Characterizing PM₁-bound PAHs and PBDEs in urban households: Levels, sources, and health risks

This study presents the first systematic characterization of PM₁-bound polycyclic aromatic hydrocarbons (PAHs) and polybrominated diphenyl ethers (PBDEs) measured in paired indoor-outdoor samples collected by active PM₁ sampling from 85 residential households in Zagreb, Croatia, with seasonal sampling in a subset of 20 homes to assess cold- and warm-season variability. PAHs exhibited predominantly outdoor-driven behavior, with indoor concentrations largely influenced by outdoor air infiltration. Higher indoor PBDE levels were observed during the cold season, with substantial variability indicating household-specific sources. Indoor-outdoor relationships further confirm indoor consumer products as the dominant PBDE source. Health risk assessment indicates that PM₁-bound PAHs exposure may pose a potential cancer risk for toddlers and adults, whereas inhalation exposure to PM₁-bound PBDEs remains very low and well below existing health-based guidance values. Overall, the detection of both PAHs and PBDEs in the PM₁ fraction highlights its relevance as a carrier of semi-volatile pollutants in residential environments and supports the need to consider ultrafine particulate fractions in inhalation exposure and risk assessments. This study provides novel data for Europe and emphasizes the importance of indoor microenvironments in contaminant exposure pathways.