Tobacco-specific N-nitrosamines and Areca-derived N-nitrosamines: chemistry, biochemistry, carcinogenicity, and relevance to humans

Nicotine and the minor tobacco alkaloids give rise to tobacco-specific N-nitrosamines (TSNA) during tobacco processing and during smoking. Chemical-analytical studies led to the identification of seven TSNA in smokeless tobacco (< or = 25 micrograms/g) and in mainstream smoke of cigarettes (1.3 micrograms TSNA/cigarette). Indoor air polluted by tobacco smoke may contain up to 24 pg/L of TSNA. In mice, rats, and hamsters, three TSNA, N'-nitrosonornicotine (NNN), 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), are powerful carcinogens; two TSNA are moderately active as carcinogens; and two TSNA appear not to be carcinogenic. The TSNA are procarcinogens, agents that require metabolic activation. The active forms of the carcinogenic TSNA react with cellular components, including DNA, and with hemoglobin (Hb). The Hb adducts in chewers and smokers serve as biomarkers for the uptake and metabolic activation of carcinogenic TSNA and the urinary excretion of NNAL as free alcohol and as glucuronide for the uptake of TSNA. The review presents evidence that strongly supports the concept that TSNA contribute to the increased risk for cancer of the upper digestive tract in tobacco chewers and for the increased risk of lung cancer, especially pulmonary adenocarcinoma, in smokers. The high incidence of cancer of the upper digestive tract especially among men on the Indian subcontinent has been causally associated with chewing of betel quid mixed with tobacco. In addition to the TSNA, the betel quid chewers are exposed to four N-nitrosamines that are formed during chewing from the Areca alkaloids, two of these N-nitrosamines are carcinogens. The article also reviews approaches toward the reduction of the carcinogenic potency of smokeless tobacco, betel quid-tobacco mixtures, and cigarette smoke. Although the safest way to reduce the risk for tobacco-related cancers is to refrain from chewing and smoking, modifications of smokeless tobacco and of cigarettes are indicated to lead to less toxic products. Another more recent approach for reducing the carcinogenic effect of tobacco products is the application of chemopreventive agents, primarily of micronutrients. Future aspects in tobacco carcinogenesis, especially as it relates to TSNA, are expected in the field of molecular biochemistry and in biomarker studies, with the goal of identifying those tobacco and betel quid chewers and tobacco smokers who are at especially high risk for cancer.

A tobacco-specific lung carcinogen in the urine of men exposed to cigarette smoke

BACKGROUND

Environmental tobacco smoke has been classified by the Environmental Protection Agency as a carcinogen causally associated with lung cancer in adults, but there have been no reports of lung carcinogens or their metabolites in the body fluids or tissues of nonsmokers exposed to environmental tobacco smoke.

METHODS

Five male nonsmokers were exposed to sidestream cigarette smoke generated by machine smoking of reference cigarettes for 180 minutes on each of two days, six months apart. Sidestream smoke is the smoke that originates from the smoldering end of a cigarette between puffs. Twenty-four-hour urine samples were collected before and after exposure. The urine samples were analyzed for 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) and its glucuronide, which are metabolites of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), a powerful lung carcinogen in rodents. NNAL is also a lung carcinogen in rodents.

RESULTS

The urinary excretion of the metabolites increased after exposure to sidestream smoke in all the men. The mean (+/- SD) amount of NNAL and NNAL glucuronide was significantly higher after exposure than at base line (33.9 +/- 20.0 vs. 8.4 +/- 11.2 ng per 24 hours [127 +/- 74 vs. 31 +/- 41 pmol per day], P < 0.001) and was correlated with urinary cotinine excretion (r = 0.89, P < 0.001). The nicotine concentrations in the air to which the men were exposed were comparable to those in a heavily smoke-polluted bar.

CONCLUSIONS

Nonsmokers exposed to sidestream cigarette smoke take up and metabolize a lung carcinogen, which provides experimental support for the proposal that environmental tobacco smoke can cause lung cancer.

