TADLE 8.-Tumor prevalence among males and females 85-69 uears of age, by type of tumor and smoking catvory (Smoken conatltutcd 86 percent of popul&tlons rtudled) Sex and type of tumor TOtd Smoking category Smoking all mcthoda Non- smokera nisk rntio aml>ng smokers Total . ..a. . . ..I... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108 3s 13 18.3 1.9 1 Number that would be exueeted II Incidence rate among smokers were eauI to that of nonsmokers. SOURCE: Kreyberg, L. (154) LUNC CANCER RELATIONSHIPS IN \VOXEN Lung cancer death rates for lvomen are presently much lourer 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, .?07) 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 footal 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, ~0). 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 Group I (~54,311). 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 nonsmoking males was somewhat higher than for nonsmoking fe- males. However, the difference in male-female rates was much greater when smokers were compared. It appears that a substantial 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, overah 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 (303) : They begin smoking later than men (114) and do not smoke cigarettes as close to the end, where proportionaIIy more nicotine and "tar" are in- haled. Women smoke more filter-tip and "low tar and nicotine" cigar&es than men. Furthermore, cigarette smoking stiII 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 lung 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. LUNG 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 (149,150) 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, Iung 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, 26.5), and the evidence concerning a separate role of air pollution in the etiology of Iung cancer is still inconclusive (228). The recent report of the Royal College of Physicians on air pollu- tion and heaIth (228) concIuded that "the study of time trends in the death rates of lung cancer in urban areas demonstrates the overwhelming effect of cigarette smoking on the distribution o? the disease. Indeed, only the detailed surveys that have taken individual smoking histories into account have succeeded in separating the relatively very small influence of the `urban factor' on the over- riding effect of cigarette smoking in the development of cancer of the lung." 278 Author. POQUhtiOn Y`,!ll-, atudird and c0untl-Y. moth& at Results Commmla re1crcnce data collection Doll. Estimated death r&ten Lung canccv morlalily (1950) PET 1,000 Authors noted that 1163, from lung c*nwr Nnlcs Fcmalcr Ncmtnokcra ce.~I:n~tL~ arc boscd on Ennlnnd in English London Olhcr urban Rural Lordott Ofhcr urbarl Rural AI1 arcad "cry few dcutha. (70). DoQulsllon and Age: ~rnons nonsmokers 26-44 ..I.,, 0.126 0.096 0.070 0.028 0.028 0.012 0.020 obtained fram 46-64 . , . , 1.612 1.264 0.861 0.194 O.lG2 0.120 0.000 general register. 65-74 .,. 3.124 2.006 1.1G4 0.440 0.326 0.288 I.219 Stocka and Death ratn in Nda lung catictr dcalh ratea 19S2-61 (PC? 100,000) (~Pc, 54-71 The authors noted the CampbeU. England and 1966, Northern Wales. Rurd (66) Mind (116) Urban (559) upward nrsdicnt amonr nonsmokers, yiyc Ewlnnd Review of Datient Nonsmokers ,~......,........,.,.,,,,,,..,.. 14 , , 131 smokers and light (266). chart or Interview Pipe . , , , . . . . . , . . 41 26 143 dgsrctt~ smokcra and the with kin or Cigarettes: Light ,. . _. 87 163 291 lack of a simllnr vhyaicisns. hloderate .~...........,,,.,,.......,,..,.. 183 132 287 gradient LrnO"Y Heavy . . ..I..I...._............,,,.,...... 363 303 304 mdcrnlc and hrsvy cigarette amokerr. Hammond 187.783 white m&s Age alandardircd dcalh rafcb due Lo bronchoonric carcinoma (mdcs) Data excluded and Horn. in 9 s!nlea. adcnocnrcinomn. when 1968, Questionnafrc Suburb Cily ol Cifv of standardized for BIL' and U.S.A. and interview. Rural 0, to*n 10,00040.000 >50.000 smoking. rural rate WLI (IN). Nonsmokers . . , , . , 4.7 (2) 9.8 (3) 14.7 (4) aHll noted to bc 26 Cigarette smokers . , . 66.2(62) 11.1(61) 70.8(58) 86.2(63) porccnt lcua than urban. Author, POlHJl~ti0n YCli-. studied and COUhY, method OC Results Comments refcrcnec data collection Hlrn3lcl 10 percent ol all ~0~. and rmokinprt.andordizcd lung conce~ rno?tiitU %%tb Standcrdircd Mortality et al., white mnle Lund (cpidermoid and undiferentiated carcinomua &VI Ratio = 100 for U.S. 1962, cancer depths in whlte males age 36 and U.S.A. U.S.A. for 19G8 Nctrovolitan countier Nonmslropditan counti Over In 1968. The authora (JJ~). for whom next of >50.000 ,,......,....119 2,EOc-50,000 , .QO rho noted I', joint kin or physiciana 10.000-60.000 . . ,151 Rural nonfarm .I4 ef?ch, cl rcaldence snd supplied smoking Z&00-10.000 ,,......... 