Thirdhand Exposures to Tobacco-Specific Nitrosamines through Inhalation, Dust Ingestion, Dermal Uptake, and Epidermal Chemistry.

Tobacco-specific nitrosamines (TSNAs) are emitted during smoking and form indoors by nitrosation of nicotine. Two of them, N'-nitrosonornicotine (NNN) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), are human carcinogens with No Significant Risk Levels (NSRLs) of 500 and 14 ng day-1, respectively. Another TSNA, 4-(methylnitrosamino)-4-(3-pyridyl) butanal (NNA), shows genotoxic and mutagenic activity in vitro. Here, we present additional evidence of genotoxicity of NNA, an assessment of TSNA dermal uptake, and predicted exposure risks through different pathways. Dermal uptake was investigated by evaluating the penetration of NNK and nicotine through mice skin. Comparable mouse urine metabolite profiles suggested that both compounds were absorbed and metabolized via similar mechanisms. We then investigated the effects of skin constituents on the reaction of adsorbed nicotine with nitrous acid (epidermal chemistry). Higher TSNA concentrations were formed on cellulose and cotton substrates that were precoated with human skin oils and sweat compared to clean substrates. These results were combined with reported air, dust, and surface concentrations to assess NNK intake. Five different exposure pathways exceeded the NSRL under realistic scenarios, including inhalation, dust ingestion, direct dermal contact, gas-to-skin deposition, and epidermal nitrosation of nicotine. These results illustrate potential long-term health risks for nonsmokers in homes contaminated with thirdhand tobacco smoke.

3-Ethenylpyridine Measured in Urine of Active and Passive Smokers: A Promising Biomarker and Toxicological Implications.

In studies of tobacco toxicology, including comparisons of different tobacco products and exposure to secondhand or thirdhand smoke, exposure assessment using biomarkers is often useful. Some studies have indicated that most of the toxicity of tobacco smoke is due to gas-phase compounds. 3-Ethenylpyridine (3-EP) is a major nicotine pyrolysis product occurring in the gas phase of tobacco smoke. It has been used extensively as an environmental tracer for tobacco smoke. 3-EP would be expected to be a useful tobacco smoke biomarker as well, but nothing has been published about its metabolism and excretion in humans. In this Article we describe a solid-phase microextraction (SPME) GC-MS/MS method for determination of 3-EP in human urine and its application to the determination of 3-EP in the urine of smokers and people exposed to secondhand smoke. We conclude that 3-EP is a promising biomarker that could be useful in studies of tobacco smoke exposure and toxicology. We also point out the paucity of data on 3-EP toxicity and suggest that additional studies are needed.

Characterization of Nicotine Salts in 23 Electronic Cigarette Refill Liquids.

INTRODUCTION: Many electronic cigarette manufacturers have begun offering liquids containing "nicotine salts," which are formed when an acid is mixed in a solution with free-base nicotine. Type of salt could play a significant role in the abuse liability of electronic cigarette liquids. As a first step to understanding nicotine salts, this study sought to identify the types of acids present in 23 commercially available electronic cigarette liquids. AIMS AND METHODS: Twenty-three electronic cigarette liquids advertised as containing nicotine salts were purchased for analysis. These liquids were tested for the presence of 11 different organic acids that were deemed likely to be used in a nicotine salt formulation. Liquids were analyzed using a combination of liquid chromatography-mass spectrometry and gas chromatography-mass spectrometry methods, then compared to authentic acid standards for identification. RESULTS: Six of the 11 possible acids were identified in the liquids, from most to least common: lactic, benzoic, levulinic, salicyclic, malic, and tartaric acid. Acid(s) could not be identified in one of the liquids. Though most liquids contained only one type, three of the liquids contained multiple acids. CONCLUSIONS: These data demonstrate that several types of salts/acids are currently being used in electronic cigarette liquids. The type and concentration of salt(s) used in these liquids may differentially alter sensations in the throat and upper airway, and overall pharmacology of the aerosols by altering liquid pH and from flavor and sensory characteristics of the acids themselves. IMPLICATIONS: This study demonstrates that at least six different types of acids are being used to create the nicotine salts in electronic cigarette liquids, with the acids lactic, benzoic, and levulinic being the most frequently identified. Identification of these acids can serve as the foundation for future research to determine if type of nicotine salt alters pharmacological and toxicological effects of electronic cigarettes.