Analysis of 1,3-butadiene and other selected gas-phase components in cigarette mainstream and sidestream smoke by gas chromatography-mass selective detection

An analytical procedure was developed for the analysis of 1,3-butadiene, acrolein, isoprene, benzene and toluene in the gas phase of cigarette smoke and environmental tobacco smoke (ETS) utilizing cryogenic gas chromatography-mass selective detection (GC-MSD). The MSD was operated in the selective ion monitoring (SIM) mode. The compounds of interest eluted in less than 15 min. The gas phase of freshly generated mainstream smoke was introduced into the GC-MSD via a 10-port gas sampling valve on a puff-by-puff basis. This method minimizes the ageing of tobacco smoke. The levels of 1,3-butadiene in the mainstream smoke ranged from 16 to 75 micrograms/cigarette. The gas phase of sidestream smoke was trapped in methanol using three midget impingers at -78 degrees C. The amount of 1,3-butadiene in the sidestream smoke ranged from 205-361 micrograms/cigarette. The concentration of 1,3-butadiene in ETS in a smoke-filled bar amounted to 2.7-4.5 micrograms/m3.

Analytical studies on tobacco-specific N-nitrosamines in tobacco and tobacco smoke

Chemical-analytical studies have led to the identification of approximately 3000 compounds in tobacco and 4000 in tobacco smoke. These include carcinogens in processed tobacco as well as tumor initiators, tumor promoters, cocarcinogens, and organ-specific carcinogens in tobacco smoke. The latter group includes N-nitrosamines, in particular those that derive from nicotine and other tobacco alkaloids, the TSNA. In vitro nitrosation of nicotine yields NNN, NNA, and NNK. Nitrosation of other tobacco alkaloids leads to the formation of NAT, and NAB. Our analytical studies using GC-TEA have led to the identification of seven TSNA in tobacco and tobacco smoke. In addition to NNN, NAT, NAB, and NNK, we also identified NNAL, iso-NNAL, and, most recently, iso-NNAC. Their levels range from 0.01 to 92 ppm in tobacco and from 6 to 530 ng/cigarette in tobacco smoke. The high levels observed in snuff are primarily due to fermentation and aging. Technological methods exist today to reduce the levels of TSNA in both tobacco and cigarette smoke.

Exposure to N-nitroso compounds in a population of high liver cancer regions in Thailand: volatile nitrosamine (VNA) levels in Thai food

The recent case-control studies in Thailand indicate that a high incidence of liver cancer in Thailand has not been associated with common risk factors such as hepatitis B infection, aflatoxin intake and alcohol consumption. While the infestation by the liver fluke Opisthorchis viverrini (OV) accounted for the high risk in north-east Thailand, there was no such exposure in the other regions of the country where the incidence of liver cancer is also high. Case-control studies suggest that exposure to exogenous and possibly endogenous nitrosamines in food or tobacco in betel nut and cigarettes may play a role in the development of hepatocellular carcinoma (HCC), while OV infestation and chemical interaction of nitrosamines may also be aetiological factors in the development of cholangiocarcinoma (CCA). Over 1800 samples of fresh and preserved food were systematically collected and tested between 1988 and 1996. All the food items identified by anthropological studies to be consumed frequently in four major regions of Thailand were analysed for volatile nitrosamines using gas chromatography combined with a thermal energy analyser. Relatively high levels of N-nitrosodimethylamine (NDMA), N-nitrosopiperidine (NPIP) and N-nitrosopyrrolidine (NPYR) were detected in fermented fish ("Plasalid"). NDMA was also detected at levels ranging from trace amounts to 66.5 microg/kg in several salted and dried fish ("Larb-pla" and "Pla-siu"). NDMA and NPYR were frequently detected in several vegetables, particularly fermented beans ("Tau-chiau") at levels ranging between 1 and 95.1 microg/kg and 0-146 microg/kg, respectively. The possible role of nitrosamines in Thai food in the aetiology of liver cancer (HCC, CCA) is discussed.

