Tobacco-specific Nitrosamines Exposure Research Articles

Exposure to Tobacco-Specific Nitrosamines Among People Who Vape, Smoke, or do Neither: A Systematic Review and Meta-Analysis.

Smoking exposes people to high levels of Tobacco-Specific Nitrosamines (TSNAs), which include potent carcinogens. We systematically reviewed TSNA exposure between people smoking, vaping, and doing neither. Databases were searched between August 2017-March 2022, using vaping-related terms. Peer-reviewed articles reporting TSNA metabolites (NNAL, NNN, NAB, and NAT) levels in bio-samples among adults exclusively vaping, exclusively smoking, or doing neither were included. Where possible, meta-analyses were conducted. Of 12 781 identified studies, 22 were included. TSNA levels fell substantially when people who smoke switched to vaping in longitudinal studies and were lower among people who vaped compared to smoked in cross-sectional studies. Levels of TSNAs were similar when comparing people who switched from smoking to vaping, to those who switched to no use of nicotine products, in longitudinal studies. Levels were higher among people who vaped compared to people who neither vaped nor smoked in cross-sectional studies.When comparing people who vaped to smoked: pooled urinary NNAL was 79% lower across three randomized controlled trials and 96% lower across three cross-sectional studies; pooled NAB was 87% lower and NAT 94% lower in two cross-sectional studies. When comparing people who neither vaped nor smoked to people who vaped, pooled urinary NNAL was 80%, NAB 26%, and NAT 27% lower in two cross-sectional studies. Other longitudinal data, and NNN levels could not be pooled. Exposure to all TSNAs was lower among people who vaped compared to people who smoked. Levels were higher among people who vaped compared to people who neither vaped nor smoked. As well as TSNAs, there are many other toxicant exposures from smoking and vaping that can increase the risk of disease. However, it is likely that the reduced exposure to TSNAs from vaping relative to smoking reduces the risk to health of those who use vaping products to quit smoking. Future high-quality research, with robust definitions of exclusive vaping and smoking, and accounting for TSNAs half-lives, is needed to fully assess exposure to TSNAs among people who vape.

Biomarkers of Toxic Exposure and Oxidative Stress Among U.S. Adult Users of Premium Cigar Versus Other Cigar Subtypes: 2013-2019.

Cigars are currently the second-highest-used combustible tobacco product among U.S. adults, but knowledge about health effects of premium cigars versus other cigar subtype use is limited. This study analyzed the biospecimen data (n = 31 875) from Waves 1-5 of the Population Assessment of Tobacco and Health Study, collected during 2013-2019. Multivariable generalized estimation equations, accounting for within-person clustering, were conducted to examine differences in urine biomarkers of exposure (BOE) from five classes of harmful and potentially harmful constituents along with a biomarker of oxidative stress (urine 8-isoprostane) among exclusive users of premium cigars versus other exclusive cigar subtypes (ie, non-premium large cigars, cigarillos, and filtered cigars), cigarettes, and non-tobacco users. In comparison to non-tobacco users, exclusive premium cigar users had higher geometric mean concentrations of the nicotine metabolite cotinine (5.8 vs. 0.5ng/mg, p < .0001), tobacco-specific nitrosamine (TSNA) (4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL): 7.8 vs. 1.3pg/mg, p < .0001), and volatile organic compound (VOC) (N-Acetyl-S-(2-cyanoethyl)-L-cysteine (CYMA, acrylonitrile): 4.7 vs. 1.6ng/mg, p < .0001). Exclusive premium cigar users were less likely to be daily users than other tobacco user groups and had comparable BOEs with exclusive non-premium large cigar users but generally lower BOEs than exclusive cigarillo, filtered cigar, and cigarette smokers. Daily exclusive premium cigar users had similar nicotine and TSNA exposure but lower exposure to polycyclic aromatic hydrocarbons and volatile organic compounds than exclusive cigarillo and filtered cigar users. Premium cigar use exhibits different exposure to toxicants from other cigar subtype users. Regulations of premium cigars need to formalize product definition and take the population's health effects into consideration. This population study provides important information on BOE and potential harm with premium cigar use and its potential health effects. At present, premium cigars appear to pose a relatively low overall population health risk due to low frequency of use. However, future regulation of other tobacco products might change the landscape of premium cigar use and alter the overall health impact.

