Heavy incense burning in temples promotes exposure risk from airborne PMs and carcinogenic PAHs

We present the mechanistic-based exposure and risk models, appraised with reported empirical data, to assess how the human exposure to airborne particulate matters (PMs) and carcinogenic polycyclic aromatic hydrocarbons (PAHs) during heavy incense burning episodes in temples. The models integrate size-dependent PM levels inside a temple from a published exploratory study associated with a human expiratory tract (HRT) model taking into account the personal exposure levels and size distributions in the HRT. The probabilistic exposure profiles of total-PAH levels inside a temple and internal PAHs doses are characterized by a physiologically based pharmacokinetic (PBPK) model with the reconstructed dose–response relationships based on an empirical three-parameter Hill equation model, describing PAHs toxicity for DNA adducts formation and lung tumor incidence responses in human white blood cells and lung. Results show that the alveolar-interstitial (AI) region has a lower mass median diameter (0.29 μm) than that in extrathoracic (ET1, 0.37 μm), brochial (BB, 0.36 μm) and bronchiolar (bb, 0.32 μm) regions. The 50% probability (risk=0.5) of exceeding the DNA adducts frequency (DAf) ratio of 1.28 (95% CI: 0.55–2.40) and 1.78 (95% CI: 0.84– 2.95) for external exposure of B[a]P and B[a]Peq, respectively. The 10% (risk=0.1) probability or more of human affected by lung tumor is approximately 7.62×10−5% (95% CI: 3.39×10−5–1.71×10−4%) and 3.87×10−4% (95% CI: 1.72×10−4–8.69×10−4%) for internal exposure of B[a]P and B[a]Peq, respectively. Our results implicate that exposure to smoke emitted from heavy incense burning may promote lung cancer risk. Our study provides a quantitative basis for objective risk prediction of heavy incense burning exposure in temples and for evaluating the effectiveness of management.