Real-time assessment of PM_1.0-bound trace metal cancer risk through high-resolution GED-ICP-MS and integrated ELCR...

This study employed a gas exchange device coupled with inductively coupled plasma mass spectrometry (GED-ICP-MS) for high-resolution analysis of trace metals in PM_1.0 within an urban area. The system was validated against conventional filter-based measurements (R²=0.57-0.97) and effectively captured diurnal variations and episodic events typically overlooked by traditional sampling. Through positive matrix factorization (PMF), we identified six distinct sources by integrating trace metal concentrations and particle size distribution (PSD). By combining temporal slope factors of mixtures (SF_m) with lung deposited surface area (LDSA), we provided insights into source-specific health risks. The average traffic-related SF_m (7.5 ×10^-4) was comparable to other traffic sites, though values increased significantly (1.0 ×10^-3) during evening rush hours. These findings revealed that vehicle-emitted metals were predominantly in the PM_1.0 size range, indicating that traditional PM₁₀-based health risk assessments may underestimate their impact. The observed lack of correlation between LDSA and SFm emphasizes that comprehensive health risk assessment requires both PSD and toxicity measurements, particularly for particles below 100 nm. The overall excess lifetime cancer risk averaged 2.9 × 10^-5, varying between peak (4.0 ×10^-5) and off-peak (2.5 ×10^-5) traffic periods, remaining within US EPA's acceptable range, while demonstrating the crucial role of trace metals in determining health risks despite their low concentrations.