9172 TABLE 8.—Tumor prevalence among males and females 85-69 years of age, by type of tumor and emoking category (Smokers constituted 86 percent of populations studied) Smoking category Expected Risk number tatio Sex and type of tumor Smoking Non- among Among Total all methods amokers emokers? smokers Males Epidermoid carcinoma ..ccccnscsnre ree sre erent eee e teenies beeeeres 434 431 3 17.0 25.4 Small cell anaplastic carcinoma ......56, wee see cee eee eens 117 116 1 8.7 20.4 Adenocarcinoma cecccseeee eee e eee teeeee 88 83 6 28.3 2,9 Brenchiololalveular carcinoma ...ccsece eee te os . dees vues os saee sone Carcinoid wise eee ee Veve vet estnaesestvsssssee : 46 $9 q $9.7 1.0 Bronchial gland Cumor ...icee creer ree eens . cane Total ccc ccc e eee etre teen e nee teen e eee RE EER EES wees 685 669 16 90.7 TA Females Epidermoid carcinoma co.cc ccs ccc c neers ese cee weeeenneneees seeene an 12 8 3 16 12.0 Small cell anaplastic carcinoma wecseiereeseneeeeenee Leneee pevtaee 8 6 3 16 6.6 Adenocarcinoma seen eee teees Sao ren teens cane 56 14 42 10.6 1.3 Bronchiolol-alveolar carcinoma@ voces ee cere ene beeen ee beet eveerrane wees ve wae vane us Carcinoid ...ceceaee eee Arn beter weenie 32 q 25 6.3 ML Bronchial gland tumor ....... pee e teem ent eee eee te sees Total ccc ccc cen cree se eee e rere aee rasta ree trier teehee ene teaee 108 35 13 18.3 1.9 ‘Number that would be expected if incidence rate among smokers were equal to that of nonsmokers. Source: Kreyberg, L. (154) LUNG CANCER RELATIONSHIPS IN WOMEN Lung cancer death rates for women are presently much lower than the corresponding rates for men. In addition, it has been ob- served that among certain strains of mice exposed to carcinogenic agents, the male animals show a greater tendency to develop lung tumors than do the females (200, 207) although there are strains for which this is apparently not so. The extent of the influence of endocrine factors in the sex variation in the incidence of lung tumors is unknown. As of 1967 in the United States, women accounted for only about one-sixth of the total deaths from lung cancer (289). However, the lung cancer death rate in women has risen by over 400 percent in the past 40 years. From 1950 to 1967 alone, the rate per 100,000 population doubled, increasing from 4.5 to 8.9 (289, 290). A number of retrospective studies concerning lung cancer and cigarette smoking among women have found that the difference in the prevalence of lung cancer between males and females is ac- counted for principally by those tumors classified as Kreyberg’s 311). These, as was noted above, are the tumors, par- ticularly in males, which show the closest relationship with smok- ing. Haenszel, et al. (113), in a study of 158 women with lung cancer, observed that the sex differential for lung cancer death rates diminishes, but does not fully disappear when only non- smokers are considered. Hammond (118) found that the death rate for lung cancer in hat higher than for nonsmoking fe- le rates was much a substantial Group I (154, nonsmoking males was somew males. However, the difference in male-fema greater when smokers were compared. It appears that part of the difference in death rates between male smokers and fe- male smokers can be explained mainly by differences in their smok- ing habits. These differences in smoking habits between males and females are of two types. First, overall consumption among females is still significantly lower than that among males. In 1966 (281), 30 per- cent of males reported that they had never smoked while for fe- males the corresponding figure was 59 percent. This study also — noted that nearly three times as Many males as females reported consuming more than 20 cigarettes per day. Second, it has been shown that women smoke differently than men (803) : They begin smoking later than men (114) and do not smoke cigarettes as close to the end, where proportionally more nicotine and “tar” are in- haled. Women smoke more filter-tip and “low tar and nicotine” cigarettes than men. Furthermore, cigarette smoking still tends to be heavily concentrated among women under the age at which lung cancer is most likely to occur. 