Impact of Ambient Particulate Matter and Ozone Exposure of Heart Transplant Recipients on All-Cause Mortality after Heart Transplant

Purpose There is limited evidence on role of air quality on chronic rejection after heart transplant (HT). We investigated the impact of particulate matter concentration (PM≥2.5 μm/m3) and ozone (O3) exposure of recipients on all-cause mortality after HT in the US. Methods UNOS Standard Transplant Analysis and Research (STAR) database (June 30, 2017) identified adult HT recipients between 2005 and 2015, and their zip code of residence at HT. Average ambient PM and daily maximum 8-hour average O3 associated with recipient residencies 1 year after HT 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. PM concentration was classified into low ( 12 μg/m3); O3 was similarly categorized (low: 42 ppb). Inverse-probability of treatment weighted Cox regression and Kaplan-Meier curves assessed the impact of PM and O3 on 1-year and long-term incidence of all-cause mortality. Results Overall, 17,893 HT patients were included; Median follow-up was 1529 days (IQR 737-2586). 21% of HT recipients had high PM exposure and 20% had high O3 exposure. While estimates were imprecise, both high exposure levels of PM and O3, compared to low exposure, appeared to increase long-term mortality (Table). High PM exposure may also increase 1-year mortality; O3 had no impact on 1-year mortality. Conclusion PM2.5 and O3 conc are only 2 aspects of air quality and appear to increase long term risk of death after HT. Additional research on other air quality measures including isolating primary and secondary components of PM2.5 and focusing on traffic-related air pollutants is warranted for all transplant recipients.