Indoor room nitric oxide and alveolar nitric oxide in the Southern California children's health study

Abstract

Introduction: Exhaled nitric oxide (FeNO) is a marker of airway inflammation that has been found to be responsive to air pollution exposure. NO is also present in outdoor and indoor air from combustion sources (e.g. traffic and cooking). ATS/ERS guidelines for single flow rate FeNO recommend inhalation of NO-scrubbed air to avoid artifacts. Sampling FeNO at multiple flows permits estimation of alveolar NO, potentially informing on localized effects of air pollution exposure. Aims: Estimate the effects of indoor room NO on alveolar NO in children. Methods: From March-June 2010, FeNO was collected at 4 flow rates (30, 50, 100, and 300 ml/s) in 1577 children, ages 12-15 from schools in 8 southern California communities, using Ecomedics CLD88-SP analyzers with DeNOx accessories for NO-free inhaled air. Alveolar NO was estimated using nonlinear mixed effects models and indoor room NO was sampled hourly. Linear regression was used to relate indoor NO to estimated alveolar NO, adjusting for potential confounders. Results: Indoor NO ranged from 0-58.5 ppb (median: 1.9 pbb). A 10 ppb increase in indoor NO was associated with a mean increase in alveolar NO of 0.12 ppb (95% CI: 0.07, 0.17), without adjustment for covariates. Similar effect estimates were observed in adjusted models that included (0.09, 95% CI: 0.04, 0.15) or excluded (0.11, 95% CI: 0.02, 0.20) the 2 testing dates with indoor NO > 28.1 ppb. Conclusions: We found small but robust associations of indoor NO with alveolar NO in children breathing NO-scrubbed air, suggesting a response of distal airway inflammation to combustion (e.g. traffic-related air pollution) or an artifact from prolonged exposure to elevated ambient NO.