277 Finally, analysis of the ratio of male and female Jung cancer death rates (283, 284, 285, 286, 287, 288, 289, 290) reveals that since 1960 this ratio has shown a steady decline, reflecting the greater relative rise in mortality from lung cancer in the female population. Lune CANCER, THE URBAN FACTOR, AND AIR POLLUTION A number of studies have been concerned with the relative influ- ences of smoking, urban residence, and air pollution in the etiology of lung cancer. Table 9 lists studies performed in the United States, Great Britain, and Japan which have dealt with this question. Kotin and Falk (249, 150) and more recently the Royal College of Physi- cians (228) have reviewed the literature concerning the influence of atmospheric and environmental factors in the pathogenesis of lung cancer. The studies listed-in table 9 show a number of important trends. Lung cancer death rates are found to be higher among urban popu- lations than among rural populations. It is not known to what ex- tent this urban factor in the etiology of lung cancer. is due to differences in the levels of air pollution. Other factors associated with urban residence which may influence the etiology of lung cancer are: differences in smoking habits between the two popula- tions, occupational differences, and possible differences in the re- porting of lung cancer deaths (228). The studies also uniformly show that within each urban/rural grouping, lung cancer death rates increase with increased smoking. Whether air pollution acts with cigarette smoking to influence lung cancer death rates in a combined manner is presently unclear (112, 126, 264, 265), and the evidence concerning a separate role of air pollution in the etiology of lung cancer is still inconclusive (228). The recent report of the Royal College of Physicians on air pollu- tion and health (228) concluded that ‘the study of time trends in the death rates of lung cancer in urban areas demonstrates the ribution of the overwhelming effect of cigarette smoking on the dist disease. Indeed, only the detailed surveys that have taken individual smoking histories into account have succeeded in separating the f the ‘urban factor’ on the over- relatively very smal] influence 0 riding effect of cigarette smoking in the development of cancer of the lung.” 278 622 TABLE 9.—Lpidemiologic investigations concerning the relationship of lung cancer to 7 gy g { Pp g smoking, air pollution, and urban or rural residence (Actual number of deaths shown in parentheses) Author, Population year, atudied and Country, method of Results Comments reference data collection Dol, Estimated death rates Lung cancer mortality (1950) per 1,000 Authors noted that 1963, from jung cancer Maics Females Nonamokera — eatirnutes are based on England in English London Otherurban Rural London Othcrurban Rural Allarcas very few deaths. (70), population and Age: among nonsmokers 26-44 ....,. 0.126 0.095 0.070 0.028 0.028 0.012 0.020 obtained from 48-64 ....., 1.572 1.264 0.861 0.194 0.162 0.120 0.090 general regiater, 65-74 2... 3.124 2.006 1.164 0.440 0.326 0.288 1219 Stocks and Death rates in Male lung cancer death rates 1952-44 (per 100,000) ages 54-74 The authors noted the Campbell, England and upward gradicnt among 1956, Northern Wales. Rural (68) Mized (118) Urban (589) nonsmokers, pipe England Review of patient Nonamokers .......... 14 oe 131 smokers and Wight (265), chartor interview Pipe ........., tee 41 26 143 cigarette smokers and the with kin or Cigarettes: Light ......:c:ceccuccecenaees 87 163 297 lack of asimilar physicians, Moderate ........ 00ers 183 132 287 gradicnt among Heavy cocci cecececcc cee aeenes 363 303 304 moderate and heavy cigarette smokers, Hammond 187,783 white males Age standardized death ratca due to bronchogenic carcinoma (males) Data excluded and Horn, in 9 states, adenocarcinoma. when 1868, Questionnatre Suburb City of City of standardized for age and U.S.A. and interview. Rural ortown 10,000-50,000 >60,000 amoking, rural rate waa (120). Nonsmokers ....... beeen nae 4.7 (2) 8.8 (8) 14.7 (4) atill noted to be 26 Cigarette smokers ....,.., 66.2(62) 71,7 (67) 70.9 (59) 85.2 (83) percent legs than urban, O8z TADLE 9.—Epidemiologic investigations concernt gmoking, air pollution, and urban or rural residence (cont.) (Actual number of deaths shown in parentheses) ng the relationship of lung cancer to Author, Population year, studied and Country, method of Results Comments reference data collection Haenszel 10 percent of all Age and amoking-standardized lung cancer mortality ratios Standardized Mortality etal, white male lung (epidermoid and undifferentiated carcinomas only) Ratio = 100 for U.S. 1962, cancer deaths in white males age 36 and U.S.A. U.S.A. for 1958 Metropolitan counties Nonmetropolitan counties over In 1958, The authors (112), for whom next of 350,000 sess eee ved l9 2,500-50,000 ....,-90 also noted"... joint kin or physiciang 10,000-50,000 .....