Comparative potency analysis of whole smoke solutions in the bacterial reverse mutation test.

Short-term in vitro genotoxicity assays are useful tools to assess whether new and emerging tobacco products potentially have reduced toxicity. We previously demonstrated that potency ranking by benchmark dose (BMD) analysis quantitatively identifies differences among several known carcinogens and toxic chemicals representing different chemical classes found in cigarette smoke. In this study, six whole smoke solution (WSS) samples containing both the particulate and gas phases of tobacco smoke were generated from two commercial cigarette brands under different smoking-machine regimens. Sixty test cigarettes of each brand were machine-smoked according to the International Organization for Standardization (ISO) puffing protocol. In addition, either 60 or 20 test cigarettes of each brand were machine-smoked with the Canadian Intense (CI) puffing protocol. All six WSSs were evaluated in the bacterial reverse mutation (Ames) test using Salmonella typhimurium strains, in the presence or absence of S9 metabolic activation. The resulting S9-mediated mutagenic concentration-responses for the four WSSs from 60 cigarettes were then compared using BMD modelling analysis and the mutagenic potency expressed as number of revertants per µl of the WSS. The quantitative approaches resulted in a similar rank order of mutagenic potency for the Ames test in both TA98 and TA100. Under the conditions of this study, these results indicate that quantitative analysis of the Ames test data can discriminate between the mutagenic potencies of WSSs on the basis of smoking-machine regimen (ISO vs. CI), and cigarette product (differences in smoke chemistry).

Cigarette whole smoke solutions disturb mucin homeostasis in a human in vitro airway tissue model.

Many cigarette smoke-associated airway diseases involve alterations in mucin homeostasis. With the rationale that relevant tissue responses can be measured to evaluate the adverse health effects of tobacco products, we assessed changes in mucin secretion and the density and size of goblet cells in an in vitro human air-liquid-interface (ALI) airway tissue model after exposure to a tobacco smoke solution. Cultures were exposed daily for up to five consecutive days to a whole smoke solution (WSS) prepared by machine smoking Marlboro Red or Marlboro Silver cigarettes using the Canadian Intense (CI) protocol. Both WSSs induced concentration- and time-related hypersecretion of mucins 5AC and 5B, accompanied by up-regulation of the respective mucin genes. Mucin secretion returned to baseline levels following a 14-day recovery period. Mucin-secreting goblet cells exhibited increased cell density and decreased size after 5 daily treatments then recovered to their normal size, but with decreased cell density, 14 days after the last treatment. The beating frequency of ciliated cells, which plays a key role in mucociliary clearance, was increased by 5 daily treatments with the CI WSSs then reverted to baseline levels following a 7-day recovery. Taken together, our results indicate that ALI cultures can be used to measure the modulation of mucin production, secretion, and clearance, disturbances that are manifested in tobacco smoke-related diseases, such as chronic obstructive pulmonary disease. Measuring tissue responses directly relevant to the respiratory toxicity of cigarette smoke may provide useful information in support of science-based regulatory decisions.

Quantitative differentiation of whole smoke solution-induced mutagenicity in the mouse lymphoma assay.

In vitro genotoxicity dose-response data have been investigated for their utility in modeling and assessing potential differences in mutagenic responses between machine-generated whole smoke solutions (WSSs) from combusted cigarette tobacco products. Our previous study observed that potency ranking by benchmark dose (BMD) analysis was a useful modeling approach for quantitative assessment of differences between the mutagenicity of several structurally diverse chemical constituents of cigarette smoke. To follow-up on these observations, we used the mouse lymphoma assay (MLA) to evaluate the mutagenicity of WSSs prepared from two commercial cigarettes smoked under two different smoking machine regimens. L5178Y cells were exposed to ≥5 concentrations of each WSS for 4 hr ± S9 activation. S9 reduced the cytotoxicity and enhanced the mutagenicity of the WSSs. The resulting S9-mediated mutagenicity dose-responses were compared between test articles using BMD analysis, the lowest dose exceeding the Global Evaluation Factor, the no observed or lowest observed genotoxic effect level, and the mutagenic potency. The BMD10 , BMD50 , BMD100 , and BMD200 , indicating a 10%, 50%, 100%, or 200% increase in the background mutant frequency, respectively, were calculated using the PROAST software package. Overall, the quantitative approaches resulted in a similar rank order of mutagenic potency for the MLA tested WSSs, with potency increasing with the level of tar. The BMD approach using covariate analysis produced the most informative comparisons. Differences in potency were associated with the number of cigarettes smoked, the cigarette product smoked, and the smoking machine protocol used to prepare the sample. Under the conditions of this study, these results suggest that our hypothesis of modeling MLA data using the BMD approach to quantitatively discriminate between the mutagenic potential of WSSs from combustible cigarettes might be an useful method. Environ. Mol. Mutagen. 59:103-113, 2018. Published 2017. This article is a US Government work and is in the public domain in the USA.

