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The Hazelwood Health Study was set up to study long term health effects of a mine fire that blanketed residents of the Latrobe Valley with smoke for 45 days in 2014. The Respiratory Stream specifically assessed the impact of fine particulate matter <2.5μm diameter (PM_2.5) exposure from mine fire smoke on lung health. The multiple breath nitrogen washout (MBW) test assesses ventilation heterogeneity, which may detect early airways dysfunction not identified using standard tests such as spirometry. This analysis assessed the association of PM_2.5 exposure with measures of ventilation heterogeneity.

Exposed (Morwell) and unexposed (Sale) participants were recruited 3.5-4 years after the fire from those who had participated in an Adult Survey. MBW was performed to measure lung clearance index (LCI), functional residual capacity (FRC), acinar (Sacin) and conductive (Scond) ventilation heterogeneity. PM_2.5 exposure was estimated with emission and chemical transport models. Multivariate linear regression models were fitted controlling for confounders.

We recruited 519 participants. MBW tests were conducted on 504 participants with 479 acceptable test results (40% male; 313 exposed, 166 unexposed). Exposure to mine fire-related PM_2.5 was associated with increasing Scond (β=2.15/kL, 95%CI: 0.67-3.63, p=0.006), which was comparable to the estimated effect on Scond of 7.9 years of aging. No other MBW outcomes were significant.

Increasing exposure to PM_2.5 was associated with increased ventilation heterogeneity in the conductive region of the lungs 4 years after the event.