Quantitative Assessment of Particulate Matter Biodistribution Using ¹⁴C-Nanotracing and Accelerator Mass Spectrometry

Particulate matter (PM) poses a major health risk, yet quantifying the biodistribution of inhaled PM at an environmentally relevant concentration remains analytically challenging. Here, we developed a ¹⁴C-nanotracing platform integrated with accelerator mass spectrometry (AMS) to achieve subpicogram sensitivity for organ-level quantification of inhaled PM. ¹⁴C-labeled black carbon PM was generated via pyrolysis of ¹⁴C-n-hexane and introduced into a controlled inhalation chamber. ICR mice (n = 7) were exposed to short-intense (1 h, high concentration) and long-mild (3 h day^-1 for 7 days, low concentration) protocols to represent acute and subchronic exposure conditions. Quantitative AMS analysis revealed systemic translocation of carbonaceous PM, with organ burdens following the order lung > liver > kidney > brain. After short-term exposure, 360 pg accumulated in the liver, 120 pg in the kidney, and 4.8 pg in brain tissue, whereas prolonged exposure increased these burdens by 3-6-fold, reaching 15 pg in the brain. These findings indicate substantial retention of PM across multiple organs including neural tissues of the brain. This ¹⁴C-nanotracing approach enables a quantitative framework for linking inhaled PM exposure to systemic burden, supporting toxicokinetic modeling and evidence-based air quality regulation.