air quality. See Ultra Low Emission Zone.

Limit value

The Air Quality Standards Regulations set ‘limit values’ for ambient concentrations of pollutants. Limit values are legally binding and must not be exceeded. See target value.

Local Air Quality Management (LAQM)

Local authorities are required to carry out regular review and assessments of air quality in their area. They must take action to improve air quality in areas where the objectives set out in the Air Quality Standards Regulations have not been achieved (or there is a risk that they will not be achieved).

Long-Term Objectives

As well as limit values and target values, the Air Quality Standards Regulations set ‘long-term objectives’ for ozone concentration. These are similar to limit values but are not legally mandatory. The UK must take all necessary measures not entailing disproportionate costs to meet the target values and long-term objectives.

M

MAGIC

The MAGIC website provides authoritative geographic information about the natural environment from across government.

N

National Atmospheric Emissions Inventory (NAEI)

The National Atmospheric Emissions Inventory compiles estimates of emissions to the atmosphere from UK sources such as cars, trucks, power stations and industrial plant. These emissions are estimated to help to find ways of reducing the impact of human activities on the environment and our health.

National Centre for Atmospheric Science (NCAS)

The National Centre for Atmospheric Science is a research centre dedicated to the advancement of atmospheric science. It is funded by the Natural Environment Research Council (NERC).

National Physical Laboratory (NPL)

The National Physical Laboratory is the UK’s National Metrology Institute, developing and maintaining the national primary measurement standards. It is a Public Corporation owned by the Department of Business, Energy and Industrial Strategy (BEIS).

Natural Environment Research Council (NERC)

The Natural Environment Research Council is a UK research council that supports research, training and knowledge transfer activities in the environmental sciences.

Net Zero

Net zero emissions are reached when anthropogenic (human-caused) emissions of greenhouse gases to the atmosphere are balanced by anthropogenic removals over a specified period.

Nickel (Ni)

Toxic metallic element found in ambient air as a result of releases from oil and coal combustion, metal processes, manufacturing and other sources.

Nitric oxide (NO)

One of the oxides of nitrogen formed in combustion processes. NO is not harmful to human health but combines with oxygen to form nitrogen dioxide.

Nitrogen Dioxide (NO₂)

One of the oxides of nitrogen formed in combustion processes. At high concentrations NO₂ is an irritant to the airways. NO₂ can also make people more likely to catch respiratory infections (such as flu), and to react to allergens.

Nitrogen Oxides (NOx)

Compounds formed when nitrogen and oxygen combine. NOx, which comprises nitric oxide (NO) and nitrogen dioxide (NO2), is emitted from combustion processes. The main sources include power generation, industrial combustion and road transport.

Non-agglomeration zone

Zone with no single large urban population contained within it. See Agglomeration zone.

O

Ozone (O₃)

Pollutant gas which is not emitted directly from any source in significant quantities, but is produced by reactions between other pollutants in the presence of sunlight. Ozone concentrations are greatest in the summer. O₃ can travel long distances and reach high concentrations far away from the original pollutant sources. Ozone is an irritant to the airways of the lungs, throat and eyes: it can also harm vegetation.

P

Particulate matter (PM)

Small airborne particles that may contain different materials such as soot, wind-blown dust or secondary components, formed within the atmosphere as a result of chemical reactions.

Some PM is natural and some is human made. Particulate matter can be harmful to human health when inhaled, and research shows a range of health effects associated with PM. In general, the smaller the particle the deeper it can be inhaled into the lung.

PM2.5

Particles which pass through a size-selective inlet with a 50 % efficiency cut-off at 2.5 μm aerodynamic diameter, as defined in ISO 7708:1995, Clause 7.1. These particles are small enough to be inhaled very deep into the lung – described as the ‘high risk respirable convention’ in the above ISO standard. PM2.5 is often described as ‘particles of less than 2.5 micrometres in diameter’ though this is not strictly correct.

PM10

Particles which pass through a size-selective inlet with a 50 % efficiency cut-off at 10 μm aerodynamic diameter, as defined in ISO 7708:1995, Clause 6. These particles are small enough to be inhaled into the airways of the lung. PM10 is often described as ‘particles of less than 10 micrometres in diameter’ though this is not strictly correct.

Pollutant

Substances that may be harmful to the environment or to human health on account of their properties and their introduction into the environment.

Pollutant Release and Transfer Register (PRTR)

Inventories of pollution from industrial sites and other sources. A PRTR is a national or regional environmental inventory of potentially hazardous chemical substances or pollutants released to air, water and soil and transferred off-site for treatment or disposal.

Polycyclic aromatic hydrocarbons (PAH)

Large group of chemical compounds that are toxic and carcinogenic. Once formed, they can remain in the environment for a long time and can be passed up the food chain. The main sources are domestic coal and wood burning, outdoor fires, and some industrial processes.

The pollutant Benzo[a]pyrene is a PAH, and because it is one of the more toxic PAH compounds it is measured as a ‘marker’ for this group of pollutants. See Benzo[a]pyrene.

Primary pollutant

Pollutant which is emitted directly into the atmosphere from a source. See: Secondary pollutant.

Q

Quality Assurance and Quality Control (QA/QC)

In order to produce data that is correct, meaningful and useful, monitoring techniques must have a sound scientific basis, and the data collected must be accurate and precise. QA/QC processes are employed to ensure this is the case.

S

Science Advisory Council (SAC)

The Science Advisory Council provides expert independent advice to the Chief Scientific Adviser and ministers to help guide Defra’s scientific priorities and planning, including long-range planning as well as dealing with immediate risks and opportunities.

Secondary pollutant

Pollutant which is formed by chemical reactions from other pollutants in the atmosphere. Ozone, for example, is a secondary pollutant. Particulate matter (PM2.5 and PM10) consists of a mix of primary material (directly emitted from sources) and secondary material (formed by reactions in the atmosphere). See Primary pollutant.