Non-targeted analytical comparison of a heated tobacco product aerosol against mainstream cigarette smoke: does heating tobacco produce an inherently different set of aerosol constituents?

Smoking-related diseases remain a significant public health concern, and heated tobacco products (HTPs) have emerged as a potential alternative to cigarettes. While several studies have confirmed that HTP aerosols contain lower levels of harmful and potentially harmful constituents (HPHCs) than cigarette smoke, less is known about constituents that are intrinsically higher in HTP aerosols. This study provides a comprehensive comparative assessment of an HTP aerosol produced with Tobacco Heating System 2.2 (THS) and comparator cigarette (CC) smoke aiming at identifying all unique or increased compounds in THS aerosol by applying a broad set of LC-MS and GC × GC-MS methods. To focus on differences due to heating versus burning tobacco, confounding factors were minimized by using the same tobacco in both test items and not adding flavorants. Of all analytical features, only 3.5%-corresponding to 31 distinctive compounds-were significantly more abundant in THS aerosol than in CC smoke. A notable subset of these compounds was identified as reaction products of glycerol. The only compound unique to THS aerosol was traced back to its presence in a non-tobacco material in the test item and not a direct product of heating tobacco. Our results demonstrate that heating a glycerol-containing tobacco substrate to the temperatures applied in THS does not introduce new compounds in the resulting aerosol compared to CC smoke which are detectable with the method portfolio applied in this study. Overall, this study contributes to a better understanding of the chemical composition of HTP aerosols and their potential impact on human health.

Mechanism of cytotoxicity induced by the cigarette smoke extract (CSE) of heated tobacco products in vascular smooth muscle cells: A comparative study of the cytotoxic effects of CSE and the ferroptosis inducer, erastin

Heated tobacco products (HTPs) are marketed worldwide as less harmful alternatives to combustible cigarettes; however, their cytotoxic mechanisms in vascular smooth muscle cells are poorly understood. Ferroptosis is defined as iron-dependent cell death caused by the accumulation of lipid peroxidation products. In this study, the cytotoxic effects of nicotine- and tar-free cigarette smoke extracts (CSE) derived from three types of HTPs and the ferroptosis inducer, erastin, on vascular smooth muscle A7r5 cells were compared. Cigarette smoke from all HTPs was generated according to the following puffing regime: 55 mL, puff volume; 30 s, puff interval; 2 s, puff duration; bell-shaped, puff profile; and no blocking of the ventilation holes. Erastin and CSE decreased mitochondrial metabolic activity and increased lactate dehydrogenase leakage. The cytotoxic effects of erastin were almost completely inhibited by the radical-trapping antioxidant, UAMC-3203; iron chelator, deferoxamine mesylate (DFO); 12/15-lipoxygenase (12/15-LOX) inhibitor, baicalein; and selective 15-LOX inhibitor, ML351. In contrast, CSE-induced cell damage was partially attenuated by UAMC-3203, baicalein, and ML351 but not by DFO. These results suggest that erastin induces ferroptosis via 15-LOX-mediated iron-dependent lipid peroxidation, whereas CSE causes iron-independent cell damage via 15-LOX-mediated lipid peroxidation-dependent and -independent mechanisms.

Tobacco usage in the home: a cross-sectional analysis of heated tobacco product (HTP) use and combustible tobacco smoking in Japan, 2023

BACKGROUND

Heated tobacco product (HTP) use continues in Japan as the second most common product after cigarettes. While the health effects of HTPs and their secondhand emissions are not well-studied, the tobacco industry has actively marketed HTPs as a smokeless, health-conscious alternative to cigarettes to encourage home consumption. We investigated the prevalence of current tobacco product use and usage at home.

METHODS

The present study conducted a cross-sectional analysis of data from the 2023 wave of a nationwide, Internet-based, self-reported survey. 29,354 individuals aged 16-74 were included in the analysis. We assessed the prevalence of current (past-30-day) use for HTPs, cigarettes, non-cigarette combustible tobacco, and dual (combustible plus HTP) use. The frequency of use (daily or more than monthly) in the home was calculated for both HTPs and combustible tobacco. Multivariable Poisson regression models were employed to identify factors associated with home usage. Adjusted prevalence ratios (APRs) and 95% confidence intervals (CIs) were computed. All analyses were weighted to address the Internet-based sample's selectivity and yield nationally representative estimates.

