B41-21 Wildfire-related PM2.5 Associates With Lower FVC and DLCO in Ever-Smokers With Pulmonary Fibrosis

Abstract Rationale Wildfire smoke episodes are increasingly frequent. Whether short-term wildfire PM2.5 relates to pulmonary function in pulmonary fibrosis (PF) and differs by prior tobacco exposure is not fully understood. We tested associations between 7-day mean wildfire-related PM2.5 and lung function (FVC and DLCO) impairment, stratified by smoking history. Methods Retrospective cohort of PF patients at the University of Chicago with repeated pulmonary function tests (PFTs). Exposure was the 7-day average wildfire PM2.5. Outcomes were forced vital capacity percent predicted (FVC%) and diffusing capacity percent predicted (DLCO%). Primary analyses were linear regressions stratified by ever-smoker vs never-smoker, with unadjusted and age/sex-adjusted models. Robustness was assessed using Pearson correlations excluding baseline visits. Pairwise correlation, chi-squared tests, and t-tests were used where appropriate. Stata 17 was used for all analyses (IRB protocol #14163-A, #IRB17-1617. Results Among 676 subjects with PF analyzed in the Midwest 326 were ever-smokers, while 285 were never smokers. In unadjusted analyses, higher PM2.5 was associated with lower FVC% among ever-smokers (β per 1 µg/m³ = −0.435; 95%CI −0.834 to − 0.035; p=0.033; N = 549), but not among never-smokers (β = +0.010; p=0.959; N = 452). After adjustment for age and sex, the association persisted in ever-smokers (β = −0.413; 95%CI −0.810 to − 0.015; p=0.042) and remained null in never-smokers (β = −0.005; p=0.979). When excluding baseline visits, FVC% correlated inversely with PM2.5 in ever-smokers (r = −0.108; p=0.0187) but not in never-smokers (r = −0.011; p=0.8325). Similarly, among ever-smokers, patterns were directionally consistent with the FVC findings and indicated effect modification by tobacco exposure. PM2.5 was associated with lower DLCO% (β = −0.761; 95%CI −1.228 to − 0.295; p=0.001; N = 474). Among never-smokers, estimates were positive and not significant (β = +0.404; p=0.098; N = 399). Conclusions Short-term wildfire-related PM2.5 exposure is associated with modest but measurable decrements in FVC% and DLCO% in PF patients with prior tobacco exposure. These findings suggest susceptibility related to historical tobacco smoke and support targeted risk communication and protective strategies for PF patients during wildfire smoke events. This abstract is funded by: None