The following was sourced from The Department of Environment and Conservation (NSW, Australia)

Carbon monoxide

Carbon monoxide (CO) is produced from incomplete combustion of fuel. Indoor sources include combustion appliances such as unflued gas or kerosene space heaters, gas cooking appliances and tobacco smoke. Effects will be greatest in buildings with inadequate ventilation. Infiltration of outdoor air contaminated by motor vehicle exhausts can also cause elevated indoor levels of CO close to busy traffic or in car parks.
CO combines with haemoglobin and reduces the ability of blood to transport oxygen. This can affect the functioning of the heart and brain and aggravate angina symptoms, cause headaches, dizziness, and affect concentration. Reduced postnatal development has been reported as a possible consequence of chronic exposure.

The NHMRC guideline for CO in indoor air (9 ppm for an 8-hour average) is the same as that recommended for ambient air. The WHO guideline for a one hour average in ambient air is 25 ppm.

Indoor CO concentrations are expected to generally follow outdoor levels except where combustion sources occur in buildings without adequate ventilation (Brown 1997). In a survey of 52 dwellings in Sydney, Ferrari et al. (1988) found CO concentrations of 1-47 ppm with levels in three dwellings exceeding the NHMRC goal. Steer et al. (1990) found CO generated from cooking appliances exceeded the WHO guideline in a small percentage of kitchens, exceeding 50 ppm in one kitchen where the appliance appeared to be malfunctioning. Exposure of individuals in such environments can be severe with the WHO guideline being exceeded on a daily basis.

Volatile organic compounds

In indoor environments the term volatile organic compounds (VOCs) refers to a range of organic compounds that are emitted from many materials, equipment and products used in buildings. Outdoors VOCs are also emitted by fuel combustion and industrial and commercial activities (see section 1.4.2). Widespread use of modern materials and furnishing products mean that virtually all buildings are subject to VOCs emissions.
Most VOCs at elevated levels can irritate the respiratory tract, eyes and nose. Others, such as benzene, are known or potential carcinogens.

The NHMRC goal for 1-hour average concentrations of total VOCs in indoor air is 500 µg/m3 and for individual VOCs, it is 250 µg/m3. When source materials are used extensively in confined areas such as caravans and mobile homes high levels can result.

Limited measurements in Australian dwellings and offices have shown average concentrations of total VOCs of 100-500 µg/m3, with peak concentrations in offices up to 2,700/µg m3 (Brown 1997).

Nitrogen dioxide

Combustion appliances such as unflued gas or kerosene space heaters and gas cooking appliances are the major indoor source of NO2. Tobacco smoking and infiltration of outdoor air contaminated by NO2 from sources such as motor vehicles can also contribute to indoor levels.

NO2 causes lung irritation, impaired pulmonary function and has been linked to increased susceptibility to infection. It has been suggested that asthma patients are particularly susceptible to the effect of NO2 on lung function.

The NHMRC has not yet introduced an indoor goal for NO2, instead establishing a level of concern of 0.3 ppm. The NHMRC 1-hour ambient goal is 0.16 ppm. The WHO 1-hour goal for both indoor and ambient air is 0.11 ppm.

Indoor hourly average levels of NO2 have been measured to be as high as 1.2 ppm in schools (SPCC 1989), over 0.7 ppm in a hospital (Ferrari et al. 1988) and over 0.8 ppm in dwellings. Figure 1.33 compares indoor and outdoor 1-hour levels of NO2 measured in a number of locations in Australia and New Zealand over the last 10 years. Clearly NO2 levels measured indoors can be significantly higher than those outdoors. Twenty percent of Sydney dwellings using unflued gas space heaters were found to have NO2 levels exceeding the NHMRC level of concern (0.3 ppm), with 58% exceeding the NHMRC ambient goal (0.16 ppm) (McPhail et al. 1988). By comparison, in Adelaide and Perth levels exceeded the level of concern in 4-5% of dwellings (Lyall 1993).