Biomarkers of Exposure for Dual Use of Electronic Cigarettes and Combustible Cigarettes: Nicotelline, NNAL, and Total Nicotine Equivalents.

INTRODUCTION: Dual use of electronic cigarettes (e-cigarettes) and combustible cigarettes is a major public health issue. It is generally accepted that exclusive e-cigarette use is less harmful than exclusive combustible cigarette use, but most e-cigarette users continue to smoke combustible cigarettes as well. To what extent the use of e-cigarettes reduces harm in people who continue to smoke combustible cigarettes has been debated. The aim of this study was to explore the utility of biomarkers as measures of dual use. METHODS: In two human studies of participants who used e-cigarettes only or both combustible cigarettes and e-cigarettes, we measured urine concentrations of the metabolites of nicotine (total nicotine equivalents) as well as two biomarkers of tobacco exposure: 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), a tobacco-specific carcinogen metabolite, and nicotelline, a tobacco alkaloid not found in significant concentrations in e-cigarette products. RESULTS: The presence of nicotine metabolites indicates either e-cigarette or combustible cigarette use. Nicotelline (half-life of 2-3 hours) indicates recent combustible cigarette use and NNAL (half-life of 10 days or more), indicates combustible cigarette use occurring within several weeks prior to sample collection. CONCLUSIONS: Nicotelline and NNAL are useful biomarkers for combustible tobacco use in users e-cigarettes. The application of these biomarkers provides a tool to help assess whether, or to what extent, dual use of e-cigarettes and combustible cigarettes reduces harm compared to sole use of combustible cigarettes. These biomarkers can also verify exclusive use of e-cigarettes over short (24 hour) or long (several week) time periods. IMPLICATIONS: To what extent dual use of e-cigarettes and combustible cigarettes reduce harm compared to smoking combustible cigarettes only is of considerable public health interest. We show that the levels of the minor tobacco alkaloid nicotelline and the nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) are extremely low in electronic cigarette fluids. The urine biomarkers nicotelline and the NNK metabolite 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) are indicative of cigarette smoking and can be used to assess recent and past smoking in dual users.

Short-term early exposure to thirdhand cigarette smoke increases lung cancer incidence in mice.

Exposure to thirdhand smoke (THS) is a recently described health concern that arises in many indoor environments. However, the carcinogenic potential of THS, a critical consideration in risk assessment, remains untested. Here we investigated the effects of short-term early exposure to THS on lung carcinogenesis in A/J mice. Forty weeks after THS exposure from 4 to 7 weeks of age, the mice had increased incidence of lung adenocarcinoma, tumor size and, multiplicity, compared with controls. In vitro studies using cultured human lung cancer cells showed that THS exposure induced DNA double-strand breaks and increased cell proliferation and colony formation. RNA sequencing analysis revealed that THS exposure induced endoplasmic reticulum stress and activated p53 signaling. Activation of the p53 pathway was confirmed by an increase in its targets p21 and BAX. These data indicate that early exposure to THS is associated with increased lung cancer risk.

Vascular endothelial function is impaired by aerosol from a single IQOS HeatStick to the same extent as by cigarette smoke.