Formation and analysis of tobacco-specific N-nitrosamines

Chemical-analytical studies during the past 4 years led to several new observations on the formation of tobacco-specific N-nitrosamines (TSNA) and their occurrence in smokeless tobacco, mainstream smoke (MS), and sidestream smoke (SS) of American and foreign cigarettes. When snuff was extracted by means of supercritical fluid extraction with carbon dioxide containing 10% methanol, analysis of this material confirmed that the extraction with organic solvents had been partially incomplete. Epidemiological studies in the northern Sudan showed a high risk for oral cancer for users of toombak, a home-made oral snuff. Toombak contains 100-fold higher levels of TSNA than commercial snuff in the U.S. and Sweden. The TSNA content in the saliva of toombak dippers is at least ten times higher than that reported in the saliva of dippers of commercial snuff. Biomarker studies have shown corresponding high levels of hemoglobin adducts with metabolites of NNN and NNK as well as for urinary metabolites of NNK. These data supported the epidemiological findings. The analyses of MS of U.S. and foreign cigarettes smoked under FTC conditions revealed comparable data for the smoke of nonfilter cigarettes and filter cigarettes except in the case of low- and ultralow-yield cigarettes, which showed reduced TSNA yields. The MS of cigarettes made from Burley or dark tobacco is exceptionally high in TSNA, primarily because of the high nitrate content of those tobacco types. Taking puffs of larger volume and drawing puffs more frequently, practices observed among most smokers of cigarettes with low nicotine yield, results in high TSNA values in the MS. The formation of the lung carcinogen NNK is favored during the smoldering of cigarettes, between puffs, when SS is generated. Consequently, in most samples from indoor air polluted with environmental tobacco smoke (ETS), the highest concentration of an individual TSNA is that of NNK. When nonsmokers had remained for up to 2 h in a test laboratory with high ETS pollution, they excreted measurable amounts of NNK metabolites in the urine, indicative of the uptake of TSNA.

Localized formation of micronuclei in the oral mucosa and tobacco-specific nitrosamines in the saliva of "reverse" smokers, Khaini-tobacco chewers and gudakhu users

"Reverse"-cigar smokers (who hold the burning end of cigars within the mouth), dippers (who place a mixture of Khaini-tobacco and slaked lime into the lower gingival groove) and users of tobacco-containing toothpaste (gudakhu) in Orissa, India, were examined for precancerous oral lesions, the frequency of micronucleated cells at 3 different intra-oral sites, and levels of tobacco-specific nitrosamines (TSNA) in the saliva. Among reverse-cigar smokers, a high incidence of leukokeratosis nicotina palati, an elevated frequency of micronucleated cells in the palate (2.5% as compared to 0.6% in non-smokers and non-chewers of tobacco) and tongue (2.1%) from which carcinomas preferentially develop, and up to 5890 ppb nitrosonornicotine and up to 1880 ppb N-nitrosoanatabine in the saliva were found. Among Khaini-tobacco chewers, the frequency of micronucleated cells was elevated to 2.1% in the gingival groove, and up to 1580 ng N-nitrosonornicotine, 690 ng N-nitrosoanatabine, 90 ng N-nitrosoanabasine, and 180 ng 4-(methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone) per ml of saliva were observed. The localized elevation of the frequency of micronuclei and cancer development is probably due to a synergistic effect of hyperthermia and tobacco-related carcinogens among reverse-cigar smokers, and to the close, prolonged contact between the mucosa and tobacco among Khaini-tobacco/slaked lime dippers. Neither pre-cancerous lesions nor an elevated frequency of micronuclei were seen in the oral mucosa of users of gudakhu, a tobacco-containing toothpaste, which may be due to the low amount of TSNA released from the gudakhu and the short exposure time, which is restricted to the period of tooth brushing.

Tobacco sidestream smoke: uptake by nonsmokers

Some epidemiological studies indicate an association between passive smoking and an increased risk for cancer, especially for cancer of the lung. Other reports, however, have failed to confirm these findings. Biochemical analyses of the physiological fluids for markers of exposure to tobacco smoke are needed as measurements of the uptake of smoke components by nonsmokers and for the estimation of relative cancer risk to passively exposed persons compared with that to active cigarette smokers. This communication reports the uptake of carbon monoxide, hydrogen cyanide, and nicotine after passive smoke exposure under controlled conditions. The results indicate that salivary nicotine values reflect the level of recent passive smoke exposure within an hour and that urinary cotinine values indicate the level of passive smoke exposure in the preceding hours. N-Nitrosoproline has been shown to serve as an indicator of endogenous N-nitrosamine formation in cigarette smokers: yet, preliminary studies do not indicate that urinary excretion of N-nitrosoproline is increased following short-term passive smoke exposure. In infants, first field studies suggest a correlation between exposure to tobacco-smoke-polluted environments and levels of cotinine in both serum and urine.

