What Are Some Indoor Air Quality Indicators
|
The following piece was published by the State of The Environment Tasmania and is a good insight into Potential Indoor Air Quality Indicators Proportion of Population Sensitive to Pollutants Reporting on the proportion of the population sensitive to indoor air pollutants would help to provide information on the health effects in those susceptible to allergens often found in indoor air. Allergens can include, dust mites, plants, animal dander, environmental tobacco smoke, volatile organic compounds (VOCs), pesticides and moulds (Maroni et. al. 1995). This issue is particularly significant for Tasmanian buildings because of the range of other issues associated with this indicator e.g. economic implications, changes to workplace environments, occupational health and safety in non-industrial workplaces, and building construction techniques.
There have only been a few studies into the proportion of the Australian population sensitive to indoor air pollutants. These, together with overseas studies, suggest that as much as a third of the population may be sensitive to air pollutants, based on all respiratory illnesses. Tasmania has very little information on the prevalence of respiratory conditions. The only published study that is available was undertaken in 1995, where a survey of seven year olds indicated that a significant proportion of children suffer from asthma (27%).
Parent-reported prevalence of asthma, hayfever and bronchitis, in seven year olds Caption: There were 6,349 parents with seven year olds who responded, from an estimated resident population with seven year olds of 7,117 (30 June 1995).
Source: Menzies Centre for Population Research, 1995, in ABS 2000 Another Tasmanian study examined 265 office workers in Hobart to determine whether volatile organic compound concentrations had an association with sick building syndrome symptoms (Mesaros 1999). Part of the study examined if sensitivity to indoor pollutants was correlated with a predisposition to allergenic disease. Results showed that a history of asthma and allergies did appear to influence symptom levels. Quantity of Asbestos Products Removed from Work Places An assessment of the quantity of asbestos products removed from work places would be useful as an unknown number of buildings still contain asbestos fibres. Asbestos fibres were used widely in building products in Australia up to the early 1980s. Asbestos is a generic term that applies to a group of impure hydrated silicate minerals that occur in various fibrous forms, which are incombustible and separable into filaments. Sources of asbestos are varied, but they mainly originate from mining and milling, manufacture of products, construction activities and disposal. In many industrialised countries most of the asbestos used was in the building sector (approximately 70-90%) (OECD 1984). The most serious effects from asbestos exposure are lung cancer and mesothelioma. While the relationship of occupational exposure to asbestos with these cancers has been established, the occurrence of asbestosis (slow developing fibrosis of the lung) has been documented more extensively than that of asbestos related malignancies. In workplaces, building maintenance personnel are at the greatest risk of exposure to these fibres. Standards are available for asbestos (0.1 f/mL for amosite/crocidolite, and 1 f/mL for chrysotile), but they are for industrial environments (NOHSC:1003 1995). Unfortunately residential buildings remain without standards. There is no specific Tasmanian information currently available on asbestos in non-industrial workplaces. It appears from the few studies undertaken in Australia, that asbestos levels are at similar concentrations to those found in other countries (Altree-Williams et al. 1985). Sprayed asbestos insulation has been extensively used in commercial buildings in Australia, and acts as a major source of asbestos fibre exposure. This exposure is greatly increased with building maintenance activities such as renovations. Therefore, it is critical that any asbestos removal be undertaken using relevant safety procedures. A quantitative assessment of non-industrial workplaces needs to be undertaken to determine the extent of asbestos product use. The assessment could also include a survey examining compliance with relevant asbestos standards and codes. This would provide a basis on which to develop and implement any ameliorative and preventative strategies. Number of Unflued Gas Heaters in Residences and Schools An indication of the number of unflued gas heaters in residences and schools would be important as unflued gas heaters have been shown to significantly contribute to indoor air pollution, by emitting harmful gases into the indoor air. Of the combustion products, nitrogen dioxide (NO2) has been the most widely investigated, and concentrations exceeding recommended standards occur relatively frequently in the domestic home (Spengler et al. 1983). NO2 is a deep lung irritant, which has been shown to generate biochemical alterations. Because NO2 mainly affects pulmonary function, asthmatics are at particular risk from exposures. Other epidemiological studies (WHO 1987) suggest that