4.2 Indoor air quality
Indoor air quality has a potential impact on human health (rather than environmental impact) with the long-term effects not fully understood, due to the limited quantitative data available.
Australians, like others from industrialised nations, spend most of their time indoors. Air quality indoors can be worse than it is outside and may pose health risks in many enclosed environments.
The impacts of indoor air quality on health and sources of pollutants continue to be investigated. Information from investigations will drive further policy development and help determine the need for targeted management strategies to minimise health impacts.
National approaches and programs to rate the operation and maintenance of buildings are currently being developed and will be critical to achieving and maintaining healthy air quality in buildings.
Introduction
Indoor air quality refers to the air quality within homes, schools, shopping centres, vehicles and indoor workplaces, especially as it relates to the health and comfort of those who inhabit them. Australians spend approximately 85% of their time indoors, much of it in the home (EPHC 2004). As a result, personal exposure to airborne substances may be more closely related to those encountered indoors than outdoor air pollution. This is accentuated by the close proximity of indoor emissions to people and because the small amounts of pollutants emitted can accumulate to higher concentrations than they would outdoors because of ineffective dispersion and dilution.
The primary concern with indoor air pollution is the link between pollutants and human health. Indoor air pollution can have a variety of impacts on human health, from irritant effects to respiratory disease, cancer and premature death. Some of the pollutants found in indoor air are suspected of contributing to long-term health effects, such as cancer and damage to the nervous, immune and reproductive systems. Other pollutants (nitrogen dioxide, formaldehyde and fine particles) can cause more immediately observable health effects, such as irritation of the upper respiratory system and breathing difficulties, especially for at-risk groups like those with asthma or other lung problems, very young children and older people. Pollutants from tobacco smoke can lead to respiratory and heart disease, cancer and foetal harm.
Although information on the main forms of indoor air pollution has improved (as discussed below), little is known about how concentrations of chemicals released from solid-fuel heaters and out-gassing from household products spread across a variety of indoor spaces. Moreover, it should be noted that the long-term health impacts of the large number of chemicals found in indoor air are poorly understood, including some suspected of contributing to adverse health effects.
Status and trends
Indoor air pollutants
The quality of indoor air depends on various parameters including:
- the type of building materials used
- the types of products used indoors (such as paint, electrical appliances, furniture and cleaning products)
- the proximity to outdoor sources of air pollution
- the types of indoor heating or cooling used
- cooking methods
- building ventilation rates
- the particular uses of the building (including whether smoking occurs)
- diurnal, seasonal and climatic conditions.
Building characteristics also play an important role.
Indoor air pollutants include biological and chemical contaminants. Examples of the latter are major contributions from combustion products and gases released from indoor materials (off-gassing emissions). Along with particulate matter, gases such as ozone, nitrogen dioxide, carbon monoxide, sulfur dioxide, microbial and volatile organic compounds (VOCs) and secondary (or 'environmental') smoke are the most common types of air pollutants encountered indoors.
Measured indoor air pollution
Monitoring in NSW homes has identified secondary tobacco smoke and emissions from solid-fuel heaters and unflued gas heaters as important indoor sources that contribute to poor indoor air quality. These are problematic as they raise concentrations of fine particles, carbon monoxide and nitrogen dioxide (Sheppeard et al. 2002; DEH 2004).
In 2003, pollutant monitoring undertaken in Sydney homes found that those using unflued gas heaters frequently had nitrogen dioxide concentrations exceeding the WHO 1-hour guideline of 110 parts per billion: the guideline was exceeded at least once on 67% of house-days tested (DEH 2004). A small number of homes also exceeded health guidelines for carbon monoxide and formaldehyde, which are also emitted by unflued gas heaters.
The NSW Health Survey Program monitors health behaviours, health status, use of, and satisfaction with, health services and other factors that influence the health of NSW residents. Data on health-related behaviours and other risk factors from the surveys showed that unflued gas heaters remain the primary form of heating in around 18% of homes, with solid-fuel heating in about 15% (NSW Health 2008). Since 1990, the Government's Gas Heater Replacement Program has been progressively replacing old-style unflued heaters in NSW public schools with low NOx emission-type unflued heaters: over 80% of the approximately 51,000 heaters have now been replaced.
The NSW Health Survey also reported that 84.3% of households in NSW were smoke-free in 2004, an increase of 14.5% since 1997 (NSW Health 2000; NSW Health 2005). Between 2001 and 2005, the Environmental Tobacco Smoke and Children community education project found that the number of smoke-free homes had increased by 56% and the number of smoke-free family cars by 42% (NSW Health et al. 2005).
Pressures
The major pressures on indoor air pollution continue to be emissions from products used in the home, unvented gas cooking, unflued combustion heating emissions and off-gassing emissions from indoor materials.
The question of indoor air quality has become even more relevant with the current trends towards energy-saving homes, which are based on very tight building structures that may lead to inadequate air exchange rates. The effects of this may result in the accumulation of indoor air pollutants.
