Assessment of the exposure to polycyclic aromatic hydrocarbons in users of various tobacco/nicotine products by suitable urinary biomarkers

Estimating lung cancer risk from e-cigarettes and heated tobacco products: applications of a tool based on biomarkers of exposure and of potential harm

BACKGROUND

Reliable epidemiological data are limited on the lung cancer risk of groups using e-cigarettes (ECIGs) and groups using heated tobacco products (HTPs).

AIM

We describe a methodology to estimate the lung cancer risk of these groups according to their levels of biomarkers of exposure (BOEs) and of potential harm (BOPHs).

METHODS

Using 28 search terms for BOEs and 82 for BOPHs we sought publications reporting biomarker-specific data from North America and Europe comparing individuals who smoke cigarettes and individuals who use other established products (ETPs; cigars, pipes, smokeless tobacco (ST) and/or snuff/snus). Publications were selected using defined inclusion/exclusion criteria. Additionally using lung cancer relative risk (RR) estimates for users of specific ETPs derived from recent meta-analyses of epidemiological studies in these regions, we derived a regression model predicting the lung cancer RR by level of each specific biomarker. Separately for groups using ECIGs and using HTPs the lung cancer risk was then estimated by combining RR estimates for selected biomarkers. Our primary estimates only considered biomarkers statistically significantly (p < 0.01) related to lung cancer risk which showed no significant (p < 0.01) misfit to the RR of 1.0 for non-users-those with no use of ETPs, ECIGs or HTPs.

RESULTS

Based on 38 available publications, we extracted biomarker-specific data for ETPs for 56 BOEs within 21 of the 28 search terms considered and for 54 BOPHs within 29 of the 82. The regression slope fitted to the lung cancer risk was significant (p < 0.01) for 22 BOEs and six BOPHs. However, the predicted RR for non-users significantly (p < 0.01) differed from 1.0 for 16 of these biomarkers. We estimated the lung cancer RR for using ECIGs, derived from 30 estimates for 10 biomarkers, as 1.88 (95% CI 1.60-2.22), the excess risk (ER = RR - 1) being 6.8% of that for smokers of cigarettes. The RR estimate varied little in most sensitivity analyses conducted, but increased markedly after removing the restriction to significant model fit. We estimated the lung cancer RR for using HTPs, combining estimates for four BOEs, as 1.44 (0.41-5.08), the ER being 3.4% of that for smokers of cigarettes.

CONCLUSIONS

Despite some methodological limitations, our approach estimates risk when reliable epidemiological data are unavailable. Using the biomarkers considered here, the model indicates that the lung cancer risk for individuals using ECIGs is much lower than for smokers of cigarettes, and suggests that the risk for those using HTPs is also low. Research using additional data could add precision to these findings.

Oral health risks in adults who use electronic nicotine delivery systems and oral nicotine pouches: a critical review of the literature and qualitative synthesis of the available evidence

BACKGROUND

Use of combustible cigarettes (CCs) and smokeless oral tobacco products are well documented risk factors for a variety of oral diseases. However, the potential oral health risks of using recently introduced (since about 2000) non-combustible tobacco/nicotine products (NCPs: electronic cigarettes (ECs), heated tobacco products (HTPs) and oral nicotine pouches (ONPs), remain poorly established.

METHODS

This review evaluates published human studies on detrimental oral health effects in people who use NCPs compared to those smoking cigarettes and those not using any tobacco/nicotine product (NU). We identified 52 studies, predominantly focusing on adults who used electronic cigarettes as an NCP. The studies exhibited significant heterogeneity regarding design, populations, endpoints and quality. Reported outcomes, based on both single and grouped endpoints were qualitatively evaluated by comparing people who use NCPs with NU and with people smoking CCs. Significant increases (indicating a worsening in oral health), significant decreases (indicating a lower level of detrimental effects) and no significant difference between groups were assigned scores of + 1, -1 and 0, respectively. Scores from studies belonging to the same single or grouped endpoints were averaged to a summary score ranging from - 1 to + 1.

RESULTS

The qualitative meta-analysis revealed that comparisons of EC versus NU groups yielded mean scores of 0.29 for pre-cancerous lesions (N = 14 observations), 0.27 for inflammatory processes (N = 83), 0.43 for oral clinical parameters (N = 93) and 0.70 for shifts in the oral microbiome (N = 10). The corresponding values for the EC versus CC group comparisons amounted to -0.33 (N = 15), -0.14 (N = 76), -0.27 (N = 78) and 0.57 (N = 7). Most studies had significant limitations regarding group sizes, duration of NCP use (mostly only a few years) and validity of self-reported exclusive NCP use. Notably, the implications of dual use (EC + CC) and prior CC use were often not adequately considered.

