The concentration of iron in real-world geogenic PM₁₀ is associated with increased inflammation and deficits in lung function in mice.

BACKGROUND: There are many communities around the world that are exposed to high levels of particulate matter <10 µm (PM₁₀) of geogenic (earth derived) origin. Mineral dusts in the occupational setting are associated with poor lung health, however very little is known about the impact of heterogeneous community derived particles. We have preliminary evidence to suggest that the concentration of iron (Fe) may be associated with the lung inflammatory response to geogenic PM₁₀. We aimed to determine which physico-chemical characteristics of community sampled geogenic PM₁₀ are associated with adverse lung responses. METHODS: We collected geogenic PM₁₀ from four towns in the arid regions of Western Australia. Adult female BALB/c mice were exposed to 100 µg of particles and assessed for inflammatory and lung function responses 6 hours, 24 hours and 7 days post-exposure. We assessed the physico-chemical characteristics of the particles and correlated these with lung outcomes in the mice using principal components analysis and multivariate linear regression. RESULTS: Geogenic particles induced an acute inflammatory response that peaked 6 hours post-exposure and a deficit in lung mechanics 7 days post-exposure. This deficit in lung mechanics was positively associated with the concentration of Fe and particle size variability and inversely associated with the concentration of Si. CONCLUSIONS: The lung response to geogenic PM₁₀ is complex and highly dependent on the physico-chemical characteristics of the particles. In particular, the concentration of Fe in the particles may be a key indicator of the potential population health consequences for inhaling geogenic PM₁₀

Deficits in lung function in response to inflammation were associated with corresponding decreases in inflammatory markers below baseline levels.

<p>Scatter plot showing the correlation (r = 0.54) between Factor 2 (lung function) and Factor 1 (inflammation) from mice 7 days post-exposure to geogenic PM₁₀. Mice with greater declines in inflammatory markers (below control levels) 7 days post-exposure tended to have better lung function.</p

Results of the principal components factor analysis for the eight outcomes included in model, with loadings for each outcome.

<p>Results of the principal components factor analysis for the eight outcomes included in model, with loadings for each outcome.</p

The lung response to geogenic particles was characterised by acute (6 hours post-exposure) inflammation and long term (7 days post-exposure) deficits in lung function.

<p>Mean(SD) scores for Factor 1 (inflammation, left) and Factor 2 (lung function, right) for all mice exposed to geogenic PM₁₀ obtained following principal components factor analysis. *indicated p<0.05 against zero.</p

Summary of the physico-chemical characteristics of the geogenic PM₁₀ from each of the sites.

<p>Two independent samples were collected at each site.</p

Results for control (saline exposed) mice for the outcome measures of interest 6 hours, 24 hours and 7 days post-exposure.

<p>Data are mean(SD).</p

Geographical location and estimated populations of permanent residents of the towns where the geogenic PM₁₀ was sampled.

<p>The numbers in parentheses indicate the total population when the itinerant population of mine workers is included.</p