This analysis was undertaken to assess if wood burning exposure was related to pulmonary function; the paper has been published in Environmental Health Perspectives. You can scroll through the executed code at https://juliedwhite.github.io/Woodsmoke_PFTs/

White, J.D., Wyss, A.B., Hoang, T.T., Lee, M.K., Richards, M., Parks, C.G., Beane-Freeman, L.E., Hankinson, J.L., Umbach, D.M., London, S.J. (2022). Residential wood burning and pulmonary function in the Agricultural Lung Health Study. Environmental Health Perspectives. 130(8). https://doi.org/10.1289/EHP10734.

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 a case-control study of asthma nested within a US 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 one second (FEV₁), forced vital capacity (FVC), their ratio (FEV₁/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 asthmatic individuals (n = 1,083), frequent wood burning was significantly associated with lower FEV₁ (β: -164 ml; 95% CI: -261, -66 ml), FVC (β: -125 ml; 95% CI: -230, -20 ml), and FEV₁/FVC (β: -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 FEV₁ and FEV₁/FVC (P_interaction FEV₁ = 0.0044; _interaction FEV₁/FVC = 0.049). Frequent wood burning was also associated with higher FeNO levels in all individuals (n = 2,598; β: 0.1 ln(ppb); 95% CI: 0.02, 0.2 ln(ppb)), 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 asthmatic individuals. This group may wish to reduce wood burning or consider using air filtration devices.