Cigarette Design Features: Effects on Emission Levels, User Perception, and Behavior.

OBJECTIVES: This paper describes the effects of non-tobacco, physical cigarette design features on smoke emissions, product appeal, and smoking behaviors - 3 factors that determine smoker's exposure and related health risks. METHODS: We reviewed available evidence for the impact of filter ventilation, new filter types, and cigarettes dimensions on toxic emissions, smoker's perceptions, and behavior. For evidence sources we used scientific literature and websites providing product characteristics and marketing information. RESULTS: Whereas filter ventilation results in lower machine-generated emissions, it also leads to perceptions of lighter taste and relative safety in smokers who can unwittingly employ more intense smoking behavior to obtain the desired amount of nicotine and sensory appeal. Filter additives that modify smoke emissions can also modify sensory cues, resulting in changes in smoking behavior. Flavor capsules increase the cigarette's appeal and novelty, and lead to misperceptions of reduced harm. Slim cigarettes have lower yields of some smoke emissions, but smoking behavior can be more intense than with standard cigarettes. CONCLUSIONS: Physical design features significantly impact machine-measured emission yields in cigarette smoke, product appeal, smoking behaviors, and exposures in smokers. The influence of current and emerging design features is important in understanding the effectiveness of regulatory actions to reduce smoking-related harm.

Quantitative analysis of the relative mutagenicity of five chemical constituents of tobacco smoke in the mouse lymphoma assay.

Quantifying health-related biological effects, like genotoxicity, could provide a way of distinguishing between tobacco products. In order to develop tools for using genotoxicty data to quantitatively evaluate the risk of tobacco products, we tested five carcinogens found in cigarette smoke, 4-aminobiphenyl (4-ABP), benzo[a]pyrene (BaP), cadmium (in the form of CdCl2), 2-amino-3,4-dimethyl-3H-imidazo[4,5-f]quinoline (MeIQ) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), in the mouse lymphoma assay (MLA). The resulting mutagenicity dose responses were analyzed by various quantitative approaches and their strengths and weaknesses for distinguishing responses in the MLA were evaluated. L5178Y/Tk (+/-) 3.7.2C mouse lymphoma cells were treated with four to seven concentrations of each chemical for 4h. Only CdCl2 produced a positive response without metabolic activation (S9); all five chemicals produced dose-dependent increases in cytotoxicity and mutagenicity with S9. The lowest dose exceeding the global evaluation factor, the benchmark dose producing a 10%, 50%, 100% or 200% increase in the background frequency (BMD10, BMD50, BMD100 and BMD200), the no observed genotoxic effect level (NOGEL), the lowest observed genotoxic effect level (LOGEL) and the mutagenic potency expressed as a mutant frequency per micromole of chemical, were calculated for all the positive responses. All the quantitative metrics had similar rank orders for the agents' ability to induce mutation, from the most to least potent as CdCl2(-S9) > BaP(+S9) > CdCl2(+S9) > MeIQ(+S9) > 4-ABP(+S9) > NNK(+S9). However, the metric values for the different chemical responses (i.e. the ratio of the greatest value to the least value) for the different chemicals ranged from 16-fold (BMD10) to 572-fold (mutagenic potency). These results suggest that data from the MLA are capable of discriminating the mutagenicity of various constituents of cigarette smoke, and that quantitative analyses are available that can be useful in distinguishing between the exposure responses.