-0-- 151 Rural nonfarm ....74 effects of residence and supplied smoking 2,500-10,000 ..rceeeeeee 39 Farm cee ABT smoking historics in the data. 2,191 cases schedule of lung-cancer with adequate rates far greater than information. those expected on the assumption of additivity of the separate effects..." Doll 41,000 male British Standardized death rates for lung cancer The authors noted that and Hid, physiciana, 1964, anne ; rural mortality data England follow-up of death Nonsmok Conurbation(49) Large Towns ($4) Small Towna (32) Rural (18) were affected hy a a weninerve oy smokers ...e. eee 0.03 0.00 OAL ‘ 0.12 significant number of . garette smokers: city residenta 1-14 0.48 0.32 0.87 0.52 retiring to the country. 15-24 1.31 1.88 1.06 1,16 >25 1.90 4.43 2.20 LAT wien. hate male and . Lung cancer death rate per 100,000—-age- and amoking-atandardized Total number of denthy Northem deaths over 3 Inner Out 1 noted under methud of Ireland years ofa ‘ t Belfast B ‘fea ne on Urban Small data colloction include (308), veuiaiar, Persoval east china atiacunaaha Towns Rural 954 controls. aa or. ersonal Males... 167 (241) 139 (167) 135 (46) 118 (186) 137 (26) 47(149) nterviews with Females 22 (38) 17 (24) 12 (6) 23 (35) 22 (6) 12 (43) kin or physicians, T8C TABLE 9.—Epidemiologic investigations concerning the relationship of lung cancer to emoking, air pollution, and urban or rural residence (cont) (Actual number of deaths shown In parentheses) Author, Population year, atudied and Country, method of Results Comments reference data collection Buell 804 Jung caneer Age-adjusted lung cancer death rates per 100,000 man yeara and mortality ratios The authors noted the lack etal, deatha among of death-rate diffcrence 1967, American San Franctaco/ All other between Los Angeles and U.S.A, Legionnaires Los Angeles San Diego California countiss San Francisco regions 449). aged 25 and over. Rate Ratio Rate Ratio Rate Ratio and concluded that Questionnairesto Nonsmokers .....ccceeeeeee . 28.1 2.6 43.0 3.9 11.2 1.0 photochemical amog fa next of kin. Smokers: : not related to 1 pack/day: <40 years of age ....... poets eenee 17 880 1.6 12.5 BOBO ccc ccc etre ere rer cere ee eees 63 3,027 4.6 17.4 GOOD cicsreceee veupee panes 84 4,186 6.9 20.5 DT0 cece cere eee teen net ee ences 16 766 9.8 23.7 Cross 140 persons Percent acctions showing changes in branchial epithelium (number of ecctions) {| The authors noted etal,, autopsied at Squamous Atypical Carcinoma that the differs 1961, Towa City Normal Hyperplasia metaplasia metaplasia tn attu Carcinoma ence between ULS.A. Veterans Nonsmokerw (81) cecceeeses G1 (062) 36 (137) 8 (33) t15 (68) - vane smokers and non. (64). Hospital Smokers (109) crvseesaver es 44(670) 43(562) 16 (197) 20(263) 1(12) 2.6(34) amokers was on whom etatlatically smoking alyuificant. data was available. L£8¢ TABLE 10,—Pathologic and cytologic findings in the tracheo-bronchial tree of smokers and nonsmokers (cont.) (Actual number of coseas ahown in parentheses) Author, Number of year, cases and country, method of TResulta Comments reference selection Averbach 12 autopsicd Number of Percent acctiona Percent scctions Percent sectiona Each ex-smoker etal, former ciga- acctions of with etlia abeent with some atypi- with 50 percent matched with s 1362, rette smoker bronchial and entirely cal ecle and atypical cells current smoker U.S.A. who had been Number epithelium alypteal cella cilia abeent andciliapresent plus never-smoker (4), amoking for Nonsmokers sae 12 3,156 0.0 O.4 0.5 for age, occupa- 2:10 years Ex-smokers oe 42 3,436 0.2 0.9 2.5 tion, and resi- and had Current amokers .... 12 3,537 8.0 19.0 $0.8 dence, There was ceased an average of 226 years ago. 60.4 acctiona per subject and none had Icas than 18 sections. 882 TABLE 10,—-Pathologic and cytologic findings in the trachco-bronchial tree of amokers and nonsmokers (cont.) (Actual number of cases shown In parentheses) Autbor, Number of year, eascs and country, method of Teeaults Cumments reference selection Auerbach 466 male and Percent eece Perecnt secs Percent sec- Major findings etal., 802 female Number of tions with tions with tions with 50 noted: 1962, smokers and acetions of eilia obacnt tomeatypi percent atynical Urbun nonsmokers ULS.A. nonsmokers bronchial and entirely cal cells and ecllg and showed more (43). autopsied and Number epithelium atypical cella cilia abeent cilia present lesion than rural. matched for Males: Both Ieslons and age, occu- Nonsmokers ........