Particle size matters: Discrepancies in the health risks posed by traditional cigarettes and e-cigarettes in mice and humans

• Published in: Journal of hazardous materials letters 2023-11, Vol.4, p.100088, Article 100088
• Main Authors: Chou, Li-Ti, Chen, Tsai-Ling, Yang, Kai-Chien, Chuang, Hsiao-Chi, Chen, Ying-Jiun, Lai, Ching-Huang, Hsiao, Ta-Chih
• Format: Article
• Language: English
• Subjects: Atherosclerosis; E-cigarette; MPPD; PSD; Tobacco cigarettes
• ISSN: 2666-9110; 2666-9110
• DOI: 10.1016/j.hazl.2023.100088

Electronic cigarettes (ECs), considered a healthier alternative to traditional cigarettes (TCs), vaporize e-liquid, which may produce harmful by-products due to thermal decomposition and metal transfer. These by-products' deposition in the respiratory tract is largely determined by particle size distribution (PSD). We employ the Multiple-Path Particle Dosimetry (MPPD) model to assess particle deposition within the human and mouse respiratory tracts. Leveraging the known connection between TC smoke inhalation and atherosclerosis, we used human aortic endothelial cells (HAECs) and ApoE-/- mice to explore the potential effects of EC aerosol inhalation on atherosclerosis. Our findings reveal that TCs exhibit a highly variable PSD, with mean diameters of approximately 300 nm for mainstream (MS) smoke and 120 nm for side stream (SS) smoke. Conversely, ECs demonstrate a more stable PSD. Combined with MPPD, the deposition fraction in the human respiratory system and mice is mainly deposited in the pulmonary region and head airway. For the Apoe-/- mice exposure experiment, preliminary findings suggest a potential impact on atherosclerosis, although not statistically significant, likely due to the limited sample size and exposure duration. This study highlights the importance of considering PSD, exposure dosage, and species-specific differences in risk assessments of EC aerosols. [Display omitted] •Examined implications of particle size distributions in e-cigarette aerosols.•Emphasized critical role of particle size in determining inhalation toxicity.•Observed stark differences in particle deposition between human and mice models.•Used exposure dosage estimation for accurate inhalation study interpretation.•Explored potential, albeit inconclusive, effects of e-cigarettes on atherosclerosis.