Ambient Air Pollution Exposure and Outcomes in Patients Receiving Lung Transplant

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Elevated ambient fine particulate matter (PM2.5) air pollution exposure has been associated with poor health outcomes across several domains, but its associated outcomes among lung transplant recipients are poorly understood. To investigate whether greater PM2.5 exposure at the zip code of residence is associated with a higher hazard for mortality and graft failure in patients with lung transplants. This retrospective cohort study used panel data provided by the United Network for Organ Sharing, which includes patients receiving transplants across all active US lung transplant programs. Adult patients who received lung transplants between May 2005 and December 2016 were included, with a last follow-up of September 10, 2020. Data were analyzed from September 2022 to May 2023. Zip code-level annual PM2.5 exposure was constructed using previously published North American estimates. The primary outcome was time to death or lung allograft failure after lung transplant. A gamma shared frailty Cox proportional hazards model was used to produce unadjusted and adjusted hazard ratios (HRs) to estimate the association of zip code PM2.5 exposure at the time of transplant with graft failure or mortality. Among 18 265 lung transplant recipients (mean [SD] age, 55.3 [13.2] years; 7328 female [40.2%]), the resident zip code's annual PM2.5 exposure level was greater than or equal to the Environmental Protection Agency (EPA) standard of 12μg/m3 for 1790 patients (9.8%) and less than the standard for 16 475 patients (90.2%). In unadjusted analysis, median graft survival was 4.87 years (95% CI, 4.57-5.23 years) for recipients living in high PM2.5 areas and 5.84 years (95% CI, 5.71-5.96 years) for recipients in the low PM2.5 group. Having an annual PM2.5 exposure level greater than or equal to the EPA standard 12 μg/m3 was associated with an increase in the hazard of death or graft failure (HR, 1.11; 95% CI, 1.05-1.18; P < .001) in the unadjusted analysis and after adjusting for covariates (HR, 1.08; 95% CI, 1.01-1.15; P = .02). Each 1 μg/m3 increase in exposure was associated with an increase in the hazard of death or graft failure (adjusted HR, 1.01; 95% CI, 1.00-1.02; P = .004) when treating PM2.5 exposure as a continuous variable. In this study, elevated zip code-level ambient PM2.5 exposure was associated with an increased hazard of death or graft failure in lung transplant recipients. Further study is needed to better understand this association, which may help guide risk modification strategies at individual and population levels.