Air toxics and indoor air quality in Australia

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

Executive summary

Air pollution continues to be an environmental problem of great concern to Australians. The Commonwealth Government is committed to working with State and Territory Governments, the community and industry to improve air quality in Australia.

The Commonwealth's actions to facilitate the development of a national strategy for the management of priority air toxics illustrate this continuing commitment to improved air quality. Announced in the 1999-2000 Budget, the Commonwealth Government's Living Cities – Air Toxics Program (the ATP), administered by Environment Australia, is the Commonwealth's primary mechanism for advancing this commitment. Approximately $5 million was allocated over three years to the ATP to support the development of a national strategy to monitor and manage air toxics.

This publication, the State of Knowledge Report on Air Toxics and Indoor Air Quality in Australia (the SoK Report) was developed as a core deliverable under the ATP. Building upon the 1999 Environment Protection Authority Victoria publication Hazardous Air Pollutants – A Review of Studies Performed in Australia and New Zealand, the SoK Report provides, for the first time, a compilation of existing information on air toxics and indoor air quality in Australia. Drawing together a broad range of information, it is intended that the SoK Report will provide a useful reference point to help governments, industry and the public work together to develop appropriate management strategies.

In developing the SoK Report, Environment Australia consulted widely with the public, industry and governments to ensure that the final report took into consideration the views of all stakeholders.

The consultation process included a national advertisement outlining the development process and inviting public submissions; the circulation of three public drafts of the SoK Report by direct mail and via the internet; and the circulation of a further two drafts to key stakeholders. Two consultative bodies established under the ATP, the Steering Group and the Technical Advisory Group, also provided a mechanism for ongoing consultation with the community, industry and State and Territory Governments.

The State of Knowledge report has four main parts:

Part A: 'Air Toxics', addresses air toxics in ambient air. This part:

Part B: 'Indoor Air Quality', addresses pollutants that impact on indoor air quality. This part:

Part C: 'Factsheets', provides information on specific pollutants. This information includes:

Part D: 'Appendices' provides additional information on a range of issues such as chemicals management in Australia and consultative bodies advising the ATP.

Presented below is an overview of the main body of the report as contained in Part A 'Air Toxics' and Part B 'Indoor Air Quality'.

Part A: Air toxics

Defining air toxics

Ambient air pollutants can be divided into two categories: criteria pollutants and air toxics.

Criteria pollutants are often considered a group of 'traditional' air pollutants, as their importance has been long recognised. These pollutants are emitted from a wide range of sources, are commonly found in the ambient air (relative to other pollutants) and have demonstrable adverse health effects. Because of these characteristics, the criteria pollutants are traditionally given high priority status by government regulators worldwide. There are six criteria pollutants recognised in Australia, namely: carbon monoxide, lead, nitrogen oxide, photochemical oxidants (as ozone), particles (as PM10) and sulfur dioxide. These pollutants are addressed at a national level by the National Environment Protection Measure (NEPM) for Ambient Air Quality.

Agreed in 1998 by the National Environment Protection Council, the NEPM for Ambient Air Quality established Australia's first national standards for air quality. Having accomplished this for criteria pollutants, the opportunity now exists for Australia's environment authorities to focus on the development of a harmonised national management strategy to address air toxics in ambient air and to also consider a national approach for managing indoor air quality.

Given the existing measures for managing criteria pollutants, the ATP specifically excludes consideration of these pollutants in addressing 'air toxics' in the ambient air. However, four of the six criteria pollutants (ie. carbon monoxide, lead, nitrogen dioxide and particles) have particular significance in the indoor environment and are considered in the SoK Report's coverage of indoor air quality (Part B).

Air toxics (also referred to as hazardous air pollutants) are pollutants present in the atmosphere in low concentrations that are known, or suspected, to cause serious health problems. While there is no universally accepted definition of air toxics, the more recognised definitions, such as those used by the US EPA and World Health Organisation, share a number of common elements. Consistent with these definitions, the ATP uses the following definition:

Air toxics are 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 and 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.

Categories of air toxics

Air toxics include heavy metals, polycyclic aromatic hydrocarbons (PAHs), volatile organic compounds (VOCs), and persistent organic pollutants (POPs).

Heavy metals and their compounds tend to be toxic, persistent, bioaccumulative and some are or may be carcinogenic. Heavy metals in the air are usually associated with particles. Examples of heavy metals of significance to air quality in either their elemental form or as compounds include arsenic, cadmium, chromium (VI), lead, mercury and nickel.

PAHs are organic compounds released into the atmosphere as a complex mixture of compounds during incomplete combustion of organic matter. They are widespread contaminants of the environment and a number of them are either known or suspected carcinogens. In most of the Australian studies, PAH emissions were attributed to domestic heating or other combustion activities common during winter. Long term exposure to PAHs has been associated with many health conditions, including lung cancer, depressed immune functions, and respiratory problems.