RESULTS

In 2023, the prevalence of current use was 12.4% (HTPs), 18.9% (cigarettes), 3.6% (non-cigarette combustible tobacco), and 7.4% (dual use). Among current users of any tobacco (N = 5,818), 49.8% reported daily tobacco usage within their homes, and 67.1% reported monthly or more frequent home usage. Compared to exclusive combustible tobacco smokers, exclusive HTP users exhibited higher prevalence of daily home usage (APR = 1.54; 95% CI = 1.43-1.67), as did dual users (APR = 1.10; 95% CI = 1.01-1.20). Daily home usage prevalence was notably higher for those without complete tobacco-free rules at home or workplaces, older individuals, and those with lower education levels. Those living with adult or child household member and current drinkers showed significantly lower daily home usage prevalence.

CONCLUSION

Home usage was more common among HTP users than among combustible tobacco smokers. Ongoing efforts to assess and address the impact of indoor tobacco product use, including HTPs, on health are warranted. Regulatory and educational strategies should be considered to discourage tobacco consumption in both public and private spaces.

The relationship between heated cigarette smoking and blood white blood cell count: a population-based cross-sectional study

OBJECTIVES

Conventional cigarette smoking increases inflammation and white blood cell (WBC) counts. However, there have been limited studies on the relationship between heated cigarette smoking and WBC counts. This study aimed to examine this relationship using nationally representative population-based health data.

STUDY DESIGN

This was a population-based cross-sectional study.

METHODS

The Korea National Health and Nutrition Examination Survey database was used to analyze this relationship. Data related to sex, age, body mass index (BMI), WBC count, and smoking history were obtained from the database. The smoking-related questionnaires included smoking status, smoking type (heated or conventional cigarettes), and smoking amount. The summary statistics of the WBC counts were calculated according to sex, smoking status, and smoking type. In addition, the exposure-response relationship between the smoking amount and WBC count was examined by smoking type, controlling for sex, age, and BMI.

RESULTS

In total, 9747 WBC measurements were used in the analyses. WBC count increased in conventional cigarette smokers, while there was no significant difference in WBC count between heated cigarette smokers and non-smokers. The WBC count showed a positive dose-response relationship with the smoking amount in both conventional and heated cigarette smokers.

CONCLUSIONS

The results confirm that conventional cigarette smoking increases WBC counts. Furthermore, the results suggest that heated cigarette smoking does not lead to a significant increase in WBC counts, although it indicates a potential dose-response relationship with WBC count. Further research with larger sample sizes is needed to confirm whether these results reflect true associations.

Human vasculature-on-a-chip with macrophage-mediated endothelial activation: The biological effect of aerosol from heated tobacco products on monocyte adhesion

Heated tobacco products (HTPs) are expected to have the potential to reduce risks of smoking-associated cardiovascular disease (CVD). However, mechanism-based investigations of the effect of HTPs on atherosclerosis remain insufficient and further studies under human-relevant situations are desired for deeper understanding of the reduced risk potential of HTPs. In this study, we first developed an in vitro model of monocyte adhesion by considering macrophage-derived proinflammatory cytokine-mediated endothelial activation using an organ-on-a-chip (OoC), which provided great opportunities to mimic major aspects of human physiology. Then biological activities of aerosol from three different types of HTPs in terms of monocyte adhesion were compared with that of cigarette smoke (CS). Our model showed that the effective concentration ranges of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) were close to the actual condition in CVD pathogenesis. The model also showed that monocyte adhesion was less induced by each HTP aerosol than CS, which may be caused by less proinflammatory cytokine secretion. In summary, our vasculature-on-a-chip model assessed the difference in biological effects between cigarettes and HTPs, and suggested a reduced risk potential of HTPs for atherosclerosis.

Heated tobacco product use and abnormal glucose metabolism: a working population-based study

AIMS

We aimed to assess the cross-sectional association of heated tobacco product (HTP) use with prediabetes and diabetes.

METHODS

The present analysis included 8950 workers from 5 companies (Study I) and 31,341 workers from another large company (Study II), who participated in the Japan Epidemiology Collaboration on Occupational Health Study. The participants were divided into five groups: never smokers, past smokers, exclusive HTP users, dual users of cigarettes and HTPs, and exclusive cigarette smokers. Diabetes and prediabetes were defined according to the fasting blood glucose and HbA1c levels and self-reported diabetes treatment, using the American Diabetes Association criteria. We analyzed the data of Study I and II separately, and then pooled these estimates using the fixed-effect models, with adjustment for a wide range of covariates.

