Indoor air is classed as an emerging issue due to its potential to cause significant impacts to human health, however there is currently inadequate information to report more fully on this issue.
Indoor air refers to air inside residential dwellings and vehicles. It does not include workplaces or occupational-related indoor air quality. Indoor air quality is significant as some people may spend 90% or more of their time indoors, and it is generally accepted that poor indoor air quality can result in health problems (Woodcock & Custovic, 1998; Scarborough, 2004). Unfortunately, impacts of indoor air quality on heath have not been investigated systematically in Australia.
Increasingly, buildings are becoming more sealed from the external environment, and this can lead to pollutants from indoor sources being found at higher concentrations in buildings that are not well ventilated. For example, office equipment such as photocopiers and printers has been shown to emit respirable particulates, ozone and a range of reactive organic compounds (Brown, 1996). In addition, more humid or temperature controlled environments inside buildings provide ideal conditions for spread of mould or mildew (especially in bathrooms). Fungi can be toxic to humans and pets, and result in breathing difficulties, dizziness, headaches and recurrent infections (Nelson, 2001). Substandard or old buildings can develop problems with rising damp, begin to decay, contain materials such as asbestos or lead, or allow entry of pests and vermin, all of which can lead to poor indoor air quality.
The use of gas stoves, unflued gas heaters and wood heaters can contribute a large percentage of indoor pollutants, including nitrogen dioxide and carbon dioxide. A national audit of wood heaters showed that many in use did not comply with Australian standards (Environment Australia, 2002b) and many were being operated incorrectly (Todd, 2003). The audit found more than 120 gas and aerosol species in homes, comprising various air pollutants (Environment Australia, 2002b). Environmental tobacco smoke is considered one of the main contributors to poor indoor air quality, releasing about 4000 chemicals, including carbon monoxide, nicotine, formaldehyde, ammonia and at least 43 other chemicals known to be human carcinogens (QuitWA, 2005).
Reactive organic compounds are irritants to the human respiratory tract and can invoke allergic reactions. They are found in solvents, floor adhesives, paints, cleaning products, furnishings, polishes and room fresheners. A relationship has been observed between children presenting to hospitals with asthma and exposure to elevated reactive organic compounds, such as benzene, ethylbenzene and toluene (Rumchev et al., 2004). Formaldehyde is found in many furnishings, glues and building materials, and can irritate eyes and may cause respiratory problems. Other indoor pollutants such as carbon monoxide, asbestos, pesticides, radon and lead have received limited study of their relationship to human health, but are generally present in very low concentrations indoors.
Biological contaminants such as moulds, dust mites, insect faeces, pollen, viruses, bacteria and protozoa are known to have allergenic or pathogenic effects on some people. Occurrence and health effects of some organisms are well-known (e.g. dust mites, and the bacterium Legionella) but there has been little investigation of the impact of other microbial contaminants on indoor air quality in Australia (Environment Australia, 2001b). Some diseases or illnesses are closely related to the indoor environment. ‘Sick building syndrome’ occurs when occupants experience acute health effects and discomfort that appears to be linked to time spent in a building, but where no specific illness or cause can be identified (United States Environmental Protection Agency, 1991). ‘Building related illness’ describes symptoms of a diagnosable illness which is identified and can be attributed directly to indoor air contaminants (United States Environmental Protection Agency, 1991). Legionnaires’ disease is a serious (and sometimes fatal) type of pneumonia caused by bacteria of the genus Legionella. It occurs naturally in soil and water but can become concentrated in artificial environments such as showers, spas, fountains, cooling towers associated with air conditioning and industrial cooling processes, and potting mixes (State Government of Victoria, 2004).
Poor indoor air quality has significant implications for human health. This may present as physical or psychological symptoms that are very individual, complex and often poorly defined. Pollutants such as sulfur dioxide, nitrogen dioxide, ozone, inhalable particulates, and reactive organic compounds can affect lung growth. In addition, they may also cause respiratory problems and lower the immune system (Department of Environmental Protection, 2000a). Occupants of buildings with poor indoor air quality can suffer from severe effects such as asthma, allergic responses, cancer risk and illnesses or have mild and generally non-specific symptoms. Some health effects may show up years after exposure, or only after long or repeated periods of exposure, and thus can be characterised as long-term health effects. These can be severely debilitating or fatal, include respiratory diseases and cancer, and are associated with indoor air pollutants such as pathogens, radon, asbestos and environmental tobacco smoke.