Assessment of the carcinogenic N-nitrosodiethanolamine in tobacco products and tobacco smoke

A simple, reproducible gas chromatography-thermal energy analyzer (g.c.-TEA) method has been developed for the analysis of N-nitrosodiethanolamine (NDELA) in tobacco and tobacco smoke. The extract of tobacco or the trapped particulates of tobacco smoke are chromatographed on silica gel. The NDELA containing fractions are concentrated, silylated and analyzed with a modified g.c.-TEA system. [14C]NDELA serves as internal standard for the quantitative analysis. Experimental cigarettes made from tobaccos which were treated with the sucker growth inhibitor maleic hydrazidediethanolamine (MH-DELA) contained 115--420 p.p.b. of NDELA and their smoke contained 20--290 ng/cigarette, whereas hand-suckered tobacco and its smoke were free of NDELA. The tobacco of US smoking products contained 115--420 p.p.b. of NDELA and the mainstream smoke from such products yielded 10--68 ng/cigar or cigarette. NDELA levels in chewing tobacco ranged from 220--280 p.p.b. and in two commercial snuff products were 3,200 and 6,800 p.p.b. Although the five analyzed MH-DELA preparations contained between 0.6--1.9 p.p.m. NDELA it is evident that the major portion of NDELA in tobacco is formed from the DELA residue during the tobacco processing. Based on bioassay data from various laboratories which have shown that NDELA is a relatively strong carcinogen and based on the results of this study the use of MH-DELA for the cultivation of tobacco is questioned.

A study of betel quid carcinogenesis. IV. Analysis of the saliva of betel chewers: a preliminary report

Betel quid chewing is strongly associated with cancer of the oral cavity, especially when tobacco is added to the quid. It is our working hypothesis that, during chewing, Areca-derived N-nitrosamines are formed and, in the presence of tobacco, Nicotiana-specific N-nitrosamines are formed as well and further that these agents may contribute to the high risk of oral cancer in betel-quid chewers. This preliminary report presents our finding of N-nitrosoguvacoline in the saliva of betel-quid chewers (2.2-350 ppb). When the quid contains tobacco, the tobacco-specific N-nitrosamines, N'-nitrosonornicotine (1.2-38.3 ppb), N'-nitrosoanatabine (3.2-39.5 ppb), and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (1.0-2.3 ppb) are also found in the saliva.

Determination of benzene, toluene and 1,3-butadiene in cigarette smoke by GC-MDS

An analytical procedure was devised for the determination of selected gas phase constituents in cigarette smoke utilizing capillary gas chromatography and mass selective detection (GC-MSD); the MSD was used in the selective ion monitoring mode (SIM). The gas of freshly generated mainstream smoke was analyzed via a 10-port gas sampling valve on a puff-by-puff basis. Benzene, toluene, and 1,3-butadiene were found in the range of 6-73, 5-88, and 16-75 micrograms/cigarette, respectively. The gas phase of sidestream smoke was trapped in methanol using 3 midget impingers at -78 degrees C. Benzene in sidestream smoke was found in the range of 490-840 micrograms/cigarette; toluene and 1,3-butadiene levels were 1,090-1,690 and 300-470 micrograms/cigarette, respectively. Environmental tobacco smoke (ETS), sampled in a smoke-filled bar, was analyzed using the cold trap method. The concentrations of benzene and toluene in this indoor air were found to be 26-36 and 41-80 micrograms/m3, respectively, while 1,3-butadiene was present at 3.3-4.5 micrograms/m3.

N-Nitrosomorpholine and other volatile N-nitrosamines in snuff tobacco

Ten popular snuff brands from the USA and Sweden were analyzed for volatile N-nitrosamines (VNA). Seven of these samples contained between 20 and 70 p.p.b. of N-nitrosomorpholine (NMOR), a strong animal carcinogen. Some of the snuff containers which were made of waxed cardboard contained morpholine. This observation and a model study with the container waxes plus [14C]morpholine indicate that NMOR possibly can be formed by way of diffusion of the morpholine into the snuff and subsequent N-nitrosation. The VNA including NMOR (60-1150 p.p.b.) together with N-nitrosodiethanolamine (NDELA; 225-3300 p.p.b.) and the four tobacco-specific N-nitrosamines (TSNA; 1300-80,000 p.p.b.) contribute significantly to the carcinogenic potential of snuff. This tobacco product, although a known human carcinogen, is becoming increasingly popular especially among young people in the USA and Sweden. A recently introduced Swedish brand with individual snuff portions wrapped in aluminum foil was free of VNA (less than 2 p.p.b.) and contained relatively low levels of NDELA (290 p.p.b.) and TSNA (4200 p.p.b.). This indicates that practical approaches towards lowering N-nitrosamine levels in these snuff products are available.