RESULTS

In this study that included 40,291 participants (mean age, 46.6 years; men, 84.3%), about half of the current tobacco-related product users reported using HTPs. Exclusive HTP users had higher odds of prediabetes (pooled odds ratio 1.36; 95% CI 1.25-1.47) and diabetes (1.68; 95% CI 1.45-1.94) than never smokers. Similarly, dual users also had increased odds of prediabetes (pooled odds ratio, 1.26; 95% CI 1.13-1.39) and diabetes (1.93; 95% CI 1.63-2.29). The strength of these associations was comparable to that of cigarette smokers. We observed significantly higher HbA1c and fasting blood glucose levels among both exclusive HTP users and dual users compared to never smokers.

CONCLUSION

HTP use was associated with an increased likelihood of prediabetes and diabetes. Prospective studies are warranted to confirm the cross-sectional association.

Chemical and in vitro toxicological comparison of emissions from a heated tobacco product and the 1R6F reference cigarette

It has previously been found that, compared with cigarette smoke, the aerosols generated by heated tobacco products contain fewer and lower harmful and potentially harmful constituents (HPHCs) and elicit lower biological activity in in vitro models and lower smoking-related exposure biomarker levels in clinical studies. It is important to accumulate such scientific evidences for heated tobacco products with a novel heating system, because different heating system may affect the quantitative aspect of the amount of HPHCs and the qualitative aspect of the biological activity of the aerosol generated. Here, the chemical properties of, and toxicological responses to aerosols emitted by DT3.0a, a new heated tobacco product with a novel heating system, and cigarette smoke (CS) were compared, using chemical analyses, in vitro battery (standardized genotoxicity and cytotoxicity) assays, and mechanistic (ToxTracker and two-dimensional cell culture) assays. Regular- and menthol-flavored DT3.0a and standard 1R6F reference cigarettes were tested. Selected HPHC yields were lower in DT3.0a aerosol than 1R6F CS. The genotoxicity-related assays indicated that DT3.0a aerosol was not genotoxic, regardless of metabolic activation. The other biological assays indicated that less cytotoxicity induction and oxidative stress response were elicited by DT3.0a aerosol compared with 1R6F CS. Similar results were found for both regular and menthol DT3.0a. Like previous reports for heated tobacco products with other heating systems, the results of this study indicated that DT3.0a aerosols have chemical and biological properties less likely to be harmful than 1R6F CS.

The spread of heated tobacco product (HTP) use across various subgroups during 2015-16 and 2017-18 in Japan

BACKGROUND

Heated tobacco product (HTP) use has increased substantially between 2016 and 2017 in Japan. This study aims to clarify how HTP use (IQOS, Ploom, and glo) spread across the different combustible cigarette smoking statuses during 2015-16 and 2017-18 in Japan.

METHODS

We compared the two periods of (i) 2015 to 2016 (N = 5,366) and (ii) 2017 to 2018 (N = 3,422) from a longitudinal study randomly sampling members from the Japan "Society and New Tobacco" Internet Survey (JASTIS). Multivariable logistic regression models for current HTP use in the previous 30 days by combustible cigarette smoking status in the previous year were used adjusting for socio-demographic factors.

RESULTS

HTP use increased by 10 times in the 2017-18 cohort compared with the 2015-16 cohort according to the adjusted odds ratio (95% confidence interval) for current HTP use as 10.2 (7.03-14.8). According to smoking status, significantly higher adjusted ORs (95% CIs) of current HTP use for the after period were observed: 2.60 (1.37-4.94) for never smokers, 7.82 (3.64-16.8) for former smokers, 21.1 (5.73-77.9) for current smokers with intention to quit, and 17.0 (9.58-30.3) for current smokers without intention to quit.

CONCLUSION

During 2015 to 2018 in Japan, HTP use dramatically increased in all subgroups except for never smokers.

