Effects of flavoring and casing ingredients on the toxicity of mainstream cigarette smoke in rats

A 7-month inhalation toxicology study in C57BL/6 mice demonstrates reduced pulmonary inflammation and emphysematous changes following smoking cessation or switching to e-vapor products

Cigarette smoking causes serious diseases, including lung cancer, atherosclerotic coronary artery disease, peripheral vascular disease, chronic bronchitis, and emphysema. While cessation remains the most effective approach to minimize smoking-related disease, alternative non-combustible tobacco-derived nicotine-containing products may reduce disease risks among those unable or unwilling to quit. E-vapor aerosols typically contain significantly lower levels of smoke-related harmful and potentially harmful constituents; however, health risks of long-term inhalation exposures are unknown. We designed a 7-month inhalation study in C57BL/6 mice to evaluate long-term respiratory toxicity of e-vapor aerosols compared to cigarette smoke and to assess the impact of smoking cessation (Cessation group) or switching to an e-vapor product (Switching group) after 3 months of exposure to 3R4F cigarette smoke (CS). There were no significant changes in in-life observations (body weights, clinical signs) in e-vapor groups compared to the Sham Control. The 3R4F CS group showed reduced respiratory function during exposure and had lower body weight and showed transient signs of distress post-exposure. Following 7 months of exposure, e-vapor aerosols resulted in no or minimal increase in pulmonary inflammation, while exposure to 3R4F CS led to impairment of lung function and caused marked lung inflammation and emphysematous changes. Biological changes observed in the Switching group were similar to the Cessation group. 3R4F CS exposure dysregulated the lung and nasal tissue transcriptome, while these molecular effects were substantially lower in the e-vapor group. Results from this study demonstrate that in comparison with 3R4F CS, e-vapor aerosols induce substantially lower biological responses including pulmonary inflammation and emphysematous changes, and that complete switching from CS to e-vapor products significantly reduces biological changes associated with CS in C57BL/6 mice.

Assessment of priority tobacco additives per the requirements of the EU Tobacco Products Directive (2014/40/EU): Part 1: Background, approach, and summary of findings

This paper is part of a series of 3 publications and describes the non-clinical and clinical assessment performed to fulfill the regulatory requirement per Art. 6 (2) of the EU Tobacco Products Directive 2014/40/EU; under which Member States shall require manufacturers and importers of cigarettes and roll-your-own tobacco containing an additive that is included in the priority list established by Commission Implementing Decision (EU) 2016/787 to carry out comprehensive studies. The Directive requires manufacturers and importers of cigarettes and Roll Your Own tobacco to examine for each additive whether it; contributes to and increases the toxicity or addictiveness of tobacco products to a significant or measurable degree; if it leads to a characterizing flavor of the product; if it facilitates inhalation or nicotine uptake, and if it results in the formation of CMR (carcinogenic, mutagenic and reprotoxic) constituents and if these substances increase the CMR properties of the respective tobacco product to a significant or measurable degree. This publication gives an overview on comprehensive smoke chemistry, in vitro toxicity, and human clinical studies commissioned by the members of the Priority Additives Tobacco Consortium to independent Contract Research Organizations (CROs) where the emissions of test cigarettes containing priority additives were compared to emissions emerging from an additive-free reference cigarette. Whilst minor changes in smoke chemistry parameters were observed when comparing emissions from test cigarettes with emissions from additive-free reference cigarettes, only two of the additives (sorbitol and guar gum) tested led to significant increases in a limited number of smoke constituents. These changes were not observed when sorbitol or guar gum were tested in a mixture with other priority additives. None of the priority additives resulted in increases in in vitro toxicity (Ames, Micronucleus, Neutral Red Uptake) or led to changes in smoking behavior or absorption (rate or amount) of nicotine measured during the human clinical study as compared to the additive-free reference cigarette.

Acridocarpus Smeathmannii (DC.) Guill. & Perr. Root enhanced reproductive behavior and sexual function in male wistar rats: Biochemical and pharmacological mechanisms

ETHNOPHARMACOLOGICAL RELEVANCE

Novel therapeutic opportunities from medicinal agents continue to arouse scientific interest in recent times. Still, there is a dearth of information as regards experimental evidence generated from medicinal plants that would yield pharmacological agents for the treatment of erectile dysfunction. Acridocarpus Smeathmannii (DC.) Guill. & Perr. Root (ASR) has a long history as an aphrodisiac in African traditional medicine. Thus, this study investigated the reproductive potentials and associated biochemical mechanisms of its hydroethanolic extract (HEASR) in male Wistar rats. Also, the bioactive compounds were identified.