99 Farm . .I. I.. .67 Bmokine histories in the data. 2,191 cnsee schedule of iuny-csncer with adeguate r~l-?_ far *re*ter lh" Incormatlon. those expected on the taumption of ~dliitlvity of the ser~nrutc ellectd . ." DOU and Hill, 1964. Enuland (70. 41,000 male British Slandardircd death rater for lunp CLIRCCY The authors noted that physiciana. rural marte.llty dub Questionnaire and Conurbatian(49) Large Towtu (34) Small Towtu (3P) Rurd (Jab were aKrcl*.d hy L follow-UP of death Nonamokero . . 0.03 0.00 0.11 0.12 slgnlncsnt number uf certihcate. Clearetle smokers: city reiidenla l-14 .~.,..,...,...,. 0.48 0.32 0.87 0.62 retiring to the cuulitry. 16-24 . . . . . . . . . . . . . . . 1.31 1.88 1.06 1.16 . >26 . . . . . . . . * 1.90 4.43 2.20 1.17 Wleken. 1.908 male and Lung cancw dcafh rate per IOO.OOO-age. and rmohirlo.rtand6rdizrd total number uf drIllha 1966, female luw ctincc-i- noted under mcthlid uf Northern deaths over 36 fnnn OUlC7 Ucllaa t Urban Small dat. cullcction lncludc Ireland years of L(lC from Dcl~d Dcllaat Environs Arta TOWl-4 Rural 964 conhols. (soa, * rc~i9t.m. Personal Malea . . , . . lG7(241) 139(167) 135(46) llB(185) 137 (26) 47(149) interviews with Femalea , t, 22 (38) 17 (24) 12 (6) 23 (36) 22 (6) 12 (43) kin or physicians. TABLE g,-Epidemiologic inue8ligalions concerning the relationeilip o/ lung cancer to mking, air pollution, and urban or rural reeidence (confi.) (Acted number ol death shown In prrmtbesm) Author. PODUhtlO" Year, atudlcd wd CouncrY. method of Results Commtnta relerence data collectlon BUell 804 IWO ernecr Apaadju~trd Lund cancer dsa;h ratra per IW.OOO man yrarr and moriolity ratior The authors noted the lack et d.. deaths .mong of dcath.rate dlllcrencu 1961, Amerlcm San Froncircol AU other bctwecn Loa Anaels, and U.S.A. Leglonnrlrcs Lor Anoslu Son Disoo Colifomio counlisc San Frw~claco rryiona 449). o ged26andovn. Ratr i2atio Rots Ratio RDId Ratio and concludrd thrt Quc~tlcnnalrem to Nonsmokers , . . . , , . . . . . . . 26.1 2.6 49.0 3.9 11.2 1.0 photochemlcal 8mw Ia next of kin. Smokers: not relstnl to <1 prcklday .b.*I.III,..I. C3.6 6.7 77.1 6.0 61.02 6.4 lung c.nccr. . . . . . . . . . . . . . . . . . . . ..a. 126.0 11.8 134.6 12.0 124.9 11.2 $: . . . . . . . . . . . . . . . . . . . . . . . 241.3 21.6 22G.0 20.2 131.6 12.8 Rltwugl, 186 male and Lung entlcer dsolh rats PET 100.000 The &uthOn DOBtUhtd L 1DbB. ternale lung e*ncer &llpht syner,zlatlc Japm deatha rnd 4,191 POuutim rsOion (11.4). et?rct betwan amoklog mrtcbcd controla Male* LOW Intsrmtdiati Hioh rnd .lr DOllUtlUn. aged 36-74. Dot& Nonamokcrr . . . . . . ..s.. ..,...........,....,,.., 11.6 8.8 4.9 from Smokers: aucstlonnrlrea l-14 clearettes/day . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.6 14.2 28.6 and Inkrvlavs.' >I6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.3 18.6 81.4 F4Vlnle# Nonsmokera . I,., II......I....,.......,....I... 4.6 6.9 a.0 Smokera: 1-14 clearetteslday ..,.. . . . . . . . . . . . . . . . . . . . 19.7 16.6 16.9 >16 .a,..a.a..nas....a ,,...,,................ 12.4 20.6 11.1 Ape and cmokinp.ndjustcd lung cotlcs? death rots pn 100,000 LOW Intsrmrdiok lliph MRlCl III~II~..I.....I..o...~.o..,...,.,,II,., 16.1 22.4 28.4 E Fomaln . . . . . . . . . . . . . . . . . . . . . ..l.......I....I.. 7.6 11.6 8.7 w __ LUNG CANCER AND OCCUPATIONAL HAZARDS C'ranium Mining The excess risk for the development of lung cancer among uran- ium and fluorspar miners has been known for more than 30 years. In a recent review, Bair (17) noted that radon and ridon-decay products are the only inhaled radionuclides to be epidemiologically related to lung cancer. Lundin, et al. (178), in a continuation of the work initiated by Wagoner, et al. (299, 300, 301)) have re- cently reported on a 1'7-year follow-up of 3,414 white underground uranium miners. The authors estimated that smoking uranium miners experienced an excess of lung cancer ten times greater than did nonsmoking miners. Saccomanno (2.3~ ), in recent testimony, analyzed the data of the United States Public Health Service (USPHS) Study Group a.! presented by Lundin, et al. (178) above. He reported that cigar- ette smoking uranium miners incurred lung cancer rates four times greater than those of other cigarette smokers. Of the 62 lung cancer deaths in this population, 60 occurred in smokers. He also observed that among 100,000 uranium miners 700 lung cancer deaths per year would be expected to occur among cigarette smokers compared with only 4 among nonsmokers. Other Occupations Nelson (199) has recently reviewed certain environmental and occupational hazards as they relate to inhalation carcinogenesis. He observed that cancer of the respiratory tract has been linked epidemiologically and, in some cases, experimentally