Increased oxidative stress and effects on inflammatory cytokine secretion by heated tobacco products aerosol exposure to mice

Although the amount of chemicals in heated tobacco products (HTPs) aerosols is reduced compared to conventional combustible cigarette smoke, the association between HTPs and reduced health effects remains unclear. In this study, we hypothesized that exposure to IQOS, an HTP, would increase oxidative stress and affect the secretion of inflammatory cytokines. First, C57BL/6 mice exposed to IQOS aerosols were evaluated to determine the adverse effects of IQOS exposure. IQOS exposure significantly decreased the concentration of GSH in alveolar macrophages in a dose-dependent manner and increased the percentage of GSSG in lung tissues. These results indicate that IQOS exposure increases oxidative stress, and GSH is consumed to remove oxidative stress. In addition, foamy alveolar macrophages were observed in the bronchial alveolar lavage fluid after IQOS exposure. Although the concentration of inflammatory cytokines, IL-6, and GM-CSF, in the plasma increased significantly after IQOS exposure, there were no significant changes in other cytokines. These results indicate that short-term exposure to IQOS aerosols may increase oxidative stress and induce the secretion of inflammatory cytokines. Lastly, the longer-term effects of IQOS aerosols exposure should be evaluated in the future.

Time-resolved online analysis of the gas- and particulate-phase of cigarette smoke generated by a heated tobacco product using vacuum ultraviolet photoionization mass spectrometry

We present a vacuum ultraviolet (VUV) lamp-based photoionization time-of-flight (TOF) mass spectrometer coupled with a capillary inlet and an aerodynamic lens to online analyze the chemical compositions of the gas- and particulate-phase of cigarette smoke of a heated tobacco product (HTP). Both phase compositions of the fresh cigarette smoke, without dilution and pretreatment, are softly photoionized and their mass spectra are measured with a time resolution of 1 s. It is shown that the gas-phase compositions with low mass are volatile organic compounds (VOCs), and the particulate-phase compositions are also clearly identified and cover the full mass range of the mass spectrometer. The time- or puff-by-puff resolved dynamic data are obtained for each species and provide abundant information to unravel the chemistry of the HTP smoke. In addition, the present results show that besides thermal vaporization, a couple of chemical reactions including pyrolysis and degradation have also occurred in the HTP smoking process, although its operation temperature is less than 350 °C. Even if not done here, this study paves the way to analyze the gas- and particulate-phase chemical compositions of a complex system in real time, like the cigarette smoke presented here, by using advanced soft ionization mass spectrometry.

Exposure to aerosol extract from heated tobacco products causes a drastic decrease of glutathione and protein carbonylation in human lung epithelial cells

Heated tobacco products (HTPs) are an emerging class of tobacco goods that claim to have lower health risks than those of smoking combustible tobacco products. In this study, we exposed human lung epithelial cell lines to extracts prepared from HTP aerosols and combustible cigarette smoke to compare cytotoxicity. We focused on the effects of aldehydes present in the aerosols of HTPs at levels close to those in combustible cigarette smoke. Significant toxicity was confirmed for the HTP extract, albeit to a lesser extent than that with the combustible cigarette extract. When redox balance was evaluated by the oxidative loss of low-molecular-weight thiols in the cells, we found that total glutathione (GSH) contents and low-molecular-weight thiol levels were significantly decreased after exposure to the aerosol extract of HTPs. These results indicated that GSH is rapidly consumed during the detoxification of xenobiotics, such as aldehydes from tobacco extracts. Accordingly, exposure to the aerosol extract of HTPs resulted in the enhanced carbonylation of many proteins. In a simple comparison, the results for HTPs were significantly different from those obtained with combustible cigarette smoke, suggesting reduced toxicity of HTPs. However, we found significant and harmful effects after exposing lung epithelial cells to the aerosol extract of HTPs. Thus, a further comprehensive study is needed to clarify the lung damage induced via the long-term inhalation of aerosols from HTPs.

Pharmacokinetic and subjective assessment of prototype JUUL2 electronic nicotine delivery system in two nicotine concentrations, JUUL system, IQOS, and combustible cigarette

RATIONALE

Electronic nicotine delivery systems and heated tobacco products are noncombustible alternatives for adult smokers. Evidence suggests sufficient nicotine delivery and satisfying effects are necessary to facilitate switching away from smoking; nicotine delivery varies across electronic nicotine delivery systems within limited nicotine concentrations.

OBJECTIVES

To assess the nicotine delivery and subjective effects of prototype JUUL2 System in two nicotine concentrations, currently-marketed US JUUL System ("JUUL"), IQOS-brand heated tobacco product, and combustible cigarettes.