children who are exposed to combustion contaminants from gas stoves and heaters have higher rates of respiratory symptoms and illness than other children. Standards for nitrogen dioxide concentrations have been under review in Australia for many years. Standards exist for industrial indoor environments (NOHSC:1003 1995) but not for residences and schools. The National Health and Medical Research Council recommends a tentative goal concentration of 200-480 µg/m3 (one hour) for indoor air, but until that figure is agreed upon and implemented, other international standards are used (e.g. World Health Organisation goal of 400 µg/m3 (one hour)). There has been no apparent systematic evaluation of the number of unflued gas heaters in residences and schools in Tasmania or in the rest of Australia. Limited measurements indicate that a large proportion of homes and schools in Australia do have unflued gas heating. The pending installation of reticulated domestic natural gas in Tasmania may increase the use of unflued gas heaters in Tasmania. Those with a pre-existing respiratory condition are particularly affected. A study into unflued gas heaters would contribute some much needed information on the true indoor air quality status of Tasmanian residential buildings. If this is undertaken, it can provide a basis on which to develop and implement any ameliorative and preventative strategies. Proportion of Residences with High House Dust Mite Allergen Assessing the proportion of residences with high house dust mite allergen would help to indicate the severity of this indoor air quality problem in Tasmania. While there is no data available for Tasmanian dwellings, Australian housing has been found to exhibit one of the highest house dust mite allergen levels in the world. Research in Australia and overseas has shown that exposure to the dust mite allergen can cause a variety of symptoms (i.e. inflammatory reactions, hay fever, and eczema), and has been implicated as the major cause of childhood asthma and bronchial hyperactivity. The reported prevalence of dust mite sensitivity among asthmatics varies from 45-85% (Platts-Mills and de Weck 1988), therefore any exposure can pose as a severe risk for asthma. This indicator is particularly significant to Tasmania because of the high incidence of respiratory disease (e.g. asthma) amongst the population (especially children). Individuals in this sector of the population may have a predisposition to react to dust mite allergens. There are no Australian guidelines for house dust mite concentrations, therefore international goals are used. The World Health Organisation recommends that allergen levels accumulated in carpet and bedding should be below 2 µg of D. pteronyssinus specific allergen per gram of fine dust to prevent risk of sensitisation, and below 10 µg/g to prevent risk of severe asthma attack. Australian coastal areas generally provide good conditions for the growth of house dust mites. High humidity is particularly important for the survival of mites. There are many regions of Australia that have ideal conditions for dust mites for most of the year, therefore it is common for dwellings to have mean allergen levels of 10-40 µg/g (Tovey 1992). On the other hand, regions with only one season suitable for dust mite growth have a dust mite allergen level of between 2-15 µg/g. Cold and dry climates generally have less than 2 µg/g. Incidence of Legionnaires Disease The incidence of the airborne bacteria Legionella pneumophila is of particular importance in relation to indoor air quality because of the health effects associated with exposure to this pathogen. Legionella spp. are ubiquitous bacteria found in soil and natural water, and the commonly used methods of water treatment do not eliminate them. Although the bacteria usually only occurs in small numbers, amplification has been shown to take place in many locations in buildings such as cooling towers (especially those poorly maintained), domestic water supplies, domestic water heaters, and in some indoor equipment such as humidifiers and heating, ventilation and air conditioning systems. Epidemiological studies have shown that the Legionella bacteria cause two types of disease, known as Legionnaires disease and pontiac fever. The occurrence of Legionnaires disease has been well documented in Australia, and methods of control in the form of codes and regulations are in place. Legionella is controlled at the source in water cooling towers by accepted standards and guidelines such as AS 3666 (1989), SAA HB23 (1992), NHMRC (1988) and NOHSC (1989). The Building Code of Australia now requires control of such sources but its enforcement for new buildings and impact on past buildings is unknown. Legionella is also a notifiable disease, therefore any outbreaks must be documented by relevant government departments. Tasmania has, overall, a very low incidence of Legionellosis. According to the Department of Health and Human Services, Tasmanian Legionellosis cases have not known to be associated with Tasmanian cooling towers since the 1989 Burnie outbreak (M. Bicevskis, pers. comm.). Reported cases were either contracted interstate or associated with other sources such as potting mix.
