Household levels of nitrogen dioxide and pediatric asthma severity
Kathleen Belanger1, Theodore R Holford, Janneane F Gent
1Center for Perinatal, Pediatric and Environmental Epidemiology, Yale University School of Public Health, New Haven, CT 06510, USA.
Insights
Indoor nitrogen dioxide (NO2) from gas stoves increases asthma severity in children. Even low levels of NO2 exposure are linked to worse asthma symptoms and increased medication use.
Area of Science:
- Environmental Health
- Pediatric Respiratory Medicine
- Epidemiology
Background:
- Children with asthma experience adverse respiratory effects linked to nitrogen dioxide (NO2) exposure.
- Indoor NO2 levels, often higher than outdoor levels, originate primarily from gas stoves used in many U.S. households.
- This study investigates the impact of indoor NO2 on asthma severity in a diverse child population, controlling for seasonal and allergen factors.
Purpose of the Study:
- To examine the association between indoor nitrogen dioxide (NO2) exposure and asthma severity in children.
- To assess the dose-dependent relationship between NO2 levels and various asthma morbidity indicators.
Main Methods:
- Recruited 1,342 children aged 5-10 with active asthma for a year-long prospective study.
- Measured indoor NO2 exposure using passive Palmes tubes over four month-long periods.
- Assessed asthma morbidity via severity scores, wheeze frequency, night symptoms, and rescue medication use, analyzed with adjusted logistic regression.
Main Results:
- A 5-fold increase in NO2 exposure above 6 ppb correlated with increased asthma severity.
- Significant dose-dependent increases in risk were observed for wheeze (OR=1.49), night symptoms (OR=1.52), and rescue medication use (OR=1.78).
- The association between NO2 exposure and asthma morbidity was evident even at levels below EPA outdoor standards.
Conclusions:
- Asthmatic children exposed to indoor NO2, even at levels below EPA outdoor standards, face increased asthma morbidity.
- These risks are not limited to inner-city children but are prevalent in urban and suburban homes with common NO2 concentrations.
- Indoor NO2 from sources like gas stoves is a significant environmental risk factor for childhood asthma exacerbation.
Background:
Adverse respiratory effects in children with asthma are associated with exposures to nitrogen dioxide (NO2). Levels indoors can be much higher than outdoors. Primary indoor sources of NO2 are gas stoves, which are used for cooking by one-third of U.S. households. We investigated the effects of indoor NO2 exposure on asthma severity among an ethnically and economically diverse sample of children, controlling for season and indoor allergen exposure.
Methods:
Children 5-10 years of age with active asthma (n = 1,342) were recruited through schools in urban and suburban Connecticut and Massachusetts (2006-2009) for a prospective, year-long study with seasonal measurements of NO2 and asthma severity. Exposure to NO2 was measured passively for four, month-long, periods with Palmes tubes. Asthma morbidity was concurrently measured by a severity score and frequency of wheeze, night symptoms, and use of rescue medication. We used adjusted, hierarchical ordered logistic regression models to examine associations between household NO2 exposure and health outcomes.
Results:
Every 5-fold increase in NO2 exposure above a threshold of 6 ppb was associated with a dose-dependent increase in risk of higher asthma severity score (odds ratio = 1.37 [95% confidence interval = 1.01-1.89]), wheeze (1.49 [1.09-2.03]), night symptoms (1.52 [1.16-2.00]), and rescue medication use (1.78 [1.33-2.38]).
Conclusions:
Asthmatic children exposed to NO2 indoors, at levels well below the U.S. Environmental Protection Agency outdoor standard (53 ppb), are at risk for increased asthma morbidity. Risks are not confined to inner city children, but occur at NO2 concentrations common in urban and suburban homes.
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