METHODS

Adult smokers (N = 40) completed a 5-arm cross-over product-use laboratory confinement study. Nicotine pharmacokinetics and subjective effects were assessed following use of: (1) JUUL2 prototype 18 mg/mL nicotine; (2) JUUL2 prototype 40 mg/mL; (3) JUUL 59 mg/mL; (4) IQOS 18 mg/g; and (5) usual brand combustible cigarette, each evaluated during ad libitum (10 min) and controlled (5 min, 10 standardized puffs) use.

RESULTS

Nicotine delivery was greatest for combustible cigarettes, followed by JUUL2 prototype 40 mg/mL, IQOS, JUUL2 prototype 18 mg/mL, and JUUL 59 mg/mL. Nicotine delivery from JUUL2 prototype 18 mg/mL was significantly greater than JUUL 59 mg/mL after ad libitum use. JUUL products were significantly more satisfying and effective at reducing craving than IQOS. JUUL2 prototype 40 mg/mL was significantly more aversive than other JUUL products.

CONCLUSIONS

Prototype JUUL2 and JUUL 59 mg/mL products were rated higher than IQOS on subjective measures associated with switching away from smoking. The JUUL2 prototype 40 mg/mL produced aversive responses and would require modifications to be a viable product for adult smokers. Nicotine delivery and subjective responses to JUUL2 prototype 18 mg/mL suggest a product based on this prototype may facilitate increased switching among adult smokers.

Carcinogenic biomarkers of exposure in the urine of heated tobacco product users associated with bladder cancer: A systematic review

To identify biomarkers of exposure present in Heated Tobacco Products (HTPs) users' urine which are associated with bladder cancer and to compare quantitative biomarker levels to those seen in combustible cigarette users. A systematic literature review was conducted in December 2020 with no date limits. Relevant studies that reported quantitative urinary biomarker of exposure in HTP users were included. Biomarkers and their parent compounds were classified by carcinogenicity according to the International Agency for Research on Cancer Monographs and were cross-referenced with the Collaborative on Health and the Environment Toxicant and Disease Database to determine associations with bladder cancer. Our literature search identified 561 articles and 30 clinical trial reports. 11 studies met inclusion criteria. These studies identified 29 biomarkers of exposure present in HTP users' urine, which reflect exposure to 21 unique parent compounds. Of these parent compounds, 14 are carcinogens and 10 have a known link to bladder cancer. HTP users' biomarkers of exposure were present at lower levels than combustible cigarette users but higher than never-smokers. Biomarkers of exposure to bladder carcinogens are present in the urine of HTP users. While levels of these biomarkers appear to be lower than combustible cigarette users, chronic urothelial exposure to bladder carcinogens is concerning and degree of bladder cancer risk remains unknown. Further long-term study is needed to elucidate the bladder cancer risk of HTP use.

Systems toxicology study reveals reduced impact of heated tobacco product aerosol extract relative to cigarette smoke on premature aging and exacerbation effects in aged aortic cells in vitro

Aging and smoking are major risk factors for cardiovascular diseases (CVD). Our in vitro study compared, in the context of aging, the effects of the aerosol of Tobacco Heating System 2.2 (THS; an electrically heated tobacco product) and 3R4F reference cigarette smoke (CS) on processes that contribute to vascular pathomechanisms leading to CVD. Young and old human aortic smooth muscle cells (HAoSMC) were exposed to various concentrations of aqueous extracts (AE) from 3R4F CS [0.014-0.22 puffs/mL] or THS aerosol [0.11-1.76 puffs/mL] for 24 h. Key markers were measured by high-content imaging, transcriptomics profiling and multianalyte profiling. In our study, in vitro aging increased senescence, DNA damage, and inflammation and decreased proliferation in the HAoSMCs. At higher concentrations of 3R4F AE, young HAoSMCs behaved similarly to aged cells, while old HAoSMCs showed additional DNA damage and apoptosis effects. At 3R4F AE concentrations with the maximum effect, the THS AE showed no significant effect in young or old HAoSMCs. It required an approximately ten-fold higher concentration of THS AE to induce effects similar to those observed with 3R4F. These effects were independent of nicotine, which did not show a significant effect on HAoSMCs at any tested concentration. Our results show that 3R4F AE accelerates aging in young HAoSMCs and exacerbates the aging effect in old HAoSMCs in vitro, consistent with CS-related contributions to the risk of CVD. Relative to 3R4F AE, the THS AE showed a significantly reduced impact on HAoSMCs, suggesting its lower risk for vascular SMC-associated pathomechanisms leading to CVD.