Tobacco-Specific Nitrosamines (NNAL, NNN, NAT, and NAB) Exposures in the US Population Assessment of Tobacco and Health (PATH) Study Wave 1 (2013-2014).

The tobacco-specific nitrosamines (TSNAs) are an important group of carcinogens found in tobacco and tobacco smoke. To describe and characterize the levels of TSNAs in the Population Assessment of Tobacco and Health (PATH) Study Wave 1 (2013-2014), we present four biomarkers of TSNA exposure: N'-nitrosonornicotine, N'-nitrosoanabasine, N'-nitrosoanatabine, and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) which is the primary urinary metabolite of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone. We measured total TSNAs in 11 522 adults who provided urine using automated solid-phase extraction coupled to isotope dilution liquid chromatography-tandem mass spectrometry. After exclusions in this current analysis, we selected 11 004 NNAL results, 10 753 N'-nitrosonornicotine results, 10 919 N'-nitrosoanatabine results, and 10 996 N'-nitrosoanabasine results for data analysis. Geometric means and correlations were calculated using SAS and SUDAAN. TSNA concentrations were associated with choice of tobacco product and frequency of use. Among established, every day, exclusive tobacco product users, the geometric mean urinary NNAL concentration was highest for smokeless tobacco users (993.3; 95% confidence interval [CI: 839.2, 1147.3] ng/g creatinine), followed by all types of combustible tobacco product users (285.4; 95% CI: [267.9, 303.0] ng/g creatinine), poly tobacco users (278.6; 95% CI: [254.9, 302.2] ng/g creatinine), and e-cigarette product users (6.3; 95% CI: [4.7, 7.9] ng/g creatinine). TSNA concentrations were higher in every day users than in intermittent users for all the tobacco product groups. Among single product users, exposure to TSNAs differed by sex, age, race/ethnicity, and education. Urinary TSNAs and nicotine metabolite biomarkers were also highly correlated. We have provided PATH Study estimates of TSNA exposure among US adult users of a variety of tobacco products. These data can inform future tobacco product and human exposure evaluations and related regulatory activities.

Biopsychosocial mechanisms associated with tobacco use in smokers with and without serious mental illness

Smokers with serious mental illness (SMI) are less responsive to cessation treatments than those without SMI. In this study, we compared smokers with and without SMI on validated measures of biological and psychosocial factors associated with tobacco use. Smokers with (n = 58) and without SMI (n = 83) who were enrolled in parallel clinical trials were compared on measures of carbon monoxide (CO) exposure, nicotine exposure, tobacco-specific nitrosamine exposure, craving, smoking motives, affect, perceived stress, environmental exposure to smoke/smokers, respiratory symptoms, tobacco-related health risk perceptions, and whether they had received recent advice to quit smoking from a health care provider. Data were collected between 2013 and 2017 in Providence, Rhode Island, USA. Samples were compared using independent-sample t-tests and chi-squared tests. Smokers with SMI had higher CO, nicotine, and tobacco-specific nitrosamine exposure levels, greater cigarette dependence, higher craving, and higher scores on eight out of eleven smoking motives (p's < 0.05). Smokers with SMI reported more severe respiratory symptoms but lower perceived health risks of tobacco (p's < 0.05). These smokers were more likely to report having received advice to quit from a medical provider in the past 6 weeks (p < 0.05). Affect, stress, and exposure to smoke/smokers did not differ across samples. Our findings advance the understanding of the elevated smoking rates of people with SMI by comparing smokers with and without SMI on validated biopsychosocial measures. There is a need for interventions that reduce craving, reduce smoking motives, and increase risk awareness among smokers with SMI.