Trends in tobacco smoke exposure and blood lead levels among youths and adults in the United States: the National Health and Nutrition Examination Survey, 1999-2008.

INTRODUCTION: Tobacco smoke is a source of exposure to thousands of toxic chemicals including lead, a chemical of longstanding public health concern. We assessed trends in blood lead levels in youths and adults with cotinine-verified tobacco smoke exposure by using 10 years of data from the National Health and Nutrition Examination Survey. METHODS: Geometric mean levels of blood lead are presented for increasing levels of tobacco smoke exposure. Regression models for lead included age, race/ethnicity, poverty, survey year, sex, age of home, birth country, and, for adults, alcohol consumption. Lead levels were evaluated for smokers and nonsmokers on the basis of age of residence and occupation. RESULTS: Positive trend tests indicate that a linear relationship exists between smoke exposure and blood lead levels in youths and adults and that secondhand smoke exposure contributes to blood lead levels above the level caused by smoking. CONCLUSION: Youths with secondhand smoke exposure had blood lead levels suggestive of the potential for adverse cognitive outcomes. Despite remediation efforts in housing and the environment and declining smoking rates and secondhand smoke exposure in the United States, tobacco smoke continues to be a substantial source of exposure to lead in vulnerable populations and the population in general.

Exposure to and deposition of fine and ultrafine particles in smokers of menthol and nonmenthol cigarettes.

INTRODUCTION: Research on the deposition of mainstream smoke particulate in the respiratory tract of smokers is needed to understand how exposure may vary based on cigarette menthol content. METHODS: We conducted a nine-participant crossover study in which smokers were randomly assigned to cigarettes differing primarily in menthol content. Participants smoked the test cigarettes ad libitum for one week, provided spot urine samples, and then smoked four test cigarettes in a laboratory session; this was repeated for the other test cigarette in week two. Fine and ultrafine particulate matter in exhaled breath were characterized, and smoking behavior was monitored. Participant-specific mainstream smoke, generated using each participant's topography data, was characterized. During home smoking, participants collected their spent test cigarette butts for estimates of mouth-level exposures (MLE) to mainstream nicotine and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). RESULTS: Participant-specific mainstream smoke NNK was higher (39%) and daily MLE to NNK was also higher (52%) when participants smoked the menthol cigarette. Nicotine was not significantly different. Participants retained more ultrafine particulate (43%) and fine particulate benzo(a)pyrene (43%) when smoking the menthol cigarette. There were no significant differences in the levels of urinary biomarkers for nicotine, NNK, or pyrene. CONCLUSION: This study demonstrates the use of noninvasive real-time techniques to measure exposure differences between cigarettes differing primarily in menthol content. Differences between NNK exposure, ultrafine particle and benzo(a)pyrene deposition, and smoking behavior were observed. Additional research using these techniques with cigarettes that differ only in menthol content is required to unequivocally attribute the exposure differences to presence or absence of menthol.

Comparison of serum cotinine concentration within and across smokers of menthol and nonmenthol cigarette brands among non-Hispanic black and non-Hispanic white U.S. adult smokers, 2001-2006.

BACKGROUND: The Food and Drug Administration (FDA) is examining options for regulating menthol content in cigarettes. There are many pharmacologic properties of menthol that may facilitate exposure to tobacco smoke, and it has been suggested that the preference for menthol cigarettes in black smokers accounts for their higher cotinine levels. OBJECTIVE: To assess cigarettes smoked per day-adjusted cotinine levels in relation to smoking a menthol or nonmenthol cigarette brand among non-Hispanic black and white U.S. adult smokers under natural smoking conditions. METHOD: Serum cotinine concentrations were measured in 1,943 smokers participating in the 2001 to 2006 National Health and Nutrition Examination Surveys (NHANES). The effect of smoking a menthol brand on cigarettes smoked per day-adjusted serum cotinine levels in these two populations was modeled by adjusting for sex, age, number of smokers living in the home, body weight, time since last smoked, and FTC (Federal Trade Commission)-measured nicotine levels. The 8- or 12-digit Universal Product Code (UPC) on the cigarette label was used to determine the cigarette brand and whether it was menthol. RESULTS: Smoking a menthol cigarette brand versus smoking a nonmenthol cigarette brand was not associated (P ≥ 0.05) with mean serum cotinine concentration in either black or white smokers. CONCLUSIONS: The higher levels of cotinine observed in black smokers compared with white smokers are not explained by their higher preference for menthol cigarette brands. IMPACT: Further studies like ours are needed to improve our ability to understand health consequences of future changes in tobacco product design.

