Investigation of solid particles in the mainstream aerosol of the Tobacco Heating System THS2.2 and mainstream smoke of a 3R4F reference cigarette

Abstract

<jats:p> Combustion of biomass produces solid carbon particles, whereas their generation is highly unlikely when a biomass is heated instead of being burnt. For instance, in the Tobacco Heating System (THS2.2), the tobacco is heated below 350°C and no combustion takes place. Consequently, at this relatively low temperature, released compounds should form an aerosol consisting of suspended liquid droplets via a homogeneous nucleation process. To verify this assumption, mainstream aerosol generated by the heat-not-burn product, THS2.2, was assessed in comparison with mainstream smoke produced from the 3R4F reference cigarette for which solid particles are likely present. For this purpose, a methodology was developed based on the use of a commercial Dekati thermodenuder operating at 300°C coupled with a two-stage impactor to trap solid particles. If any particles were collected, they were subsequently analyzed by a scanning electron microscope and an electron dispersive X-ray. The setup was first assessed using glycerine-based aerosol as a model system. The removal efficiency of glycerin was determined to be 86 ± 2% using a Trust Science Innovation (TSI) scanning mobility particle sizer, meaning that quantification of solid particles can be achieved as long as their fraction is larger than 14% in number. From experiments conducted using the 3R4F reference cigarette, the methodology showed that approximately 80% in number of the total particulate matter was neither evaporated nor removed by the thermodenuder. This 80% in number was attributed to the presence of solid particles and/or low volatile liquid droplets. The particles collected on the impactor were mainly carbon based. Oxygen, potassium, and chloride traces were also noted. In comparison, solid particles were not detected in the aerosol of THS2.2 after passing through the thermodenuder operated at 300°C. This result is consistent with the fact that no combustion process takes place in THS2.2 and no formation and subsequent transfer of solid carbon particles is expected to occur in the mainstream aerosol. </jats:p>

Chemical Composition and In Vitro Toxicity Profile of a Pod-Based E-Cigarette Aerosol Compared to Cigarette Smoke

“…ACM is predominantly formed of liquid droplets containing nicotine, propylene glycol, and glycerol, recognized impurities in Pharmacopoeia-quality nicotine, and eight thermal decomposition products of propylene glycol or glycerol, whereas TPM contains solid particles, formed from tobacco combustion, with the majority of these particles identified as carbon. 15,36 The data are consistent with other studies in older generation e-cigarette products that have found no quantifiable levels of tested toxicants, including HPHCs, or extremely low levels of measurable constituents relative to cigarette smoke in older generation products. 11,15,18,37 Although this study included a wide range of potential toxicants, heavy metals were not analyzed.…”

New ideas, old problems? Heated tobacco products – a systematic review

“…selected indoor air constituents were measured -the concentrations of respirable suspended particles, ultraviolet particulate matter, fluorescent particulate matter, solanesol, 3-ethenylpyridine, formaldehyde, acrolein, crotonaldehyde, acrylonitrile, benzene, 1,3-butadiene, isoprene, toluene, CO, NO and NO x after the use of THS2.2 under 3 environmental conditions were equivalent to the concentrations found in background indoor air -THS2.2 use resulted in increased acetaldehyde and nicotine concentrations in indoor air, but these concentrations were considerably lower than those found in conventional cigarettes The tobacco industry claims that the aerosol formed during the heating process has around 90-95% lower levels of toxicants than conventional cigarette smoke [13][14][15]23,24]. This was partially confirmed by independent studies [27,28].…”

“…However, further research is needed to describe the profile and characteristics of HTP users. According to the tobacco industry data, aerosols formed during the heating process have around 90-95% lower levels of toxicants than conventional cigarette smoke [13][14][15]23,24]. Independent studies have confirmed that the concentration of chemical compounds generated by HTPs is lower than that generated by traditional cigarettes [27,28,33].…”

“…The tobacco industry claims that during HTP use, emissions of toxic chemicals are reduced due to the lower working temperature of the devices [13][14][15]23,24]. The results of independent studies suggest that toxic compounds are not completely removed from the HTP aerosol and these products are still not risk-free (Table 1) [7,19,[25][26][27][28][29][30][31][32][33][34][35].…”

A Comparative Study of Non-Volatile Compounds Present in 3R4F Cigarettes and iQOS Heatsticks Utilizing GC-MS

“…[7] [8] for a general discussion of ENDS; [9] [10] for comparative studies of the effect of ENDS on active and passive smokers; or [11] [12] for general literature reviews; and 2) tobacco heated systems (THS), also addressed as heat-not-burn tobacco products (HNB)-see e.g. [13] [14] for a general discussion of THS2.2 devices; [15] [16] for studies comparing the emission from THSs with that of ordinary cigarettes; or [17] [18] for modelling of aerosol formation in THSs and their analysis. Note that one of the THSs is commercially known as iQOS, which is the THS used in the present investigation.…”