VOCs are released from burning fuels containing carbon, and from solvents, paints, glues and other products used in the workplace or at home. Motor vehicles are also an important source of VOCs. Many VOCs can cause serious health problems such as eye, nose and throat irritation, headaches, loss of coordination, nausea, damage to the liver, kidneys and central nervous system. Some VOCs are known or suspected to cause cancer. Some VOCs such as formaldehyde and ethylene may also harm plants. Examples of commonly encountered VOCs include benzene, toluene and 1,3-butadiene.

POPs are toxic, bioaccumulative and environmentally persistent substances that can be transported between countries by the earth's oceans and atmosphere. On 23 May 2001, Australia and 90 other countries signed the Stockholm Convention, an international agreement on POPs which sets out a variety of control measures to reduce and eliminate POPs releases, including bans on production, import, export, and use of some POPs. The control measures will apply to an initial list of 12 chemicals: aldrin, chlordane, dichlorodiphenyltrichloroethane (DDT), dieldrin, dioxins, furans, endrin, hexachlorobenzene (HCB), heptachlor, mirex, polychlorinated biphenyls (PCBs) and toxaphene. Australia is well advanced in meeting the potential obligations of the Convention because all of the commercially produced POPs have been banned domestically or are being phased out. In addition, Australia has well-established national plans to manage POPs waste.

Sources of air toxics

Sources of air toxics can generally be divided into two categories: point sources and diffuse sources. Point sources comprise industrial, and other stationary facilities, which emit large amounts of air toxics in a localised area. Diffuse sources include mobile sources (such as motor vehicles and aircraft) and 'area based' sources (such as solid fuel combustion, dry cleaning, building materials, use of paints and thinners, etc). Although air toxics can be released from natural sources such as bushfires, the major sources of emissions are related to human activities. These include motor vehicles, industry, lawn mowers, combustion of fossil fuels (by industry or at home), cigarette smoking, household chemicals, releases from carpets, furniture or paints.

Industrial sources are a major source of air toxics emissions due to the volume and range of chemicals used by industry and its significant energy requirements, which are largely sourced from the combustion of fossil fuels. There are only a limited number of investigations into emissions of air toxics from industrial sources. An emissions inventory undertaken by the EPA Victoria in 1995–96 found that industry was the largest source of half of the air toxics monitored. Investigations into landfill and mining emissions indicate they have minimal influence on ambient levels of air toxics.

Emissions associated with motor vehicles are typically the largest source of air pollutants in urban areas. Motor vehicles have been found to be the largest source of benzene, toluene, 1,3-butadiene and lead in the ambient air. Ambient levels of benzene, 1,3-butadiene, formaldehyde, toluene and xylene are often found to be highest in heavy traffic areas. Freeways have been found to contribute, in their vicinity, around 60% of downwind benzene and toluene levels in the air.

Domestic solid fuel combustion can be a significant contributor to emissions, especially in winter months. Air toxic emissions from woodheaters include benzene, aldehydes, PAHs and metals. The use of dry seasoned wood and increasing the burn rate and flame intensity to increase combustion efficiency decreases emissions of pollutants. Environment Australia has commissioned a study (managed by the CSIRO) that is currently assessing the emissions of air toxics from domestic wood heaters using different wood fuel types and operating conditions.

Priority air toxics

Given the large number of pollutants that can be classified as air toxics, it was necessary to identify a group of air toxics that should be given priority attention. Twenty-eight priority air toxics were identified for the ATP by its consultative bodies (the Steering Group and the Technical Advisory Group). This priority list of air toxics (shown below) will be open to review as new information comes to hand. The priority list of pollutants will be used as a starting point for focusing attention on the development of national strategies for the management of air toxics.

Priority air toxics
Acetaldehyde Methylenebis (phenylisocyanate)
Acrolein Nickel and compounds
Acrylonitrile Polycyclic aromatic hydrocarbons (PAHs)
Arsenic and compounds Polychlorinated biphenyls (PCBs)
Benzene Phthalates
1,3-Butadiene Polychlorinated dioxins and furans
Cadmium and compounds Styrene
Chromium (VI) compounds Tetrachloroethylene
Dichloromethane Toluene
Fluoride compounds Toluene-2,4-diisocyanate
Formaldehyde Total volatile organic compounds
Mercury and compounds Trichloroethylene
Methyl ethyl ketone Vinyl chloride monomer
Methyl isobutyl ketone Xylenes
Health effects

Exposure to air toxics can result in a variety of health effects ranging from mild and immediate effects such as watery eyes, to more extreme effects such as lung damage, nervous system damage or even birth defects and cancer. The extent to which these adverse effects present themselves depends on a number of factors, such as the type of pollutant to which a person is exposed and the length and severity of the exposure.