Identification and analysis of a nicotine-derived N-nitrosamino acid and other nitrosamino acids in tobacco

Research on carcinogenic, tobacco-specific N-nitrosamines (TSNA) led to the identification and analysis of 4-(methylnitrosamino)-4-(3-pyridyl)butyric acid (iso-NNAC) in tobacco and tobacco smoke. In order to isolate iso-NNAC, an aqueous tobacco extract at pH 4 was partitioned with ethyl acetate after the other N-nitrosamino acids and TSNA were removed at pH 2 and pH 9 respectively. The structure of iso-NNAC was confirmed by GC-MS after enrichment of the methylated pH 4 fraction by chromatography on an alumina column. Iso-NNAC, 3-(methylnitrosamino)propionic acid, 4-(methylnitrosamino)butyric acid, N-nitrosoproline and TSNA were determined by GC-TEA in various smokeless tobaccos as well as in reference cigarettes. The levels of iso-NNAC in tobacco products ranged from 0.01 p.p.m. in chewing tobacco to 0.95 p.p.m. in dry snuff. The transfer rate of unchanged iso-NNAC into the mainstream smoke of a non-filter cigarette amounted to 0.85%. Iso-NNAC does not induce DNA repair in primary rat hepatocytes and is inactive as a tumorigenic agent in strain A mice.

Oral lesions, genotoxicity and nitrosamines in betel quid chewers with no obvious increase in oral cancer risk

A link between the generation of areca nut-related N-nitrosamines in the saliva, the induction of genotoxic damage in the oral mucosa, as judged by an increase in micronucleated exfoliated cells (MEC), and a low incidence of oral cancer was studied in 2 population groups characterized by their habit of chewing quids without tobacco: Guamanians, who chew areca nuts (Areca catechu) with or without the addition of betel leaf (Piper betle); Taiwanese, who use areca nut, betel leaf or inference and slaked lime. The levels of N-nitrosoguvacoline (NG) in the saliva of chewers of fresh green areca nuts were very high (70.8 ng/ml) as compared to those reported for individuals using the more complex Indian betel quids (0.91 ng/ml or 5.6 ng/ml). None of the other areca nut-related nitrosamines (N-nitrosoguvacine (NGC), 3-(methylnitrosamino)propionitrile (MNPN) and 3-(methylnitrosamino)propionaldehyde (MNPA)) were detected in the saliva of Taiwanese betel quid chewers. The addition of slaked lime to the areca nut enhances the formation of NG during a chewing session. The frequency of MEC did not increase in the oral mucosa of areca nut chewers who do not use slaked lime, but showed a small but significant elevation in individuals using lime-containing quids. The elevation of MEC in Taiwanese, who are at low risk for oral cancer, is relatively small as compared to that found in chewers of Indian betel quids (pan), who show a highly elevated oral cancer risk. The results seem to suggest that NG may play only a minor role, if any, in the etiology of oral cancer among betel quid chewers.

Volatile nitrosamines and tobacco-specific nitrosamines in the smoke of Thai cigarettes: a risk factor for lung cancer and a suspected risk factor for liver cancer in Thailand