BACKGROUND: Heated tobacco products (also called 'heat-not-burn' products) heat tobacco at temperatures below that of combustion, causing nicotine and other compounds to aerosolise. One such product, IQOS from Philip Morris International, is being marketed internationally with claims of harm reduction. We sought to determine whether exposure to IQOS aerosol impairs arterial flow-mediated dilation (FMD), a measure of vascular endothelial function that is impaired by tobacco smoke. METHODS: We exposed anaesthetised rats (n=8/group) via nose cone to IQOS aerosol from single HeatSticks, mainstream smoke from single Marlboro Red cigarettes or clean air for a series of consecutive 30 s cycles over 1.5-5 min. Each cycle consisted of 15 or 5 s of exposure followed by removal from the nose cone. We measured pre-exposure and postexposure FMD, and postexposure serum nicotine and cotinine. RESULTS: FMD was impaired comparably by ten 15 s exposures and ten 5 s exposures to IQOS aerosol and to cigarette smoke, but not by clean air. Serum nicotine levels were similar to plasma levels after humans have smoked one cigarette, confirming that exposure conditions had real-world relevance. Postexposure nicotine levels were ~4.5-fold higher in rats exposed to IQOS than to cigarettes, despite nicotine being measured in the IQOS aerosol at ~63% the amount measured in smoke. When IQOS exposure was briefer, leading to comparable serum nicotine levels to the cigarette group, FMD was still comparably impaired. CONCLUSIONS: Acute exposures to IQOS aerosol impairs FMD in rats. IQOS use does not necessarily avoid the adverse cardiovascular effects of smoking cigarettes.

An Electronic Cigarette Vaping Machine for the Characterization of Aerosol Delivery and Composition.

INTRODUCTION: Characterization of aerosols generated by electronic cigarettes (e-cigarettes) is one method used to evaluate the safety of e-cigarettes. While some researchers have modified smoking machines for e-cigarette aerosol generation, these machines are either not readily available, not automated for e-cigarette testing or have not been adequately described. The objective of this study was to build an e-cigarette vaping machine that can be used to test, under standard conditions, e-liquid aerosolization and nicotine and toxicant delivery. METHODS: The vaping machine was assembled from commercially available parts, including a puff controller, vacuum pump, power supply, switch to control current flow to the atomizer, three-way value to direct air flow to the atomizer, and three gas dispersion tubes for aerosol trapping. To validate and illustrate its use, the variation in aerosol generation was assessed within and between KangerTech Mini ProTank 3 clearomizers, and the effect of voltage on aerosolization and toxic aldehyde generation were assessed. RESULTS: When using one ProTank 3 clearomizer and different e-liquid flavors, the coefficient of variation (CV) of aerosol generated ranged between 11.5% and 19.3%. The variation in aerosol generated between ProTank 3 clearomizers with different e-liquid flavors and voltage settings ranged between 8.3% and 16.3% CV. Aerosol generation increased linearly at 3-6V across e-liquids and clearomizer brands. Acetaldehyde, acrolein, and formaldehyde generation increased markedly at voltages at or above 5V. CONCLUSION: The vaping machine that we describe reproducibly aerosolizes e-liquids from e-cigarette atomizers under controlled conditions and is useful for testing of nicotine and toxicant delivery. IMPLICATIONS: This study describes an electronic cigarette vaping machine that was assembled from commercially available parts. The vaping machine can be replicated by researchers and used under standard conditions to generate e-cigarette aerosols and characterize nicotine and toxicant delivery.

Cigarette Smoke Exposure and the Acute Respiratory Distress Syndrome.

OBJECTIVE: The association between cigarette smoke exposure and the acute respiratory distress syndrome in patients with the most common acute respiratory distress syndrome risk factors of sepsis, pneumonia, and aspiration has not been well studied. The goal of this study was to test the association between biomarker-confirmed cigarette smoking and acute respiratory distress syndrome in a diverse cohort. DESIGN: Prospective cohort. SETTING: Tertiary care center. PATIENTS: Four hundred twenty-six critically ill patients with acute respiratory distress syndrome risk factors (excluding trauma and transfusion) INTERVENTIONS: : None. MEASUREMENTS AND MAIN RESULTS: We obtained smoking histories and measured urine 4-(methylnitrosamino)-1-(3-pyridyl)-1- butanol (a biomarker of cigarette smoke exposure) on urine samples obtained at the time of study enrollment. The association between cigarette smoke exposure and acute respiratory distress syndrome differed based on acute respiratory distress syndrome risk factor (p < 0.02 for interaction). In patients with nonpulmonary sepsis as the primary acute respiratory distress syndrome risk factor (n = 212), 39% of those with acute respiratory distress syndrome were current smokers by history compared with 22% of those without acute respiratory distress syndrome (odds ratio, 2.28; 95% CI, 1.24-4.19; p = 0.008). Likewise, cigarette smoke exposure as measured by urine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol was significantly associated with acute respiratory distress syndrome in this group. The increased risk of acute respiratory distress syndrome in nonpulmonary sepsis was restricted to patients with 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol levels consistent with active smoking and was robust to adjustment for other acute respiratory distress syndrome predictors. Cigarette smoke exposure as measured by history or 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol was not associated with acute respiratory distress syndrome in patients with other risk factors (e.g., pneumonia and aspiration). CONCLUSIONS: Cigarette smoking measured both by history and biomarker is associated with an increased risk of acute respiratory distress syndrome in patients with nonpulmonary sepsis. This finding has important implications for tobacco product regulation and for understanding the pathogenesis of acute respiratory distress syndrome.