-5. 47 2,346 te O14 0.7 atypleal nuclel pation, and Cigarette amokers ....,, 76 3,393 6.9 21.2 18.5 were much legs residence, Females: we frequent In none Nonsmokera ..ceseeeees 47 2,879 . 01 0.6 emokers and less Cigarette smokers ....., 76 3,607 2.5 18.8 62.6 frequent In pipe Males: and cigar smokers Nonsmokerg ....ess.s0. 85 1,706 os 0.2 0.5 than in cigarette Cigar smokers ... . 85 1,733 0.8 10.0 10.7 smokers, Cigarette amokers ...... 35 1,526 12.8 27.3 83.1 67.1% of cases hud 50-66 sections 81.5% of cases had 40-49 sections 9.3% of casca had 30-89 acctiona 4.6% of cases had 16~29 sections Robbins, 103 studenta Percent in each cytologic class Smokera defined a8 1966, 17-24 years Slightly Moderately Strongly those having con- U.S.A, of age who : Normal atypical atypical atypical sumed 210 ciga- (222), underwent Nonsmokers (45) .oscceeveevseaes 1. 86.7 44 8.9 we rettes a day for merosol Smokers (58) .. 85.2 32.8 10,8 1.7 zh year. sputum | Induction. #87 TABLE 10,—-Pathologic and cytologic findings in the tracheo-bronchial tree of smokers and nonsmokera (cont,) (Actual number of cascy ahown in parentheses) Author, Number of year, caoxes and country, method of Results Comments reference selection Maltoni 1,000 healthy Number Percont showing metaplasia etal., matics who Oy vee eee ee 294 41,16 1968, underwent Smokers: Italy sputum 1-30 clgarcttes/day 189 47.09 (182). induction, M-20 vs. 886 61.43 21-80 ....0, bee enas 93 61.29 280 eee eee . 39 60.23 Nasiell, 60 nonsmoking Sputum cytologic changes Percent with t Regarded by 1968, vutpatients, Porcent Percent with atypical author as “real Sweden 398 umokera Number Males Mean age metaplasia metaplasiat premalignant (198). participating Nonamokers ..........,. » 60 , 42 67.1 18 change,” in general Smokers ......, reeeeenes 898 73 45.6 62 health exam- ination who underwent sputum induction. Spain . 157 males and Number Percent with metaplasia The authors found etal., 78 females Males; no evidence of 1970, autopsied fo). Nonsmokers 36 60.0 carcinoma in eity U.S.A. lowing sudden Ex-smokers 21 67.7 or prencoplaatic (258). or accidental 1 pack ...,. Teese ees Senet beeen tence Nee vaes beeen aeruce ‘ 68 73.5 whom smok- Females: ing data were Nonsmokers 34 84.2 available (ex <1 pack ...., oe 18 33.3 amokers ex- >1 pack 26 46.1 cluded from female data). In order to facilitate understanding of the relationships of the various compounds to one another, the third column presents the presently understood relative importance of each of the various groups of compounds. These compounds have been tested only in animals or tissue cultures, and it should be stressed that the rela- tive importance of one compound may not be the same in man as it ig in animals. Table 11 is divided into two major sections. The first section details those compounds which are considered to be or are suspected of being cancer initiators. These are compounds which induce irreversible changes in responsive cells. In the second section are listed those compounds which are considered to be or are suspected of being tumor promoters. These compounds promote the malig- nant reproduction of cells in which neoplastic changes have been initiated. A number of these initiators may also act as complete carcinogens in their own right. The evidence concerning the two stage initiation-promotion mechanism is still rather limited for respiratory tract carcinogenesis. The polynuclear aromatic hydrocarbons (PAH) listed are pres- ently considered to play a very significant role in pulmonary car- cinogenesis due to tobacco smoking. These compounds act as tumor initiators or complete carcinogens. The particular role of these agents in environmental and occupational carcinogenesis has been reviewed by Falk, et al. (93). That such hydrocarbons are pro- duced from tobacco during human smoking has been shown by Kiryu and Kuratsune (146). These authors reported the presence of benz{aJanthracene, chrysene, benzo[a]pyrene, and benzo- [b]fluoranthene in the ‘tar’ produced by normal smoking and measured in either filters or stubs. Two hydrocarbons