MATERIALS AND METHODS

Fifty-four male albino rats (180 ± 20 g) were divided into nine groups of six rats/group. Control, group 1 received normal saline (10 mL/kg). Groups 2-6 rats were administered sildenafil (1.43 mg/kg/day), mesterolone (0.36 mg/kg/day), doxazocin (0.03 mg/kg/day), HEASR1 (50 mg/kg/day) and HEASR2 (200 mg/kg/day) respectively. Others received co-administration of HEASR2 with standard drugs. Treatment lasted for 28 days via oral gavage.

RESULTS

An acute oral toxicity of HEASR up to 2 g/kg produced no mortality in mice p.o. while the median lethal dose was estimated to be 810 mg/kg i.p. HEASR2 administration or in combination with sildenafil, mesterolone and doxazocin increased mounting frequencies on day 28 by 77.44%, 122.65%, 148.5% and 93.88% and sperm counts by 38.29%, 55.21%, 42.48%, and 48.98% respectively in treated rats. HEASR2 + sildenafil elevated testosterone and follicle stimulating hormone levels by 36.33% and 24.55% while HEASR2 + doxazocin elevated luteinizing hormone levels by 97.44% in rats. HEASR modulated prostate-specific antigen and malondialdehyde levels respectively. Reduced glutathione, superoxide dismutase, and catalase activities were raised in five selected organs. Serum nitric oxide but not cyclooxygenase-2 or tumor necrosis factor-α levels was moderately improved in rats.

CONCLUSION

Overall, the results obtained demonstrated the potential of HEASR as a male reproductive enhancer, thus justify its folklore applications. Further, octadecanoic acid ethyl ester was the most abundant bioactive component present.

The impact of tobacco additives on cigarette smoke toxicity: a critical appraisal of tobacco industry studies

Cigarette production involves a number of substances and materials other than just tobacco, paper and a filter. Tobacco additives include flavorings, enhancers, humectants, sugars, and ammonium compounds. Although companies maintain that tobacco additives do not enhance smoke toxicity and do not make cigarettes more attractive or addictive, these claims are questioned by independent researchers. This study reviewed the studies on the effects of tobacco additives on smoke chemistry and toxicity. Tobacco additives lead to higher levels of formaldehyde and minor changes in other smoke analytes. Toxicological studies (bacterial mutagenicity and mammalian cytoxicity tests, rat 90 days inhalation studies and bone-marrow cell micronucleus assays) found that tobacco additives did not enhance smoke toxicity. Rodent assays, however, poorly predicted carcinogenicity of tobacco smoke, and were clearly underpowered to disclose small albeit toxicologically relevant differences between test (with tobacco additives) and control (without tobacco additives) cigarettes. This literature review led to the conclusion that the impact of tobacco additives on tobacco smoke harmfulness remains unclear.

Flavored little cigar smoke induces cytotoxicity and apoptosis in airway epithelia

Addition of flavors reduces the harsh taste of tobacco, facilitating the initiation and maintenance of addiction among youths. Flavored cigarettes (except menthol) are now banned. However, the legislation on little cigars remains unclear and flavored little cigars are currently available for purchase. Since inhaled tobacco smoke directly exerts toxic effects on the lungs, we tested whether non-flavored and flavored little cigar smoke exposure had the potential for harm in cultured pulmonary epithelia. We cultured Calu-3 lung epithelia on both 96-well plates and at the air–liquid interface and exposed them to smoke from non-flavored Swisher Sweets and flavored (sweet cherry, grape, menthol, peach and strawberry) Swisher Sweets little cigars. Irrespective of flavor, acute little cigar smoke exposure (10×35 ml puffs) significantly increased cell death and decreased the percentage of live cells. Chronic exposure (10×35 ml puffs per day for 4 days) of smoke to Calu-3 cultures significantly increased lactate dehydrogenase release, further indicating toxicity. To determine whether this exposure was associated with increased cell death/apoptosis, a protein array was used. Chronic exposure to smoke from all types of little cigars induced the activation of the two major apoptosis pathways, namely the intrinsic (mitochondrial-mediated) and the extrinsic (death receptor-mediated) pathways. Both flavored and non-flavored little cigar smoke caused similar levels of toxicity and activation of apoptosis, suggesting that flavored and non-flavored little cigars are equally harmful. Hence, the manufacture, advertisement, sale and use of both non-flavored and flavored little cigars should be strictly controlled.