Notification of Legionellosis received by State and Territory health authorities in the period 1991-01 (month of March)
Source: Communicable diseases network - Australia and New Zealand notifiable diseases surveillance system Exposure to Volatile Organic Compounds (VOCs) and Formaldehyde Reporting on the exposure to volatile organic compounds (VOCs) and formaldehyde within indoor environments would help to provide information on their potential health effects. Volatile organic compounds (VOCs) and formaldehyde have been identified as significant environmental pollutants, and of particular concern are their carcinogenic properties associated with long- and short-term exposure (Fisk 1995). VOCs are ubiquitous in the indoor environment and their sources are numerous ranging from pollutants released by building materials, cleaning products, tobacco smoke, human and biological agents. In 1989 the US Environment Protection Agency identified 900 organic compounds in the indoor environment.
Compounds most frequently observed in 83 offices and their concentration distribution Caption: This study examined 83 European offices. The figures are expected to be higher in new buildings or those that have been recently renovated
Source: De Bortoli et. al. 1990 The health effects from VOC exposure is varied and can range from acute to chronic effects. In general, the health effects arising from low-level or intermittent exposures are still unclear. Many of the VOCs present are potent narcotics and result in depression of the central nervous system. VOCs can also result in irritation of the eyes, skin, and the respiratory tract. At higher concentrations many of these chemicals have been shown to result in liver and kidney damage. Mobile homes are significant sources of indoor pollution because of the materials used in their construction and low ventilation rates. Mobile homes have a high content of pressed wood-products (e.g. particle board, MDF, and plywood), which use urea formaldehyde resins in large quantities as glues. Emissions from these products result from the outgassing or release of chemicals, namely formaldehyde. Indoor concentrations are influenced by temperature, humidity, environmental tobacco smoke, product usage, and the presence of combustion sources. Also of concern is the use of urea formaldehyde foam insulation as a wall and ceiling cavity insulation (Brown 1991). Many Australian buildings, and mobile homes have such insulation, particularly those that were constructed in the 1980s. The symptoms displayed from formaldehyde exposure are varied. Short-term exposures from formaldehyde include irritation of the eyes, nose and throat, coughing, and nausea. Irritation of the skin is also common following exposure to formaldehyde vapour. More long-term health effects are well documented and include sensitisation, neuropsychological symptoms, chronic lung disease, mutagenic and carcinogenic effects. As with many other indoor air pollutants, certain population groups are at greater risk to formaldehyde gases than others. For example, children exposed to formaldehyde fumes are more prone to respiratory tract infections. In Australia, the National Health and Medical Research Council has recommended a goal concentration of 130 µg/m3 (ceiling) of formaldehyde in residences and schools. To regulate VOCs in the indoor environment European researchers coined the total volatile organic compound (TVOC) concept (Molhave and Nielsen 1992). The TVOC is seen as an indicator for sensory irritation or 'provisional guideline' for acceptable ranges. Australia has accepted this concept and the National Health and Medical Research Council has recommended an indoor air level of 500 µg/m3 for one hour.
