SoE 2003 > Atmosphere > 3.5 Indoor air quality

3.5 Indoor air quality

Data is limited but indoor air quality is emerging as an important issue

People spend approximately 75–95% of their time indoors where the quality of the air can often be poorer than outdoors. This makes indoor air quality an important issue for human health. Indoor air quality is affected by tobacco smoke, solid fuel and unflued heaters, building ventilation rates, prevailing climatic conditions and the use of pollutant-emitting materials. Some pollutants, such as dust mites, formaldehyde, mould, radon and some pesticides, are mainly found indoors. Recent research confirms that concentrations of some indoor air pollutants reach much higher levels indoors than outdoors.

Until recently data on indoor air quality was limited and the community knew little about the issue. However, this situation is now beginning to change as advances in technology make inexpensive monitoring equipment readily available.

NSW indicator

Importance of the issue

The National Health and Medical Research Council (NHMRC) defines indoor air quality as 'air within a building occupied for at least one hour by people of varying states of health'. This definition includes air within homes, offices, schools, restaurants and public buildings (NHMRC 1996). It does not include workplaces where workers are otherwise covered by occupational health standards or air within motor vehicles, although clearly similar issues apply to these spaces.

The quality of indoor air depends on a range of factors, such as the type of building materials used in construction, the proximity of road traffic, types of indoor heating used, the degree of building ventilation and diurnal, seasonal and climatic conditions.

The primary concern with indoor air pollution is the potential link between pollutants and health. Even at relatively low levels, some indoor air pollutants can cause breathing difficulties, especially for people with respiratory problems, such as asthmatics, very young children and frail older people. It is also generally accepted that smoke pollution from tobacco can lead to heart problems, cancer and babies with low birth weights.

Response to the issue

Until recently there has been very little data on indoor air quality and the community knew little about the issue or the factors that can contribute to its quality. During the winter of 1999 NSW Health studied a cross-section of NSW homes to evaluate air pollutants and identify their principal sources. The study found that homes where tobacco is smoked had the highest levels of particles (PM₁₀). Nitrogen dioxide levels were significantly higher in homes where unflued gas appliances were used. Levels of formaldehyde varied significantly between regions, house age, and house and heater type, although they were generally quite low (Sheppeard et al. 2002a).

Results from the NSW Health survey indicate that levels of indoor pollutants should be considered on a regional basis and local risks to indoor air quality identified.

In 2001–02, a study in four city centres (Sydney, Melbourne, Perth and Adelaide) aimed to determine the significant sources of personal exposure to total volatile organic compounds, including benzene, toluene, ethyl benzene, o-xylene, m-xylene and p-xylene (Environment Australia 2003). The major sources of personal exposure to these substances were identified as motor vehicle exhausts from attached garages and car parks, tobacco smoke, consumer products such as building materials, paints and varnishes, wood smoke, domestic gas appliances and petrol stations.

Tobacco smoke

The presence of smoking in homes and public places is associated with an increase in PM₁₀ often exceeding comparable established outdoor health-based goals such as the National Environment Protection Measure for Ambient Air Quality (see Atmosphere 3.3). In 1998 a study by South Sydney Council investigated air quality at hospitality venues, with a particular emphasis on environmental tobacco smoke (Sheppeard et al. 2002b). The study demonstrated that peak indoor PM₁₀, carbon monoxide and carbon dioxide levels were highly correlated with average weekly measures of environmental tobacco smoke. The high levels of carbon dioxide found in some venues indicated that ventilation was ineffective. The study also found that levels of fine particles where smoking occurs exceed health-based goals and are likely to be associated with a significantly increased risk of respiratory and cardiovascular disease for patrons and employees, particularly the latter. In contrast, the study indicated that outdoor exposure to PM₁₀, even on busy roads, was much lower (Sheppeard et al. 2002b).

