Air toxics and indoor air quality in Australia

State of knowledge report
Environment Australia, 2001
ISBN 0 6425 4739 4


Acute: Sharp, severe, having rapid onset, severe symptoms, and a relatively short duration. Contrast with chronic.

Acute exposure: A single exposure of relatively short duration.

Additive: The interaction of two or more chemicals that results in an effect equal to the sum of their separate effects.

Acute toxicity: A toxic effect which occurs immediately or shortly after a single exposure.

Aerosol: Particles or liquid droplets that can remain suspended in air for long periods of time because of their extremely small size and light weight.

Airshed: A geographic area, usually containing some significant atmospheric emission sources. The boundary of the area is determined largely by characteristic trajectories followed by parcels of polluted air due to interaction of synoptic-scale winds and local winds (eg sea breezes, valley winds and winds steered by topographic features). Characteristic trajectories can include recirculation and oscillatory patterns of airflow. These lead to accumulation of air pollutants and also increase the time pollutants are resident in the airshed. The increased residence time is especially significant for secondary air pollutants such as ozone.

Air toxics: Gaseous, aerosol or particulate pollutants (other than the six criteria pollutants) which are present in the air in low concentrations with characteristics such as toxicity or persistence so as to be a hazard to human, plant or animal life. The terms 'air toxics' and 'hazardous air pollutants' (HAPS) are used interchangeably.

Antagonistic: An interference or inhibition of the effect of one chemical by the action of another.c

Ambient air: As defined in the Ambient Air Quality National Environment Protection Measure: 'ambient air means the external air environment, it does not include the air environment inside buildings or structures.'

Anthropogenic: Human made.

Atopic: Having a hereditary tendency to develop immediate hypersensitivity states (such as allergic asthma or hayfever), especially to allergens that provoke no reaction in nonatopic individuals.

Bioaccumulation: The tendency of chemicals to accumulate in organisms (eg fish) at higher concentrations than in the ambient environment (eg water).

Body burden: The amount of a particular chemical stored in the body at a particular time, especially a potentially toxic chemical, resulting from exposure. Body burdens can be the result of long-term storage (eg of a metal in bone or of a lipophilic substance such as polychlorinated biphenyls in adipose tissue) or short-term storage (eg carbon monoxide [as carboxyhaemoglobin] in the blood).c

Chronic: Occurring over a long period of time, either consistently or intermittently. Contrast with acute.

Chronic effects: Effects that last a long time even if caused by a single acute exposure.

Chronic toxicity: A toxic effect which occurs after repeated or prolonged exposure. Chronic effects may occur some time after exposure has ceased.

Criteria pollutants: In Australia six criteria pollutants have been identified: carbon monoxide, lead, nitrogen dioxide, photochemical oxidants (measured as ozone), particles as PM10 (particles of 10 micrometres or less) and sulfur dioxide. The criteria air pollutants require special focus due to their abundance in the environment and their demonstrated adverse health effects.

Diurnal: Occurring every day or having a daily cycle.

Dose: A level of exposure which is a function of a pollutant's concentration, the length of time a subject is exposed, and the amount of the pollutant that is absorbed. Dose is determined by the concentration of the pollutant and the length of time that the subject is exposed to it.b

Dose-response: The relationship between the dose of a pollutant and the response (or effect) it produces on a biological system.b

Dose-response curve: A graphical representation of the quantitative relationship between the administered, applied or internal dose of a chemical, and a specific biological response to that chemical.c

Emission factor: For stationary sources, the relationship between the amount of pollution produced and the amount of raw material processed or burned. For mobile sources, the relationship between the amount of pollution produced and the number of vehicle miles travelled. Emissions for a given source can be calculated from the emission factor of a pollutant and specific data regarding quantities of materials used by the source. This approach is used in preparing an emissions inventory.b

Emissions: Releases of contaminants from a facility, area or volume source (routine or accidental).

Environmental impact assessment: A systematic process to assess the actual or potential effects of policies, objectives, programs, plans or activities on the local or global environment. An assessment of risks to the environment either directly or indirectly as a result of human activities.

Environmental tobacco smoke (ETS): Primarily a combination of sidestream smoke from the burning end of a cigarette, pipe or cigar, and exhaled mainstream smoke from the smoker. Other components include smoke emitted at the mouthpiece during puff drawing.b

Epidemiology: The study of the occurrence and distribution of disease within a population.b

Evaporative emissions: Emissions from evaporating gasoline, which can occur during vehicle refuelling, vehicle operation, and even when the vehicle is parked. Evaporative emissions can account for two-thirds of the hydrocarbon emissions from gasoline-fuelled vehicles on hot days.b

Exposure: Contact with a chemical or physical agent that can occur through breathing, drinking, eating and by direct skin contact.

Fugitive emission: Atmospheric emissions due to leaks (eg from processing plants, storage facilities and their interconnections). Generally fugitive emissions occur near to the ground.

Goal: As used in national environment protection measures, a goal is the desired outcome, for example:

The term 'goal' carries the implication of the outcome to be achieved. It may be something desirable in the future and not immediately attainable. It should, however, represent the aspiration of the Australian people for environmental quality.