Tobacco alkaloids and tobacco-specific nitrosamines in dust from homes of smokeless tobacco users, active smokers, and nontobacco users.

Smokeless tobacco products, such as moist snuff or chewing tobacco, contain many of the same carcinogens as tobacco smoke; however, the impact on children of indirect exposure to tobacco constituents via parental smokeless tobacco use is unknown. As part of the California Childhood Leukemia Study, dust samples were collected from 6 homes occupied by smokeless tobacco users, 6 homes occupied by active smokers, and 20 tobacco-free homes. To assess children's potential for exposure to tobacco constituents, vacuum-dust concentrations of five tobacco-specific nitrosamines, including N'-nitrosonornicotine [NNN] and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone [NNK], as well as six tobacco alkaloids, including nicotine and myosmine, were quantified by liquid chromatography-tandem mass spectrometry (LC-MS/MS). We used generalized estimating equations derived from a multivariable marginal model to compare levels of tobacco constituents between groups, after adjusting for a history of parental smoking, income, home construction date, and mother's age and race/ethnicity. The ratio of myosmine/nicotine was used as a novel indicator of the source of tobacco contamination, distinguishing between smokeless tobacco products and tobacco smoke. Median dust concentrations of NNN and NNK were significantly greater in homes with smokeless tobacco users compared to tobacco-free homes. In multivariable models, concentrations of NNN and NNK were 4.8- and 6.9-fold higher, respectively, in homes with smokeless tobacco users compared to tobacco-free homes. Median myosmine/nicotine ratios were lower in homes with smokeless tobacco users (1.8%) compared to homes of active smokers (7.7%), confirming that cigarette smoke was not the predominant source of tobacco constituents in homes with smokeless tobacco users. Children living with smokeless tobacco users may be exposed to carcinogenic tobacco-specific nitrosamines via contact with contaminated dust and household surfaces.

Biomarkers of secondhand smoke exposure in automobiles.

OBJECTIVES: The objectives of this study were: (1) to characterise the exposure of non-smokers exposed to secondhand smoke (SHS) in a vehicle using biomarkers, (2) to describe the time course of the biomarkers over 24 h, and (3) to examine the relationship between tobacco biomarkers and airborne concentrations of SHS markers. METHODS: Eight non-smokers were individually exposed to SHS in cars with fully open front windows and closed back windows over an hour from a smoker who smoked three cigarettes at 20 min intervals. The non-smokers sat in the back seat on the passenger side, while the smoker sat in the driver's seat. Plasma cotinine and urine cotinine, 3-hydroxycotinine (3HC) and 4-(methylnitrosoamino)-(3-pyridyl)-1-butanol (NNAL) were compared in samples taken at baseline (BL) and several time-points after exposure. Nicotine, particulate matter (PM2.5) and carbon monoxide (CO) were measured inside and outside the vehicle and ventilation rates in the cars were measured. RESULTS: Average plasma cotinine and the molar sum of urine cotinine and 3HC (COT+3HC) increased four-fold, urine cotinine increased six-fold and urine NNAL increased ∼27 times compared to BL biomarker levels. Plasma cotinine, urine COT+3HC and NNAL peaked at 4-8 h post-exposure while urine cotinine peaked within 4 h. Plasma cotinine was significantly correlated to PM2.5 (Spearman correlation rs=0.94) and CO (rs=0.76) but not to air nicotine. The correlations between urine biomarkers, cotinine, COT+3HC and NNAL, and air nicotine, PM2.5 and CO were moderate but non-significant (rs range = 0.31-0.60). CONCLUSIONS: Brief SHS exposure in cars resulted in substantial increases in levels of tobacco biomarkers in non-smokers. For optimal characterisation of SHS exposure, tobacco biomarkers should be measured within 4-8 h post-exposure. Additional studies are needed to better describe the relationship between tobacco biomarkers and environmental markers of SHS.

