Particulate matter (PM) exposure has been linked epidemiologically to exacerbations of lung disease, including respiratory infections. We investigated the effects of geogenic (earth-derived) PM₁₀ (PM < 10 μm diameter) on the response to a respiratory viral infection.

Geogenic dust was sampled from four communities in arid environments in Western Australia. Adult female BALB/c mice were intranasally exposed to chronic doses of PM₁₀ (10 μg/day for 10 days), and/or infected with influenza (A/Mem/1/71) virus. Inflammation (cells, IL-6, IFN-γ) was measured in bronchoalveolar lavage. Lung mechanics were measured using the forced oscillation technique.

Geogenic PM₁₀ induced lung inflammation (neutrophils, macrophages) with additive effects in mice also infected with influenza. PM₁₀ also modified the influenza-induced IL-6 and IFN-γ responses. Geogenic PM₁₀ increased airway resistance, and increased hysteresivity in those exposed to both insults. Viral titres were significantly higher after PM₁₀ exposure. Iron concentration was inversely associated with IFN-γ and positively associated with viral titre and hysteresivity.

Geogenic PM₁₀ exposure increases inflammation, impairs lung function and increases viral load, exacerbating the response to respiratory viral infection. Iron in the particles may be a driver of these responses. This has important implications for respiratory health in communities exposed to high geogenic PM₁₀, such as those in arid environments.