Biological responses in rats exposed to mainstream smoke from a heated cigarette compared to a conventional reference cigarette

The heated cigarette (HC) generates mainstream smoke by vaporizing the components of the tobacco rod using a carbon heat source at the cigarette tip. Mainstream smoke of HC contains markedly less chemical constituents compared to combusted cigarettes. Mainstream smoke from HC was generated under Health Canada Intense regimen and its biological effects were compared to those of Reference (3R4F) cigarettes, using nose-only 5-week and 13-week inhalation studies. In the 13-week study, SD rats were necropsied following exposure to mainstream smoke from each cigarette at 200, 600 or 1000 µg wet total particulate matter/L for 1 h/day, 7 days/week or following a 13-week recovery period. Histopathological changes in the respiratory tract were significantly lesser in HC groups; e.g. respiratory epithelial hyperplasia in the nasal cavity and accumulation of pigmented macrophages in alveoli. After a 13-week recovery, the lesions were completely or partially regressed, except for accumulation of pigmented macrophages in alveoli, in both HC and 3R4F groups. In the 5-week study, SD rats were necropsied following exposure to mainstream smoke of either cigarette at 600 or 1000 µg/L for 1 h, two times/day (with 30 min interval), 7 days/week or following a 4-week recovery period. Bronchoalveolar lavage fluid (BALF) analysis of neutrophil percentages and enzyme levels like γ-GT, ALP and LDH indicated that pulmonary inflammation was significantly less in HC groups compared to 3R4F groups. In conclusion, HC demonstrated significantly lower biological effects compared to 3R4F, based on the BALF parameters and histopathology.

Comparison of biological responses in rats under various cigarette smoke exposure conditions

A variety of exposure regimens of cigarette smoke have been used in animal models of lung diseases. In this study, we compared biological responses of smoke exposure in rats, using different smoke concentrations (wet total particulate matter [WTPM]), daily exposure durations, and total days of exposure. As a range-finding acute study, we first compared pulmonary responses between SD and F344 strains after a single nose-only exposure to mainstream cigarette smoke or LPS. Secondly, F344 rats were exposed to cigarette smoke for 2 or 13 weeks under the comparable daily exposure dose (WTPM concentration x daily exposure duration; according to Haber's rule) but at a different WTPM concentration or daily exposure duration. Blood carboxylhemoglobin was increased linearly to the WTPM concentration, while urinary nicotine plus cotinine value was higher for the longer daily exposure than the corresponding shorter exposure groups. Gamma glutamyl transferase activity in bronchoalveolar lavage fluid (BALF) was increased dose dependently after 2 and 13 weeks of cigarette smoke exposure, while the neutrophil content in BALF was not increased notably. Smoke-exposed groups showed reduced body weight gain and increased relative lung and heart weights. While BALF parameters and the relative lung weights suggest pulmonary responses, histopathological examination showed epithelial lesions mainly in the upper respiratory organs (nose and larynx). Collectively, the results indicate that, under the employed study design, the equivalent daily exposure dose (exposure concentration x duration) induces equivalent pulmonary responses in rats.

Scientific assessment of the use of sugars as cigarette tobacco ingredients: a review of published and other publicly available studies

Sugars, such as sucrose or invert sugar, have been used as tobacco ingredients in American-blend cigarettes to replenish the sugars lost during curing of the Burley component of the blended tobacco in order to maintain a balanced flavor. Chemical-analytical studies of the mainstream smoke of research cigarettes with various sugar application levels revealed that most of the smoke constituents determined did not show any sugar-related changes in yields (per mg nicotine), while ten constituents were found to either increase (formaldehyde, acrolein, 2-butanone, isoprene, benzene, toluene, benzo[k]fluoranthene) or decrease (4-aminobiphenyl, N-nitrosodimethylamine, N-nitrosonornicotine) in a statistically significant manner with increasing sugar application levels. Such constituent yields were modeled into constituent uptake distributions using simulations of nicotine uptake distributions generated on the basis of published nicotine biomonitoring data, which were multiplied by the constituent/nicotine ratios determined in the current analysis. These simulations revealed extensive overlaps for the constituent uptake distributions with and without sugar application. Moreover, the differences in smoke composition did not lead to relevant changes in the activity in in vitro or in vivo assays. The potential impact of using sugars as tobacco ingredients was further assessed in an indirect manner by comparing published data from markets with predominantly American-blend or Virginia-type (no added sugars) cigarettes. No relevant difference was found between these markets for smoking prevalence, intensity, some markers of dependence, nicotine uptake, or mortality from smoking-related lung cancer and chronic obstructive pulmonary disease. In conclusion, thorough examination of the data available suggests that the use of sugars as ingredients in cigarette tobacco does not increase the inherent risk and harm of cigarette smoking.

