Heated Tobacco Products: Insights into Composition and Toxicity

Research progress and prospect on the safety of heated tobacco products

In recent years, Heated tobacco products (HTP) have gradually entered the market and become more and more popular with consumers because of their low risk (compared with traditional cigarette). With the increasing popularity and proportion of HTP in the international market, people pay more and more attention to the safety evaluation of HTP, but there is still a lack of systematic review of HTP safety research. In this review, the harmful components of HTP, multi-organ functional programming effects (including respiratory system, cardiovascular system, etc.), and mechanism of the effect generation (including oxidative stress, inflammatory response, etc.) were systematically reviewed, the safety effects of HTP and traditional cigarettes were compared in detail, and the shortcomings and future research directions in the field of HTP safety were discussed. In summary, this review conforms to the general trend of contemporary "tobacco and health", helps people to understand and evaluate HTP more systematically, and provides a strong theoretical support and literature basis for the tobacco industry to carry out HTP risk assessment and exposure improvement.

A single and short exposure to heated tobacco vapor or cigarette smoke affects macrophage activation and polarization

The toxicity of heated tobacco products (HTP) on the immune cells remains unclear. Here, U937-differentiated macrophages were exposed to a single and short-term exposure (30 minutes) of HTP vapor or cigarette smoke (CS) in an air-liquid interface (ALI) system to evaluate the effects on macrophages' early activation and polarization. In our system, HTP released lower amounts of polycyclic aromatic hydrocarbons (PAHs), but higher nicotine levels than CS into the cell culture supernatant. Both tobacco products triggered the expression of the α-7 nicotinic receptor (α7 nAChR) and reactive oxygen species (ROS) production. When challenged with a bacterial product, lipopolysaccharide (LPS), cells exposed to HTP or CS failed to respond properly and enhance ROS production upon LPS stimuli. Furthermore, both tobacco products also impaired bacterial phagocytosis and the exposures triggered higher IL-1β secretion. The α7 nAChR antagonist treatment rescued the effects caused only by HTP exposure. The CS-exposed group switched macrophage to the pro-inflammatory M1, while HTP polarized to the suppressive M2 profile. Associated, data highlight that HTP and CS exposures similarly activate macrophages; nonetheless, the α7 nAChR pathway is only involved in HTP actions, and the distinct subsequent polarization caused by HTP or CS may influence the outcome of host defense.

Patterns and socioeconomic differences in secondhand exposure to cigarettes, e-cigarettes, and heated tobacco products at home in Hong Kong adolescents

INTRODUCTION

Smoke or aerosols from cigarettes, e-cigarettes (ECs), or heated tobacco products (HTPs) are harmful. Yet, there is little knowledge about the specific patterns of secondhand tobacco exposure by source within household settings and the socioeconomic status (SES) differences in adolescents.

METHODS

We used territory-representative student data from a cross-sectional school-based survey in 2020-2021 to calculate the weighted prevalence of secondhand exposure to cigarettes, e-cigarettes, and HTPs in the past seven days. Parental education and perceived family affluence were used as indicators of socioeconomic status. Generalized linear mixed models were used to analyze associations.

RESULTS

Among 22039 participants, 29.8% reported any secondhand tobacco exposure (SH-Any) at home, primarily from cigarettes (27.4%), followed by e-cigarettes (4.0%) and HTPs (0.9%). Tertiary parental education level was associated with lower SH-Any exposure (Adjusted odds ratio, AOR=0.49; 95% CI: 0.45-0.53, p<0.001), fewer exposure days (β= -0.685, p<0.001), lower exposure to cigarettes (SH-CC) (AOR=0.49; 95% CI: 0.45-0.54, p<0.001) and to e-cigarettes or HTPs (SH-EC/HTP) (AOR=0.57; 95% CI: 0.45-0.71, p<0.001). 'Poor' family affluence was associated with higher exposures [AOR(SH-Any) =1.14; 95% CI: 1.06-1.22, p=0.001; β(days)=0.160, p<0.001; AOR(SH-CC) =1.15; 95% CI: 1.07-1.24, p<0.001], except for SH-EC/HTP exposure, which was higher in students in an affluent family (AOR =1.66; 95% CI: 1.25-2.21, p<0.001). Significant SES differences in SH-EC/HTP exposure were found only in groups with low parental education level. Dose-response relationships were found between lower SH-Any and SH-CC and higher SES categories (p for trend<0.001).

CONCLUSIONS

Adolescents experienced a high prevalence of tobacco smoke exposure at home, primarily from cigarettes. Higher SES was associated with lower tobacco exposure, except for SH-EC/HTP, which was higher among adolescents from affluent families. Additionally, high parental education level was protective against exposure to SH-EC/HTP. Comprehensive control measures to reduce the use of these tobacco products are needed to protect adolescents of diverse socioeconomic backgrounds.

Evaluation of Cytotoxic and Genotoxic Effects in Buccal Mucosal Cells in Non-Smokers and Users of Traditional Combustible Tobacco Products and Non-Combustible Alternatives

AIMS/OBJECTIVES

The aim of this cross-sectional observational study was to investigate cytogenetic damage to the buccal mucosa in non-smokers and consumers of traditional combustible tobacco products and non-combustible alternatives.

METHODS

A total of 160 participants were divided into four groups according to the type of product used, including non-smokers, users of conventional combustible tobacco (cigarettes), heated tobacco, and electronic, tobacco-free vapor products (e-cigarettes). Buccal mucosa samples were analyzed using the micronucleus cytome assay to assess cytotoxic and genotoxic damage.

RESULTS

E-cigarette users showed significantly higher values for all tested parameters in the micronucleus test compared to non-smokers (p < 0.05). Similarly, users of tobacco heating products showed an increase in all parameters (p < 0.05), with the exception of the number of cells with micronuclei. Conventional cigarette smokers showed a notable increase in the number of binucleated cells and cells with karyorrhexis and karyolysis (p ≤ 0.05). When assessing the differences between users of traditional combustible tobacco products and non-combustible alternatives, these did not appear to be significant, except for e-cigarette users, who had significantly more cells with condensed chromatin (p ≤ 0.001), while users of tobacco heating products had more pyknotic cells (p ≤ 0.001).

CONCLUSION

The results of this study underscore the heightened occurrence of cytotoxic and genotoxic damage in users of both conventional combustible tobacco products and non-combustible alternatives compared to non-smokers, emphasizing the detrimental impact of these products on the oral mucosa.