Mutagenicity of 11 cigarette smoke condensates in two versions of the mouse lymphoma assay.

Cigarette smoke condensate (CSC) is genotoxic in nearly all assays in which it has been tested. In this study, we investigated the mutagenicity of 11 CSCs using the microwell and soft-agar versions of the mouse lymphoma assay (MLA). These CSCs were prepared from commercial or experimental cigarettes, 10 of them were produced using International Organisation for Standardisation (ISO) conditions and one CSC was generated using intense Massachusetts Department of Public Health (MDPH) conditions. In the presence of rat liver S9, the L5178Y/Tk(+/-) mouse lymphoma cells were treated with 11 CSCs at different concentrations (25-200 µg/ml) for 4 h. All CSCs resulted in dose-dependent increases of both cytotoxicity and mutagenicity in both versions of the MLA. The mutagenic potencies of the CSCs were calculated as mutant frequency per microgram CSC from the slope of the linear regression of the dose-response curves and showed no correlations with the tar yield of the cigarette or nicotine concentrations of the CSCs. Comparing two CSCs produced from the same commercial cigarettes using two different smoking conditions, the one generated under ISO conditions was more mutagenic than the other generated under intense conditions on a per microgram CSC basis. We also examined the loss of heterozygosity (LOH) at four microsatellite loci spanning the entire chromosome 11 for the mutants induced by 11 CSCs. The most common type of mutation observed was LOH with chromosome damage spanning less than ∼34 Mbp. These results indicate that the MLA identifies different genotoxic potencies among a variety of CSCs and that the results from both versions of the assay are comparable.

Cytotoxicity of eight cigarette smoke condensates in three test systems: comparisons between assays and condensates.

Cytotoxic properties of tobacco smoke are associated with chronic tobacco-related diseases. The cytotoxicity of tobacco smoke can be tested with short-term predictive assays. In this study, we compare eight mainstream cigarette smoke condensates (CSCs) from commercial and experimental cigarettes in three different cytotoxicity assays with unique and overlapping endpoints. The CSCs demonstrated cytotoxicity in all assays. In the multiple cytotoxicity endpoint (MCE) assay with TK-6 cells, the cigarette varieties that had the highest EC50s for reduced cell growth also showed a positive dose-response relationship for necrotic cells. In the IdMOC multiple cell-type co-culture (MCTCC) system, all CSCs reduced the viability of the cells. Low concentrations of some CSCs had a stimulatory effect in lung microvascular endothelial cells and small airway epithelial cells. In the neutral dye assay (NDA), except for a 100% flue-cured tobacco CSC, there was little consistency between CSCs producing morphological evidence of moderate or greater toxicity and the CSCs with the lowest EC50s in the MCE or MCTCC assays. Overall, cigarettes made with flue-cured tobacco were the most cytotoxic across the assays. When results were expressed on a per-mg of nicotine basis, lower tar cigarettes were the most cytotoxic in primary human respiratory cells.

Tobacco smoke exposure and levels of urinary metals in the U.S. youth and adult population: the National Health and Nutrition Examination Survey (NHANES) 1999-2004.

We assessed 12 urine metals in tobacco smoke-exposed and not exposed National Health and Nutrition Examination Survey participants. Our analysis included age, race/ethnicity, and poverty status. Gender and racial/ethnic differences in cadmium and lead and creatinine-adjusted and unadjusted data for group comparisons are presented. Smokers' had higher cadmium, lead, antimony, and barium levels than nonsmokers. Highest lead levels were in the youngest subjects. Lead levels among adults with high second-hand smoke exposure equaled smokers. Older smokers had cadmium levels signaling the potential for cadmium-related toxicity. Given the potential toxicity of metals, our findings complement existing research on exposure to chemicals in tobacco smoke.

