CONTENTS Irritation: Acute Exposure IrritantS in Environmental Tobacco Smoke Irritating and AMoying Efhta of Environmental Tobacco Smoke Studies of Healthy Individuals Field Studies Experimental Studies Studies of Sensitive Individuals Children Allergic Individuals Effects on the Lung Effect9 of Cigarette Smoking on Respiratory Epitheli- urn: Studies in Humans Effect of Cigarette Smoking on Lung Inflammatory C&f3 Studies in Humans Experimental Models Effects of Cigarette Smoking on Lung Parenchyma: Studies in Humans Summary of Lung Effects Carcinogenicity of Environmental Tobacco Smoke Inhalation Experiments Other In Vivo Bioassays In Vitro Assays Summary of Carcinogenicity Conclusions Beferehces 227 Irritation: Acute Expoeure Irritants in Emirogmental Tobacco Smoke Tobacco smoke is a complex aerosol that contams several thousand different constituents (Hoffmann, Haley, Brunnemann 1983). Little is known about the health effects of most of these compounds individually and even less is known about their interactions. Tobacco smoke contains compounds established as irritants, toxins, muta- germ, and carcinogens. The main irritanta identified in environmen- tal tobacco smoke @Z'S) to date are respirable particulates, certain aldehydes, phenol, ammonia, nitrogen oxides, sulfur dioxide, and toluene. The range of concentrations of these irritants measured m mainstream smoke, in side&ream smoke, and in smoky air under "realistic" and "natural" conditions or as results of field studies is summarized in Table 1. The levels of irritants in air contaminated with ETS vary considerably (Table 1). Some of this variation is due to differences ir the number of cigarettes smoked, the amount of ventilation, the adsorptive properties of the surroundings, and measurement me& odology. Triebig and Zober (1984) compared the measured concentra- tions of these irritants with the maximum permissible concentration (MAK) values for working areas and the maximum emission concentration (MIK) values for outdoor air pollution in the Federal Republic of Germany. They concluded that concentrations approxi- mating or in excess of the MIK values can be found for respirable particulates, nitrogen dioxide, and acrolein. The other irritants generally do not reach the existing threshold limit values under realistic conditions. For phenol there is no MIK value. An evaluation of the hygienic and medical importance of the compounds in EC'S based on threshold limit values is problematic for two reasons: first, MAK values for industries are established for healthy adults with an Shour exposure per day; MYIK values are for the outdoor environ- ment, and no indoor limit values exist for "everyday life." Second, the threshold limit values are valid only for single compounds; E'l'S contains many different irritants, which might interact to produce more toxicity than anticipated from the concentrations of individual compounds. Many of the constituents of tobacco smoke are also produced by other sources that contribute contaminants to the indoor or outdoor environment. For example, sources unrelated to smoking such as urea formaldehyde foam insulation or certain wood materials can emit formaldehyde and may give rise to mean air concentrations as high as 100 to 400 ppb (Triebig and Zober 1984). In measuring the contribution of tobacco smoke to the levels of these constituents, some researchers (Weber et al. 1979a; Weber and Fischer 1980) have subtracted the measured indoor concentrations from the levels TABLE l.-Major irritants in environmental tobacco smoke (ETS), their concentrations in mainstream smoke (MS), sidestream smoke (SS) to mainstream smoke (MS) ratios, and levels in smoky air under realistic and natural conditions kritant MS (per ciweth) ss/Ms (ratio) smoky air (range) Acmlein lo-140 pg Formaldehyde ~~Irg Ammonia Nitrogen oxides Pyridine Sulfur dioxide Phenol Toluene Respirable particulatea 32 w 10 l-75 ppb NA 20-150 p6 2.6 106 I% 5.6 0.1-40 In6 1.3-1.9 10-20 a50 44-100 4.7-50 6-m Ppb 30-60 Ppb. CO l-43 pbb) lOOk pbb" l-370 ppb NOc (MO pbb NO,c NAd l-69 ppbc 7.4-115 pg/m' 0.04-1.04 n&m' 5962 mg/m* * Meeaured under experimental conditions only. b Fischer (1979). c Difference: indoor concentration minus control value (unoccupied mom or outdoon). d NA = not available. SOURCE: Date from Cdlishaw et al. MFA). Remmer W&5). Triebig and zober WM), US DIUB WW, except where noted. measured either in the unoccupied room or in the outdoor environ- ment near the room. The measured concentrations of irritants listed in Table 1 are primarily the mean values in air samples collected over intervals of onehalf hour to several hours. Substantial variation in levels can occur, depending on the proximity to a smoker and the air-mixing conditions in the room. Weber and Fischer (1983) measured peak concentrations of 3,330 to 99,680 ng/ms for the particulates and 41 to 750 ppb for nitrogen oxide in the "blowing cloud" 1 meter from the smoker immediately after smoke exhalation. These high concentra- tions decreased very rapidly with time (half-life between 2 and 20 seconds) and distance from the smoker. Ayer and Yeager (1982) measured formaldehyde and acrolein concentrations in the side stream smoke plume rising from a cigarette between puffs and obtained concentrations of some constituents up to three orders of magnitude above the occupational limits established for more extended exposures. 