From Size-Resolved PAC Emissions to Age-Specific Respiratory Deposition: Toxicity Potential of Particulate PACs from Residential Coal and Biomass Combustion

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.