In September 2000 the Smoke-free Environment Act 2000 introduced an immediate ban on smoking in most enclosed public places, including restaurants and their bars, cafes, cafeterias, shopping centres, malls, plazas, community centres and common areas of hotels and motels. In September 2001, smoking was banned in dining areas on premises with a hotelier's or nightclub licence, and registered clubs. Casino, bar and gaming machine areas are exempt from the smoking bans.

The Environmental Tobacco Smoke and Children community education project aims to reduce infant and child exposure to environmental tobacco smoke in cars and homes in NSW. A task force is managing this four-year project with members from NSW Health, the Cancer Council NSW, the Heart Foundation (NSW Division), Sudden Infant Death Syndrome Association, and Asthma NSW. In September 2002 a television and radio campaign was launched with the tagline 'Car and home smoke-free zone'. A community grants program, a professional development strategy and a number of special community activities aims to ensure that this message registers with all members of the community.

Unhealthy buildings

As buildings have become increasingly insulated from the external environment, pollutants released from indoor sources such as carpets, building materials and architectural coatings are being found at higher concentrations. Many of the substances that contribute to indoor air pollution originate from solvents and resins used in manufacturing materials; the operation of office equipment and heating appliances; or auto exhausts in air from attached garages.

In April 2001, in response to growing knowledge about the implications of poor indoor air quality, the NSW Legislative Assembly Standing Committee on Public Works published a report on 'sick building syndrome' (SCPW 2001). The committee recommended that the Government establish a working group to address the issue and make indoor air quality a specific focus of building codes and standards.

Legionnaire's disease

Legionnaire's disease is usually contracted by inhaling mist from water sources such as spa baths, showers, or airconditioning cooling towers that are contaminated with Legionella bacteria. As part of the preparation for the Sydney Olympics, the Public Health (Microbial Control) Regulation 2000 was introduced in NSW to deal with air quality in relation to legionnaire's and other diseases. It makes the water treatment industry more responsible and accountable for ensuring that water cooling and water-heating systems, are installed, operated and maintained correctly. Where previously NSW Health approved disinfection processes, it is now the responsibility of the building occupier and the water treatment company to ensure that such systems are treated using effective and certified microbial growth-controlling processes. Additionally, building occupiers now have an option to follow a performance-based maintenance system developed by Standards Australia for cooling water systems, instead of fulfilling prescriptive maintenance requirements (Standards Australia 2002).

Heating appliances

EPA programs to reduce outdoor air pollution from solid fuel heaters are also effective in cutting indoor PM₁₀ emissions from the appliances. Tighter emission standards have been introduced for new wood heaters. An EPA wood smoke website provides information on how to minimise the impact of wood heaters on winter air quality. The EPA's 'Don't light tonight unless your heater's right' campaign continues each winter. A Woodsmoke Reduction Program during winter 2002 in regional areas encouraged a shift away from pollution-generating wood heaters to cleaner forms of heating and advised how to use wood heaters cleanly and efficiently (see Atmosphere 3.3).

Effectiveness of responses

Although pollutants commonly found in indoor air are responsible for many harmful effects, there is considerable uncertainty about what concentrations or periods of exposure produce specific health problems. Further research and monitoring is needed to better understand which health effects occur after exposure to the average pollutant concentrations found in homes and to establish the extent of the problem so that effective responses can be made.

The Smoke-free Environment Act 2000 is the single most important and effective response taken in recent years to improve indoor air quality in public places and buildings. Anecdotal evidence suggests that the Act has contributed to significant improvements in public place indoor air quality.

Future directions

Indoor air quality can be managed at the design and installation stages of domestic appliances and furnishings; through the development of building codes that eliminate and control the sources of pollution; and by increasing ventilation in general. Reducing or eliminating tobacco smoke in homes will also improve indoor air quality.

Governments need to continue research and monitoring to better understand which health effects occur after exposure to pollutant concentrations found in homes and to quantify the extent of the problems so that effective responses can be developed.

Linked issues

3.3 Urban air quality

3.4 Air toxics