Deposition characteristics of sub-micron particles emitted from cigarettes, e-cigarettes and incense in the human respiratory tract

This study explored the respiratory deposition characteristics of sub-micron particles (particulate matter (PM 1 )) emitted from cigarettes, e-cigarettes and incense to assess the health impacts of indoor PM 1 exposure. A smoke chamber was used to simulate the emission process, and the particle size distributions were determined by employing a universal scanning mobility particle sizer. The highest number concentration of PM 1 was observed in cigarette smoke, followed by incense and e-cigarette smoke. The size distributions of cigarette and incense smoke exhibited a unimodal distribution, while the e-cigarette smoke exhibited a bimodal distribution. Furthermore, a multiple-path particle deposition model was used to estimate the deposition fractions of PM 1 emitted from various smoke sources. Results indicated that the total deposition fraction of PM 1 from e-cigarette smoke in the respiratory tract (24.4%) was significantly greater than those of cigarette smoke (15.8%) and incense smoke (17.3%). PM 1 deposition fractions followed the order of pulmonary > tracheobronchial > oral cavity, with the right lower lung lobe showing higher deposition. Additionally, the highest particle deposition fraction was observed in 9-year-old children. These findings highlight the urgent need for stricter indoor air pollution control measures to protect public health, especially amongst sensitive populations like children and infants.