In Thailand, smoking of commercial cigarettes and of handmade cigarettes has drastically increased in recent decades. Cancer of the lung and of the upper aero-digestive tract have also increased in Thailand as they have in many other countries. It is our working hypothesis that the increase of primary cancer of the liver, especially of cholangiocarcinoma in the north-eastern provinces of Thailand is associated with the use of tobacco in men infested with the liver fluke Opisthorchis viverrini (OV). Bioassays have shown that volatile nitrosamines and tobacco-specific nitrosamines induce cholangiocarcinoma in laboratory animals and that the hepatocarcinogenic action of nitrosodimethylamine in hamsters is significantly increased by infestation with the liver fluke OV. The endogenous formation of nitrosamines is significantly increased by OV infestation. This report presents analytical data on the concentration of volatile nitrosamines and tobacco-specific nitrosamines in mainstream smoke of nine leading brands of commercially produced Thai cigarettes which represent approximately 85% of the market share in Thailand. Observed ranges (ng/cigarette) were 8.5-31.9 for nitrosodimethylamine, 8.8-49.6 for nitrosopyrrolidine and 4.2-18.9 for nitrosodi-n-butylamine. These values are exceptionally high compared with the smoke of light and blended cigarettes from North America and Western Europe. Among the tobacco-specific nitrosamines, the range was 28-730 for nitrosonornicotine and 16-370 for 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone. There was a correlation between volatile and tobacco-specific nitrosamines, and tar and nicotine deliveries in the mainstream smoke. The analytical data are in line with the rate for lung cancer and support our working hypothesis that nitrosamines, and especially the tobacco-specific nitrosamines, are associated with the increased risk for primary liver cancer among those Thai people who smoke cigarettes and also carry OV infestation.

Chemical profile of two types of oral snuff tobacco

The chemical-analytical profile of two US brands of oral moist snuff was determined. These two brands were bought in five geographical locations (NY, MA, CO, CA and KY in the US). They were mixed thoroughly to yield representative samples. Brand A had a pH of 5.84 and nicotine content of 0.42%, while brand B had a pH of 7.99 and nicotine content of 2.73%. At pH 5.84, only 1% of the nicotine is present as a free base while 59% of nicotine is present in unprotonated form at pH 7.99. It is the unprotonated form of nicotine that is most readily absorbed through the mucous membrane in the oral cavity. Snuff A contained also significantly lower levels of moisture, nitrate, nitrite and tobacco-specific nitrosamines than snuff B. The University of Kentucky reference snuff 1S3 was analyzed as an external control sample. These two snuff brands are currently being assayed with rats in a short-term and in long-term bioassays to test the concept that the tobacco-specific N-nitrosamines are major contributors to the carcinogenic activity of oral snuff.

Analysis of tobacco-specific N-nitrosamines in indoor air

A method was developed and applied for the assessment of tobacco-specific N-nitrosamines (TSNA) in indoor air polluted with tobacco smoke. Air samples were collected on Cambridge filters treated with 0.01 M potassium bisulfate, extracted with dichloromethane and enriched by column chromatography. The fraction containing the TSNA was concentrated and placed on a thermal desorption cartridge packed with Tenax GR. The sample was thermally desorbed and analyzed by capillary GC using a thermal energy analyzer. When the method was applied in a test laboratory in which one, two and four cigarettes were smoked during 30 min, linearity was observed. Field studies included sampling in bars, restaurants and trains. The concentration of N'-nitrosonornicotine (NNN) ranged from not detected to 23 pg/l, that of N'-nitrosoanatabine ranged from not detected to 9 pg/l, while 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) was detected in concentrations ranging from 1 to 29 pg/l. This means an exposure to NNN and NNK of 0.1-0.3 cigarette equivalents. Thus, non-smokers can be exposed to highly carcinogenic TSNA.

The need for regulation of carcinogenic N-nitrosamines in oral snuff

Oral snuff is carcinogenic to humans and laboratory animals. The major carcinogenic agents in snuff are the N-nitrosamines, especially the tobacco-specific N-nitrosamines. During the past decade, a gradual reduction of the levels of carcinogenic N-nitrosamines was observed in the leading snuff brands in the USA and in Sweden. However, in 1990 a newly introduced snuff brand in the USA contained the highest concentration of carcinogenic N-nitrosamines ever to be determined in a commercial tobacco product. The elevated pH and relatively high levels of nitrite in this snuff favoured the formation of N-nitrosamines. 2 yr after the product first appeared, it was replaced by a new preparation of snuff under the same brand name, and, according to chemical analyses, this material would be expected to have about the same carcinogenic potential as the leading snuff products. The interdependence of the formulation and manner of preparation of snuff products with their carcinogenic potential emphasizes the need for regulation and control of the harmful substances in smokeless tobacco, especially in view of the trend of increasing consumption of snuff.