Discriminatory power of standard toxicity assays used to evaluate ingredients added to cigarettes

A tiered approach for testing ingredients in a cigarette matrix was developed and includes chemical-analytical testing and a standard battery of biological toxicity assays. These assays were adapted for comparative evaluation of mainstream smoke from experimental cigarettes with or without ingredients at various inclusion levels. This adaptation to test cigarette mainstream smoke may impact assay response. Since it is difficult to a priori determine discriminatory power, it was evaluated using a large experimental dataset from a multi-year program of cigarette ingredient testing performed at two separate laboratories. A statistical method, minimum detectable difference (MDD), was used as a measure of assay discriminatory power. MDD of cigarette smoke constituents ranged from 6% to 29% of the average. Salmonella mutagenicity and cytotoxicity test MDDs ranged from 20% to 81% and 18% to 49%, respectively. Body weight gain in 90-day nose-only inhalation studies yielded an MDD of 30-40%. Histopathological findings with severity scores between 0.5 and 1.5 had the lowest MDDs of 23% and higher. In general, discriminatory power decreased with increasing biological complexity and toxicological relevance of the assay. Beyond statistical analysis, however, a weight-of-the-evidence analysis by experienced researchers is required for toxicological assessment of a cigarette ingredient.

Toxicological assessment of cigarette ingredients

Ingredients have been used in industrial manufacture of tobacco products since the early part of the 20th century. However, unlike other consumer goods, until now no regulatory authority has determined how tobacco ingredients should be assessed. Although there is currently no consensus on how added cigarette ingredients should be evaluated, this paper reviews some of the institutional guidance alongside published literature with a view to determining if there is a generally accepted approach in the absence of any strict regulation. Our aim was to review the recommendations, to compare them to the working practices as demonstrated from published studies, and to draw conclusions on currently used methodologies for testing ingredients added to cigarettes. The extent of testing is discussed in the light of practical and theoretical constraints and an example of an industry testing program is presented.

Non-clinical safety and pharmacokinetic evaluations of propylene glycol aerosol in Sprague-Dawley rats and Beagle dogs

Aerosolized propylene glycol (PG) was generated as log-normally distributed particulate clouds in different concentrations using a novel capillary aerosol generator (CAG) and evaluated in a battery of non-clinical studies intended to assess its potential inhalation and systemic toxicity in 2 species before ICH-compliant "first-time-in-man" studies. Exposures were nose-only in rats, and via face mask with oropharyngeal tube in dogs. The CAG-generated PG aerosol had a mass median aerodynamic diameter (MMAD) of 2.29μm, with a 1.56 geometric standard deviation (GSD) in the rat studies, and a MMAD of 1.34μm (1.45 GSD) in the dog studies, consistent with expected particle size exposures in man. International Congress on Harmonization (ICH) Guidelines were followed, which recommend preliminary non-clinical safety studies using the vehicle and device (CAG-PG) prior to the first human exposure including safety pharmacology, pharmacokinetic (PK) studies, single dose toxicity studies, and repeated dose toxicity studies in two species. In the rat, the only biologically relevant findings included clinical signs of ocular and nasal irritation indicated by minor bleeding around the eyes and nose, and minimal laryngeal squamous metaplasia. This finding is commonly observed in inhalation studies in the rat, and likely related to the unique sensitivity of the tissue, as well as the circuitous airflow pathway through the larynx which increases particle deposition. In the female Beagle dog, treatment-related decreases in hemoglobin, red blood cells and hematocrit were observed in the two highest exposure groups, equivalent to approximately 18 and 60mg/kg/day. In male dogs from the high dose group, similar small decreases, albeit, non-statistically significant decreases were observed in these hematological markers as well. PK studies in rats and dogs showed that the absorption of PG following pulmonary inhalation exposure occurs rapidly, and equilibrium between lung tissue and plasma is achieved quickly. With daily inhalations of PG aerosols, there is evidence of minor tissue accumulation of PG in each species. Inhalation exposure to CAG-generated PG aerosols achieved PG concentrations in the systemic circulation that were similar to those attained via the oral route. Systemic elimination of PG appears to be saturable, presumably via hepatic metabolism. PG elimination in the high dose groups for both species showed terminal plasma and lung concentration-time profiles suggesting a zero-order elimination process. There was no apparent tissue toxicity of the lung, liver and kidney in these studies. Under the conditions of these studies, the NOEL for the rat was determined to be 20mg/kg/day for the 28-day study. In the Beagle dog, the NOEL was approximately 6.05mg/kg/day for the 28-day study. Overall, these studies allowed us to conclude that PG aerosol generated with the capillary aerosol generator could be administered safely in man, with an adequate margin of safety needed to conduct "first-time-in-man" human exposure studies.

A comprehensive evaluation of the toxicology of cigarette ingredients: aliphatic and aromatic carboxylic acids

CONTEXT

Aromatic and aliphatic carboxylic acids are present in tobacco and tobacco smoke.