Formaldehyde

The most common sources of formaldehyde are building and furnishing materials including insulating materials, pressed wood products such as chipboard and plywood, and some fabrics and carpets. Emissions from these products are generally greater when new. If not well cured, these products can continue to emit formaldehyde for long periods. Levels of emissions in existing houses can become elevated after renovation. The introduction of new production techniques has substantially reduced emissions by Australian made products, however this may not be the case with some imported materials. Formaldehyde is also emitted by gas stoves and tobacco smoke.

Formaldehyde can cause irritation of the respiratory tract, wheezing and coughing, fatigue, skin rash and severe allergic reactions, and is a suspected carcinogen.

Formaldehyde levels seldom exceed the NHMRC goal of 0.1 ppm in conventional dwellings and other buildings. However, in new dwellings, mobile homes, mobile offices and caravans, where use of source materials is often extensive, levels above the NHMRC goal can occur frequently. In new mobile buildings and caravans the concentrations of formaldehyde can exceed the NHMRC goal for several years. In buildings insulated with urea-formaldehyde foam insulation, (seldom used in Australia) levels of up to ten times the goal have been recorded soon after installation although after several months these generally declined to below the goal (Brown 1991).

Pesticides

Pesticides used to control insects have been associated with a variety of health effects ranging from irritation to carcinogenic effects. Indoor levels of pesticides can be elevated as a result of intrusion of termaticides through foundations, use of consumer products or contamination of house dust (Brown 1997). There is no guideline for indoor pesticide concentrations in Australia.
Data on indoor pesticide levels is scarce, but houses treated with termaticides have had levels of 10-50 µg/m3 of termaticide in the first few months after treatment degrading to less than 2 µg/m3 after several years (Meaklin 1992). New termaticides which decay more rapidly and new application techniques may reduce these levels. However the new termaticides have to be reapplied more frequently and the opportunity for high doses persists.

Environmental tobacco smoke

ETS, a significant indoor pollutant with serious health effects, is composed of a large variety of contaminants including respirable particles, carbon monoxide, nitrogen dioxide, tars, nicotine, formaldehyde, ammonia and hydrogen cyanide.

Health effects linked with ETS include eye, nose and throat irritation, headaches and lung cancer. For children it may lead to increased risk of lower respiratory tract infections (e.g. bronchitis and pneumonia), ear infections, build up of fluid in the middle ear, increased severity and frequency of asthma episodes and decreased lung function (US EPA 1996).

There is no Australian goal for ETS and the WHO advises that there is no safe level. High exposure to ETS can be expected in public buildings where smoking is prevalent, however, effects can be experienced anywhere tobacco is smoked. The most commonly used measure of ETS is respirable suspended particulates (RSP). Measurements of RSP in buildings with smokers have been found to be 150-430 µg/m3 (SoEAC 1996). Poor ventilation will exacerbate the situation although results of ETS measurements in recreational buildings show high levels of ETS pollutants even when ventilation rates satisfied existing guidelines (SoEAC 1996). (For additional information related to ETS see the discussion on particles and polyaromatic hydrocarbons below.)

In Australia the number of smokers is currently declining and the designation of smoke free zones in restaurants, shopping malls and recreation establishments is increasing.

Particles

Sources of particles within buildings include combustion appliances (e.g. cookers, heaters), tobacco smoking, deterioration of building materials particularly carpet, dust mite faeces, human skin and the intrusion of outdoor dust.

The health problems associated with particles depend on particle size. Smaller particles, less than PM10, are of most concern. Recent health studies indicate an association between mortality and elevated particle levels in ambient air (Morgan et al. in prep a), and elevated PM10 levels have also been linked to impaired lung function and respiratory symptoms.