which have frequently appeared in the litera- ture on experimental tobaceo carcinogenesis may not actually be present in tobacco smoke. They have been used as representatives of carcinogenic PAH, a class which includes many constituents that have been identified in cigarette smoke condensate. They” are 7,12-dimethylbenz[aJanthracene and 3-methylcholanthrene and have been frequently used as tumor initiators or complete carcino- gens, particularly in skin painting and tracheal implantation experiments. The nitrosamine compounds listed are potent carcinogens affect- ing many organ systems, including the respiratory tract (188, 189). Magee and Barnes (181) have presented a detailed account of experiments in this area. Nitrosamines have been identified in trace amounts in tobacco “tar’’ and the conditions required for their formation (the presence of secondary amines and nitric oxide) are 290 TABLE 11.—Identified or suspected tumorigenic agents in cigarette smoke* Components Eatimated concentra- tion in 100 cigarettes (85 mm. non filter) Presently understood relative importance in experimental tobacco carcinogenesis I. Complete carcinogens and tumor initiators: Polynuclear aromatic hydrocarbons I. Benzo(a)pyrene 2. Dibenz(a,h)anthracene 3. Benzo(b) fluoranthene 4. Benzo{j) fluoranthene 5. Dibenzo(a,i) pyrene 6. Benz{s) anthracene 1. Chrynene 8. Indeno(1,2,3-cd) pyrene 9. Benzo(c)phenanthrene? 10. Methylbenzo(a) pyrenes 11. Methyichrysenes N-heterocyclic hydrocarbons ...----+-++++> 3. Dibenz{a,h)acridine .-.- 2. Dibenz(a,j) acridine 3. TH-dibenzo(¢,g) carbazole N-nitrosamines? .. 1. Dimethylnitrosamine 2. Diethylnitrosamine 3. Methyl-n-butyinitrosamine 4. Nitrosopyrrolidine 5. Nitrosopiperidine Epoxides, peroxy compounds, and lactones: lL. Epoxides 2. Peroxides 3. Lactones a. g-Levantenolide b. p-Levantenolide N-aikyl-heterocyclics: 1. I-metbylindole Pesticides and fungicides :*¢ 1.TDE .... 2.0,p-DDD .- 3. DDT ...- : 4. Maleic hydrazide ...-------eeer cnt Beta-naphthylamine ..-------serereretttt Polonium 210 22-6... eee eee ttt Nickel compounds ...-.---+-serertrrrre 1-2 0.01 1.0 0.07 1-10 No data Present Present 10-100 10-100 10-100 10-100 1-50 picocuries Tumor initiators. Tumor initiators. Suspected carcinogens of possible importance (presence in fresh smoke possible) . Certain of these compounds are known carcinogens; presence in amoke condensate not established. Possible initiator. No essential contribution suspected. Suspected bladder carcinogen; of doubtful significance at reported levels. Of some importance only in the case of relatively high concen- tration, but not important at reported levels. Suspected carcinogens of some importarce. 291 TABLE 11.—Identified or suspected tumorigenic agents in cigarette smoke? (cont.) Estimated concentra- tion in 100 Presently understood relative Components cigarettes importance in experimental (85 mm. tobacco carcinogeness nonfiiter} Il. Tumor promoting agents: Neutral promoters (polymers) Nodata Of possible importance, (unknown strictures.) Volatile phenols ....------- eee e erect 20-30 mg. Of possible importance. 1. Phenol 2. Cresol Nonvolatile fatty acids -...-+---- reer certt 20-100 mg. Of minor importance. 1. Stearic acid 2. Oleic acid N-alkyl heterocyclics: Of possible importance. 1. @-methylearbazole «1... eee eee Present 1 Modified and expanded from (3519, 320) with reference to (5%, 40, 89, 111, 129, £02, 262, 209, 294, 295). 2 Has not been tested as an initiator, but is a known complete carcinogen. 3 See Neurath, (202). *See (111, 128). found in tobacco smoke (38). However, nitrosamines may be arti- facts dependent on the method of smoke collection (201). Neurath (202) considers the nitrosamines listed in table 11 as being present in fresh cigarette smoke (253, 254). However, con- clusive confirmation of their presence in fresh smoke is not available (38, 188, 155, 319). Certain of the pesticides and fungicides presently in use on tobacco have been found to be carcinogenic (91, 273, 280). A num- ber of these, such as DDT, are now being phased out of regular domestic use. The compounds listed have been shown to be present in trace amounts in mainstream tobacco smoke (1171, 1 28) . A recent, extensive review by Guthrie (171) provides more detailed informa- tion concerning these agents. Radioactive isotopes can be found in tobaeco and tobacco smoke (105). Potassium-40, while present in tobacco leaf, is not