Abstract
Knowledge of the deposition of inhaled smoke aerosol in the human respiratory tract has great value for risk assessments of the inhalation toxicology of tobacco products. In this study, differential mobility spectrometry (DMS) was used to characterize smoke particles generated from a conventional cigarette, e-cigarette and heat-not-burn product. The aerosol properties obtained by DMS were then applied to a Multiple Path Particle Dosimetry (MPPD) model to predict the deposition of aerosol particles in the human respiratory tract. The DMS results showed that the particle size distribution of aerosol from the three products differed considerably, with a count median diameter of 14.2–25.4 nm, 50.6–55.3 nm and 172–179 nm for the e-cigarette, heat-not-burn product and conventional cigarette, respectively. However, there was no significant difference in the particle number concentration of aerosol from the three products. The MPPD model indicated that the total deposition fraction of aerosol particles from the e-cigarette and heat-not-burn product was higher than that from the conventional cigarette, and deposition of particles from the e-cigarette in the three human airway regions (head airway, tracheobronchial and pulmonary regions) was higher than that from the heat-not-burn product and conventional cigarette; the particle number concentration deposited in the pulmonary region was the highest, comprising more than 60% of total deposition. Lastly, among the lung lobes, the highest number deposition fraction occurred in the right lower lobe. The relationship between deposition fraction and airway generation was relatively similar among the three aerosols, and the highest deposition fraction occurred in the 20th to 23rd generation airways. The deposition results showed that smaller particles, such as those from the e-cigarette aerosol, were more easily deposited in the human respiratory tract. Combined with knowledge of the harmful aerosol constituents, these deposition data will provide important information for hazard evaluation of new tobacco products.
Highlights
Numerous studies have confirmed the health risks of cigarette smoking, which is generally considered to be the leading preventable cause of various diseases, such as lung cancer, cardiovascular disease and stroke (Church et al, 2009; Barua and Ambrose, 2013; Hackshaw et al, 2018; WHO, 2008)
The physical properties of three different sample aerosols were measured by smoking cycle simulator (SCS)-differential mobility spectrometry (DMS) over a puff number of 6, 10, and 6 for one conventional cigarette (#1, 3R4F, a standard reference cigarette developed by the University of Kentucky Centeror Tobacco Reference Products that is used throughout the tobacco industry and academic laboratories as a consistent and uniform test item for inhalation toxicology research), one e-cigarette (#4), and one HnB product (#7), respectively
The DMS data showed that the count median diameter (CMD) and geometric standard deviation (GSD) of the three products remained essentially the same across the puffs; and the number concentration (NC) of the 3R4F cigarette and HnB product tended to increase with puff number, while that of e-cigarette did not vary with puff number (Fig. S1– S3)
Summary
Numerous studies have confirmed the health risks of cigarette smoking, which is generally considered to be the leading preventable cause of various diseases, such as lung cancer, cardiovascular disease and stroke (Church et al, 2009; Barua and Ambrose, 2013; Hackshaw et al, 2018; WHO, 2008). New types of product have emerged in the tobacco market Products such as e-cigarettes and heat-not-burn (HnB) products are becoming increasing popular owing to their claimed function of being able to reduce or even eliminate toxicity or mutagenicity of cigarette smoke (Chen, 2017; Simonavisius et al, 2018; Boue et al, 2020). It is the chemicals carried by smoke particles that are associated with disease (U.S Department of Health and Human Services, 2014). Smoke exposure and hazard evaluation should focus on the chemicals, and account for the deposition of aerosol particles
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