230 F Water PI&X8 dtility otimpact comparnds -----B--w--------- I niih EY= Ammonis FW TWtChea Aaolein Ptilstes - - ------a---------- Medium __3( 1. Bronchh 6uMvdioxlde Bnmchbleri Paftiadatea ,,Q --------------I Low smlwida Nurogen dioxide Abdi Pattidates capiltaliaa F'IGURE l.-Places of impact, and irritants in the eyes and respiratory tract in relation to water solubility souBcE:vdentin(le86). Irritating and Annoying Effecta of Environmental Tobacco Smoke The main effects of the irritants pr&ent in El's occur in the conjunctiva of the eyes and in the mucous membranes of the nose, throat, and lower respiratory tract. The main ocular symptoms are reddening, itching, and increased lachrymation; the main respira- tory tract symptoms are itching, cough, and sore throat. The relationship of the site of the effect of some irritanta in the eyes and in the respiratory tract to their water solubility is illustrated in Figure 1. The penetration of the particulatea into the lung depends on their size; because most of the particulates in tobacco smoke are smaller than 1 pm, they can penetrate to the smallest airways. Studies of Healthy Individuals Field Studies Several studies have shown that annoyance and irritation are the most common acute effects of EZ'S exposure. Shephard and Labarre (1978) surveyed more than 1,000 Canadian citizens aged 10 to 80 years. The interviewed population was representative of southern 231 ontio with respect to both income and profession but underrepre- sentative of the elderly. Seventy-three percent of the nonsmokers were disturbed by tobacco smoke in restaurants and 53 percent by tobacco smoke in offices. The most frequently reported symptom was eye irritation. Complaints of nausea, dizziues~, and wheezing as well as rhinorrhea were also reported, although much less frequently than stinging eyes. Similar results were obtained in a survey conducted in three restaurants in Switzerland (Weber et al. 1979a). A multiplechoice questionnaire was administered to 220 guests. One-third to two- thirds of the respondents complained about air quality, and up to 12 percent reported eye irritation. In another survey of more than 2,100 white-collar employees, Barad (1979) found that nearly one-fourth of the nonsmokers reacted to smoke exposure with frustration and hostility. Weber and Fischer (1930) surveyed employees in 44 worksite workrooms, located in seven different companies, that included offkes, rooms for design and technical and clerical work, and conference rooms. The choice of companies and worksites was based on availability and therefore was not a random sample. In all workrooms, the concentrations of carbon monoxide (CO), nitrogen oxide (NO), acrolein, particulate matter (PM), and nicotine were measured in the air. The contribution of tobacco smoke to these levels was obtained by subtracting background levels obtained before working hours from the concentrations during working hours. These differences from the background levels were called SCO, 5N0, and so on. Measurements were conducted in each room on 2 successive days (12 l-hour mean values per workroom), and 472 employees were questioned about irritation and annoyance as well as about their opinions on involuntary smoking. Some of the exposure results are summarized in Table 2. The comparison of these 6 values with the measured absolute indoor concentrations revealed that 30 to 70 percent of the measured indoor concentrations of carbon monoxide, .nitrogen oxide, and particulate matter were due to tobacco smoke. The correlations between the gas phase components 5CO and &NO were relatively high (Pearson correlation coefficient r=0.73). However, the correlations of SC0 with Gnicotine and 5PM were low. Nicotine values were generally in the range of the lower detection limit of the method of measurement used (gas chromatography). The low correlation of the gaseous components with the particulate matter is probably due to the different physical properties (sedimentation, adsorption, and desorp- tion of the particulates) and to the fact that the &PM values include particulates from sources other than tobacco smoke. Approximately one-third of the employees described the quality of air at work as %ad" with regard to tobacco smoke. Forty percent 232 TABLE %--Air pollution due to tobacco m&e in 44 workrooms NumberOf Mean component s-d- veluea deviation Maximum 6&rbon monoxide @pm) 363 1.1 1.3 6.5 SNitrc@n oxide @pb) 348 32 60 280 6Pa1ticulat.e matter @g/m') 429 133 130 962 were disturbed by smoke. One-fourth reported eye irritation at work Seventy-two percent of the interviewed nonsmokers and 67 percent of the smokers were in favor of a separation of the workrooms mt,o smoking and