Analysis of furans and pyridines from new generation heated tobacco product in Japan

Background

In recent years, heated tobacco products (HTPs), which are widely used in Japan, have been sold by various brands using additives such as flavors. It has been reported that the components of mainstream smoke are different from those of conventional cigarettes. In this study, we established an analytical method for furans and pyridines in the mainstream smoke, which are characteristic of HTPs and particularly harmful among the generated components, and investigated the amount of component to which the smokers are exposed.

Methods

We established a simple analytical method for simultaneous analysis of gaseous and particulate compounds in the mainstream smoke of HTPs (IQOS, glo, ploom S) in Japan by combining a sorbent cartridge and glass fiber filter (Cambridge filter pad (CFP)). Both the sorbent cartridge and CFP were extracted using 2-propanol and analyzed via GC-MS/MS to determine the concentration of furans and pyridines generated from each HTP.

Results

The results showed that the levels of target furans such as furfural, 2-furanmethanol, 2(5H)-furanone, and 5-methylfurfural tended to be higher in the mainstream smoke of glo than in standard cigarettes (3R4F). Pyridine, which is generated at a high level in 3R4F as a combustion component, and 4-ethenylpyridine (EP), which is a known marker of environmental tobacco smoke, were detected. Among these components, 2-furanmethanol and pyridine are classified as Group 2B (possibly carcinogenic to humans) by the International Agency for Research on Cancer (IARC). Therefore, it is possible that they will contribute to the health effects caused by use of HTPs.

Conclusions

Using the new collection and analytical method for furans and pyridines in the mainstream smoke of HTPs, the level of each compound to which smokers are exposed could be clarified. By comprehensively combining information on the amount of ingredients and toxicity, it will be possible to perform a more detailed calculation of the health risks of using HTPs. In addition, the components detected in this study may be the causative substances of indoor pollution through exhaled smoke and sidestream smoke; therefore, environmental research on the chemicals generated from HTPs would be warranted in future studies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12199-021-01008-1.

The association between heated tobacco product use and cigarette cessation outcomes among youth smokers: A prospective cohort study

INTRODUCTION

The U.S. Food and Drug Administration authorized the marketing of heated tobacco products (HTPs) with modified-risk information for adults on July 7, 2020. However, the effects of HTP use on cigarette cessation among youth smokers remain unclear. This study aimed to explore the association of HTP use with cigarette abstinence and cessation outcomes among youth smokers in Hong Kong who were willing to receive telephone counseling for smoking cessation.

METHODS

This prospective cohort study included youth smokers aged ≤25 years who were enrolled in the Hong Kong Youth Quitline service. From December 1, 2016, to September 30, 2019, this study identified as HTP users 106 youth cigarette smokers who reported using HTPs on at least 1 of the past 30 days at enrollment, and identified as non-HTP users 473 smokers who reported smoking at least one conventional cigarette in the past 30 days and never using HTPs. The participants received follow-ups at 1 week and 1-, 3-, and 6-months postenrollment. The primary outcome was self-reported 7-day point prevalence of cigarette abstinence (PPA) at the 6-month follow-up. Secondary outcomes included reduction in cigarette smoking (excluding quitters), the number of cessation attempts, and the level of readiness to quit.

RESULTS

The self-reported 7-day PPA was statistically significantly lower among HTP users than among non-HTP users after 6 months (19.0% vs. 34.2%; p = 0.009), with an adjusted relative risk of 0.47 (95% confidence interval: 0.24-0.91; p = 0.03). The study identified no significant differences in secondary outcomes between the two groups.

CONCLUSIONS

Youth HTP users were less likely to abstain from tobacco use than their non-HTP-using counterparts. These results suggest that HTPs should not be promoted as smoking cessation or reduction aids among the youth population.

Comparative and cumulative quantitative risk assessments on a novel heated tobacco product versus the 3R4F reference cigarette

Novel tobacco products that heat rather than burn tobacco (heated tobacco products or HTPs) have been shown to produce lower levels of harmful and potentially harmful constituents than conventional combusted cigarettes. The present study uses a quantitative risk assessment approach to compare non-cancer and cancer risk estimates for emissions generated by an HTP with smoke from a reference cigarette (3R4F). Fifty-four analytes were evaluated from the HTP aerosol and the 3R4F cigarette smoke. Emissions were generated using the ISO and the Health Canada Intense smoking regimes. The measured values were extrapolated to define a conservative exposure assumption for per day use and lifetime use based on an estimated maximum usage level of 400 puffs per day i.e., approximately 8 HTP tobacco capsules or 40 combustible cigarettes. Non-cancer and cancer risk estimates were calculated using these exposure assumptions for individual and per health outcome domains based on toxicological reference values derived by regulatory and/or public health agencies. The results of this assessment showed a reduction of non-cancer and cancer risk estimates by more than 90 % for the HTP versus the 3R4F cigarette, regardless of the smoking regime.