OBJECTIVE

A battery of tests was used to compare the toxicity of mainstream smoke from experimental cigarettes containing eight aromatic and aliphatic carboxylic acids and the salt of one acid that were added individually at three different levels (lowest and highest target inclusions were 100 and 90,000 ppm, respectively).

MATERIALS AND METHODS

Mainstream smoke from cigarettes containing each of the test ingredients was evaluated using analytical chemistry and assays to measure in vitro cytotoxicity (neutral red uptake) and Salmonella (five strains) mutagenicity. For four of the compounds (citric, lactic, benzoic acids, and sodium benzoate), 90-day rodent inhalation studies were also performed.

RESULTS

Although sporadic statistically significant differences in some experimental cigarette smoke constituents occurred, none resulted in significant changes in mutagenicity or cytotoxicity responses, nor in responses measured in the inhalation studies, except for lactic acid (LA). Inclusion of LA resulted in dose-dependent increase in water and caused a dose-dependent decrease in cytotoxicity. Incorporation of LA into cigarettes resulted in several dose-related reductions in histopathology, which were largely restricted to the nasal passages. Incorporation of LA also ameliorated some of the typical decrease in body weight gain seen in cigarette smoke-exposed rats.

CONCLUSIONS

Inclusion of these ingredients at exaggerated use levels resulted in sporadic dose-related and treatment effects for some smoke constituents, but no toxicological response was noted in the in vitro and in vivo tests performed.

A comprehensive evaluation of the toxicology of cigarette ingredients: cocoa-derived ingredients

CONTEXT

Cocoa-derived ingredients are used in cigarette tobacco.

OBJECTIVE

A battery of tests was used to compare toxicity of mainstream smoke from experimental cigarettes containing different added levels of cocoa-derived ingredients.

MATERIALS AND METHODS

Five cocoa-derived ingredients chocolate (CH), cocoa (COC), cocoa-grand prix black (CGPB), cocoa nibs tincture (CNT) and cocoa shells extract (CSE) were added individually to experimental cigarettes at three different levels. Smoke from each of the experimental cigarette types was evaluated using analytical chemistry; in vitro cytotoxicity and mutagenicity testing were performed for four of the five compounds. For CH, COC and CNT, 90-day smoke inhalation studies were performed with 6-week recovery periods.

RESULTS

No consistent changes were found in the analytical chemistry results. Results of the cytotoxicity and mutagenicity were unaffected by any of the ingredients. Two of the three inhalation studies showed very few differences between the groups. The inhalation study with COC showed several increases in mean histopathology severity scores in groups exposed to different levels of COC, compared with the controls. These apparent effects of COC on histopathology lesion severity scores were only present in a single sex and none were dose-related, which is not consistent with a true increase in biological activity. Also there were effectively no differences in the patterns of recovery for any of the compounds.

CONCLUSIONS

Even at high inclusion levels there was a lack of toxicological response in these COC derived ingredients.

Insights from a multi-year program designed to test the impact of ingredients on mainstream cigarette smoke toxicity

CONTEXT

Cigarette tobacco ingredients may alter the distribution of chemical constituents present in smoke. When considering the toxicological relevance of potential ingredient-related effects on chemical and biological measurements assessing cigarette smoke toxicity, it is critical to understand the intrinsic variability of tobacco and cigarette smoke that is influenced by the environmental conditions during growing, agricultural practices during preparation, cigarette manufacturing tolerances, and stability of the assay methods.

OBJECTIVE

To understand possible effects of ingredients on cigarette smoke toxicity, various chemical and biological endpoints were measured in smoke from experimental cigarettes (added ingredient) to the intrinsic variability of control cigarettes (no added ingredient).

MATERIALS AND METHODS

Data were collected during a multi-year program testing a variety of cigarette ingredients from several chemical classes. Chemical analysis of mainstream cigarette smoke,and biological procedures (Salmonella mutagenicity, cytotoxicity, and smoke inhalation) were performed using validated and controlled laboratory methods. The within-study and temporal variation of control cigarettes manufactured in parallel with experimental cigarettes was calculated and used to measure intrinsic variability.

RESULTS

The overwhelming majority of data generated from experimental cigarettes fell within the experiment variability represented by the pooled standard error of the entire multi-year dataset for the control cigarettes.

CONCLUSION

The results of this evaluation add to a growing body of the literature regarding a weight of evidence assessment of cigarette ingredient toxicity. When assessed against the variability of assay methodology, natural agricultural change, and manufacturing control, the ingredients studied here demonstrated little relevant influence on the mainstream cigarette smoke toxicity endpoints measured.