Genotoxicity of 10 cigarette smoke condensates in four test systems: comparisons between assays and condensates.

The particulate fraction of cigarette smoke, cigarette smoke condensate (CSC), is genotoxic in many short-term in vitro tests and is carcinogenic in rodents. However, no study has evaluated a series of CSCs prepared from a diverse set of cigarettes and produced with different smoking machine regimens in several short-term genotoxicity tests. Here we report on the genotoxicity of 10 CSCs prepared from commercial cigarettes that ranged from ultra-low tar per cigarette (< or =6.5 mg) to full flavor (>14.5 mg) as determined by the Federal Trade Commission (FTC) smoking regimen, a reference cigarette blended to be representative of a U.S. FTC-regimen low-tar cigarette, and experimental cigarettes constructed of single tobacco types. CSCs were tested in the presence of rat liver S9 in the Salmonella plate-incorporation assay using frameshift strains TA98 and YG1041; in micronucleus and comet assays in L5178Y/Tk(+/-) 7.3.2C mouse lymphoma cells, and in CHO-K(1) cells for chromosome aberrations. All 10 CSCs were mutagenic in both strains of Salmonella, and the rank order of their mutagenic potencies was similar. Their mutagenic potencies in Salmonella spanned 7-fold when expressed as rev/mug CSC but 158-fold when expressed as rev/mg nicotine; the range of genotoxic potencies of the CSCs in the other assays was similar regardless of how the data were expressed. All 10 CSCs induced micronuclei with a 3-fold range in their potency. All but one CSC induced DNA damage over a 20-fold range, and all but one CSC induced chromosome aberrations over a 4-fold range. There was no relation among the genotoxic potencies of the CSCs across the assays, and a qualitative advantage of the addition of the other assays to the Salmonella assay was not supported by our findings. Although consideration of nicotine levels may improve the relevance of the quantitative data obtained in the Salmonella and possibly comet assays, compensatory smoking habits and other factors may make the data from the assays used here have qualitative but not quantitative value in assessing risk of cigarette types and cigarette smoking to human health.

Young adult smoker risk perceptions of traditional cigarettes and nontraditional tobacco products.

OBJECTIVE: To explore risk perceptions of traditional and nontraditional tobacco products (NTPs) among young adult smokers. METHODS: Focus groups with African Americans, non-Hispanic whites, and Hispanics. Risk ratings of light, regular, and menthol cigarettes and of NTPs and marijuana and cigarettes were compared. RESULTS: Participants tended to view light cigarettes as safer than regular cigarettes. Shisha and herbal products were rated as safer than traditional cigarettes, but there were differences in ratings by race/ethnicity, related to preferred cigarette variety. CONCLUSIONS: Health communication messages about the use of cigarettes and NTPs should consider risk perceptions about the products and racial/ethnic differences.

Epidemiology of menthol cigarette use.

Approximately one-fourth of all cigarettes sold in the United States are mentholated. An understanding of the consequences, patterns, and correlates of menthol cigarette use can guide the development and implementation of strategies to reduce smoking prevalence and smoking-attributable morbidity and mortality. This paper summarizes the literature on the health effects of mentholated cigarettes and describes various patterns of use as indicated by consumption and survey data from the United States and other nations. The epidemiological literature on menthol cigarettes and cancer risk is inconclusive regarding whether these cigarettes confer a risk for cancer above that of nonmentholated varieties. Available data indicate that mentholated cigarettes are at least as dangerous as their nonmentholated counterparts. In addition, because mentholation improves the taste of cigarettes for a substantial segment of the smoking population and appears to mask disease symptoms, this additive may facilitate initiation or inhibit quitting. Menthol market share is high in the Philippines (60%), Cameroon (35%-40%), Hong Kong (26%), the United States (26%), and Singapore (22%). Newport has become the leading menthol brand in the United States. Surveys from four nations indicate that menthol use among adult smokers is more common among females than males. Among U.S. smokers, 68.9% of Blacks, 29.2% of Hispanics, and 22.4% of Whites reported smoking a mentholated variety. Research is needed to better explain factors that may influence menthol preference, such as marketing, risk perceptions, brand formulation, and taste preferences. Such research would guide the development of potentially more effective programs and policies.