Randomised controlled trial investigating the effects of nitrogen dioxide in classrooms on the respiratory health of asthmatic primary school children.

Abstract

A study to determine the effects of a randomised controlled trial of unflued gas heater replacement on asthma in children. 18 schools using unflued gas heaters in winter were randomly allocated an intervention of heater replacement with either flued gas heaters, or electric, or remained unflued. The main eligibility criteria were doctor-diagnosed asthma with no unflued gas sources at home (a priori sample). The sample was extended to asthmatic children with home gas cooking. Participants kept a daily diary of symptoms for 12 weeks in order to establish symptom rates in the intervention and control groups. Indoor NO₂ was monitored in classrooms and homes during the study period. In the a priori sample, difficulty breathing, chest tightness and asthma attack rates were significantly decreased in the intervention group compared to the control group. In the extended group, symptom rates were not significantly different. Reduced NO₂ levels in classrooms were accompanied by more than a 50% reduction in some asthmatic symptoms in the intervention a priori group.