Abstract :
Background: In low- and middle-income countries, burning biomass indoors for cooking or heating has been associated with poorer lung function. In high-income countries, wood, a form of biomass, is commonly used for heating in rural areas with increasing prevalence. However, in these settings the potential impact of chronic indoor woodsmoke exposure on pulmonary function is little studied. Objective: We evaluated the association of residential wood burning with pulmonary function in case-control study of asthma nested within a U.S. rural cohort. Methods: Using sample weighted multivariable linear regression, we estimated associations between some and frequent wood burning, both relative to no exposure, in relation to forced expiratory volume in 1 s (FE[V.sub.1]), forced vital capacity (FVC), their ratio (FE[V.sub.1]/FVC), and fractional exhaled nitric oxide (FeNO). We examined effect modification by smoking or asthma status. Results: Among all participants and within smoking groups, wood burning was not appreciably related to pulmonary function. However, in individuals with asthma (n = 1,083), frequent wood burning was significantly associated with lower FE[V.sub.1] [[beta]: -164 mL; 95% confidence interval (CI): -261, -66 mL], FVC ([beta]: -125 mL; 95% CI: -230, -20 mL), and FE[V.sub.1]/FVC ([beta]: -2%; 95% CI: -4, -0.4%), whereas no appreciable association was seen in individuals without asthma (n = 1,732). These differences in association by asthma were statistically significant for FE[V.sub.1] ([p.sub.interaction] = 0.0044) and FE[V.sub.1]/FVC ([p.sub.interaction] = 0.049). Frequent wood burning was also associated with higher FeNO levels in all individuals (n = 2,598; b: 0.1 ln(ppb); 95% CI: 0.02, 0.2), but associations did not differ by asthma or smoking status. Discussion: Frequent exposure to residential wood burning was associated with a measure of airway inflammation (FeNO) among all individuals and with lower pulmonary function among individuals with asthma. This group may wish to reduce wood burning or consider using air filtration devices. https://doi.org/10.1289/EHP10734