Long‐term exposure to low concentrations of air pollution and decline in lung function in people with idiopathic pulmonary fibrosis: Evidence from Australia

Background and Objective
Little is known about the association between ambient air pollution and idiopathic pulmonary fibrosis (IPF) in areas with lower levels of exposure. We aimed to investigate the impact of air pollution on lung function and rapid progression of IPF in Australia.

Methods
Participants were recruited from the Australian IPF Registry (n = 570). The impact of air pollution on changes in lung function was assessed using linear mixed models and Cox regression was used to investigate the association with rapid progression.

Results
Median (25th–75th percentiles) annual fine particulate matter (<2.5 μm, PM2.5) and nitrogen dioxide (NO2) were 6.8 (5.7, 7.9) μg/m3 and 6.7 (4.9, 8.2) ppb, respectively. Compared to living more than 100 m from a major road, living within 100 m was associated with a 1.3% predicted/year (95% confidence interval [CI] −2.4 to −0.3) faster annual decline in diffusing capacity of the lungs for carbon monoxide (DLco). Each interquartile range (IQR) of 2.2 μg/m3 increase in PM2.5 was associated with a 0.9% predicted/year (95% CI −1.6 to −0.3) faster annual decline in DLco, while there was no association observed with NO2. There was also no association between air pollution and rapid progression of IPF.

Conclusion
Living near a major road and increased PM2.5 were both associated with an increased rate of annual decline in DLco. This study adds to the evidence supporting the negative effects of air pollution on lung function decline in people with IPF living at low-level concentrations of exposure.