Exposure-response relationships between road traffic, railway, and aircraft noise and annoyance in Bulgarian cities

This study aimed to develop exposure-response relationships (ERRs) between road, rail, and air traffic noise and high noise annoyance (HNA) and to assess the HNA disease burden. In 2023, 4640 adults were cross-sectionally sampled from the five largest cities in Bulgaria. Participants' road, rail/tram, and air traffic HNA was defined as the top two categories (60% cut-off point) of a 5-point scale. A 72% cut-off approximation was also used. European Noise Directive maps were used to assign day-evening-night equivalent sound levels (L_den) to residences. ERRs were derived and used, together with the new WHO disability weight for HNA, to calculate disability-adjusted life years (DALYs). DALYs were monetised based on Bulgaria's gross domestic product (GDP) per capita and the value of a life year (VOLY). In fully adjusted models, L_den was non-linearly associated with HNA. Road traffic L_den [range 42.5-77.5 dB] was positively associated with HNA only above 62.5 dB, whereas the upward trend for rail [range 37.5-72.5 dB] and air traffic L_den [range 37.5-57.5 dB] started at 40-45 dB. Using this study's ERRs, the burden among people exposed to ≥40 dB was 3476 (1896-5056) DALYs, $ 39 138 953 (21 348 520-56 929 386) based on GDP, and € 243 310 984 (94 796 487-505 581 266) based on VOLY. Using the WHO's curves, the burden was 4312 (2352-6273) DALYs, $ 48 559 330 (26 486 907-70 631 753), and € 301 873 648 (117 613 110-627 269 918). In conclusion, we could only derive a plausible ERR for railway noise annoyance. Until better ERRs are derived for the Bulgarian population, we recommend using the WHO curves for road traffic and aircraft noise annoyance.