There is much uncertainty regarding both typical exposure levels in Australia and the level of exposure that may present health risks. Australian standards exist for some air toxics, set by bodies such as the National Health and Medical Research Council1. There are also overseas standards but these standards vary from country to country and may not be applicable under the specific Australian circumstances.

Management of air toxics

A number of international agencies have initiated strategies for the management of air toxics, including the US EPA (National Air Toxics Program – The Integrated Urban Strategy), the OECD (Advanced Air Quality Indicators and Reporting), New Zealand Ministry of the Environment (New Zealand Ambient Air Quality Guidelines) and Canada (National Air Pollution Surveillance Network, Accelerated Reduction/Elimination of Toxics Program).

In Australia, each State and Territory has developed its own approach to the management of air toxics. Most measures include an emphasis on performance based cooperative approaches and the prevention, or minimisation, of emissions through cleaner production and pollution control measures. Enforcement mechanisms include load-based licenses, maximum discharge limits, works approvals for potential pollution sources and notices or directions issued to control pollution from premises. An air quality management plan or policy provides an underlying framework for the management of air quality in each jurisdiction. Efforts are also being made in several jurisdictions to integrate air management considerations into urban transport and land use planning. The extent to which air toxics in ambient air are being monitored also varies from jurisdiction to jurisdiction. Some jurisdictions have well established air toxics monitoring programs although parameters such as frequency, duration, coverage, analytical and sampling methods and pollutants monitored differ.

Risk assessment is increasingly being used to inform policy makers on the potential effects of air pollution on human health and to guide the development of air quality standards. Risk assessment is a systematic approach to characterising the nature and magnitude of the human health risks associated with environmental hazards. Hazard is the potential for harm; and the assessment of risk comprises an estimate of the likelihood of adverse effects occurring. The availability of appropriate air pollution data is critical to any risk assessment. For the criteria pollutants, air monitoring data is routinely collected by State environment agencies and quite extensive databases exist. Existing data on air toxics is not as consistent or as extensive. The information relevant to air toxics is dispersed among different industries and government agencies and often the data collection methods differ, reducing the comparability of the information gathered. Consequently, there is very limited information available on the potential exposure of the Australian population to air toxics.

Air toxics – conclusions

Ambient air quality is an issue of concern to the Australian community. In June 1998 a cooperative national approach for the six criteria pollutants was agreed and is currently being implemented under the National Environment Protection Measure (NEPM) for Ambient Air Quality. At the time it was recognised by many that a national approach to air toxics was also needed. This is not to say that these pollutants have been left unmanaged, as a range of measures to manage emissions of air toxics are generally well established in the individual States and Territories.

Arguably, the information currently available on the health effects resulting from community exposure to air toxics is limited. While there are data on sources and ambient levels on a range of air toxics, the extent of information varies from pollutant to pollutant as well as across Australia. Similarly, management actions employed by individual jurisdictions to minimise the adverse effects of air toxics vary across Australia. Recognising this, the Commonwealth Government is committed to working with the State and Territory Governments, community and industry to develop appropriate harmonised national actions for the management of air toxics.

Several projects currently being conducted under the auspices of the Living Cities – Air Toxics Program will directly address existing gaps in knowledge of air toxics identified during the preparation of the SoK Report. Some of these projects will reconcile the existing data on air toxics available from State and Territory jurisdictions while other projects will result in new data becoming available which can then be used to aid the development of appropriate national management strategies. Details of these studies are available on the Internet at

Existing national programs will also assist over time in evaluating the scale and the nature of the problem. For example, the National Pollutant Inventory (the NPI) will provide nationally consistent data on emissions of most air toxics in Australia. However, there is no comparable source of information on ambient concentrations of air toxics.

The management of air toxics would benefit from a consistent national approach. One possible management option is the development of an Air Toxics NEPM.

Part B: Indoor air quality

Defining indoor air

National Health and Medical Research Council (NHMRC) defines indoor air as any non-industrial indoor space where a person spends a period of an hour or more in any day. It is generally recognised that Australians spend as much as 90% or more of their time indoors and that indoor air quality can result in significant adverse impacts on human health. The CSIRO estimates that the cost of poor indoor air quality in Australia may be as high as $12 billion per year.

Sources of indoor air pollutants

The quality of indoor air is determined by the quality of ambient air and the magnitude of emissions of pollutants from indoor sources. Generally, due to the period of exposure and the concentrations of pollutants in the air, exposure to air pollutants is higher indoors than it is outdoors.

