Thermal?UV synergy accelerates HBCD emissions from back-coated textiles via volatile and nanoscale particle pathways

Hexabromocyclododecane (HBCD), a brominated flame retardant in legacy back-coated textiles, persists despite restrictions. This study quantifies HBCD emissions from back-coated fabrics subjected to thermal aging (25?90??C), ultraviolet irradiation (UVA-340, 1.25?W m?2), and mechanical abrasion (25,000 cycles), emphasizing synergistic thermal?UV interactions. Emissions were characterized using first-order kinetic, dynamic headspace sampling, and size-resolved particulate analysis. Thermal aging at 90??C yielded 0.167???0.01% volatilization, while UV exposure alone generated 0.162???0.02%. Combined thermal?UV stress accelerated kinetics, yielding a synergy factor S?=?1.92???0.25 (p?=?0.014) and a 0.233???0.03% cumulative release. The rate constant increased from 0.018 d?1 (thermal) to 0.129 d?1 (combined). Mechanical abrasion released particulate-associated HBCD at 6.53??g m?2?cycle?1. UV pre-aging shifted particle emissions toward nanoscale fractions (30?260?nm), increasing particle chemical content from 12.5% to 29.2%. Airborne particle concentrations were ? 250??g m?3 (unaged) and 0.8 ?60??g m?3 (UV-aged). While cumulative volatile release was low (?0.233%), matrix depletion reached 48.4%, suggesting polymer-embedded transformation dominate HBCD fate. These findings show multi-stressor environmental conditions significantly alter emission pathways, affecting exposure assessments for legacy materials.