The NHMRC indoor goal for TSP is an annual mean of 90 µg/m3. The US EPA goals for PM10 are 50 µg/m3 for an annual mean and 150 µg/m3 for 24 hours. Most buildings are affected to some extent but the particulate levels are generally most severe in public buildings where smoking is prevalent. In a Sydney study of 18 clubs and 10 hotels where people were smoking, peak particulate levels reached over 1,300 µg/m3 in clubs and almost 1,000 µg/m3 in hotels (figure 1.34). Cooking can result in high particle levels in kitchens particularly when ventilation is inadequate. In a study of seven kitchens in Sydney, the short-term mean TSP level exceeded 400 µg/m3 with levels over 1,370 µg/m3 measured at one premises (Ferrari et al. 1988). A study of RSP levels in Sydney homes (Ferrari et al. 1988) found an average RSP concentration of 86 µg/m3 in homes with wood fires compared to 28 µg/m3 in homes without.
Source: Cummins et al. 1990

Lead

Lead levels in indoor air are generally low, with the main source being flaking of paints with high lead content. These paints were in extensive use prior to 1970 and pose a particular risk during the renovation of older houses. Flakes from deteriorating painted surfaces can be ingested, particularly by young children, and dust generated by sanding operations or from disturbance of dust in roof cavities can be respired. Lead can also be introduced into indoor air by infiltration of air contaminated by lead from motor vehicle emissions and in areas close to some lead-based industries (see Illawarra Case Study).

Exposure to lead is associated with a decrease in IQ levels in preschool children which can result in learning and behavioural difficulties. Elevated blood lead levels are also associated with a range of health problems in adults, including hypertension.

The NHMRC goal for lead in air is a 3-month average of 1.5 µg/m3. There is insufficient data to determine typical lead levels in indoor air in NSW (see also section 2.13).

Polycyclic aromatic hydrocarbons

Polycyclic aromatic hydrocarbons (PAHs) is the collective name for a number of organic compounds some of which are known carcinogens. Sources of PAHs include combustion appliances such as unflued gas space heaters and stoves, poorly vented slow combustion heaters and open fires, and tobacco smoke. Infiltration of contaminated air from busy streets can be a source of indoor air pollution in some situations. There are no NHMRC or WHO goals for PAHs.

Measurements taken in eight clubs and five hotels in Sydney, where people were smoking, found PAH levels of 19-131 µg/m3 in clubs and 22-75 µg/m3 in hotels (Cummings 1991). These levels are significantly higher than levels measured in ambient air in Sydney.

Ozone

Indoor sources of ozone include photocopying machines, laser printers, ionisers and electrostatic precipitators for air cleaning.

Ozone is an irritant and affects the mucous membranes, lung tissue and lung function. At ozone levels above 0.1 ppm sensitive individuals, particularly during exercise, can experience impaired lung function accompanied by respiratory symptoms.

The NHMRC goals for ozone in indoor air are 0.1 ppm for a one hour average and 0.08 ppm for a four hour average, equivalent to the goals for ambient air. While quantitative study has been limited, ozone concentrations in indoor air are generally expected to be lower than ambient levels except in situations where photocopiers are operated in areas with insufficient ventilation.

Asbestos

While asbestos products have been banned in Australia, pre-existing use of these materials can result in asbestos fibre in indoor air. Asbestos building materials were widely used in commercial and industrial buildings in Australia. The main indoor sources are exposed and deteriorating insulation materials and unsealed or fraying building wall and ceiling asbestos cement surfaces. Asbestos fibres, when respired, can cause asbestosis (a lung disease) and mesothelioma (tumours in the lungs, heart or abdomen). There is no indoor health goal for asbestos.

Studies have shown that levels in buildings in Australia are well below levels at which health effects could be expected. Provided existing surfaces are not subject to severe deterioration, indoor levels will remain low. Codes to minimise the risk of exposure to fibres during the removal or renovation of these products in existing buildings are in place.

Fungi

Fungi such as moulds and yeast are common in damp humid conditions within buildings particularly in bathrooms, laundries and air conditioning systems. Modern building construction and design make new houses more airtight and there is a tendency for an increased number of bathrooms and internal laundries. It is increasingly common for houses to be left closed up for long periods of the day. These trends have resulted in the increasing prevalence of the humid conditions suitable for the growth of these organisms.

There has been very little research into the impact of fungi on indoor air quality although it is known that they can cause inflammation and trigger allergic reactions. There is no goal for fungi concentrations in indoor environments.