CONCLUSIONS

The evaluated studies suggest that use of ECs is associated with relatively fewer detrimental oral health effects compared to smoking, yet oral health status remains poorer compared to not using any tobacco/nicotine products. These results have to be interpreted with caution due to a number of limitations and uncertainties in the underlying studies, particularly the potential biases and confounding factors inherent in cross-sectional study designs.

Identification of Specific Hemoglobin Adduct Patterns in Users of Different Tobacco/nicotine Products by Nontargeted GC-MS/MS Analysis

Tobacco smoke contains several electrophilic constituents which are capable of forming adducts with nucleophilic sites in DNA and proteins like hemoglobin (Hb) and albumin. New nicotine and tobacco products are discussed as less harmful forms of tobacco use compared to smoking combustible cigarettes (CC) due to reduced exposure to harmful constituents. Hence, the adduct profile in users of various tobacco/nicotine products is expected to differ characteristically. In this article, we present a novel nontargeted screening strategy using GC-MS/MS for Hb adducts based on the analysis of the respective derivatized N-terminal valine adducts after modified Edman degradation. We analyzed blood samples from a clinical study with habitual users of CCs, electronic cigarettes, heated tobacco products (HTPs), oral tobacco, nicotine replacement therapy products and nonusers of any tobacco/nicotine products. Our nontargeted approach revealed significant differences in the Hb adduct profiles of the investigated tobacco/nicotine product user groups. Adduct identification was performed by means of an internal database, retention time estimations based on the theoretical boiling points, as well as in-house synthesized reference compounds. Several chemicals that form adducts with Hb could be identified: methylating and ethylating agents, ethylene oxide, acrylonitrile, acrylamide, glycidamide and 4-hydroxybenzaldehyde. Levels were elevated in smokers compared to all other groups for Hb adducts from methylating agents, ethylene oxide, acrylonitrile, acrylamide and glycidamide. Our approach revealed higher concentrations of Hb adducts formed by ethylation, acrylamide and glycidamide in users of HTPs compared to nonusers. However, concentrations for the latter two were still lower than in smokers. Due to their long half-lives, Hb adducts related to acrylonitrile, acrylamide (glycidamide), and ethylene oxide exposure may be useful for the biochemical verification of subjects̀ compliance in longitudinal and cross-sectional studies with respect to smoking and HTP use/abstinence.

A comprehensive non-targeted approach for the analysis of biomarkers in exhaled breath across different nicotine product categories

In the context of the evolving landscape of nicotine consumption, the assessment of biomarkers plays a crucial role in understanding the health impact of different product categories. Exhaled breath (EB) emerges as a promising, non-invasive matrix for biomarker analysis, complementary to conventional urine and plasma data. This study explores distinctive EB biomarker profiles among users of combustible cigarettes (CC), heated tobacco products (HTP), electronic cigarettes (EC), smokeless/oral tobacco (OT), and oral/dermal nicotine products (NRT). We have successfully developed and validated a non-targeted GC-TOF-MS method for the analysis of EB samples across the aforementioned product categories. A total of 66 compounds were identified, with significantly elevated levels in at least one study group. The study found that CC users had higher levels of established VOCs associated with smoking, which supports the proof-of-concept of the method. Breathomic analysis identified increased levels of p-cymene and α-pinene in EC users, while HTP users showed potential biomarker candidates like γ-butyrolactone. This study underscores the utility of EB biomarkers for a comprehensive evaluation of diverse nicotine products. The unique advantages offered by EB analysis position it as a valuable tool for understanding the relationship between exposure and health outcomes.

Benzo[b]fluoranthene damages coronary artery and affects atherosclerosis markers in mice and umbilical vein endothelial cells

Polycyclic aromatic hydrocarbons (PAHs) exposure is associated with cardiovascular diseases. Toxic effects of PAHs are diverse, while cardiovascular consequences of benzo[b]fluoranthene (B[b]F) are unclear. Here, we reported the impacts of B[b]F on coronary artery and atherosclerosis markers both in mice and umbilical vein endothelial EAhy.926 cells. In mice, we found that B[b]F decreases heart-to-body weight ratio, affects aortic physiology, elevates serum low-density lipoprotein and total cholesterol, increases aortic levels of collagen fiber and atherosclerotic marker vascular cell adhesion molecule-1 (VCAM-1), and downregulates oxidative stress related nuclear factor erythroid 2-related factor 2 (Nrf2). In EAhy.926 cells, we showed that B[b]F inhibits cell proliferation and migration in a dose-dependent manner, induces cell cycle arrest and apoptosis, increases reactive oxygen species, upregulates VCAM-1 level, and suppresses expression of Nrf2. Taken together, our findings reveal that B[b]F exposure may contribute to coronary artery damage and potentially induce atherosclerosis, possibly via the Nrf2-related signaling pathways.

