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Glossary of terms and abbreviations

Accumulation mode
A part of the size spectrum of airborne particles, between approximately 0.1-2 µm diameter, in which particles have a long atmospheric lifetime

Aeroallergens
Airborne antigens that cause allergy in a sensitive individual, e.g. pollen, house dust mite

Aerodynamic diameter
The diameter of a unit density sphere (density = 1 µg/cm³), which has the same settling velocity as the particle in question

Aerosol
An atmosphere containing particles which remain airborne for a reasonable length of time

Alveolar region of the lung
The part of the lung where gas exchange between the blood and the air takes place. The air is contained in small spaces (alveoli) each about 0.3 µm in diameter

Anthropogenic
Made by man

Asthma
A disease in which the lung's airways become inflamed and prone to become narrowed in response to provoking stimuli, including allergens and irritating chemicals

Benign
A term used to describe a type of tumour which grows locally but does not spread through the body via the blood or lymphatic system

Black Smoke (BS)
Non-reflective (dark) particulate matter, associated with the smoke stain measurement method (BS 1747 pt 2; BSI 1969)

Bronchoconstriction
Narrowing of the airways, such as occurs during asthma attacks and can be reversed by use of a reliever inhaler. May be prevented by use of a preventer inhaler

Brownian motion
Constant small movement of suspended particles due to bombardment by surrounding molecules

Carboxyhaemoglobin
Carbon monoxide combines with haemoglobin to produce carboxyhaemoglobin. The capacity of the blood to carry oxygen is thereby reduced

Carcinogen
A compound which can cause cancer

Chamber studies
Studies involving the exposure of volunteers to controlled concentrations of gases or aerosols

Chronic bronchitis
A chronic inflammatory disease of the lungs commonly caused by cigarette smoking

Coarse particle fraction
That part of PM₁₀ made up of particles of diameter 10-2.5 µm

Coarse particle mode
A part of the size spectrum of airborne particles, greater that about 2 µm diameter, in which particles have arisen mostly from disintegration of bulk solid and liquid materials

Cohort studies
Studies in which a group or cohort of people are followed over time to see whether they develop a disease in response to exposure to the factor of interest

COPD
Chronic Obstructive Pulmonary Disease (often taken to mean chronic bronchitis and emphysema)

Count median diameter (CMD)
Term used to characterise the size distribution of particles in an aerosol. 50% of particles are of diameter less that the count median diameter

Cytokines
A large group of inflammatory peptide or protein mediators

DNA
Deoxyribo Nucleic Acid. The material found in the nucleus of cells which carries the genetic code.

EMEP
European Monitoring and Evaluation Programme

Emphysema
A chronic lung disease in which destruction of the alveolar region of the lung takes place. Cigarette smoking is a common cause

Enzymes
Proteins which act as catalysts for chemical reactions in the body

Epidemiology
The study of the distribution and determinants of health and disease in populations

ETS
Environmental Tobacco Smoke. Smoke generated directly by burning tobacco or exhaled into air by smokers

Ferrous
Containing a particular type of iron (Fe²⁺)

FEV₁
The volume of air which can be expired during the first second of a forced expiration, i.e., during blowing out as hard as possible

Fibrinogen
A protein which plays an essential role in blood clotting during which it is converted into strands of fibrin

Fine particles
Particles smaller that about 2 mm diameter, which arise mainly from condensation of hot vapours and chemically driven gas-to-particle conversion processes. Often refers to the PM_2.5 fraction

FVC
Forced Vital Capacity. The volume of air expired in a forced expiration following maximum inspiration

Genotoxic
A term used to describe carcinogens which act directly, or after transformation in the body, on the genetic material (DNA) of cells

Haemoglobin
The protein found in red blood cells which transports oxygen

Heart failure
Failure of the heart to pump blood efficiently. Heart failure may be produced by myocardial infarction

Hygroscopic growth
Growth of particles due to uptake of water from the atmosphere

Immune system
The defensive system of the body which deals with infections and also destroys cells which have undergone malignant change. Diseases such as asthma and some forms of arthritis involve the immune system

Inhalable particles
Particles which may be breathed in. Small enough to be inhaled through the nose and mouth

Leukaemia
A disease in which the number of white cells in the blood is increased due to cancerous multiplication of immature white cells