Detection and quantification of 4-hydroxy-1-(3-pyridyl)-1-butanone (HPB) from smoker albumin and its potential as a surrogate biomarker of tobacco-specific nitrosamines exposure and bioactivation

4-(Methylnitrosamino)-l-(3-pyridyl)-1-butanone (NNK) and N-nitrosonornicotine (NNN), two tobacco specific nitrosamine carcinogens, can form adducts with DNA and proteins via pyridyloxobutylation upon phase I enzyme-mediated bioactivation. Such DNA modifications have been proposed as the root cause to initiate carcinogenesis. Upon hydrolysis, both DNA and protein modifications would release 4-hydroxy-1-(3-pyridyl)-1-butanone (HPB). The released HPB, being tobacco carcinogen specific, has the potential to serve as a surrogate biomarker for both tobacco exposure and carcinogen bioactivation. Because of its easy access, blood is a great source of such investigations with the potential in epidemiological application. HPB quantification from haemoglobin (Hb), however, has been demonstrated with limited success. To further explore this potentially paradigm-shift opportunity, we reported, for the first time, the detection and quantification of HPB from albumin (Alb) adducts formed by the tobacco-specific nitrosamines in mice and in human smokers. The time-course quantitative analysis of HPB from mouse Alb upon NNK exposure suggests that such an Alb adduct is stable. The amounts of HPB from Alb adducts in smoker plasma averaged 1.82 ± 0.19 pg/mg Alb (0.42 to 3.11 pg/mg Alb), which was 36 times the value in nonsmokers (0.05 ± 0.01 pg/mg Alb). Importantly, HPB level from Alb correlated positively with the level of human tobacco exposure estimated by urinary total nicotine equivalent (TNE) (R2 = 0.6170). For comparison, HPB level from Alb was 16.5 times that of Hb (0.12 ± 0.02 pg/mg Hb) in the plasma and red blood cell (RBC) samples of the same smokers. In addition, there was no significant correlation between HPB levels from Hb and TNE (R2 = 0.0719). These data overall suggest that HPB from Alb adducts can serve as a surrogate biomarker to monitor the level of tobacco exposure and carcinogenic nitrosamine bioactivation.

Tobacco Product Use Patterns, and Nicotine and Tobacco-Specific Nitrosamine Exposure: NHANES 1999-2012.

Background: Few studies have examined differences in product consumption patterns and nicotine and tobacco-specific nitrosamines (TSNA) exposure between single versus dual- and poly-tobacco users. We applied the Tobacco Product Use Patterns (T-PUPs) model to fill this gap in the literature.Methods: Data from adults (age ≥18 years) who used any tobacco products during the 5 days prior to participating in the 1999-2012 National Health and Nutrition Examination Survey (NHANES) were analyzed. Participants were classified into seven T-PUPs: (1) cigarettes only, (2) noncigarette combustibles only, (3) noncombustibles only, (4) dual noncigarette combustibles and noncombustibles, (5) dual cigarettes and noncombustibles, (6) dual cigarettes and noncigarette combustibles, and (7) poly-tobacco use. Weighted regression models were used to compare product consumption, serum cotinine, and urinary total 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (i.e., NNAL) levels between single-, dual-, and poly-tobacco T-PUPs.Results: Dual- and poly-tobacco T-PUPs were associated with lower product consumption compared with single-product T-PUPs only in some cases (e.g., dual cigarette and noncombustible users smoked cigarettes on 0.6 fewer days in the past 5 days compared with cigarette-only users; P < 0.05). Dual- and poly-tobacco T-PUPs had either nondistinguishable or higher levels of serum cotinine and urinary total NNAL than corresponding single-product T-PUPs.Conclusions: Product consumption, and nicotine and TSNAs exposure of dual- and poly-tobacco product category users somewhat differ from those of single-product category users as defined by the T-TUPs model.Impact: Higher levels of cotinine and NNAL among dual- and poly-tobacco T-TUPs users compared with the single-product T-TUPs users may indicate health concerns. Cancer Epidemiol Biomarkers Prev; 26(10); 1525-30. ©2017 AACR.

Evaluation of tobacco specific nitrosamines exposure by quantification of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in human hair of non-smokers.