Cancer potencies and margin of exposure used for comparative risk assessment of heated tobacco products and electronic cigarettes aerosols with cigarette smoke

Health risk associated with the use of combustible cigarettes is well characterized and numerous epidemiological studies have been published for many years. Since more than a decade, innovative non-combusted tobacco products have emerged like heated tobacco products (HTP) or electronic cigarettes (EC). Long-term effects of these new products on health remain, however, unknown and there is a need to characterize associated potential health risks. The time dedicated to epidemiological data generation (at least 20 to 40 years for cancer endpoint), though, is not compatible with innovative development. Surrogates need, therefore, to be developed. In this work, non-cancer and cancer risks were estimated in a range of HTP and commercial combustible cigarettes based upon their harmful and potentially harmful constituent yields in aerosols and smoke, respectively. It appears that mean lifetime cancer risk values were decreased by more than one order of magnitude when comparing HTPs and commercial cigarettes, and significantly higher margin of exposure for non-cancer risk was observed for HTPs when compared to commercial cigarettes. The same approach was applied to two commercial ECs. Similar results were also found for this category of products. Despite uncertainties related to the factors used for the calculations and methodological limitations, this approach is valuable to estimate health risks associated to the use of innovative products. Moreover, it acts as predictive tool in absence of long-term epidemiological data. Furthermore, both cancer and non-cancer risks estimated for HTPs and ECs highlight the potential of reduced risk for non-combusted products when compared to cigarette smoking.

A meta-analysis of microRNAs expressed in human aerodigestive epithelial cultures and their role as potential biomarkers of exposure response to nicotine-containing products

The expression of some microRNAs (miRNA) is modulated in response to cigarette smoke (CS), which is a leading cause of major preventable diseases. However, whether miRNA expression is also modulated by the aerosol/extract from potentially reduced-risk products is not well studied. The present work is a meta-analysis of 12 in vitro studies in human organotypic epithelial cultures of the aerodigestive tract (buccal, gingival, bronchial, nasal, and small airway epithelia). These studies compared the effects of exposure to aerosols from electronic vapor (e-vapor) products and heated tobacco products, and to extracts from Swedish snus products (in the present work, will be referred to as reduced-risk products [RRPs]) on miRNA expression with the effects of exposure to CS or its total particulate matter fraction. This meta-analysis evaluated 12 datasets of a total of 736 detected miRNAs and 2775 exposed culture inserts. The t-distributed stochastic neighbor embedding method was used to find similarities across the diversity of miRNA responses characterized by tissue type, exposure type, and product concentration. The CS-induced changes in miRNA expression in gingival cultures were close to those in buccal cultures; similarly, the alterations in miRNA expression in small airway, bronchial, and nasal tissues resembled each other. A supervised clustering was performed to identify miRNAs exhibiting particular response patterns. The analysis identified a set of miRNAs whose expression was altered in specific tissues upon exposure to CS (e.g., miR-125b-5p, miR-132-3p, miR-99a-5p, and 146a-5p). Finally, we investigated the impact of RRPs on miRNA expression in relation to that of CS by calculating the response ratio r between the RRP- and CS-induced alterations at an individual miRNA level, showing reduced alterations in miRNA expression following RRP exposure relative to CS exposure (94 % relative reduction). No specific miRNA response pattern indicating exposure to aerosols from heated tobacco products and e-vapor products, or extracts from Swedish snus was identifiable.