Lung function tests
Measurement designed to investigate lung functions, e.g. measurements of lung volume or the maximum rate of air flow through the airways

Lymphatic system
The system of vessels and lymph nodes which is involved in returning tissue fluid to the blood stream and in the production of antibodies

 
Malignant
A term used to describe a type of tumour which spreads through the body by the blood or lymphatic systems and which may invade other tissues

Mass concentration
The concentration of particles in air expressed as mass per unit volume

Mediator
A term used to describe chemicals produced in the body which provoke a specific response e.g., inflammatory mediators provoke inflammation

Meta-analysis
A statistical technique which allows the results of a number of studies to be combined and a type of average result to be derived. The technique allows studies to be given different weightings depending, often, upon their size and quality of design

MMEF
Maximal Mid-Expiratory Flow rate of air from the lungs

Morbidity
Illness

Myocardial infarction
Death of heart muscle, usually due to blockage of a coronary artery

Nanoparticles
Particles of less that 50 nm diameter

Neurotoxic
Damaging to the nervous system

nm
Nanometre: one millionth of a millimetre

Nucleation mode
A part of the size spectrum of airborne particles, below about 100 nm diameter, in which particles arise mostly from combustion processes and gas-to-particle conversion

Number concentration
The concentration of particles in air expressed as number of particles per unit volume

Organic compounds
Chemicals containing carbon, e.g., benzene or 1,3-butadiene

PAH compounds
Polycyclic Aromatic Hydrocarbons. Chemicals containing carbon atoms arranged in several rings

PEFR
Peak Expiratory Flow Rate, the maximum flow achieved during a forced expiration

Pharynx
The anatomical region at the rear of the nose and mouth but above the larynx and oesophagus

Photochemical smog
Smog caused by the formation of particles due to chemical reactions driven by sunlight

Photochemistry
Chemical reaction brought about by the action of ultraviolet light

PM₁₀
Particulate matter less than 10 µm aerodynamic diameter (or, more strictly, particles which pass through a size selective inlet with a 50 % efficiency cut-off at 10 µm aerodynamic diameter)

PM_2.5
Particulate matter less than 2.5 µm aerodynamic diameter (or, more strictly, particles which pass through a size selective inlet with a 50 % efficiency cut-off at 2.5 µm aerodynamic diameter)

ppb
Parts per billion, 1 part by volume in 10⁹

ppm
Parts per million, 1 part by volume in 10⁶

Regression analysis
A statistical technique designed to characterise the relationship between changes in some factor (e.g., concentration of a pollutant) and a biological response (e.g., narrowing of the airways)

Relative humidity
Actual vapour pressure/saturated vapour pressure expressed as a percentage. A measure of the degree of saturation of the air with water vapour

Respirable particles
Particles which can penetrate to the alveolar regions of the lung

Smoke
Particulate matter, <15µm, derived from the incomplete combustion of fuels

Surfactant
A fatty material lining the alveoli (air sacs), which prevents them collapsing

Strong Acidity
Measure of the amount of strong acid (mainly sulphuric acid) in airborne particles

Susceptible group
A group of people who, as a result of genetic predisposition, illness or unusual exposure, are more affected by toxic substances than other people.

Suspended Particulate Matter (SPM)
A general term embracing all airborne particles

Synergistic effects
If a person is exposed to two chemicals and the resulting effects are greater than the sum of the effects that would occur if he were exposed to the chemicals singly, then the chemicals are said to act synergistically

TEOM
Tapered Element Oscillating Microbalance, an instrument for the continuous measurement of suspended particulate matter in air

Thoracic particle mass
Describes that fraction of the particles which penetrates beyond the nasopharynx and larynx

Total Suspended Particulate (TSP)
A term describing the mass or airborne particles, most commonly associated with use of the US high volume air sampler in which particles are collected on a filter for weighing

Trace metals
Metallic elements present in low abundance in airborne particles

Trachea
The wind pipe

Troposphere
Layer of the atmosphere extending upwards from the earth's surface for about 10 km

Ultrafine particles
Particles of less than 100 nm diameter

µm
Micrometre: one thousandth of a millimetre

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Published 17 May 2001

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Expert Panel on Air Quality Standards

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Air and Envirnonmental Quality

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Environmental Protection Index

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