Development of an LC-HRMS non-targeted method for comprehensive profiling of the exposome of nicotine and tobacco product users - A showcase for cigarette smokers

The global prevalence of electronic cigarettes, heated tobacco products, and other smokeless alternatives has grown significantly in the last ten years. These products have been suggested as combustion-free alternatives for conventional tobacco products like cigarettes, aiming to reduce the negative health impacts associated with smoking. However, the impact of those products on the health and safety of the general population are still unclear, as the absolute exposure from those products has not been thoroughly studied, yet. In this project, a non-targeted LC-HRMS method was developed comprising four different analytical modes for the investigation of the exposure profile in urine of the product users. The method is characterized by its high sensitivity and reproducibility, as shown during method validation. As a proof of concept, we first applied this method to detect significant differences in biomarkers of exposure (BoEs) between smokers and non-smokers. We observed a total of 171 BoEs significantly elevated in smokers, including several well-known biomarkers of smoke exposure like nicotine and its metabolites, mercapturic acid derivatives, and phenolic compounds. Some of the detected biomarkers are present at low ng/mL concentrations in urine, proving the high sensitivity needed for a holistic exploration of the exposome. Moreover, we were able to identify BoEs that have not been reported previously for smoking, such as 2,6-dimethoxyphenol and 7-methyl-1-naphthol glucuronide.

Renal excretion of 1,2-dihydroxynaphthalene (DHN) in firefighting instructors after exposure to polycyclic aromatic hydrocarbons (PAHs) during live fire training

Exposure of firefighting instructors to polycyclic aromatic hydrocarbons (PAHs) such as naphthalene is unavoidable during live fire training. The study aimed to investigate naphthalene uptake by measuring the urinary excretion of the naphthalene metabolite 1,2-dihydroxynaphthalene (DHN), to describe the DHN elimination kinetics and to evaluate the results by comparison to further biomarkers of PAH exposure. N = 6 male non-smoking firefighting instructors completed five training sessions each in a residential fire simulation unit under respiratory protection. All participants provided two urine samples before and another seven samples within an 18-h-interval after each session. DHN was detected by gas chromatography/tandem mass spectrometry (GC-MS/MS) in all samples (n = 237) with median concentrations ranging from 3.3 µg/g crea. (range 0.9-10.2) before exposure to 134.2 µg/g crea. (43.4-380.4) post exposure. Maximum elimination found 3.3 h (median) after onset of exposure decreased with a mean half-life of 6.6 h to 27.1 µg/g crea. (15.7-139.5) 18 h after training. DHN sensitively indicated a presumed dermal naphthalene intake during training, showing similar elimination kinetics like other naphthalene metabolites. Internal exposure of the participants transiently exceeded exposures determined for non-smokers in the general population, but was lower than at other workplaces with PAH exposure. Despite limited uptake, accumulation is possible with daily exposure.

The Product Science of Electrically Heated Tobacco Products: An Updated Narrative Review of the Scientific Literature

Heated tobacco products represent a novel category of tobacco products in which a tobacco consumable is heated to a temperature that releases nicotine from the tobacco leaf but not to a temperature sufficient to cause combustion. Heated tobacco products may therefore have the potential to be a less harmful alternative for adult smokers who would otherwise continue to smoke cigarettes, as their use should result in exposure to substantially fewer and lower levels of toxicants. This update represents a two-year extension to our previous narrative review, which covered peer-reviewed journal articles published up to August 31, 2021. The scientific evidence published between 2021 and 2023 continues to indicate that aerosols produced from heated tobacco products contain fewer and substantially lower levels of harmful and potentially harmful constituents and that these observed reductions consistently translate to reduced biological effects in both in vitro and in vivo toxicological studies. Biomarker and clinical data from studies in which product use is controlled within a clinical setting continue to suggest changes in levels of biomarkers of exposure, biomarkers of potential harm, and clinical endpoints indicating the potential for reduced harm with switching to exclusive use of heated tobacco products in adult smokers. Overall, the available peer-reviewed scientific evidence continues to indicate that heated tobacco products offer promise as a potentially less harmful alternative to cigarettes, and as such, the conclusions of our original narrative review remain valid.