Many of the pollutants classified as air toxics or criteria pollutants can be emitted into the air from indoor sources. Four out of six criteria pollutants, namely carbon monoxide, oxides of nitrogen, lead and compounds and respirable particles (PM10 and PM2.5) have been identified under the ATP as being relevant to the indoor air environment. A range of substances which are considered air toxics are also relevant in this context, most notably VOCs and PAHs.

Indoor air pollutants are not restricted to chemical pollutants as there are many biological substances found indoors which are allergens (substances capable of causing allergic reactions). These allergens affect the 30–40% of individuals who are predisposed to developing allergies. Biological sources of indoor air pollutants include bacteria (e.g. legionella), house dust mites, fungi, cockroaches, rodents, pets and even humans.

There are many indoor sources of air toxics and criteria pollutants. Some of the major sources are glues, sealants, lacquers, carpets, unflued gas appliances and cigarettes. Other sources include common building materials, furnishings, appliances and consumer products.

Releases of toxic fumes from furniture, carpets, paints, glues and sealants used in building products are greatest in new homes. Levels of these pollutants may remain high for several months. A recent CSIRO study found very high levels of volatile organic compounds in all the 27 new houses that were tested.

The use of pesticides in the home exposes the occupants to a range of toxic substances, some of which are carcinogenic. The application of termiticides (chemicals to control termites) to building foundations can result in these chemicals entering the house. Residues from the past use of organochlorine termiticides, such as chlordane, may persist in the soil beneath buildings for many years.

The prevalent pollutants in indoor air vary depending on the type of indoor air environment. Depending on whether it is a residential building, workplace, shopping mall, hotel or vehicle cabin, the actual composition of air pollutants can be quite different (eg. carbon monoxide, benzene, 1,3 butadiene and particles would be prevalent in the cabin of a motor vehicle while formaldehyde, nitrogen dioxide, carbon monoxide and allergens would be prevalent in a typical residential building).


Ventilation rate also significantly influences the quality of indoor air. Since the energy crisis of the 1970s there has been a trend towards designing 'tight buildings' in order to minimise energy losses through natural ventilation. For the same reason there has been a move to reduce rates of mechanical ventilation. In recent years the need to minimise greenhouse gas emissions has seen further efforts to reduce the energy used in heating and cooling buildings. While reducing ventilation rates is one way to achieve this, lower ventilation rates tend to result in poorer indoor air quality. Air pollutants emitted from indoor sources tend to accumulate in the indoor air unless they are dispersed by adequate ventilation.

Health effects

Human health responses to multiple factors present in the indoor environment are individual, complex and often not well defined. Health effects that may be experienced by the occupants of buildings with poor indoor air quality range from severe effects (asthma, allergic response, cancer risks) to mild and generally non-specific symptoms. Building Related Illness (BRI) is a clinically diagnosed illness directly related to indoor exposure and the widely known Sick Building Syndrome (SBS) is a subset of BRI.

Indoor air quality – conclusions

As Australians spend at least 90% of their time indoors, it is important to ensure that indoor air is of a sufficient quality to adequately protect their health and well being.

As with air toxics in ambient air, the information available on levels of pollutants in indoor air and their sources and health effects is not comprehensive enough to allow a confident evaluation of these issues. Several projects currently being conducted under the ATP aim at addressing gaps in knowledge of indoor air quality identified during the preparation of the SoK Report.

Ambient air quality impacts on indoor air quality. In Australia, ambient air quality is already being addressed, either by existing measures (for criteria pollutants), or will be addressed by measures being developed (for air toxics). It is, however, only a starting point. Given the length of time people spend indoors and the multitude of indoor sources of pollutants a need and an opportunity exist to improve the quality of indoor air.

One avenue to achieve this improvement is through reducing emissions of indoor air pollutants (either by eliminating their sources or by minimising the emissions from those sources). This is relevant to residential dwellings and public buildings such as schools, hospitals, libraries, etc. It should be noted that indoor air quality in an occupational sense is already managed under occupational health and safety legislation but there are no similar mechanisms in place for non-workplace indoor air environments. Increased ventilation rates are also likely to result in improved indoor air quality. As poor indoor air quality, like global warming, has health and social costs, the challenge is to strike a balance between the need to minimise energy consumption, and the need to ensure indoor air quality is not compromised by poor ventilation.


1 On 19 March 2002, the National Health and Medical Research Council rescinded its publication "Ambient Air Quality Goals and Interim National Indoor Air Quality Goals". The Council has made this publication available on its Internet Archives site as a service to the public for historical and research purposes only.

The publication is available at: 

The Internet Archives site also contains the following statement made by the National Health and Medical Research Council:

Rescinded publications are publications that no longer represent the Council's position on the matters contained therein. This means that the Council no longer endorses, supports or approves these rescinded publications.


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