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Asthma Health Outcomes Project

Overviews of Surveyed Asthma ProgramsSeptember 2005

International Programs: Australia (cont’d)Back to Index

Randomized controlled trial of unflued gas heater replacement on respiratory health of asthmatic schoolchildren

Flinders University of South Australia

Wagga Wagga, NSW 2650 Australia

Louis S. Pilotto, MBBS, PhD

61 2 69335111      


Previous studies do not provide a clear picture of the relationship between nitrogen dioxide (NO2) exposure and asthma; therefore, a randomized controlled trial of unflued gas heater replacement on respiratory health of school children with asthma was conducted in Adelaide, Australia.

Eighteen schools using unflued gas heating in winter were randomly allocated to either retain their heaters (10 control flued gas or electric heaters installed at the beginning of winter (8 intervention schools). Fortnightly telephone interviews were used to record daily individual asthma symptoms that occurred over 12 weeks (including winter). Lung function and histamine challenge tests were performed at baseline and the end of the study. NO2 was measured in each school classroom on nine days and in each household on three days spread over the study period.

From 199 primary school children that met the eligibility criteria, 45 intervention and 73 control children agreed to participate. Baseline characteristics were similar between groups. Difficulty breathing during the day (Relative Risk [RR] = 0.41; 95% CI: 0.07, 0.98) and night (RR = 0.32; 95% CI: 0.14, 0.69), chest tightness during the day (RR = 0.45; 95% CI: 0.25, 0.81), and daytime asthma attacks (RR = 0.39; 95% CI: 0.17, 0.93) were significantly reduced in the intervention group. Percentage predicted forced expiratory volume in one second (FEV1), the concentration of histamine inducing a 20% fall in FEV1 (PD20), and the dose–response slope (DRS) were similar between groups at follow-up. Mean (standard deviation) NO2 levels were 15.5 (6.6) parts per billion (ppb) and 47.0 (26.8) ppb in the intervention and control schools respectively (P < 0.001).

Asthma symptoms were reduced following a replacement intervention that removed high exposure to NO2. Such replacement should be considered a public health priority for schools using unflued gas heating during winter.

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