Nitrogen dioxide exposure in school classrooms of inner-city children with asthma.

Background: Ambient and home exposure to nitrogen dioxide (NO ₂ ) causes asthma symptoms and decreased lung function in children with asthma. Little is known about the health effects of school classroom pollution exposure.
Objective: We aimed to determine the effect of indoor classroom NO ₂ on lung function and symptoms in inner-city school children with asthma.
Methods: Children enrolled in the School Inner-City Asthma Study were followed for 1 academic year. Subjects performed spirometry and had fraction of exhaled nitric oxide values measured twice during the school year at school. Classroom NO ₂ was collected by means of passive sampling for 1-week periods twice per year, coinciding with lung function testing. Generalized estimating equation models assessed lung function and symptom relationships with the temporally nearest classroom NO ₂ level.
Results: The mean NO ₂ value was 11.1 ppb (range, 4.3-29.7 ppb). In total, exposure data were available for 296 subjects, 188 of whom had complete spirometric data. At greater than a threshold of 8 ppb of NO ₂ and after adjusting for race and season (spirometry standardized by age, height, and sex), NO ₂ levels were associated highly with airflow obstruction, such that each 10-ppb increase in NO ₂ level was associated with a 5% decrease in FEV ₁ /forced vital capacity ratio (β = -0.05; 95% CI, -0.08 to -0.02; P = .01). Percent predicted forced expiratory flow between the 25th and 75th percentile of forced vital capacity was also inversely associated with higher NO ₂ exposure (β = -22.8; 95% CI, -36.0 to -9.7; P = .01). There was no significant association of NO ₂ levels with percent predicted FEV ₁ , fraction of exhaled nitric oxide, or asthma symptoms. Additionally, there was no effect modification of atopy on lung function or symptom outcomes.
Conclusion: In children with asthma, indoor classroom NO ₂ levels can be associated with increased airflow obstruction.
(Copyright © 2017 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.)