Guideline: As used in national environment protection measures, 'guidelines' provide guidance on how:


Hazard: An intrinsic capacity to cause harm associated with an agent or process.

Health: 'A complete state of physical, mental and social well being and not merely the absence of disease or infirmity'.c

Hydrocarbons: Compounds containing various combinations of hydrogen and carbon atoms. They may be emitted into the air by natural sources (eg trees) or as a result of fossil and vegetative fuel combustion, fuel volatilisation, and solvent use. Hydrocarbons are a major contributor to smog.b

Indoor air: The NHMRC defines indoor air as any nonindustrial indoor space where a person spends a period of an hour or more in any day. This can include the office, classroom, motor vehicle, shopping centre, hospital and home.

Inhalation: Breathing in.

Material safety data sheet (MSDS): In relation to a chemical or to a product or substance containing a chemical, a document that is prepared in accordance with the National Occupational Health and Safety Commission National Code of Practice for the Preparation of Material Safety Data Sheets, Australian Government Publishing Service, Canberra, 1994.

Mutagenic: The ability of a chemical or physical agent to produce heritable changes in the DNA of living cells.b

Occupational exposure standard (air): An airborne concentration of a particular substance in a person's breathing zone, as established by the National Occupational Health and Safety Commission Exposure Standards for Atmospheric Contaminants in the Occupational Environment and National Exposure Standards.c

Olefin: Unsaturated hydrocarbons having the general formula CnH2n.b

Organic compounds: Chemical compounds containing mainly carbon, hydrogen, nitrogen, and oxygen. All living organisms are made up of organic compounds.

Particulate matter (PM): Any material, except pure water, that exists in the solid or liquid state in the atmosphere. The size of particulate matter can vary from coarse particle windblown dust to fine particle combustion products.b

Persistence: Refers to the length of time a compound stays in the atmosphere (or other media) once introduced. A compound may persist for less than a second or indefinitely.b

Polycyclic aromatic hydrocarbons (PAHs): Organic compounds that include only carbon and hydrogen with a fused ring structure containing at least two benzene (six-sided) rings. PAHs may also contain additional fused rings that are not six-sided. The combustion of organic substances is a common source of atmospheric PAHs.b

Prescribed burning: The planned application of fire to vegetation to achieve any specific objective on lands selected in advance of that application.b

Primary air pollutants: Substances contained in an atmospheric emission that degrade air quality by their presence in the atmosphere.

Respirable suspended particles: The proportion of total suspended particles of a size smaller than 10 micrometres. They have the ability to penetrate deeply into the lungs. Depending on their source and the existing meteorological conditions, respirable suspended particles can be made up of a number of different constituents.

Risk: The probability of adverse human health or environmental effects from exposure to toxic substances or materials released into the environment.

Risk assessment: A qualitative or quantitative evaluation of the environmental and/or health risk resulting from exposure to a chemical or physical agent (pollutant).

Risk factor: A characteristic (eg age, sex, race) or variable (eg smoking, occupational exposure level) associated with increased probability of an adverse health effect.

Risk management: A decision-making process that entails considerations of political, social, economic and engineering information with risk-related information to develop, analyse, and compare regulatory options in order to select the appropriate regulatory response to a potential health hazard.

Secondary air pollutants: Products of atmospheric chemical reactions involving one or more primary air pollutants.

Smog: A combination of smoke and other particles, ozone, hydrocarbons, nitrogen oxides, and other chemically reactive compounds which, under certain conditions of weather and sunlight, may result in a murky brown haze that causes adverse health effects.b

Smoke: A form of air pollution consisting primarily of particulate matter (ie particles released by combustion). Other components of smoke include gaseous air pollutants such as hydrocarbons, oxides of nitrogen, and carbon monoxide. Sources of smoke may include fossil fuel combustion, agricultural burning, and other combustion processes.b

Soot: Very fine carbon particles that have a black appearance when emitted into the air.

Source: Any place or object from which air pollutants are released. Sources may be either stationary (fixed in space) or mobile (move in space).b

Synergistic: The interaction of two or more chemicals that results in an effect greater than the sum of their separate effects.c

Standard: A standard is a quantifiable characteristic of the environment against which environmental quality can be assessed. It is a surrogate for the environmental values that are to be protected.

Temperature inversion: A layer of warm air in the atmosphere that prevents the rise of cooling air and traps pollutants beneath it.

Topography: The configuration of a surface, especially the Earth's surface, including its relief and the position of its natural and human-made anthropogenic features.b

Total suspended particles (TSPs): Particles of solid or liquid matter – such as soot, dust, aerosols, fumes, and mist – up to approximately 30 micrometres in size.b

Toxicity: The quality or degree of being poisonous or harmful to plant, animal or human life.

Vapour: The gaseous phase of liquids or solids at atmospheric temperature and pressure.b

Vapour density: The amount of mass of a vapour per unit volume of the vapour. The vapour density is expressed in grams per litre and is compared to the density of air, which is equal to 1.b

Volatile: Able to pass readily into the vapour state.

a Definitions adapted from United States Environmental Protection Agency.
b Definitions adapted from California Air Resources Board.
c NOHSC (1995).


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