Levels of selected carcinogens and toxicants in vapour from electronic cigarettes.

SIGNIFICANCE: Electronic cigarettes, also known as e-cigarettes, are devices designed to imitate regular cigarettes and deliver nicotine via inhalation without combusting tobacco. They are purported to deliver nicotine without other toxicants and to be a safer alternative to regular cigarettes. However, little toxicity testing has been performed to evaluate the chemical nature of vapour generated from e-cigarettes. The aim of this study was to screen e-cigarette vapours for content of four groups of potentially toxic and carcinogenic compounds: carbonyls, volatile organic compounds, nitrosamines and heavy metals. MATERIALS AND METHODS: Vapours were generated from 12 brands of e-cigarettes and the reference product, the medicinal nicotine inhaler, in controlled conditions using a modified smoking machine. The selected toxic compounds were extracted from vapours into a solid or liquid phase and analysed with chromatographic and spectroscopy methods. RESULTS: We found that the e-cigarette vapours contained some toxic substances. The levels of the toxicants were 9-450 times lower than in cigarette smoke and were, in many cases, comparable with trace amounts found in the reference product. CONCLUSIONS: Our findings are consistent with the idea that substituting tobacco cigarettes with e-cigarettes may substantially reduce exposure to selected tobacco-specific toxicants. E-cigarettes as a harm reduction strategy among smokers unwilling to quit, warrants further study. (To view this abstract in Polish and German, please see the supplementary files online.).

Levels of cotinine in dried blood specimens from newborns as a biomarker of maternal smoking close to the time of delivery.

The precise quantitation of smoking during pregnancy is difficult in retrospective studies. Routinely collected blood specimens from newborns, stored as dried blood spots, may provide a low-cost method to objectively measure maternal smoking close to the time of delivery. This article compares cotinine levels in dried blood spots to those in umbilical cord blood to assess cotinine in dried blood spots as a biomarker of maternal smoking close to the time of delivery. The California Genetic Disease Screening Program provided dried blood spots from 428 newborns delivered in 2001-2003 with known umbilical cord blood cotinine levels. Cotinine in dried blood spots was measured in 6.35--mm punches by using liquid chromatography--tandem mass spectrometry (quantitation limit, 3.1 ng/mL). Repeated measures of cotinine in dried blood spots were highly correlated (R(2) = 0.99, P < 0.001) among 100 dried blood spots with cotinine quantitated in 2 separate punches. Linear regression revealed that cotinine levels in dried blood spots were slightly lower than those in umbilical cord blood and predicted umbilical cord blood cotinine levels well (ß = 0.95, R(2) = 0.80, and P < 0.001 for both cotinine levels in log10 scale). When defining active smoking as a cotinine level of 10 ng/mL or more and using umbilical cord blood cotinine as the criterion standard, we found that measurements of cotinine in dried blood spots had high sensitivity (92.3%) and specificity (99.7%) in the prediction of maternal active smoking. Cotinine levels in dried blood spots are an accurate biomarker of maternal smoking close to the time of delivery.

Nicotelline: a proposed biomarker and environmental tracer for particulate matter derived from tobacco smoke.

Particulate matter (PM) derived from tobacco smoke contains numerous toxic substances. Since the PM and gas phase of tobacco smoke may distribute differently in the environment and substances in them may have different human bioavailability, multiple tracers and biomarkers for tobacco smoke constituents are desirable. Nicotelline is a relatively nonvolatile alkaloid present in tobacco smoke, and therefore, it has the potential to be a suitable tracer and biomarker for tobacco smoke-derived PM. We describe experiments demonstrating that nicotelline is present almost entirely in the PM, in both freshly generated cigarette smoke and aged cigarette smoke. An excellent correlation between the mass of nicotelline and the mass of the PM in aged cigarette smoke was found. We also describe experiments suggesting that the main source of nicotelline in tobacco smoke is dehydrogenation of another little-studied tobacco alkaloid, anatalline, during the burning process. We show that nicotelline metabolites can be measured in the urine of smokers and that nicotelline can be measured in house dust from homes of smokers and nonsmokers. We conclude that nicotelline should be useful as a tracer and biomarker for PM derived from tobacco smoke.