Comparison of bladder carcinogenesis biomarkers in the urine of traditional cigarette users and e-cigarette users

Background

During the use of electronic cigarettes (e-cigarettes), users are still exposed to carcinogens similar to those found in tobacco products. Since these carcinogens are metabolized and excreted in urine, they may have carcinogenic effects on the bladder urinary tract epithelium. This meta-analysis aimed to compare bladder cancer carcinogens in the urine of tobacco users and e-cigarette users using a large number of samples.

Methods

A systematic meta-analysis was performed using data obtained from several scientific databases (up to November 2023). This cumulative analysis was performed following the Preferred Reporting Items for Systematic Evaluation and Meta-Analysis (PRISMA) and Assessing the Methodological Quality of Systematic Evaluations (AMSTAR) guidelines, according to a protocol registered with PROSPERO. This study was registered on PROSPERO and obtained the unique number: CRD42023455600.

Results

The analysis included 10 high-quality studies that considered polycyclic aromatic hydrocarbons (PAHs), volatile organic compounds (VOCs) and tobacco-specific nitrosamines (TSNAs). Statistical indicators show that there is a difference between the tobacco user group and the e-cigarette user group in terms of 1-Hydroxynaphthalene (1-NAP) [weighted mean difference (WMD)10.14, 95% confidence interval (CI) (8.41 to 11.88), p < 0.05], 1-Hydroxyphenanthrene (1-PHE) [WMD 0.08, 95% CI (-0.14 to 0.31), p > 0.05], 1-Hydroxypyrene (1-PYR) [WMD 0.16, 95% CI (0.12 to 0.20), p < 0.05], 2-Hydroxyfluorene (2-FLU) [WMD 0.69, 95% CI (0.58 to 0.80), p < 0.05], 2-Hydroxynaphthalene (2-NAP) [WMD 7.48, 95% CI (4.15 to 10.80), p < 0.05], 3-Hydroxyfluorene (3-FLU) [WMD 0.57, 95% CI (0.48 to 0.66), p < 0.05], 2-Carbamoylethylmercapturic acid (AAMA) [WMD 66.47, 95% CI (27.49 to 105.46), p < 0.05], 4-Hydroxy-2-buten-1-yl-mercapturic acid (MHBMA) [WMD 287.79, 95% CI (-54.47 to 630.04), p > 0.05], 4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNAL) [WMD 189.37, 95% CI (78.45 to 300.29), p < 0.05], or N0-nitrosonornicotine (NNN) [WMD 11.66, 95% CI (7.32 to 16.00), p < 0.05].

Conclusion

Urinary bladder cancer markers were significantly higher in traditional tobacco users than in e-cigarette users.Systematic review registration: PROSPERO (CRD42023455600: https://www.crd.york.ac.uk/PROSPERO/).

A sensitive GC-MS/MS method for the quantification of benzo[a]pyrene tetrol in urine

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous pollutants formed during the incomplete combustion of organic matter such as tobacco. Among these, benzo[a]pyrene (BaP) has been classified as a known carcinogen to humans. It unfolds its effect through metabolic activation to BaP-(7R,8S)-diol-(9S,10R)-epoxide (BPDE), the ultimate carcinogen of BaP. In this article, we describe a simple and highly sensitive GC-NICI-MS/MS method for the quantification of urinary BaP-(7R,8S,9R,10S)-tetrol (( +)-BPT I-1), the hydrolysis product of BPDE. The method was validated and showed excellent results in terms of accuracy, precision, and sensitivity (lower limit of quantification (LLOQ): 50 pg/L). In urine samples derived from users of tobacco/nicotine products and non-users, only consumption of combustible cigarettes was associated with a significant increase in BPT I-1 concentrations (0.023 ± 0.016 nmol/mol creatinine, p < 0.001). Levels of users of potentially reduced-risk products as well as non-users were all below the LLOQ. In addition, the urine levels of six occupationally exposed workers were analyzed and showed the highest overall concentrations of BPT I-1 (844.2 ± 336.7 pg/L). Moreover, comparison with concentrations of 3-hydroxybenzo[a]pyrene (3-OH-BaP), the major detoxification product of BaP oxidation, revealed higher levels of 3-OH-BaP than BPT I-1 in almost all study subjects. Despite the lower levels, BPT I-1 can provide more relevant information on an individual's cancers susceptibility since BPDE is generated by the metabolic activation of BaP. In conclusion, BPT I-1 is a suitable biomarker to distinguish not only cigarette smokers from non-smokers but also from users of potentially reduced-risk products.