Analysis of volatile N-nitrosamines in mainstream and sidestream smoke from cigarettes by GLC-TEA

Volatile N-nitrosamines were quantitatively determined in mainstream and sidestream smoke of commercial cigarettes using gas chromatography-thermal energy analysis (GLC-TEA). The smoke was trapped in ascorbic acid solution buffered at pH 4.5 and then extracted with dichloromethane; the organic phase was chromatographed on basic alumina and analyzed by GLC-TEA. The mainstream smoke of 22 different commercial cigarettes from Germany and Switzerland contained between 0.1 and 27 ng dimethylnitrosamine (DMN), 1.5 and 29 ng nitrosopyrrolidine (NPY) and traces of methylethylnitrosamine (MEN). The sidestream smoke of these cigarettes contained between 143 and 415 ng DMN, 3.1 and 27 ng MEN and 28 and 150 ng NPY. In a final experiment we measured the DMN concentration in a sealed experimental chamber as a function of the number of cigarettes smoked and recovered 68-87% of the DMN values found when using the sidestream collection device applied in the other experiments.

Assessment of major carcinogens and alkaloids in the tobacco and mainstream smoke of USSR cigarettes

Tobacco and mainstream smoke of USSR cigarettes were analyzed for carcinogens. The pH values of suspensions of the tobacco (5.4-5.6) and the nitrate content of the tobaccos (0.4-1.7%) were as expected for flue-cured and sun-cured tobaccos and mixtures thereof. The nicotine levels of the cigarette tobaccos (0.76-0.94%) and total alkaloid content (0.85-1.08%) were relatively low compared with tobaccos used in Western European and US cigarettes. The concentrations of tobacco-specific N-nitrosamines in the cigarette tobaccos were also low (N'-nitrosonornicotine 0.36-0.85 microgram/g) compared with those in bright, oriental and blended cigarette tobaccos in Western countries (0.3-19 microgram/g). The 2 non-filter and 4 filter cigarettes from the USSR had slow burning rates and yielded 14.0-16.7 puffs/cigarette, while puff yields for commercial cigarettes in Western countries average less than or equal to 11 puffs/cigarette. Consequently, tar and benzo(a)pyrene yields in the smoke of all cigarettes as well as nitrosamine yields were high, especially in the smoke of the filter cigarettes. It appears that an increase in the burning rates of these cigarettes should lead to lower smoke yields.

A critical look at N-nitrosamines in environmental tobacco smoke

The amounts of cigarette smoke carcinogens released into the environment as sidestream smoke (SS) constituents are generally twice as high as the levels of the carcinogens that are inhaled as mainstream smoke (MS). However, certain carcinogens in undiluted SS, such as nitrosamines, exceed MS levels up to 50 times. Regardless of the fact that SS is usually substantially diluted before being inhaled, its constituents can be determined in environmental tobacco smoke (ETS) by modern analytical methods and levels of exposure of involuntary smokers can be assessed by the use of specific markers. Currently, the uptake of ETS by nonsmokers is determined by measuring nicotine and its metabolite cotinine in saliva, serum and/or urine. In on-going studies, we are now exploring the determination of the two highly carcinogenic nicotine-derived nitrosamines N'-nitrosonornicotine (NNN) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), respectively of their metabolites, in physiological fluids of smokers and nonsmokers.

Identification and analysis of a new tobacco-specific N-nitrosamine, 4-(methylnitrosamino)-4-(3-pyridyl)-1-butanol

A new tobacco-specific N-nitrosamine, 4-(methylnitrosamino)-4-(3-pyridyl)-1-butanol (iso-NNAL) was isolated from snuff tobacco. Structural characterization of this N-nitrosamine was confirmed by mass spectral analysis. Five popular US brands of moist snuff and three popular US brands of dry snuff tobacco were analyzed for moisture, nicotine and tobacco-specific N-nitrosamines. The moisture content varied from 20 to 53% in moist snuff and from 4.7 to 5.6% in dry snuff. The nicotine levels in these samples varied from 0.6 to 3.2%. The newly identified iso-NNAL was present in concentrations ranging from 0.07 to 2.5 p.p.m. whereas other tobacco-specific N-nitrosamines, N-nitrosonornicotine, N-nitrosoanatabine, N-nitrosoanabasine and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone were found to range from 0.1 to 178 p.p.m. Iso-NNAL was not detected in mainstream and sidestream smoke of cigarettes. Iso-NNAL is genotoxic in primary rat hepatocytes; its tumorigenic properties are currently being tested in mice and rats.