A comprehensive evaluation of the toxicology of cigarette ingredients: aromatic and aliphatic alcohol compounds

CONTEXT

Various aromatic and aliphatic alcohol compounds are found in tobacco and tobacco smoke.

OBJECTIVE

A battery of tests was used to compare the toxicity of mainstream smoke from experimental cigarettes containing eight aromatic and aliphatic alcohol compounds that were added individually to experimental cigarettes at three different levels. The lowest target inclusion level was 100 ppm and the highest level was 24,400 ppm.

MATERIALS AND METHODS

Mainstream smoke from each of the cigarette types was evaluated using analytical chemistry and assays to measure in vitro cytotoxicity (neutral red uptake) and Salmonella (five strains) mutagenicity. For three of the compounds (benzyl alcohol, propyl paraben, and rum flavor), 90-day smoke inhalation studies with 6-week recovery periods were also performed using rats.

RESULTS

Inclusion of eugenol produced several dose-related reductions in concentrations of selected smoke constituents. Cytotoxicity and mutagenicity were unaffected by any of the test ingredients, except for dose-related reductions in cytotoxicity of the gas vapor phase produced by the inclusion of eugenol. The three smoke inhalation studies showed a few sporadic differences between the groups and there were no differences in the patterns of recovery for any of the ingredients.

CONCLUSIONS

Despite using exaggerated inclusion levels of the eight aliphatic and aromatic alcohol compounds in experimental cigarettes, there was minimal toxicological response, which is consistent with published reports of studies using mixtures of compounds added to tobacco.

A comprehensive evaluation of the toxicology of cigarette ingredients: aromatic carbonyl compounds

CONTEXT

Aromatic carbonyls are typically used in the processing or flavoring of tobacco used in the manufacture of cigarettes.

OBJECTIVE

A battery of tests was used to compare the toxicity of mainstream smoke from experimental cigarettes containing different added levels of aromatic carbonyl compounds.

MATERIALS AND METHODS

Ten aromatic carbonyl compounds, nine of which have been reported in tobacco or in tobacco smoke, were added individually to experimental cigarettes at three different levels. The tenth compound, not found naturally in tobacco, was 2-phenoxyethyl isobutyrate. The lowest target inclusion level was 100 ppm and the highest was 10,000 ppm. Smoke from each of the 10 experimental cigarette types was evaluated using analytical chemistry, in vitro cytotoxicity, and mutagenicity testing. For one of the compounds, ethyl vanillin, a 90-day smoke inhalation study using rats was also performed.

RESULTS

Smoke chemistry was effectively unchanged by the addition of any of the compounds. Cytotoxicity, assessed by the neutral red uptake assay and using both gas-vapor and particulate phases of smoke, was unaffected by the addition of any of the test compounds. Mutagenicity, assessed by five strains of Salmonella typhimurium treated with smoke condensate, also was unaffected by any of the test compounds. In the rat inhalation study, there were effectively no differences between cigarettes without added ethyl vanillin and cigarettes containing ~8000 ppm of ethyl vanillin.

CONCLUSION

Even at the exaggerated inclusion levels in cigarette tobacco used in these tests, no adverse toxicological responses occurred for any of aromatic carbonyl compounds tested.

A comprehensive evaluation of the toxicology of cigarette ingredients: essential oils and resins

CONTEXT

A total of 32 essential oils and resins were added individually to experimental cigarettes.

OBJECTIVE

A battery of tests was used to compare the toxicity of mainstream smoke from these experimental cigarettes. The lowest target inclusion level was 100 ppm and the highest was 100,000 ppm.

MATERIALS AND METHODS

Smoke from each of the experimental cigarette was evaluated using analytical chemistry and in vitro bacterial (Salmonella, five strains) mutagenicity and cytotoxicity (neutral red uptake) assays. For seven of the ingredients (carob bean, carob bean extract, carrageenan, chamomile flower Hungarian oil, guar gum, peppermint oil, and spearmint oil), 90-day smoke inhalation studies with rats were also performed.

RESULTS

In general, inclusion levels resulted in minimal changes in smoke chemistry; the exceptions were PO and SO, where reductions to 40-60% of control values were noted, possibly indicating a tobacco displacement effect. Cytotoxicity and mutagenicity were unaffected by any of the test ingredients, except for a dose-related reduction in cytotoxicity for SO. There were very few statistically significant differences within any of the seven inhalation studies; when present, the differences were sporadic and inconsistent between sexes. The addition of SO appeared to depress body weight gain and increase the atrophy of olfactory epithelia, but only in males.

CONCLUSION

The essential oils and resins tested here as ingredients in experimental cigarettes show minimal toxicological sequelae, even at high inclusion levels. The highest inclusion level for SO showed some equivocal responses.