Thirdhand smoke causes DNA damage in human cells.

Exposure to thirdhand smoke (THS) is a newly described health risk. Evidence supports its widespread presence in indoor environments. However, its genotoxic potential, a critical aspect in risk assessment, is virtually untested. An important characteristic of THS is its ability to undergo chemical transformations during aging periods, as demonstrated in a recent study showing that sorbed nicotine reacts with the indoor pollutant nitrous acid (HONO) to form tobacco-specific nitrosamines (TSNAs) such as 4-(methylnitrosamino)-4-(3-pyridyl)butanal (NNA) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). The goal of this study was to assess the genotoxicity of THS in human cell lines using two in vitro assays. THS was generated in laboratory systems that simulated short (acute)- and long (chronic)-term exposures. Analysis by liquid chromatography-tandem mass spectrometry quantified TSNAs and common tobacco alkaloids in extracts of THS that had sorbed onto cellulose substrates. Exposure of human HepG2 cells to either acute or chronic THS for 24h resulted in significant increases in DNA strand breaks in the alkaline Comet assay. Cell cultures exposed to NNA alone showed significantly higher levels of DNA damage in the same assay. NNA is absent in freshly emitted secondhand smoke, but it is the main TSNA formed in THS when nicotine reacts with HONO long after smoking takes place. The long amplicon-quantitative PCR assay quantified significantly higher levels of oxidative DNA damage in hypoxanthine phosphoribosyltransferase 1 (HPRT) and polymerase ß (POLB) genes of cultured human cells exposed to chronic THS for 24h compared with untreated cells, suggesting that THS exposure is related to increased oxidative stress and could be an important contributing factor in THS-mediated toxicity. The findings of this study demonstrate for the first time that exposure to THS is genotoxic in human cell lines.

Tobacco-specific and combustion pollutants in settled house dust in Malta.

Aim: Most of the carcinogenic pollutants coming from tobacco smoking or other combustion processes tend to accumulate in settled house dust (SHD) over time. This study evaluated the load of these pollutants in smokers and non-smokers' houses from relatively fresh SHD collected in five different districts on the island of Malta. Methods: An improved, efficient extraction method to obtain three fractions from a 200 mg of SHD was developed. It was validated for the analysis of nicotine and polycyclic aromatic hydrocarbons (PAH) by GC-MS/MS and nicotelline and TSNA by LC-MS/MS. Kruskal-Wallis H tests were used to evaluate differences across districts, while a Mann-Whitney U test was used to check differences between smokers and non-smokers' houses. Diagnostic ratios were used to evaluate the carcinogenicity of PAH in SHD in Malta. Results: For all analytes, no statistical difference was observed across different districts, but, in smokers' houses, 97.9% of the total concentration of all target analytes found in SHD is nicotine, 0.1% is TSNA, and 2.0% is PAH. In non-smokers' houses, nicotine represents 16.8% of the load, while 0.4% and 82.8% are TSNA and PAH, respectively. The carcinogenicity of the PAH mixture in Maltese SHD, expressed as the mean benzo(a)pyrene equivalent (BaPeq) is 371 ng/g. Conclusion: Indoor activities, ventilation practices, and infiltration of outdoor pollutants contribute to a complex SHD composition. Although the BaPeq is on the lower end of carcinogenicity, the effects of a mixture including tobacco-related potent carcinogens in SHD are largely unknown. In view of indoor, continuous exposure to SHD through several pathways, further research is warranted.

Determination of 4-(Methylnitrosamino)-1-(3-Pyridyl)-1-Butanone (NNK) arising from tobacco smoke in airborne particulate matter.

