PURPOSE OF THE STUDY.
To determine the impact of nitrogen dioxide on the respiratory health of children with asthma.
New Zealand subjects (n = 349), ages 6 to 12, with physician-diagnosed asthma and symptoms in the past 12 months, who lived in a home with an unflued gas heater or plug-in electric heater for at least 2 winter periods, were included in this prospective study.
Passive diffusion tubes were used to measure nitrogen dioxide levels over four 4-week periods in the 349 living rooms. The subjects measured their peak expiratory flow rate (PEFR) and forced expiratory volume in 1 second (FEV1) daily via small handheld spirometers. Daily measures of asthma severity (cough and wheeze at night, waking, and during the day; and number of preventer and reliever medication puffs) and upper respiratory symptoms (runny nose, sore throat, hoarse voice) were recorded by symptom diaries.
There was a consistent and significant increase in asthma severity symptoms and upper respiratory tract symptoms when subjects were exposed to increased nitrogen dioxide (1.14, 95% confidence interval [CI] 1.12–1.16). Increased indoor nitrogen dioxide was associated with a decrease in lung function as measured by FEV1 and PEFR (–13.21, 95% CI –26.03 to –0.38; and –17.25, 95% CI –27.63 to –6.88, respectively). Outdoor nitrogen dioxide was not found to be associated with respiratory tract or asthma symptoms, medication use, or lung function measurements.
The results of the study indicate that high levels of indoor nitrogen dioxide (most commonly from unflued gas heaters) are associated with poor pulmonary function and more frequent cough and wheeze in children with asthma.
Children breathe more air per kilogram of body weight than adults, exposing their airways to a higher percentage of gaseous constituents that can potentially negatively impact respiratory disease. This study adds to the growing literature that nitrogen dioxide from unflued gas heaters (that is, gas heaters with exhaust vents that empty into the home) is a significant contributor to worse asthma severity in children. Health care providers should inquire how their patients’ families heat their homes during the winter in their assessments of potential asthma triggers.
- Copyright © 2012 by the American Academy of Pediatrics