nonsmoking sections; 49 percent supported a partial or total prohibition of smoking at work, Contradictory results were reported by Sterling and Sterling (1964), who found no relationship between smoking conditions in ofices and comfort complaints. A self-administered work environ- ment questionnaire was given to approximately 1,100 employees working in nine buildings. Data were analyzed according to the smoking habits of the respondents and the office rules regulating smoking. The distribution of the responses to questions assessing the presence of symptoms (headache; fatigue; nose, throat, and eye irritations; sore throat and cold symptoms) were similar in environ- ments +ith and without smoking. The researchers concluded that "smoking is not a pivotal source of indoor pollution of health-related building complaints." No objective measurements of air pollution were carried out, however, and there were no descriptions of building ventilation. The researchers used a "building illness index" that included several different symptoms in addition to irritation (e.g., headache, fatigue), and the irritating effects on the most sensitive organ-the eyes-may have been masked by this use of an overall symptom index. Experimental Studies Harke and Bleichert (1972) examined the acute physiological response to ETS in a 170 m3 room. The electrocardiogram, blood pressure, heart rate, and skin temperature showed no change with expcsure to ETS, even at extremely high exposure levels (150 cigarettes smoked in 30 minutes, corresponding to a carbon monox- ide concentration of 60 ppm at the end of the exposure). The infhrence of the temperature and humidity of room air on odor perception and irritation was investigated by Kerka and Humphrey (1956). They found that odor intensity was somewhat reduced by increasing the temperature at a constant humidity. Both odor and bfit.ation intensity were reduced by increasing the humidity. Johansson and Ronge (1966) also observed that acute irritation is increased in warm and dry air. Johansson (1976) exposed 12 subjects in a 6.7 m3 climatic chamber for 29 minutes to the El% produced by the smoking of 10 cigarettes. The air in the chamber was cold (18" or 19" C) or warm (25" or 26" C), and at each temperature, the relative humidity was evaluated at three levels from 30 to 80 percent. Under all conditions, subjective irritation, asses& by a questionnaire, increased during exposure; eye irritation increased more than nose irritation. No marked effect of temperature on the degree of irritation was observed, probably owing to the limited temperature range studied (1P to 26" C). Kerka and Humphrey (1956) demon- strated a thermal effect when the temperature range was greater than 8O C. The low relative humidity (7 to 20 percent) in aircraft may be responsible for the substantial level of perceived irritation due to TS among passengers, despite the low levels of pollutants measured n aircraft (WHO 1984). Basu and colleagues (1978) studied the effects of ETS on human tear fihu and observed a reduction in the stability of the preccmeal tear film in subjects exposed to a smoke concentration corresponding to approximately 20 ppm CO. In the presence of EYE!, the tear fti breakup time was significantly reduced by 35 to 40 percent com- pared with baseline measurements without smoke. The researchers suggested that this reflects an alteration in the relative proportions of the constituents of tear film. In these studies, the quantitative exposures to JITS either were not measured or were determined in a relatively imprecise way. More systematic studies, including measurements of several compounds of ETS, were carried out by Weber and collaborators (Weber et al. 1976, 1979a,b; Weber, Fischer, Grandjean 1977; Weber, Fischer, Gierer et al. 1977; Weber and Fischer 1983) and Muramatsu, Weber, and colleagues (1983). These experiments were carried out in a climatic chamber of 30 m3, with an air temperature of 20" to 24" C and a relative humidity between 40 and 60 percent. The ventilation rate could be varied between 0.1 and 16 air changes per hour. The smoke was produced by a Borgwald smoking machine under standardixed conditions, and only the side&ream smoke of cigarettes was used. Healthy students were exposed to the sidestream smoke of cigarettes in groups of two or three in the climatic chamber. They all also participated in a control exposure with identical conditions, but without sidestream smoke in the air. The concentrations of the following compounds were continuously recorded: carbon monoxide, 234 nitrogen oxide, formaldehyde, acrolein, and partictite matter. me background levels before smoke production were subtracted from the measured concentrations during smoking; the resultmg values were called SCO, 5N0, and so forth. The degree of irritating and annoymg effects of the ~rcposed subjects was determined every 10 minutes by means of queetion.mires and by measuring the eye bh& rate, considered an objective measure for eye irritation. In the first study, 33 subjects were exposed