The free-standing gas heater, a familiar sight to generations of schoolchildren, may not be as benign as it appears, according to a major Australian study.
The study has found a reduction in asthma attacks and chest tightness in asthmatic children associated with the removal of unflued gas heater exposure from school classrooms.
The study, published this week in the International Journal of Epidemiology, said the reduction was associated with lower levels of nitrogen dioxide in the classrooms without unflued gas heaters. Nitrogen dioxide, which is produced as the gas burns, is a known irritant to the air passages.
The study showed that unflued gas heaters released nitrogen dioxide directly into the rooms they occupied, reaching levels over three times as high as those in classrooms that had electric or flued gas heaters. Such levels were associated with higher rates of asthma attacks.
The study's Chief Investigator is Professor Louis Pilotto, Head of the Department of General Practice and Director of the Flinders Centre for Epidemiology and Biostatistics at Flinders.
Professor Pilotto received funding from the National Health and Medical Research Council to conduct the study while he was based at the Clinical Epidemiology and Health Outcomes Unit at the Queen Elizabeth Hospital.
Professor Pilotto said that while previous research has shown a link between unflued gas exposure and asthma, the results of this study were more conclusive as they were based on a randomised control trial of unflued gas heater replacement. This type of study eliminates many of the biases believed to complicate the results of previous studies. Dr Monika Nitschke was responsible for implementing the study as part of the successful completion of her doctoral thesis at the University of Adelaide.
Professor Jonathan Samet and Michelle Bell from Johns Hopkins Bloomberg School of Public Health in the USA, in a commentary on nitrogen dioxide and asthma in the same issue of the Journal, say that the study complements previous research evidence, and used a method that avoided some potential limitations of previous studies.
They suggest that this study, along with other previous research done in Australia by Professor Pilotto and by Associate Professor Brian Smith from the Queen Elizabeth Hospital, "provide consistent evidence for an adverse effect on asthma", and suggest that this recent study "provides a rationale for moving forward with replacing unflued heaters in classrooms."