Dynamics of airway macrophage responses and lung function changes after ozone exposure in humans.

In 30 seconds

This randomized, single-blind crossover exposure study examined airway myeloid-cell responses and lung function after ozone in 44 healthy adults aged 18–40 years. Participants underwent paired 3-h exposures to ozone (0.2 ppm) and filtered air, with assessments through 72 h. Ozone caused immediate reductions in FEV1, FVC, and FEV1/FVC and increased distal airway resistance; these impairments were not evident at 24–72 h. Lung-function improvement over that period was associated with higher airway monocyte-derived macrophage ratios relative to neutrophils and monocytes, suggesting these cell dynamics may contribute to recovery.

Key findings

• Compared with filtered air, ozone increased airway monocyte percentages at 24 h and monocyte-derived macrophage percentages at 24–72 h.
• Immediately after ozone exposure, FEV1, FVC, and FEV1/FVC decreased, while distal airway resistance measures R5 and R10 increased.
• The immediate functional impairments were not evident at 24–72 h after exposure.
• Improvement in large-airway function correlated with a higher monocyte-derived macrophage-to-neutrophil ratio; R5 improvement was associated with a higher macrophage-to-monocyte ratio.

Why it matters

The study links the time course of airway immune-cell changes with recovery of lung function after controlled ozone exposure in humans. It adds human evidence to the proposed role of macrophage dynamics in resolving pollutant-related lung injury, while showing that functional changes and airway-cell composition vary across the first 72 h.

What to keep in mind

The study involved healthy adults aged 18–40 years exposed under controlled conditions, so the findings may not represent people with pulmonary disease or responses to ambient exposure.