to continuously increasing smoke concentrations (Weber et al. 1976). `&e majn re~uh are Summarized in &Ure 2. The concentrations of CC, NO, formaldehyde (HCHO), and acrolem increased with the number of cigarettes smoked. Both mean subjective eye irritation and mean eye blink rate increased with increasing smoke concentration. S&j&ve nose and throat irritation was also evaluated. Nasal symptoms were less pronounced than eye symptoms, and the throat was the least ElffWti?d. h a second series of studies, acute effects were analyzed in relation to smoke concentration and duration of exposure (Weber et al. 1979; Muramatsu, Weber et al. 1983). The tobacco smoke concentrations corresponded to 1.3, 2.5, 5, and 10 ppm CO @CO). Subjects were exposed to these smoke concentrations for 1 hour, each smoke concentration increasing linearly during the first 5 to 10 minutes and then remaining constant at the desired level for the rest of the hour. Because very high correlations (r > 0.9) were obtained in the first experimental series between 6CO and each of the other ~m~unds, only 500 was used tc quantify the level of exposure to E3.S. The results obtained for subjective eye irritation and eye blink rati me shown in Figures 3 and 4. The mean reported level of eye irritation as well as the eye blink rate increased with increasing smoke concentration. Both irritation parameters E&O increased with the duration of exposure under conditions of constant smoke concentration. The same, but less pronounced, results were observed for nose and throat irritation. Annoyance increased rapidly as soon as smoke production began and increased with increasing smoke concentration, but after 10 to 15 minutes the level of annoyance remained approximately constant during the rest of the exposure. Thus, the intensity of exposure was important in determining the degree of annoyance and the duration of exposure was less importam. mese experiments demonstrated an objective irritant response in h&thy adult subjects at levels of smoke exposure substantially lower than the levels at which an airway response has been demonstrated. Whether this difference represents a difference in threshold for irritation in the eye and airway or a limitation in the &l&y to measure subtle changes in the airway is uncertain. 235 Eye blink ratelmin AC0 AU0 AHW AAuoleln ,:,,:,I:, 0.06 . . . . . r I I I I 1 0.W 0.18 0.32 0.47 0.62 0.64 ppm r I I I I I 0 0.05 0.11 0.16 0.20 0.20 ppm 1 I I No.ofriiQmtten 0 10 20 - EyeiniWhindex -*--*-- Eye blinkmte FIGURE 2.Mean subjective eye irritation, mean eye bliuk rate, and concentrations of some pollutants during continuous smoke protection in an unventilated climatic chamber NOTE:33eubjectqOmin: mdesnrement before smoke procluction. SOURCE: WabsretaL(1976). Hugod and colleagues (1978) and Weber and colleagues (Weber, Fischer, Grandjean 1977; Weber, Fischer, Gierer et al. 1977; Weber et al. 1979b) canid out several experiments in order to determine which compounds in ETS are responsible for irritation and annoy- ance. The resulta of the two studies were somewhat conflicting. Hugod and colleagues exposed 10 subjects in an unventilated 68 ma room to high concentrations of sidestream smoke (concentrations corresponding to 20 ppm Co), to the gas phase of sidestream smoke alone, and to acrolein alone at concentrations three times those found in sidestream smoke alone. Irritation was assessed via a 236 20 30 40 50 60 (min) Exposure duration FIGURE 3.-Mean subjective eye irritation related t,o smoke concentrations (ppm delta CO) and duration of exposure questionnaire. Both annoyance and irritation were reported at similar levels in the subjects exposed to the whole sidestream smoke or to the gas phase only. Exposure to acrolein caused only slight discomfort. Weber and colleagues (Weber, Fischer, Grandjean 1977; Weber, Fischer, Gierer et al. 1977; Weber et al. 1979b) exposed students in groups of two or three in a 30 mS climatic chamber to whole sidestream smoke, to acrolein alone, to formaldehyde alone, or to the gas phase of smoke. Subjective irritation and annoyance as well as eye blink rate were measured. The results indicated that acrolein and formaldehyde did not produce substantial irritation or annoy- ance at the levels used. The gas phase exposure resulted in high levels of reported annoyance, but was less important as a determi- nant of irritation. The objectively measured eye blink rate, as well as subjective eye irritation, was much lower with the gas phase alone 237 40.0 35.0 30.0 5" `E 25.0 g m 20.0 15s Eye Mink rele Smokewncentralion (deltacarbonmonoxide) I 1 I I 8 1 1 0 10 20 30 40 50 60 mm Exposure duratlon FIGURE 4.