Recommended emission limits for low-emitting materials and products for commercial buildings
Source: Tucker 1990
VOC concentrations in some Australian buildings
Source: Mesaros 1995 New building construction is a common activity in Australia, and the number of new buildings constructed is considered an environmental indicator for occupant exposure to VOCs and formaldehyde (Australian State of Environment Committee 2001). Most new buildings constructed are residential buildings where occupants will be located for large periods of time. Therefore, individuals living in these 'new' indoor environments are exposing themselves to VOCs and formaldehydes for extended periods of time.
Number of new buildings in Australia ('000)
Source: ABS 1998 Past studies in Australia have indicated that formaldehyde concentrations in mobile buildings range in concentrations of between 20-1,200 ppb (see table below). Studies in the US and Canada have shown that mobile homes have typical average concentrations of between 160-400 ppb (Marbury and Kreiger 1991). Formaldehyde concentrations in Australian mobile homes far exceed US and Canadian concentrations, and exceed the NHMRC goal of 130 µg/m3.
Formaldehyde concentrations in Australian buildings
Source: Dingle and Olden 1992, McPhail 1991 Formaldehyde concentrations are known for some building types, though mobile homes and caravans are less well known, even though they typically have some of the highest concentrations. The 1996 Census showed Tasmania had 1,467 people living in mobile homes, caravans and houseboats. Because there has been no systematic investigation of mobile buildings in Tasmania, typical formaldehyde concentrations in these environments remain unknown. Long periods of time are also spent in the workplace, where exposure to VOCs can be significant. For example, a study examining 11 office buildings in Hobart (Mesaros 1999), found that weekly TVOC levels ranged from 25-1,934 µg/m3. The mean TVOC concentrations (over seven sampling days) exceeded the NHMRC one hour goal of 500 µg/m3 on fourteen occasions (over a ten week period). Although what is not known is whether these TVOC values were steady during the seven day sampling period or whether they peaked at some time during the week and maintained a low value for the remainder. Results also revealed that building occupants had 20% more irritative symptoms of the eyes, nose and throat when TVOC concentrations reached a range of 200-3,000 µg/m3. When compared to other Australian studies, Tasmanian offices clearly have exceedingly high VOC concentrations. The precise reasons for this are unknown, but it appears to be associated with a combination of factors (e.g. temperature, physical pollutants and types of cleaning fluids used). Proportion of Insulated Houses An assessment of the proportion of houses that have insulation, and what type of product is used, would help to provide information on the effects of the insulation upon indoor air quality. A quantitative investigation shortly after installation of insulation, would be useful to determine if TVOC and formaldehyde concentrations exceed relevant standards. An examination of climatic variations between states would also be valuable in determining if houses in colder climates have increased pollutant concentrations due to buildings being heated for longer periods of time. In addition to this, an assessment comparing insulated and non-insulated buildings and their levels of air pollution, would provide some useful information. Exposure to Indoor Air within Vehicles Reporting on the exposure to indoor air within vehicles (time spent in city traffic) would provide information on the degree of exposure to vehicle exhausts. The time spent in transit, 70 minutes per day on average, is of particular concern from the perspective of exposure to vehicle exhausts. The compounds carbon monoxide, respirable particulates, 1,3 - butadiene and benzene, are most significant in these indoor environments, especially when the traffic moves slowly (e.g. city traffic). The health effects from these compounds are well documented and range from effects on the heart, lungs and nervous system, to carcinogenic effects. As with many other indoor pollutants, individuals with a predisposing condition (e.g. asthma and respiratory disease) are most affected. There are no acceptable levels or standards for indoor air quality in vehicles, but given the findings of some studies, it is clear that there needs to be some form of regulatory control. For example, studies have found that benzene concentrations within vehicles in urban traffic are 20-150 µg/m3, which are much higher than the outdoor benzene exposure level recommended by the United Kingdom Health and Safety of 3 µg/m3 as an annual average (Australian State of Environment Committee 2001). It is believed that a significant proportion of daily exposure to these pollutants can occur in this environment, but the lack of research into this indicator makes any evaluation difficult. |
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