The most important tobacco-specific nitrosamine found in cigarette smoke and formed in ageing smoke after cigarettes are extinguished is 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). It is formed from nitrosation of nicotine, under particular conditions both in indoor and outdoor environments. NNK has been classified as a potent lung carcinogen which is expected to be found primarily in the particle-phase and to be stable in particulate matter. In this study tests have been carried out to show that a bisulfate-treated filter is more efficient than an untreated filter to collect both nicotine and NNK, and that the latter is stable in outdoor particulate matter. To characterize NNK in the outdoor environment, airborne samples were collected from 11 cities in USA, UK, Hong Kong and Malta with characteristics varying from low to high population densities and from urban to suburban to rural, and with desert characteristics and distinct climates. It has been shown that airborne particle + gas phase nicotine and particle-phase NNK behave in a linearly correlated manner. A seasonal analysis was carried out on a subset of data available from five sites in California, where the load of NNK in PM10 is driven by long range transport of the air masses passing over densely populated cities. In the winter season, the load of NNK in PM is higher than in summer in a statistically significant manner. The contamination of PM with NNK shows variability, but is observed at all sites. This paper highlights the potential risk of chronic exposure to NNK in particulate matter by the inhalation pathway.

Biomarkers increase detection of active smoking and secondhand smoke exposure in critically ill patients.

OBJECTIVES: The association between tobacco smoke exposure and critical illness is not well studied, largely because obtaining an accurate smoking history from critically ill patients is difficult. Biomarkers can provide quantitative data on active and secondhand cigarette smoke exposure. We sought to compare cigarette smoke exposure as measured by biomarkers to exposure by self-report in a cohort of critically ill patients and to determine how well biomarkers of cigarette smoke exposure correlate with each other in this population. DESIGN, SETTING, AND PATIENTS: Serum and urine cotinine and trans-3'-hydroxycotinine, urine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol, and hair and nail nicotine levels were measured in 60 subjects enrolled in an observational cohort of critically ill subjects at a tertiary academic medical center in Tennessee. Smoking history was obtained from patients, their surrogates, or the medical chart. Cigarette smoke exposure as measured by biomarkers was compared to exposure by history. MEASUREMENTS AND MAIN RESULTS: By smoking history, 29 subjects were identified as smokers, 28 were identified as nonsmokers, and 3 were identified as unknown. The combination of serum cotinine and urine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol identified 27 of the 28 nonsmokers by history either as active smokers (n = 6, 21%) or as exposed to secondhand smoke (n = 21, 75%). All biomarker levels were strongly correlated with each other (r = .69-.95, p < .0001). CONCLUSIONS: The combination of serum cotinine and urine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol identified considerably more active smokers than did smoking history and detected a high prevalence of secondhand smoke exposure in a critically ill population. These markers will be important for future studies investigating the relationship between active smoking and secondhand smoke exposure and critical illness.

Comparison of urine cotinine and the tobacco-specific nitrosamine metabolite 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) and their ratio to discriminate active from passive smoking.

OBJECTIVES: Cotinine is the most widely used biomarker to distinguish active versus passive smoking. However, there is an overlap in cotinine levels when comparing light or occasional smokers versus heavily exposed passive smokers. 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) is a tobacco-specific nitrosamine measurable in urine with a much longer half-life than cotinine. The aim of the study was to determine optimal cutoff points to discriminate active versus passive smokers and to compare sensitivity and specificity for the use of cotinine, NNAL, and the ratio of the NNAL/cotinine in urine. METHODS: Cotinine and NNAL were measured in urine of 373 active smokers and 228 passive smokers. RESULTS: Geometric mean cotinine levels were 2.03 ng/ml (interquartile interval: 0.43-8.60) and 1,043 ng/ml (658-2,251) and NNAL levels were 5.80 pg/ml (2.28-15.4) and 165 pg/ml (90.8-360) pg/ml in passive and active smokers, respectively. NNAL/cotinine ratio in urine was significantly higher for passive smokers when compared with active smokers (2.85 vs. 0.16, p < .01). The receiver operating characteristics analysis determined optimal cutoff points to discriminate passive versus active smokers: 31.5 ng/ml for cotinine (sensitivity: 97.1% and specificity: 93.9%), 47.3 pg/ml for NNAL (87.4% and 96.5%), and 0.74 x 10⁻³ for NNAL/cotinine ratio (97.3% and 87.3%). CONCLUSIONS: Both urine cotinine and NNAL are sensitive and specific biomarkers for discriminating the source of tobacco smoke exposure. Cotinine is the best overall discriminator when biomarkers are measured while a person has ongoing exposure to tobacco smoke. NNAL because of its long half-life would be particularly useful when there is a delay between exposure and biomarker measurement. The NNAL/cotinine ratio provides similar sensitivity but poorer specificity at discriminating passive versus active smokers when compared with NNAL alone.