-Mean effecta of environmental tobacco smoke on eye blink rate NOTE: 32 to 43 subjecta; 0 min: measurement before smoke production; 0 to 5 min: increasing smoke conantrntion; 6 ta 60 min: co&ant smoke production. SOURCE: Muramatau. Weber et al. (199%. than with the total sidestream smoke, suggesting that the particu- late phase is the major determinant of irritation. The researchers postulated that the irritating effects of the particulate phase are due to the semivolatile irritant compounds. These compounds, which volatilize rapidly during the process of combustion, recondense on the particulates with cooling and may deposit irritants in relatively high concentrations on the mucous membranes. Studies of Sensitive Individu& Children Several investigators have used questionnaires to examine the subjective symptoms of children and young people with ElTS exposure Gameron 1972; Muramatsu 1977; Muramatsu, Muramatsu et al. 1983). The last group found that 81 percent of B-year-old children disliked involuntary smoking and 82 percent complained of one or more kinds of irritation, the most common being eye irritation. Several epidemiological studies have shown that children with parents who smoke have an increased risk for respiratory illness (see Chapter 2). Allergic Individuals A few studies have asses& the effects of ETS on allergic individuals. Speer (1968) found that allergic individuals report irritation more frequently than healthy individuals. Weber and Fischer (1980) observed that employees suffering from hay fever reported significantly more eye irritation at work than those without hay fever. Effects on the Lung Cigarette smoking is associated with prominent changes in the numbers, types, and functions of respiratory epithelial and i&Jam- matory cells. These alterations have been implicated in the develop- ment of pulmonary emphysema, chronic bronchitis, and respiratory tract cancers and in an increased susceptibility to infections. Chronic exposure to environmental tobacco smoke might cause similar changes. Because studies that directly address the effect of chronic exposure to environmental tobacco smoke on lung structure and biochemistry have not been conducted, this section reviews those studies in humans and animals that provide evidence on smoke exposures that may be relevant to ETS exposure. Effects of Cigarette Smoking on Respiratory Epithelium: Studies in Humans Extensive evidence shows that exposure to cigarette smoke has adverse effects on respiratory epithelial cells, and dose-respon~ relationships have been established from these changes (Auerbach et al. 1961; Auerbach, Hammond, Garfinkel 1970). Studies involving the systematic examination of the bronchial mucosa from large numbers of human smokers have recorded three principal types of epithelial changes: epithelial hyperplasia, loss of cilia, and nuclear atypia. In an autopsy study of 402 adult male subjects (Auerbach et al. 1961), 98 percent of the sections of the tracheal and bronchial TABLE 3.Cections with one or more epithelial changes, by packs of cigarettes per day Group Subjects without lung cancer Never smoked regularly Smoked 50 per group). The application of CSC to mouse skin is the most widely employed assay for the evaluation of its carcinogenic potential. The mouse skin bioassays in tobacco carcinogenesis have been reviewed (Hoffmann, Wynder et al. 1983). A typical experiment uses two to three dose levels of condensate, generally 25, 50, and 75 mg of CSC, which are administered topically to the shaved backs of mice three to six times weekly for approximately 78 weeks. The CSC is most frequently applied as an acetone suspension (25, 33, or 50 percent). At the conclusion of such a study, skin tumors, some of which are malignant, generally are observed among the treated animals in a dose-related fashion. Such studies have shown that the carcinogenic activity of CSC! is also a function of tobacco variety, is influenced by replacement materials such as tobacco sheet or semisynthetics, and may be influenced by the use of additives. Although such bioassays have been extensively performed for the tars from mainstream cigarette smoke, only one study has examined the carcinogenic potential of the condensate of sidestream cigarette smoke. Cigarette tar from the sidestream smoke of nonfilter cigarettes that had settled on the funnel covering a multiple-unit smoking machine was suspended in acetone and applied to mouse skin for 15 months (Wynder and Hoffmann 1967). Out of a group of 30 Swiss- ICR mice, 14 animals developed benign skin tumors and 3 animals had carcinomas. In a parallel assay of MS from the same cigarettes, a 50 percent CSCacetone suspension applied to deliver a comparable dose of CSC to 100 Swiss-ICR female mice led to benign skin tumors in 24 mice and to malignant skin tumors in 6 mice. This indicates that this smoke condensate of SS had greater tumorigenicity on mouse skin than MS tar (p > 0.05). In Vitro Assays Several short-term bioassays have been performed to evaluate the genotoxicity of the MS of cigarettes. These studies have been the subject of two reviews (DeMarini 1983; Obe et al. 1984). Although most of these studies have evaluated the effects of CSC, some investigations were focused on either the gas phase or the whole smoke. In recent years, there has been increased use of short-term assays to attempt to evaluate the relative genotoxic potential of environmental tobacco smoke.