From Size-Resolved PAC Emissions to Age-Specific Respiratory Deposition: Toxicity Potential of Particulate PACs from...

Residential solid fuel combustion (RSFC) emits particulate polycyclic aromatic compounds (PACs), but their distribution across the full particle size spectrum and their age-specific deposition are still not well quantified. Here, we combusted six Chinese coals and six biomass fuels at 500 °C (LIT) and 800 °C (HIT). We measured PM and particle-phase PACs (16 parent PAHs and 9 oxygenated PAHs) in 14 size bins ranging from 0.016 to 10 μm. Higher ignition temperature shifted PAC composition toward more toxic species, with biomass showing a stronger shift than coal. Submicron particles (0.10-0.60 μm) carried most of the PAC burden and toxicity, accounting for >60% of total PACs and dominating the equivalent toxicity. Ultrafine particles (UFPs, <0.10 μm) contributed only ∼3% of PM mass but carried up to ∼20% of total PACs. Their mass-specific toxicity (equivalent toxicity per unit PM mass) was 2-10 times higher than that of submicron particles. Respiratory deposition modeling showed clear age dependence: under the same exposure scenario, children had ∼40% higher total respiratory deposition of particulate PACs than adults. About 70% of UFP-bound PACs deposited in the pulmonary region, with their contribution to pulmonary deposition being higher in children than in adults.