trans- mitted in any substantial amount to mainstream smoke (230). Polonium-210 (Po.,.), however, is transmitted into the mainstream smoke (94, 123, 142, 145, 215, 217). A number of autopsy studies (table A12) have shown that the bronchial epithelium of smokers contains significantly more Pozo than that of nonsmokers. Little, et al. (172, 173, 174) have also noted that the concentration of polonium was markedly higher at sites of bronchial bifurcation. These authors stress the importance of this finding for pulmonary carcinogenesis by noting that bronchogenic carcinomas are fre- 292 quently located at bifurcations and that the polonium levels which they found in those regions probably have biologic significance (216). Other investigators (123, 217) have not observed this excess at bifurcations, and in a recent discussion Wynder and Hoff- mann (320) concluded that it appears unlikely that Po.,,. in the amounts present in cigarette smoke plays a role in tobacco car- cinogenesis. Although not listed as a separate group, there are a number of agents in cigarette smoke which are potent inhibitors of ciliary movement. Their importance in carcinogenesis derives from the increased amount of time which they afford the known carcinogens to be present on the surface of the bronchial epithelium. These inhibitors include volatile aldehydes, hydrogen cyanide, nitrogen oxides, volatile phenols, and certain volatile acids such as formic and acetic (129). Experimental Studies In some respects, the animal and tissue culture studies detailed below apply to neoplastic transformations, not only in the lung but in other tissues in which tobacco smoke, particularly cigarette smoke, is believed to play a role. These general experiments will be presented here, however, with the experiments which bear on lung tissue directly. Skin Painting and Subcutaneous Injection Numerous animal studies on rats, mice, and rabbits, have been performed utilizing known carcinogens, whole tobacco “tar,” and various tobacco condensate subfractions, or compounds known to be present in tobacco smoke. These experiments involve the single or repeated painting of shaved or unshaved anima] skin. A selected number of these studies is presented in table A13. Numerous other studies, performed prior to and following 1953, are reviewed by Wynder and Hoffmann (319). . The skin painting method is still considered to be a valid pro- cedure for the identification of agents suspected of participating in pulmonary carcinogenesis, as well as for the quantification of the reduction in tumorgenicity of specific agents. Tissue and Organ Culture The exposure of tissue and organ cultures to cigarette smoke, its condensates, or its constituent compounds has been shown to sig- nificantly alter patterns of cell growth and reproduction. Table A14 presents an outline of these experiments. Once again, less severe effects have been noted when filtered smoke was used (165). 293 Tracheobronchial Implantation and Instillation More complex experiments concerning the carcinogenicity of cigarette and tobacco smoke are represented by those which involve the direct implantation, instillation, or fixation of suspected ma- terials into the tracheobronchial tree of animals. Certain of these experiments are outlined in table A15, Recent reviews by Saffiotti (233, 234) Laskin, et al. (159), and Montesano, et al. (189) as well as that by Wynder and Hoffmann (319) provide more detailed and extensive accounts of these experiments. Of note among the results outlined in this table are the following: The enhanced carcinogenicity found when benzofal]pyrene (B[{a]lP) js combined with a carrier such as hematite dust (235), and the definite increase in bronchial epithelial preneoplastic and neo- plastic changes among dogs treated with smoke condensate as com- pared with those undergoing only physical bronchial stimulation (224). Inhalation Various species, including mice, rats, hamsters, and dogs, have been exposed to cigarette smoke or aerosols of its constituents. These inhalation experiments are outlined in table A16. It must be noted that the majority of the studies listed involve the passive inhalation of the material presented usually in a chamber. Active inhalation experiments, exemplified by the work of Rockey and Speer (223) and Auerbach and his colleagues (11, 119) involved animals which were trained to inhale voluntarily, thus more closely simulating