Ubiquitous atmospheric contamination by tobacco smoke: Nicotine and a new marker for tobacco smoke-derived particulate matter, nicotelline.

Second Hand Smoke (SHS) has always been primarily linked with indoor pollution. To date nicotine was the favoured marker for SHS alongside measurements of particulate matter (PM) levels. As nicotine is mainly found in the gas-phase and reactive in the outdoor environment it is not ideal as a marker for the SHS-driven particulate component in PM. Nicotelline, a minor tobacco alkaloid that is stable, found almost exclusively in the particle phase and easy to quantify even at low concentrations, is being proposed as a better marker. It is the first study using bisulfate-treated quartz fiber filters to show that airborne nicotine (gas+particle phase) is directly proportional to airborne nicotelline in countries that have different climates. The analytical method developed has been validated to show that the use of untreated filters is suitable for the quantification of nicotelline even at low concentrations. Although nicotelline exhibits a seasonal and geographical variation, this is the first comprehensive study which demonstrates the ubiquitous presence of nicotelline in PM from outdoor air samples collected in the USA (0.1-285.6 pgm-3), UK (2.3-9.1 pgm-3), Hong Kong (3.8-109.3 pgm-3) and Malta (4.2-280.8 pgm-3). From the nicotelline apportionment factor of 1589 ng/mg of tobacco smoke PM we estimate the fraction of outdoor airborne PM derived from SHS to be in the range of 0.03-0.08%. While it is unlikely for tobacco smoke-related toxics in outdoor PM to be considered a major health hazard, in heavily polluted microenvironments this marker would be useful in tracing the presence of SHS and emerging Third Hand Smoke components that form or are found in airborne and settled PM that could induce serious health effects.

Differences in nicotine intake and effects from electronic and combustible cigarettes among dual users.

AIM: To describe systemic nicotine exposure and subjective effects of electronic cigarettes (e-cigarettes) in people who use both e-cigarettes and cigarettes (dual users), including within-subject comparisons of e-cigarette and cigarette use. DESIGN: Two-arm, counterbalanced cross-over study. Participants used their usual brand of e-cigarette or cigarette during a standardized session in a 2-week study. SETTING: Hospital research ward, San Francisco, CA, USA. PARTICIPANTS: Thirty-six healthy (eight women, 28 men) participants. MEASUREMENTS: Plasma nicotine was analyzed by gas chromatography-tandem mass spectrometry; nicotine withdrawal, urge to smoke and vape, affective states, craving, satisfaction and psychological reward were measured by standardized questionnaires. FINDINGS: Compared with cigarettes, average maximum plasma nicotine concentration (Cmax ) was lower with e-cigarettes [6.1 ± 5.5 ng/ml, mean ± standard deviation (SD) versus 20.2 ± 11.1 ng/ml, P < 0.001] and time of maximal concentration (Tmax ) was longer (6.5 ± 5.4 versus 2.7 ± 2.4 minutes, P < 0.001). Use of both products resulted in a reduction in the severity of withdrawal symptoms, negative affect and urge to use either product. E-cigarettes were less rewarding and satisfying and reduced craving to a lesser degree than cigarettes. We were not able to detect any differences in withdrawal symptoms, affective states and urge to smoke cigarettes between e-cigarette and cigarette use. CONCLUSION: Systemic nicotine exposure was, on average, lower with single use of e-cigarettes compared with cigarettes, and e-cigarettes were judged to be less satisfying and rewarding and reduced craving less than cigarettes.