Chronic exposure to specific carcinogens present in secondhand smoke has been associated with different types of cancers. Hair is an ideal matrix to develop a proper biomarker as it absorbs substances in circulation and allows measuring their average concentration over long periods of time. A method was developed for the simultaneous quantification of nicotine, cotinine, NNN, NNK and NNAL in 20 mg human hair samples. Concentrations were significantly different depending on the declared exposure. This study shows for the first time that NNK is present in hair samples from non-smokers in concentrations much higher than any other tobacco specific nitrosamine. NNN could also be detected in samples from the most exposed non-smokers while, as previously reported, NNAL was undetectable. NNK correlates well with nicotine and cotinine (rsp = 0.774 and rsp = 0.792 respectively, p < 0.001 in both cases). However, NNN concentrations did not correlate with any of the other analytes. Ratios between NNK and nicotine show variability with different concentrations of NNK present in samples with similar nicotine values. NNK has proven to be the best marker of tobacco specific nitrosamines in hair. Monitoring NNK may provide a good estimation of cancer risk associated with exposure to secondhand smoke.

TSNA Exposure: Levels of NNAL Among Canadian Tobacco Users.

Tobacco smoke contains more than 7,000 chemicals, including known carcinogens, such as tobacco-specific nitrosamines (TSNAs). TSNA levels in cigarettes vary considerably within and across markets; however, the extent to which these different TSNA levels translate into differences in human exposure and risk remains unclear. The current study sought to examine TSNA exposure among Canadian tobacco users. Data from the 2007-2009 Canadian Health Measures Survey were used to measure levels of urinary NNAL [4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol], a metabolite of the TSNA NNK [4-(methylnitrosamino-1-(3-pyridyl)-1-butanone], among tobacco users (n = 507). Geometric mean concentrations of total urinary NNAL and creatinine-corrected total urinary NNAL were calculated. A linear regression model was used to examine predictors of urinary levels of NNAL. The mean population level of total urinary NNAL and creatinine-corrected total urinary NNAL was 71.2 pg/ml and 82.0 pg/mg creatinine, respectively. NNAL levels were higher among older respondents (p = .02), among females (p = .04), and among those with greater daily cigarette consumption (p < .0001), greater levels of urinary free cotinine (p < .0001), and greater levels of urinary creatinine (p < .0001). Overall, the mean level of urinary total NNAL among Canadian tobacco users was approximately one fourth that of their U.S. counterparts. The study findings provide the first nationally representative characterization of TSNA exposure among Canadian tobacco users. Although the findings indicate marked differences in TSNA exposure between Canadian and American populations of tobacco users, it is not known whether these differences in exposure translate into differences in risk.

TSNA exposure from cigarette smoking: 18 Years of urinary NNAL excretion data

The objective of this work was to characterize trends over time in urinary excretion of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) among cigarette smokers in the US. We identified 35 studies presenting data that either reported, or could be converted to, common units of total urinary NNAL excretion as pmol/mg creatinine. The studies spanned 18years, reported urinary NNAL excretion estimates for 61 defined populations, and included a combined total of 3941 study participants. Analyses show that urinary NNAL excretion trends downward with study publication year, and the trend is statistically significant. The trend does not appear to be accounted for by a reduction in cigarettes smoked per day by study participants over the same time period. This trend is consistent with reductions in tobacco specific nitrosamine (TSNA) levels in both cigarette tobacco filler and mainstream cigarette smoke observed over the past decade and with efforts by the tobacco industry and the agricultural community to reduce levels of TSNAs in tobacco and cigarette smoke.

Exposure to nicotine and carcinogens among Southwestern Alaskan Native cigarette smokers and smokeless tobacco users.

