Polybrominated Diphenyl Ethers (PBDEs) in PM1 of Residential Indoor Air: Levels, Seasonal Variability, and Inhalation Exposure Assessment

Indoor exposure to polybrominated diphenyl ethers (PBDEs), particularly those bound to fine particulate matter (PM₁, particles < 1 µm), may pose a health concern, especially in light of prolonged indoor occupancy and the capacity of ultrafine particles to reach the lower respiratory tract. This study investigates indoor exposure to PBDEs associated with PM₁ in residential homes in Zagreb, Croatia, across warm and cold seasons. BDE-47 was consistently detected in all samples, while BDE-183 was consistently absent. Elevated concentrations and increased detection frequencies of BDE-99 and BDE-100 were observed during the colder season. Consequently, total PBDE (ΣPBDE) levels in the cold season were approximately 2.5 times higher than in the warm season. Although estimated daily inhalation intakes were below established oral reference doses, the potential for deep pulmonary deposition and systemic distribution underscores the need for further investigation. These findings represent the first reported data on indoor PM₁-associated PBDEs in Europe, emphasizing the impact of seasonal dynamics on inhalation exposure due to variation on indoor contaminant levels.