human smoking. Results of note among these experiments include the following: Miihlbock (195) observed that cigarette smoke inhalation en- hances the already substantial rate of spontaneous alveolar cell carcinoma formation in hybrid mice, and various investigators in- duced adenomas in experimental animals (108, 168, 206). Harris and Negroni (121) found that exposure to cigarette smoke achieved some enhancement of adenocarcinoma formation in mice but did not observe proven squamous cell carcinoma, Some of their mice had also been exposed to Swine influenza virus aerosol. In a related study, Boren (32) exposed hamsters to cigarette smoke at set inter- vals over a 48-hour period. The author observed alterations in pul- monary cell kinetics (the pattern of DNA synthesis) as demon- strated by H*-thymidine autoradiography. The pattern of the label- ing response to cigarette smoke was significantly different from that of the response to high oxygen concentrations. Auerbach, et al. (11) have reported the development of early 294 invasive squamous cell bronchogenic carcinoma in dogs following a period of direct inhalation of cigarette smoke. These investiga- tors trained beagle dogs to inhale cigarette smoke through a tracheostoma (50) and divided the animals into groups according to dosage as detailed in table 17. A number of dogs died during the course of the experiment which ran for 875 days, or approximately 29 months. The causes of death are Hsted in table 18. All of the remaining dogs, with the exception of group “h” (high exposure, heavy weight), were sacrificed shortly after day 875; the survivors among the heavier dogs are continuing to smoke. Examination of the respiratory tree of the animals revealed a number of tumors (table 19). Most of these were similar to the type of tumor which in man is referred to as bronchiolo-alveolar. This tumor arises in the bronchiolar and alveolar epithelium and tends to be multicentric. Two striking characteristics of these bronchiolo- alveolar tumors were the existence of a histologic spectrum (from a tumor resembling the benign condition of adenosis to frankly malignant tumors with invasion of the pleura and surrounding parenchyma) and the marked tendency to squamous change. Inva- sive bronchiolo-alveolar tumors were found in 12 dogs in the group which had been exposed to the largest dosage of cigarette smoke. Several had tumors of more than one category. Ten of these dogs had invasive bronchiolo-alveolar tumors which did not extend into the pleura, one dog had an invasive bronchiolo-alveolar tumor which extended to the pleura, and four had invasive bronchiolo- alveolar tumors extending into the pleura beyond the pleural- pulmonary junctions. In addition, two bronchogenic squamous cell carcinomas were found in this group (table 19). The dosage de- pendence of tumor formation is shown in figures 2 and 3. Major findings of the study were twofold. First, that smoking filter-tip cigarettes was less harmful, both in terms of pulmonary parenchymal damage and lung tumors, than smoking identical cigarettes without filters. This supports the generally held view that total particulate matter is a meaningful indicator of the car- cinogenic potential of a cigarette. Second, lung cancer of two types found in man was produced by the inhalation of cigarette smoke. Two of the dogs were found to have early invasive squamous cell carcinoma of the bronchus, and both belonged to the high-dosage group. These carcinomas were indistinguishable from early invasive squamous cell carcinomas found in the bronchial] tubes of human beings who smoke cigarettes. The majority of tumors found in the dogs were of a bronchiolo-alveolar type, which although not as common as squamous cell cancer in man, is not rare in humans. This type is often included in the category of adenocarcinoma. A number of studies have shown an excess of these tumors among 295 962 TABLE 17.—Data on pedigrecd male beagle dogs of groupa F, L, H,h,andN (Some of the figures apply only to doga surviving 876 days or longer) No Filter fitee iter filter Nonamokers ¢ rou group oe sroup g 7 Pp ; N Number of dogs on day No. 67* ..... vase neeeee an ‘ 12 12 24 $8 8 Welght at start (day No.1) mean weight (pounds) ...... 