Respiratory tract deposition of inhaled wood smoke particle in healthy volunteers and patients with chronic obstructive pulmonary disease

Respiratory deposition of air pollution particles in the lungs is important as these particles are strongly linked with adverse health effects. This study was aimed to determine the size-resolved deposition fraction (DF) of sooty wood smoke particles in the lungs of healthy subjects and patients with chronic obstructive pulmonary disease (COPD). Methods 12 healthy and 6 COPD subjects inhaled diluted wood smoke from incomplete soot-rich combustion in a common wood stove. The DF of smoke particles (10-500 nm) was measured during three 15-min exposures in each subject during spontaneous breathing using Respiratory Particle Deposition Instrument (RESPI) technique. Lung function was measured using standard spirometry. Results DF in healthy subjects and COPD patients in the particle size range of 10-500nm was 32% and 35% respectively. This can be compared with DF of 21-23% during previous wood pellet combustion experiments. DF in COPD was particularly high for particles sized 50-300 nm where the majority of the particle mass was present. DF and breathing frequency were negatively correlated (R2=-0.72, p=0.001). Conclusions The DF of the investigated sooty wood smoke particles was higher than the previously investigated particles generated by other wood smoke combustion processes. Together with toxicological studies, which have indicated that incomplete biomass combustion particles rich in soot and poly-aromatic hydrocarbon (PAHs), are especially harmful, these data highlight the health risks of inadequate wood combustion. The high deposition rate in COPD, may contribute to increased morbidity for this group.

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