The prevalence of tobacco use, both cigarette smoking and smokeless, including iqmik (homemade smokeless tobacco prepared with dried tobacco leaves mixed with alkaline ash), and of tobacco-related cancer is high in Alaskan Native people (AN). To investigate possible mechanisms of increased cancer risk we studied levels of nicotine and tobacco-specific nitrosamines (TSNA) in tobacco products and biomarkers of tobacco toxicant exposure in Southwestern AN people. Participants included 163 cigarette smokers, 76 commercial smokeless tobacco, 20 iqmik, 31 dual cigarette smokers and smokeless tobacco, and 110 nontobacco users. Tobacco use history, samples of tobacco products used, and blood and urine samples were collected. Nicotine concentrations were highest in cigarette tobacco and TSNAs highest in commercial smokeless tobacco products. The AN participants smoked on average 7.8 cigarettes per day. Nicotine exposure, assessed by several biomarker measures, was highest in iqmik users, and similar in smokeless tobacco and cigarette smokers. TSNA exposure was highest in smokeless tobacco users, and polycyclic aromatic hydrocarbon exposure was highest in cigarette smokers. Despite smoking fewer cigarettes per day, AN cigarette smokers had similar daily intake of nicotine compared to the general U.S. population. Nicotine exposure was greatest from iqmik, likely related to its high pH due to preparation with ash, suggesting high addiction potential compared to other smokeless tobacco products. TSNA exposure was much higher with smokeless tobacco than other product use, possibly contributing to the high rates of oral cancer. Our data contribute to an understanding of the high addiction risk of iqmik use and of the cancer-causing potential of various forms of tobacco use among AN people.

The molecular basis for induction of human cancers by tobacco specific nitrosamines

Cellular DNA damage that is misrepaired or not repaired, constitutes a necessary, although not sufficient prerequisite for induction of cancer. For carcinogenic oral snuffs with extremely high concentrations of tobacco specific nitrosamines (TSNA) the DNA adduct levels predicted from animal experiments exceed those found in “unexposed” individuals. On the other hand, and supported by extensive Swedish epidemiological data, no significant increase of TSNA-induced DNA damages can be anticipated in humans from the use of low-nitrosamine oral snuffs. The extrapolated adduct concentrations are orders of magnitude lower than those found in the corresponding human tissues, a discrepancy that is difficult to account for by species differences. Furthermore, in exposed subjects the observed increment in the background levels of pyridyloxobutyl(POB)–hemoglobin adducts – a relevant indicator for TSNA activation – lie in a range predicted by rodent data. When based on the same type of tissues this provides justification for extrapolating rates of TSNA induced adduct formation from animals to humans. A TSNA exposure that does not affect the background level of pro-mutagenic DNA lesions should be considered as “virtually safe”. The high background concentrations of methylated and POB–DNA adducts in “unexposed” humans must be ascribed to other sources than tobacco.

Nucleophilic reactions between thiols and a tobacco specific nitrosamine metabolite, 4-hydroxy-1-(3-pyridyl)-1-butanone.

4-Hydroxy-1-(3-pyridyl)-1-butanone (HPB) is a metabolite of the tobacco specific nitrosamines, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and N'-nitrosonornicotine (NNN). HPB is also a breakdown product of covalently bound pyridyloxobutyl adducts resulting from NNK and NNN exposure. HPB released from DNA or hemoglobin has been used as an important dosimeter of tobacco specific nitrosamine exposure in a variety of studies. This compound is not reactive with cellular nucleophiles under biological conditions. We have discovered that HPB reacts with nucleophiles under acidic conditions to form cyclic tetrahydrofuranyl reaction products. Dithiothreitol, 2-mercaptoethanol, and N-acetylcysteine all reacted with HPB under these reaction conditions. In addition, reactions were observed with buffer chemicals such as 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid and tris(hydroxymethyl)aminomethane. The resulting cyclic adducts were unstable at room temperature. Their half-lives were significantly longer under neutral conditions than under acidic conditions. NMR studies established that the cyclic form of HPB, 2-hydroxy-2-(3-pyridyl)-2,3,4,5-THF, is present at significant concentrations in acidic solutions. The observation of this cyclic compound suggests that the reaction with nucleophiles may occur via a cyclic oxonium ion intermediate. This reaction was significant in our biological samples; there was up to 40% conversion of [5-(3)H]HPB to cyclic DTT-derived compounds when acidic DNA repair reactions containing [5-(3)H]pyridyloxobutylated DNA were stored overnight at -20 degrees C. Therefore, long-term storage of acid hydrolysates of pyridyloxobutylated DNA or protein for the analysis of HPB-releasing adducts could result in an underestimation of HPB-releasing adduct in those samples. In addition, these observations provide a mild synthetic method to prepare large quantities of cyclic 2-(3-pyridyl)-2,3,4,5-THF adducts predicted to result from pyridyloxobutylation of important cellular nucleophiles as a result of NNK and/or NNN exposure.