Like citizens of other highly urbanised societies, most Australians spend more than 90% of their time indoors, leading to concern about the possible impacts of indoor air quality on our health. Such concern is heightened in situations where indoor pollutant concentrations equal or exceed outdoor levels and indoor exposure becomes the dominant form of exposure.150
Symptoms associated with poor indoor air quality can range from acute to chronic, and from mild and generally nonspecific (eye, nose and throat irritation, and headaches and dizziness) to severe (asthma, allergic responses and cancer risk).95,151-152 Despite the potentially significant health effects of indoor air, data on indoor air quality in Australia are limited, providing no firm basis upon which to form assessments of overall status and trend.
Until recently, there has been no comprehensive study of indoor air quality in typical Australian dwellings; previous studies tended to focus on situations with particular air quality issues, such as emissions from unflued gas heaters and gas cooking appliances. The release in 2010 of a two-part report by CSIRO and the Bureau of Meteorology of 40 typical homes in Melbourne has filled that gap, at least for temperate urban areas.153 The study found concentrations of indoor air pollutants to be either lower than or comparable with concentrations found in previous Australian studies. The study showed weekly average concentrations of carbon dioxide, carbon monoxide, nitrogen dioxide, formaldehyde, other carbonyls, BTEX (benzene, toluene, ethylbenzene and xylene) and total VOCs to be higher indoors than outdoors, whereas PM10, ozone and fungi concentrations were higher outdoors. Across the 40 dwellings, the ambient 24-hour NEPM advisory reporting standard for PM2.5 was equalled or exceeded on 3% of days. In dwellings that relied on gas appliances for cooking, levels of carbon dioxide, carbon monoxide, nitrogen dioxide, PM2.5, formaldehyde, benzene and total VOCs were significantly higher than in households that solely used electric cooking appliances. The effect of proximity to major roads on indoor air quality was limited to an increase in nitrogen dioxide levels (accounting for around 20% of indoor nitrogen dioxide in these situations).153 Unfortunately, although the study has significantly expanded our knowledge of indoor air quality in Australian homes, as the authors note in a separately published overview of the study, ‘the absence of specific guidelines for indoor air quality in Australia prevents an objective assessment of the quality of observed indoor air’.154