ACT State of the Environment 2007
Indicator: Indoor air quality
Indoor air quality is not regularly recorded and few data are available on indoor air quality in Canberra buildings. Data available from elsewhere is sparse. However, it is clear that tobacco smoke is a major source of indoor air pollution in those homes or venues in which smoking occurs.
Workplace machinery and activities can also be significant sources of pollution.
Legislation banning smoking in public buildings and licensed premises in the ACT has greatly improved indoor air quality for many people.
Occasional monitoring within a selected number of public and private buildings would be desirable to give some idea of the range and concentrations of pollutants present in Canberra buildings.
Many studies have shown that most Australians spend 90% of their time indoors (including within vehicles) yet we know little about the quality of the air inside compared with that outside. The studies that have been carried out – both in Australia and internationally – show that indoor air quality can be quite different from outside air although, as might be expected, ambient air has a broad influence.
What the results tell us about the ACT
Information from studies in other parts of Australia shows an extraordinary range of potential indoor air pollutants. Sources of indoor air pollutants include:
- building operations and construction materials
- household products
- various human activities, such as smoking
- external factors (from outdoors).
A source of air pollutants does not necessarily cause an indoor air quality 'problem'. It obviously depends on the type of pollutant and the concentration at which it exerts an effect, as well as how rapidly it is broken down or dispersed. It depends on the rate at which it is released from its source, and the degree of ventilation available in the home to allow fresh air in. As well, individuals vary greatly in their sensitivity to airborne chemicals. A concentration that could cause symptoms in one person may have no discernable effect in another. Generally, the very old and the very young and those with respiratory conditions or other illnesses are likely to be most sensitive to airborne chemicals.
Some of the more worrying indoor pollutants are chemicals released from some types of materials used to construct and fit out a new house or renovate an existing one. Emissions of pollutants into indoor air are therefore usually worse in new houses or renovated homes, but normally decline to insignificant levels over a year in the life of the house (or renovation). In principle, the situation would be exacerbated if the house were kept tightly sealed and not ventilated, to minimise the loss (or gain) of heat energy through air movements between the house and outside. In practice, however, while new houses, meeting minimum energy performance standards are more tightly sealed than most older houses, few houses in the ACT even approach the level of air tightness that is normal in new houses in North America or northern Europe. Moreover, the ACT climate is such that, even in mid winter, there are few days on which opening windows for ventilation in the middle of the day will result in significant heat loss. Consequently, while the level of air pollutants in new houses may well be higher than in older houses, the absolute levels are unlikely to be a cause for concern.
Conversely, old houses may suffer from other indoor air quality problems. For example, deep-seated mould may release spores and old carpets, furniture and mattresses may harbour dust mites. However, the drier climate in the ACT makes the dust mite problem less severe than in coastal Australia. Other factors in both new and old homes, such as treatment of a house for pests, or use of cleaning solvents and paints, may also introduce a range of air pollutants. A good airing of any house is a sensible precautionary practice. This same principle applies to other buildings.
- The main indoor air pollutants are:
- formaldehyde from pressed wood products and laminates
- volatile organic compounds (VOCs),1 from some synthetic fabrics, varnishes, cleaning products, office equipment, and various building products such as paints, carpets and glues
- nitrogen dioxide, from burning natural gas (if heaters and cookers are correctly flued most of the pollutant will be dispersed outside)
- carbon monoxide, from wood burning (the fluing and chimney efficiency has a significant effect), from internal combustion engines (such as idling cars) and from tobacco smoke.
Pesticides may also be present in some homes.
Older homes may also have lead in their dust from paint manufactured before the 1970s. In addition, there may be allergens (substances that cause allergic reactions in sensitised individuals) from dust mites (found in nearly all homes), pollen and mould. Following a report from the Asbestos Taskforce to the ACT Government in 2005, new laws have been introduced for managing asbestos, including a ban on using asbestos in products for the home.
Workplaces may have specific pollutants depending on the nature of the work. Office furniture and equipment releases VOCs. Often, the level of ventilation in office buildings is substantially less than in houses so concentrations can build up. Specific equipment, such as laser printers and photocopiers, can emit a range of pollutants. In general, pollutant emitting equipment and activities should be confined to certain areas with a high level of separate ventilation. Workplace air quality is covered by occupational health and safety regulations.
Air quality within some vehicles is likely to be less than ideal. However, the quality would depend on the type and age of the vehicle, the ambient air quality, and the ventilation rate.
Data sources and references
For more information on indoor air quality, and how to improve it, see Healthy Homes: A guide to indoor air quality in the home for buyers, builders and renovators published by the federal Department of Health and Ageing, Canberra, available at www.nphp.gov.au/enhealth/council/pubs/pdf/healthyhomes.pdf last viewed 28 March 2008
For further information on asbestos management in the ACT see http://www.asbestos.act.gov.au/ last viewed 28 March 2008
1 VOCs are chemicals that contain carbon and that are volatile (that is, readily able to evaporate into air). In general, higher temperatures cause more VOCs to be released. The concentration may vary considerably from one room of the house to another, depending on the source. For example, the smell of new paint may persist for some weeks in a freshly painted room. There are hundreds of different VOCs and they differ in their toxicity but not enough is known about all of them, or about possible interactions between them.