A comprehensive evaluation of the toxicology of cigarette ingredients: aliphatic carbonyl compounds

CONTEXT

Aliphatic carbonyl compounds are used as ingredients in cigarette tobacco or cigarette filters.

OBJECTIVE

A battery of tests was used to compare toxicity of mainstream smoke from experimental cigarettes containing 15 aliphatic carbonyl compounds that were added individually to experimental cigarettes at three different levels.

MATERIALS AND METHODS

Smoke from experimental and control cigarettes were evaluated using analytical chemistry, in vitro cytotoxicity (neutral red uptake), and mutagenicity (five bacterial strains) studies. For one compound, glycerol triacetate (GTA), two 90-day inhalation studies were also performed, using different inclusion levels into either tobacco or cigarette filter.

RESULTS

Several smoke constituent concentrations were reduced with the highest inclusion level of GTA in tobacco; incorporation of GTA into the filter, and the other compounds into tobacco, produced effectively no changes. Cytotoxicity was reduced by the highest inclusion of GTA into tobacco for both gas-vapor and particulate phases of smoke; incorporation of GTA into the filter, and the other compounds into tobacco, showed no changes. Mutagenicity was reduced by the middle and high inclusion levels of GTA into tobacco (TA1537 strain with S9); incorporation of GTA into the filter, and the other compounds into tobacco, showed no changes.

CONCLUSION

Inclusion of GTA in tobacco at 100,000 ppm reduced the biological effects of the smoke in the various test systems reported in this study, although inclusion into the filter did not appear to have any major effect on the endpoints studied. The other 14 aliphatic carbonyl compounds that were tested lacked a toxicological response.

A comprehensive evaluation of the toxicology of cigarette ingredients: heterocyclic nitrogen compounds

CONTEXT

Three heterocyclic nitrogen compounds, 2,3-diethylpyrazine (DEP), 2,3,5,6-tetramethylpyrazine (TMP), and 2-acetyl pyridine (AP), are naturally present in tobacco and are also added to tobacco as flavor ingredients.

OBJECTIVE

A battery of tests was used to compare the toxicity of mainstream smoke from experimental cigarettes containing the three heterocyclic nitrogen compounds added individually at three different levels. The lowest target inclusion level of the ingredient was 10 ppm, and the highest was 10,000 ppm.

MATERIAL AND METHODS

Smoke from experimental and control cigarettes was evaluated in analytical smoke chemistry, in vitro cytotoxicity, and mutagenicity assays.

RESULTS

The cigarettes with added DEP produced some minor (approximately 10%) changes in smoke chemistry when compared with the cigarettes containing no DEP. Smoke chemistry was effectively unchanged by the addition of either AP or TMP. Cytotoxicity, assessed by the neutral red uptake assay using both gas-vapor and particulate phases of smoke, was unaffected by the addition of any of the test ingredients. Mutagenicity, assessed in five strains of Salmonella treated with mainstream cigarette smoke condensate, also was unaffected by any of the test ingredients.

CONCLUSIONS

Despite the exaggerated ingredient levels relative to commercial-use levels, there was a lack of a toxicological response for the three heterocyclic nitrogen compounds in the test systems used.

An evaluation of the toxicity of 95 ingredients added individually to experimental cigarettes: approach and methods

CONTEXT

Ingredients have been used in modern cigarette manufacturing to facilitate tobacco processing, provide flavor, and preserve tobacco. Concern has been raised regarding the use of ingredients in cigarette manufacturing due to the possible generation of toxic chemicals resulting from their combustion when added to tobacco.

OBJECTIVE

Investigate the impact of individual ingredients on cigarette smoke toxicity.

MATERIALS AND METHODS

A total of 95 ingredients were tested individually through addition at different concentrations to the tobacco of experimental cigarettes. Mainstream cigarette smoke chemistry analysis, bacterial mutagenicity testing, and cytotoxicity testing were conducted. Additionally, 31 of the ingredients were tested in 90-day nose-only rat inhalation studies using mainstream cigarette smoke. Studies were designed following conventional toxicity testing methods employed for food additives and other consumer products.

RESULTS

The studies reported here demonstrate that high levels of some ingredients can change the quantity of some smoke constituents, altering the smoke chemistry profile. From the panel of biological endpoints monitored, these added ingredients produced minimal changes in the overall toxicity profile of mainstream cigarette smoke. In some cases, the addition of high levels of an ingredient caused a small reduction in toxicity findings, probably due to displacement of burning tobacco.

CONCLUSION

The battery of testing results presented here is a useful addition to the available scientific information for cigarette ingredients and extends the dataset which can be used for evaluating their appropriate use.