25.0 25.1 26.0 819 30.7 Cigarettes per dog in 875 dayp corse ever eee ences tees 6,143 3,103 6,129 6,129 none Mean number of cigarettes per day .... beens 7.02 3.64 1.0 7.0 Equivalent number of cigarettes per day for 150 pound man 42,1 21.2 42.0 32.9 — Type of cigarettes :? Milligrams of tar per cigarette ...., 17.8 34.8 34.8 84.8 ne Milligrams of nicotine per cigarette .... 117 1.86 1.85 1.85 —_ Total dosage in 875 days: Grams of tar per dog voce cece eee eeerene cea eeneenee 109.3 103.5 207.8 207.8 _ Grams of nicotine per dog occ. cece cece reece een eee : TAY 6.56 11,12 1412 — Dosage in 875 days relative to starting weight: Grams tar/pounds weight ........ denen bene eeenee . 4.37 4,12 8.81 6.81 — Grams nicotine/pounds weight .......0005 Reine) 0.29 0.22 0.44 0.35 — 1 The smoking dogs were divided into groups F, L, H, and b on day No, 57. 2 Doge of groupa L, H, and b amoked filter-tip cigarettes during a training period at the start of the exper! Sounce: Adapted from Hammond, E. C. et al. (119). tment, but smoked nonfilter cigarettes thereafter. L672 TABLE 18.—Summary of principal cause of death (days No. 57 through No. 875) in dogs of groups F, L, H, h, and N (Each death classified according to most severe condition—some doga dicd of a combination of causes listed) Filter No No No tip filter filter filter Nonsmokers Principal cause of death Group Group Group Group Group F L H N Pulmonary emphysema and fibrosis .........00.005 seneee _ ~ 2 _ _- Cor pulmonale (pulmonary emphysema and fibrosis with right heart enlargement) _— —_ 8 6 _ Pulmonary infarction ........05 1 1 2 5 _ Bronchonneumonia a _ a 1 _ Aapiration of food .. 1 1 - ~~ - Uncertain .,...... _— _ 2 1 _ Number of deaths ....... sae 2 2 12 12 _ Number surviving 875 days 10 10 12 26 8 Total number of dogs ..... 12 12 24 a8 8 Source: Hammond, E. C. et al. (£18), B6c TABLE 19.—Data on dogs with lung tumors indicating type of tumor and lobe in which the tumor was found Early squamous Group Day of Nusper ace Lobes with bronchbiolo-alveolar tumors cell bronchial death cigarettes (years) Non-invasive Tuvagive carcinoma Group N (nonsmokers) .+.ee> eens eee ely 904a _ 5.1 LA _ _ N 904b _ 4.9 RA - _ Group F (filter-tip) sect nensereeeeenee 8788 6,161 6.1 LA _- _ F 8798 6,170 47 LA - _ F 8850 6,224 5.2 LA _ _ F 890a 6,269 54 LA - _ Group L (no filter} ..ceaeenae seveee steels 347 1,055 3.8 LA, LC = _— L 812 2,847 5.1 RA - _ L 8760 3,103 BL LA, RA _ _ L 8778 3,107 6.2 LA, LC _ _ L 882a 3,127 8.2 LA, LD - _ L ROGa 3,183 6.3 LA, RD _ - iL Bue S196 G4 LA _ 7 Group H (no filter) cccsescereer reece eee ell 136 BiK 26 RE _ ~— YW 269 Vai dat LA, RA, RD - _ H 063 3.404 47 LD, RA _ - Il 716 4,089 6.0 te LA _ H 783 6,050 3.8 Rl LA, RA, RD - H 160 G.OBS 2 LA -- _ H 86K 6,970 $3 LA _ - H s7ha GLY 4.9 ae LA, LD, RA _ H HT? 7a G,134 64 oe LA LALB H Sika 6,147 6.3 RA LA _ H 882n 6,183 6.4 LA _ _ H Sh3u 6,192 4.7 RA, RD, RI LA -- H 8850 6,210 6.0 os LA, RA LMU H 8890 6,246 6.0 oe LA -— H 8908 6,255 4.9 LA _— _ H 8920 6,273 6.7 LC, RA _ a H 8o2b 6,273 5.3 oe LA, RA _ H 8970 6,318 5.2 RA a - H ROTb 6,318 4.6 Lc LA _ 66¢ TABLE 19.—Data on dogs with lung tumors indicating type of twmor and lobe in which the tumor was found (cont.) Number Age at Early squamous Group Day of of death Lobes with bronchiolo-alveolar tumors cell bronchial death cigarettes (years) Non-invasive Invasive carcinoma Grouph (no filter) .....c.ae, pe eeee ene BD 606 3,769 46 LA _ _ h 626 3,928 44 we LA, RI _ b 649 4,143 5.0 RI LA, RA _ h 794 5,400 B.1 LA, RA _ _ LA, left apical lobe; LC, left cardiac; LD left diaphragmatic; RA, right spical; RC, right cardiac; RI, right intermediate; RD, right diaphragmatic: LABB, left apical branch bronchus; LMB, left main bronchus. For smoking dogs, the day of death indicates the number of days since start of smoking. The letter “a” or “b” follows the day of death sacrificed after day #875. Source: Auerbach, O. etal. (11), of dogs ao b 79.2 . a 58.3 Oo 60 ° a Done seen te uw ° L e - : ry r 2 40+ 3 tl “3 “ 4 i ot GROUP N: GROUP F: GROUP L: GROUP H: NONSMOKING FILTER-TIP NO FILTER NO FILTER OA as many cigarettes) as Group H TUMORS 2 4 7 19 DOGS 8 12 i2 24 Ficure 2.—Percent of smoking dogs with tumors. Source: Adapted from Auerbach, O., et al. (11). 60 + o . ad a ° + 40} = ° k 5 5 S 20.8 a 2 20 14.3 4.8 we TERY 3.6 2, 4 0 rs fa . el GROUP N: GROUP F: | GROUP L: GROUP H: NONSMOKERS FILTER-TIP NO FILTER NO FILTER CA as many cigarettes) as Group H TUMORS 2 A 32 35 LOBES 56 B4 84 168 Ficure 3.—Percent of lung lobes with tumors in smoking dogs. Source: Adapted from Auerbach, O., et al. (11). 300