Electronic nicotine delivery systems (ENDS): A convenient means of smoking?

Electronic nicotine delivery systems (ENDS), which are becoming increasingly popular in many parts of the world, have recently become more sophisticated in terms of their more active content and better controlled vaporisation. This review begins by describing how cigarette smoking led to the development of ENDS as a means of combatting nicotine addiction. ENDS are usually categorised as belonging to one of only three main generations, but a fourth has been added in order to differentiate the latest, most powerful, most advanced and innovative that have improved heating efficiency. Descriptions of the principal substances contained in ENDS are followed by considerations concerning the risk of toxicity due to the presence of albeit low concentrations of such a variety of compounds inhaled over a long time, and the increasingly widespread use of ENDS as a means of smoking illicit drugs. We also review the most widely used pharmacotherapeutic approaches to smoking cessation, and recent epidemiological data showing that ENDS can help some people to stop smoking. However, in order to ensure their appropriate regulation, there is a need for higher-quality evidence concerning the health effects and safety of ENDS, and their effectiveness in discouraging tobacco smoking.

Time trend of exposure to secondhand tobacco smoke and polycyclic aromatic hydrocarbons between 1995 and 2019 in Germany - Showcases for successful European legislation

Starting in 2002, regulations and legislative amendments in Germany focused on the non-smoker protection with several measures to reduce exposure to secondhand tobacco smoke (SHS). The present work aimed to evaluate the relationship between polycyclic aromatic hydrocarbons (PAHs) and SHS exposure and to determine to which extent enforced non-smoking regulations and smoking bans affected the exposure of the non-smoking population in Germany since their implementation in the early 2000s until today. For this purpose, cotinine and selected monohydroxylated PAHs (OH-PAHs) were analyzed by means of (UP)LC-MS/MS in 510 24-h-urine samples of the Environmental Specimen Bank collected over a time span of 24 years from 1995 to 2019. Median urinary cotinine levels were found to steadily and significantly decline by 82% from 1995 to 2019. A significant decrease of urinary 3-hydroxybenzo[a]pyrene (19%), 1-OH-pyrene (39%), 1-naphthol (66%), 1- (17%), 2- (25%), and 3-OH-phenanthrene (22%) was also observed throughout the same time span. The decline in urinary levels of cotinine and several OH-PAHs can most likely be attributed to smoking bans and regulations limiting SHS and PAH exposure. This study therefore emphasizes the relevance of human biomonitoring to investigate the exposure of humans to chemicals of concern, assess the effectiveness of regulatory measures, and help policies to enforce provisions to protect public health.

Assessment of the Exposure to Aromatic Amines in Users of Various Tobacco/Nicotine Products

Aromatic amines such as ortho-toluidine (o-Tol), 2-aminonaphthalene (2-AN), and 4-aminobiphenyl (4-ABP) are human bladder carcinogens and occur at various workplaces, in ambient air, in food products, as well as in tobacco smoke. In a clinical study comprising a period of 74 h under confinement, we investigated the exposure to these three aromatic amines as well as to 3-aminobiphenyl (3-ABP) by measuring them in urine of habitual users of combustible cigarettes (CCs), electronic cigarettes (ECs), heated tobacco products (HTPs), oral tobacco (OT), and nicotine replacement therapy products (NRTs). Non-users (NU) of any tobacco/nicotine products served as (negative) control group. Smokers (CC) exhibited the highest levels for all four aromatic amines measured, significantly elevated compared to NU and non-CC users. Urinary levels in users of EC, HTP, NRT (mostly nicotine gum), and OT (mostly snus) were not significantly different from those in NU. Users of HTP showed slightly elevated urinary excretion levels of o-Tol, 3-ABP, and 4-ABP compared to some other non-CC groups. Dose markers such as daily consumption, urinary nicotine equivalents (Nequ), and plasma cotinine (CotP) were found to be consistently and significantly correlated with the excretion of aromatic amines for smokers (CC) only. Excretion levels of 3- and 4-ABP in smokers were significantly lower in the urine collected overnight compared to that collected during the day, which is just the opposite of what we observed for other biomarkers in this study. The possible reason for this observation is discussed. In conclusion, in contrast to smoking of CCs, the use of ECs, HTPs, nicotine gum, and oral tobacco was not observed to be associated with significant exposure to the aromatic amines o-Tol, 2-AN, 3-ABP, and 4-ABP. The observed slight increase in o-Tol, 3-ABP, and 4-ABP excretions in HTP users has to be verified in larger studies.