The great indoors

Further evidence for the role of indoor pollutants in the development of childhood asthma The prevalence of asthma (especially childhood asthma) is high, and children in particular spend a lot of time in their homes. In addition, our homes contain many pollutants so, understandably, we’d like to know to what extent pollutants in the home environment cause and/or worsen asthma in our children. In many children asthma is closely associated with allergy, and many asthmatic children are allergic to dust mite and pet allergens. For them, reduction of exposure is likely to be beneficial. But does this mean that mite and pet exposure causes asthma? This issue is surprisingly complex. Whereas studies suggest that exposure to specific allergens increases sensitisation to those allergens, this does not necessarily mean that such exposures also increase the incidence of asthma.1,2 Some studies even suggest that early life exposure to pets (and other animals) may reduce the incidence of asthma.3–7 Compared with the already complex role of exposure to allergens and other biological contaminants, the evidence with respect to chemicals such as nitrogen oxides, sulfur oxides, and particles produced by combustion appliances, environmental tobacco smoke, and volatile organic compounds (VOCs) is even less clear. In this issue of Thorax two new studies from Australia attempt to provide further evidence for the role of unvented heating appliances and of VOCs, respectively. Phoa et al 8 retrospectively collected data on unvented heater exposure in a sample of children aged 8–11 …