Impact of Ambient Particulate Matter (PM) Exposure of Lung Donors and Recipients on Bronchiolitis Obliterans Syndrome (BOS) and Mortality after Lung Transplant (LT)

Abstract

A Belgian study found proximity to a motorway increased risk of BOS after LT. Using zip codes as a surrogate for habitat location we investigated the impact of PM2.5 concentration (conc) (PM≥ 2.5 μm/m3) exposure of donors and recipients on BOS and mortality after LT in the US. UNOS Standard Transplant Analysis and Research (STAR) database (June 30, 2017) identified adult LT recipients and their donors between 2005 and 2015, and their zip code of residence at LT. Average ambient PM2.5 conc (PM≥ 2.5 μm/m3) associated with donor and recipient residencies 1 year prior to LT were estimated by mapping each zip code to a census tract, using a crosswalk from HUD, downscaled from a 12 × 12-km sq grid resolution detailed chemistry - transport model application using a Bayesian space-time downscaler, and then fused with surface observations. PM2.5 conc was classified into low (<8 μg/m3), medium (8-12 μg/m3) and high (>12 μg/m3) exposure categories. Cox proportional hazards regression and Kaplan-Meier curves assessed the impact of PM2.5 on 1 year and long term incidence of BOS and all cause mortality. 17,760 LT were analyzed. Median followup was 1101 days (IQR 511-2073, range 1-4448). 25% of LT had high donor exposure and 24% had high recipient exposure. Recipient exposure to PM2.5 had no impact on 1-year survival. However, higher PM2.5 donor exposure appeared to increase risk of early death, although estimates were imprecise (Table). Higher concentration of recipient or donor PM2.5 did not increase long-term mortality risk, and curiously higher recipient PM reduced BOS incidence (Table). PM2.5 is only one aspect of air quality and does not appear to increase long term risk of BOS or death after LT. Donor PM. exposure may have a small impact on 1 year survival after LT. Additional research on other air quality measures including isolating primary and secondary components of PM2.5 and focusing on traffic-related air pollutants is needed.