A study of 40 dwellings in Victoria found 75% had indoor mould growth and a third of those had viable mould concentrations above 2,000 colony forming units (CFU)/m3 (Godish et al. 1993). Around 13% had levels above 10,000 CFU/m3. Other studies found much lower levels with median levels ranging from 500-1,150 CFU/m3 while concentrations in office buildings have been found to reach 2,500 CFU/m3 but mainly range between 200-1,500 CFU/m3 (Brown 1997).

House dust mites

House dust mites live in carpets, bedclothes and furnishings, consuming shed human skin. Mites, or more specifically their faeces, are a major source of the allergens found in house dust.

Dust mites can cause respiratory impairment, especially in those suffering from asthma or hay fever. There is no goal for dust mites, but mean allergen levels above 2 µg/g in fine dust (equivalent to 100 mites per gram) may increase the risk of sensitisation and of symptoms while levels exceeding 10 µg/g (500 mites per gram) increase the risk of acute or severe asthma attacks (SoEAC 1996).

House dust mites are prevalent in Australia, with levels, particularly in warm humid areas such as coastal NSW, believed to be among the highest in the world. Mean allergen levels in the range of 10-40 µg/g are commonly found in dwellings in coastal areas of Australia (Tovey 1992). The high incidence of asthma in Australia, with approximately 5% of adults and 15% of children suffering from the condition, make the incidence of house dust mites an important environmental concern.

Radon

Radon, an inert radioactive gas, is emitted from soil and rocks and from rock-based building materials. Underground buildings and dwellings or those constructed with affected material or in areas where emissions from the soil are high can experience elevated levels. Radon gives off alpha particles, a very damaging form of radiation which is a known carcinogen and can cause lung cancer at elevated concentrations. The recommended NHMRC goal is an annual mean of 200 becquerels/m3.

A nationwide survey of 3,413 home conducted by the Australian Radiation Laboratory found an annual average radon concentration of 12 becquerels/m3 (Langroo et al. 1990). Three of the homes exceeded the NHMRC goal and the survey estimated that nationwide 2,000-3,000 homes may exceed the goal (SoEAC 1996).

Bacteria

Bacteria also occur in damp humid conditions. Outbreaks of the Legionella bacteria, for example, have most commonly been associated with contaminated drift from air-conditioning cooling towers entering the building via the air conditioning system. Legionella has also been associated with spa pools, composted animal manures, composted vegetable and plant material and commercial potting mixes. The bacteria are commonly found in low numbers in soil and water, but can multiply rapidly in warm, moist environments (SoEAC 1996). Infection with the Legionella bacteria can result in a pneumonia-like lung infection and impaired kidney function. The fatality rate from Legionella is approximately 15%. Between 1991 and 1994 there were 251 notifications of legionnaire's disease in NSW, an incidence rate of 4.2 per 100,000 people (SoEAC 1996).

Although there are no goals for bacteria concentrations in indoor environments, some controls do exist. Australian Standards (AS3666-1989 and ASNZ3666-1995) which address the maintenance of air conditioning systems have been developed in an effort to control the incidence of Legionella. State legislation such as the NSW Public Health Act (No.10, 1991, Part 4-Microbial control) and associated regulation (Part 6, Microbial control) also address this issue.

Sick building syndrome

Sick building syndrome refers to a number of symptoms among occupants which are believed to be building related. The effects associated with sick building syndrome are often non-specific, making assessment difficult, but include allergy sensitivity, irritated eyes, nose or throat, tiredness, headaches and poor concentration. These symptoms are generally thought to occur as a result of indoor emission of VOCs and poor building ventilation.

The type of environments where sick building syndrome is diagnosed include generally poorly maintained air conditioning, new commercial or office buildings fitted with modern materials, or older domestic buildings with damp conditions and mould growth. Temperatures above 21°C, poor lighting, flicker from fluorescent tubes and the absence of windows may also contribute to the problem (SoEAC 1996).

Assessment of building-related illnesses in Australia has been very limited but research so far suggests a dissatisfaction with office air environments (SoEAC 1996).