A comprehensive evaluation of the toxicology of cigarette ingredients: carbohydrates and natural products

CONTEXT

Eleven carbohydrates and natural product ingredients were added individually to experimental cigarettes.

OBJECTIVE

A battery of tests was used to compare toxicity of mainstream smoke from these experimental cigarettes to matched control cigarettes without test ingredients.

MATERIALS AND METHODS

Smoke fractions from each cigarette type were evaluated using analytical chemistry; in vitro cytotoxicity (neutral red uptake) and in vitro bacterial (Salmonella) mutagenicity (five strains) testing. For 10 ingredients (β-cyclodextrin, cleargum, D-sorbitol, high fructose corn syrup, honey, invert sugar, maltodextrin, molasses, raisin juice concentrate, and sucrose), 90-day nose-only smoke inhalation studies using rats were also performed.

RESULTS

In general, addition of each ingredient in experimental cigarettes resulted in minimal changes in smoke chemistry; the exceptions were D-sorbitol and sucrose, where reductions in amount of 60% to 80% of control values for some smoke constituents were noted. Additionally, each ingredient resulted in small increases in smoke formaldehyde concentrations. Except for a reduction in cytotoxicity by inclusion of maltodextrin and an increase by inclusion of plum juice concentrate, the cytotoxicity and mutagenicity results were unaffected by addition of the other ingredients in experimental cigarettes. There were also very few statistically significant differences within any of the 10 inhalation studies, and when present, the differences were largely sporadic and inconsistent between sexes.

CONCLUSION

The carbohydrates and natural products tested here as ingredients in experimental cigarettes as a class increased formaldehyde, but resulted in minimal toxicological responses, even at high inclusion levels compared with the levels used in commercial cigarette products.

Comparison of the physiological and morphological effects of cigarette smoke exposure at comparable weekly doses on Sprague-Dawley rats

A variety of dose x duration exposure regimens have been used in inhalation toxicity studies using rodents. We evaluated the effects of differences in smoke concentration and daily exposure duration under similar weekly cumulative exposures in rats to determine potential variation in type and severity of adverse effects in 13-week exposure studies. The weekly cumulative dosages were 2100 and 4200 μg wet total particle matter (WTPM)/L, and the daily exposure durations were 1 and 6 h. Weekly exposure duration was 5 or 7 days/week for groups exposed 1 h/day and 7 days/week for groups exposed 6 h/day. Recovery duration was 6 and 13 weeks. Mainstream smoke exposure suppressed body weight (BW) gain in both regimens. Lower dose groups exposed 1 h/day had a consistently greater of BW gain compared with corresponding 6 h/day groups. Respiratory rate, tidal volume, and minute volume (MV) were suppressed in a dose-dependent manner in both regimens. Higher MV in rats exposed for 6 h/day compared with rats exposed 1 h/day suggested that a lower concentration for longer duration resulted in a greater total inhaled mass (TIM) in rats exposed 6 h/day. Groups exposed for 6 h/day had lower blood carboxyhemoglobin and plasma nicotine levels than groups exposed 1 h/day, reflecting the lower carbon monoxide (CO) and WTPM concentrations in the 6 h/day groups. Data from examination of bronchoalveolar lavage fluids (BALF) and respiratory tract tissues indicated comparable effects between both regimens. Exposure-induced histopathological changes regressed similarly for both regimens after the recovery periods.

Toxicological considerations on the use of propylene glycol as a humectant in cigarettes

Propylene glycol (PG) is a humectant commonly used in cigarettes. Previous toxicological examinations of the effects on the addition of PG to tobacco used mixtures with several other flavoring agents. In the present work, toxicological comparisons were made of experimental cigarettes containing no added PG against otherwise similar cigarettes with three different amounts of PG added to the tobacco. The main toxicological comparison was a sub-chronic inhalation study with mainstream smoke in Sprague-Dawley rats (exposures of 150 mg/m(3) of total particulate matter, 6h exposure per day, for 90 consecutive days). The target PG concentrations in the tobacco of the four cigarette types were 0, 4, 7 and 10%. Additional studies with mainstream smoke were bacterial mutagenicity (5 Salmonella strains, both with and without metabolic activation, particulate phase only), cytotoxicity of both particulate and gas/vapor phases (using the neutral red uptake assay), and analytical chemistry (41 analytes). The graded inclusion of PG into experimental cigarettes resulted in increases in the smoke concentrations of propylene oxide, at very low concentrations. Broadly similar responses were seen across the four cigarette types, and the responses were similar to those previously described in the scientific literature. The addition of PG to experimental cigarettes reduced concentrations of some smoke components (e.g. nicotine), but had minimal effects on the biological responses. Most of the changes produced in the 90-days of exposure were resolved in a 42-day post-inhalation period.