Comprehensive chemical characterization of the aerosol generated by a heated tobacco product by untargeted screening

A suite of untargeted methods has been applied for the characterization of aerosol from the Tobacco Heating System 2.2 (THS2.2), a heated tobacco product developed by Philip Morris Products S.A. and commercialized under the brand name IQOS®. A total of 529 chemical constituents, excluding water, glycerin, and nicotine, were present in the mainstream aerosol of THS2.2, generated by following the Health Canada intense smoking regimen, at concentrations ≥ 100 ng/item. The majority were present in the particulate phase (n = 402), representing more than 80% of the total mass determined by untargeted screening; a proportion were present in both particulate and gas-vapor phases (39 compounds). The identities for 80% of all chemical constituents (representing > 96% of the total determined mass) were confirmed by the use of authentic analytical reference materials. Despite the uncertainties that are recognized to be associated with aerosol-based untargeted approaches, the reported data remain indicative that the uncharacterized fraction of TPM generated by THS2.2 has been evaluated to the fullest practicable extent. To the best of our knowledge, this work represents the most comprehensive chemical characterization of a heated tobacco aerosol to date. Graphical abstract.

Comparison of cytotoxicity of IQOS aerosols to smoke from Marlboro Red and 3R4F reference cigarettes

This study compared the cytotoxicity of IQOS aerosols to smoke from Marlboro Red (MR) and 3R4F reference cigarettes. Aerosol/smoke solutions were tested as the gas vapor phase (GVP), particulate phase (total particulate matter or TPM), or whole aerosol/smoke (WA), the latter being what smokers actually inhale. Cytotoxicities were evaluated using the LDH, MTT and neutral red uptake (NRU) assays in conjunction with eight different cell types, mainly from the respiratory system. Most test solutions did not compromise the plasma membranes of cells (LDH). However, mitochondrial activity (MTT) and dye uptake/lysosomal activity (NRU) were equally depressed by IOQS aerosols and cigarette smoke solutions at the high concentrations. Our NRU data with mouse NIH/3T3 transformed fibroblasts were similar to those previously reported by the IQOS manufacturer and showed little cytotoxicity in the NRU assay. In both studies with NIH/3T3 cells, the results were significantly different from 3RF4 cigarette smoke, suggesting reduced toxicity with IQOS. However, by expanding evaluations to a broader spectrum of cells that included respiratory system cells and by including higher concentrations of GVP, as well as WA, cytotoxicity equivalent to that of Marlboro Red and 3R4F cigarettes was frequently observed with IQOS aerosols in the MTT and NRU assays.

Accurate measurement of main aerosol constituents from heated tobacco products (HTPs): Implications for a fundamentally different aerosol

ISO 4387 Standard determines the main aerosol constituents (total particulate matter, water, nicotine, and nicotine-free-dry-particulate matter, referred to as "tar") in cigarette mainstream smoke (ISO, 2000). Heated Tobacco Products (also called Tobacco Heating Products or Heat-not-Burn Products) are designed to form aerosol by heating tobacco rather than burning like in combustible cigarettes. In this study we have evaluated the suitability of ISO 4387 Standard to be adapted for quantifying main aerosol constituents for HTP aerosol. HTP emissions have much higher levels of water and humectants (e.g., glycerol) in dynamic equilibria between gaseous and particulate phases. Several modifications to ISO 4387 Standard on aerosol collection were tested to improve the accuracy and reliability of aerosol capturing, with minimal deviation to the standard method. The proposed modifications are readily adoptable by laboratories already practicing the Standard for cigarette smoke analyses. Taking collectively with other available aerosol chemistry and biological results on HTPs in the literature, they show a fundamentally different aerosol in HTPs and call for category-specific product standards and terminology.

Criminal mercury vapor poisoning using heated tobacco product

We report an unusual case of mercury vapor poisoning from using a heated tobacco product. The suspect had added grains of mercury into 20 cigarettes in a pack. When a 36-year-old Japanese man inserted one of these cigarettes into the battery powered holder, it was heated to a temperature of 350 °C, and he inhaled vaporized mercury. After using 14 of the cigarettes over 16 h, he noticed he had flu-like symptoms so he visited the hospital. Although no physical abnormalities were revealed, 99 μg/L of mercury was detected in his serum sample. His general condition improved gradually and his whole blood mercury level had decreased to 38 μg/L 5 days later. When the remaining six cigarettes in the pack were examined, many metallic grains weighing a total of 1.57 g were observed. Energy dispersive X-ray fluorescence spectrometry confirmed the grains as elemental mercury. Accordingly, the victim was diagnosed with mercury poisoning. Because the mercury was incorporated into cigarettes, an unusual and novel intoxication occurred through the heating of the tobacco product. Both medical and forensic scientific examination confirmed this event as attempted murder.