Acute Controlled Wood Smoke Exposure Induces Sensory Airway Irritation Without Detectable Changes in Small Airway Mechanics in Healthy Adults: A Randomized Crossover Study.
Abstract
Background
Residential wood combustion is a major source of ambient particulate matter in Northern Europe and is associated with adverse respiratory health outcomes. However, the acute effects of short-term wood smoke exposure on small airways remain incompletely characterized.
Objective
To investigate the acute effects of controlled wood smoke exposure on airway function in healthy adults, with specific emphasis on small airway mechanics, spirometry, and respiratory symptoms.
Methods
In a randomized, double-blind crossover-designed study, 14 healthy non-smoking adults (11 men, 3 women; mean age 26 years) underwent 2-hour chamber exposures, under two occasions, to wood smoke (PM1: 453 ± 13 μg/m3) and to filtered air separated by a three-weeks washout period. Lung function was assessed before and after each session using Forced Oscillation Technique (FOT, tremoFlo®) and spirometry. Symptoms were recorded on a modified Borg scale at 30-minute intervals.
Results
Exposure to wood smoke significantly elicited nasal irritation (p = 0.003) and showed trends toward increased cough and unpleasant odor perception. No exposure-specific changes were detected in spirometric parameters or oscillometric resistance parameters (R5, R5-R19, R5-R20). Reactance (X5) and resonant frequency (Fres) showed significant time-dependent changes irrespective to exposure condition (p < 0.001 and p = 0.022, respectively).
Conclusions
Short-term controlled wood smoke exposure induced sensory upper airway irritation without detectable changes in small airway mechanics in healthy adults. Peripheral airway mechanical changes may require higher exposure concentration, longer durations, or susceptible populations. Furthermore, reliance on spirometry may underestimate early health effects, as irritative symptoms precede measurable mechanical dysfunction. TRIAL REGISTRATION ClinicalTrials.gov NCT03302117.