Responses
Tobacco smoke
The Smoke-free Environment Act 2000 introduced smoking bans in restaurants and their bars, cafes and cafeterias, shopping centres, malls and plazas, community centres and the dining areas of hotels. Amendments to the Act in 2004 introduced phased-in restrictions on smoking in licensed venues culminating in a total ban on smoking in enclosed public areas of licensed premises in July 2007.
In April 2008, the NSW Government released a discussion paper, Protecting Children from Tobacco (NSW Government 2008), to engage the community on reforms to dissuade young people from taking up smoking and protect children and young people from the harmful effects of environmental tobacco smoke. A comprehensive community consultation process supported the discussion paper. Following passage of the Public Health (Tobacco) Act 2008, smoking was banned in motor vehicles with any passengers under the age of 16.
Home heating
In 2007 the Australian Environmental Health Committee (enHealth) released a review on the use of unflued gas heaters in the indoor environment. The Health Effects of Unflued Gas Heater Use in Australia (enHealth 2007) was developed to provide evidence to guide policy on regulating and managing unflued gas heaters in Australia and New Zealand. The document reviews data on the levels of pollutants produced by unflued heaters and summarises the evidence for any links between use of these heaters and adverse health outcomes (based on a review of the scientific literature).
Home renovation dusts
The Think Asbestos program was developed by the NSW Government and industry in 2007 to increase awareness of the asbestos products that home renovators might encounter. Asbestos products can be unknowingly disturbed, releasing harmful fibres into the indoor environment.
The NSW Government website, DIY Safe, developed in 2005, contains information about the hazards and risks that home renovators may face from a range of chemicals or materials, including asbestos.
Volatile emissions from surfaces, furnishings and consumer products
A working group of the Environment Protection and Heritage Council is examining the potential of a number of strategies to reduce volatile organic compound (VOC) emissions from various categories of coating products. The working group is expected to report back to the council in late 2009.
Legionnaire's disease
The Public Health (Microbial Control) Regulation 2000 continues to be the main tool by which air and water quality is controlled in relation to legionnaire's and other diseases.
National Indoor Air Project
The Australian Department of the Environment, Water, Heritage and the Arts (DEWHA) has been examining indoor air issues, in consultation with health agencies. The aim is to assess whether there are grounds for a national response to Australia's indoor air problems. To complement this work, DEWHA has commissioned the Commonweath Scientific and Industrial Research Organisation (CSIRO) to study the levels of major indoor air pollutants inside and outside the average Australian home. This study will also assess the influence of a range of factors, including proximity to major roads, on levels of indoor air pollutants. It will help determine the need for management strategies to minimise health impacts.
Building rating schemes
Introduced in 2003, Green Star is a voluntary environmental rating system administered by the Green Building Council of Australia. Green Star evaluates the performance of a building at the design stage. There are eight Green Star Rating Tool Categories, one of which is Indoor Environmental Quality. The system assesses a number of factors – ventilation, lighting, occupant comfort and indoor pollutants – against performance-based, non-prescriptive targets. Rating tools have been developed for the educational, retail, health care, multi-unit residential, commercial and industrial sectors.
The National Australian Built Environment Rating System (NABERS) is a suite of voluntary environmental rating tools to measure the actual environmental impact of Australian buildings. NABERS is an initiative of federal, state and territory governments, managed in NSW by the Department of Environment, Climate Change and Water. NABERS rates commercial offices, hotels and residential buildings on the basis of their measured operational impacts on the environment.
NABERS rates buildings on a scale of 1 to 5 stars. Ratings benchmark a building against the current market performance, with 2.5 stars representing average market performance. A 5-star rating demonstrates best-practice, market-leading performance, while a 1-star rating means the building is performing well below average market practice and has considerable scope for improvement.
The NABERS Indoor Environment rating for offices was launched in May 2008. This measures five parameters: thermal comfort; air quality; acoustic comfort; lighting; and office layout. The rating is based on the results of two sets of measurements: 'physical' measurements and a survey of occupants to measure their satisfaction with the office space. The physical measurements include air quality monitoring for carbon monoxide, carbon dioxide, total VOCs, PM10 and formaldehyde; noise monitoring; light readings; air speed; temperature; and relative humidity in the office space.
Future directions
There is growing awareness of the importance of good indoor air quality, and researchers and governments are still developing their understanding of the pollutants and associated health risks found in indoor environments (in particular the possible long-term health impacts of low levels of chemical mixtures – see Land 5.2). Although a few types of indoor air pollutants are being addressed by policies, programs or laws, policy responses to other indoor air quality problems are less developed. Emissions from unflued gas heating and from surfaces, furnishings and consumer products are in need of attention.
There is also growing interest in the potential to control areas such as:
- building construction materials
- better ventilation and management of indoor air quality at the design stage (such as via new building code rules)
- the construction and installation of domestic appliances and furnishings.
In 2004 the Australian Building Codes Board recommended that future building codes should include sustainability criteria towards these ends (ABCB 2004), but new building code rules have not yet been implemented.
Potential responses are also being examined by the DEWHA Indoor Air Program, which include the development of national guideline values for indoor air pollutants, emissions labelling for products such as particleboard and paint, and information resources for consumers.
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