with occupa- tional exposure to the following materials: chromium, nickel, arsenic, and asbestos. Doll (72) and Goldblatt (IOU), in earlier reviews, also noted an association with coal, natural gas, and graphite exposures. Nickel Morgan (194) noted that much of the nasal and lung cancer at- tributed to nickel exposure may have been due to arsenical impuri- ties found in processed nickel prior to 1925. Doll (69) found that the number of excess deaths among nickel workers under 50 years of age had declined following the change in nickel manufacturing processes. The experiments of Hueper (134) and Sunderman, et al. ( 267,268,269) have shown that both guinea pigs and rats develop lung cancer following chronic exposure to nickel carbonyl or nickel dust. Sunderman and Sunderman (270) also reported that ciga- rette smoke contains nickel and that this concentration of nickel 282 may be capable of inhibiting the induction of lung aryl hydroxylase, an enzyme lvhich is able to detoxify aromatic hydrocarbons includ- ing known carcinogens such as benzo[a]pyrene. Asbestos In 1955. Do11 (71) found that lung cancer was a definite hazard among asbestos vvorkers. In a more recent study, Selikoff, et al. (251, 252) examined the relationship of smoking and asbestos ex- posure to lung cancer. These authors followed 370 people who had been asbestos workers during the years 1942-1962. Over a 5-year follow-up period, 94 deaths occurred in this group, of which 24 were due to bronchogenic carcinoma. The authors noted that according to data obtained from Hammond (118)) only 3.16 deaths from lung cancer would have been expected among smokers, and calculated a 7.6 to 1.00 mortality ratio due to asbestos exposure. None of the 87 nonsmokers or pipe and cigar smokers died of lung cancer. When the expected number of nonsmoker deaths (0.26) is compared with the actual number (24) which occurred among the smoking asbes- tos workers, an extremely high mortality ratio of 92 to 1 is obtained, thus reflecting the possible interaction of asbestos exposure and cigarette smoking. Exposure of mice (179) and rats (106) to asbestos dust or the intratracheal injection of chrysotile asbestos dust has resulted in the production of significant numbers of primary pulmonary car- cinomas. AIiller, et al, (184) exposed hamsters to intractracheal injections of benzo[a]pyrene. These authors observed that the addi- tion of the chrysotile variety of asbestos to the injections appeared to promote benzo[a]pyrene carcinogenesis in the respiratory tract, as determined by the time of appearance and yields of papillomas and carcinomas. Arsenic A recent epidemiologic study by Lee and Fraumeni (163) Ffai indicated an excess of lung cancer deaths among smelter workers exposed to arsenic for more than one year. Cigarette smoking was not taken into account in their computations. Experimental work on the induction of cancer in animals using arsenic has yielded either negative or inconclusive results (133, 135). Chromium Exposure to industrial bichromate compounds has been associ- ated \vith an excess of lung cancer deaths (22,P55). Laskin, et al. (159) have recently reported that intrabronchial pellet implanta- 283 tion of various chromium compounds in rats is associated with the development of squamous cell carcinomas and adenocarcinomas. However, Nettesheim, et al. (ZOO) exposed mice to chromium oxide dust and observed that it had no discernible effect on lung tumor incidence. PATHOLOGICALSTUDIES Investigators who have conducted detailed autopsy studies on patients who died of lung cancer have reported the increased pres- ence, when compared to noncancer patients, of bronchial epithelial changes which they considered to be precursors of bronchogenic carcinoma (7, 8, 23, 51,. 104, 208, 220, 279, 309). Such changes include squamous metaplasia, atypical squamous metaplasia (with acanthosis, dyskeratosis, and numerous mitotic figures), and car- cinoma in situ. Cames (52) noted that carcinoma in situ was pres- ent in 119 cases or^ lung cancer but not in any of the 119 controls who were matched for age, sex, and race. Autopsy studies comparing the frequency of these cancer- related changes in the lungs of smokers and nonsmokers are pre- sented in table 10. Virtually al] the studies noted an increased prevalence of these epithelial alterations among smokers as com- pared with nonsmokers. Definite dosage-dependent relationships were evident in the results of many of the reports. Also, Auerbach, et al. (14) observed that the number of cells with atypical nuclei decreases progressively in the bronchial mucosa of ex-cigarette smokers, depending upon the number of years between cessation of smoking and death, although it usually remains above that found in nonsmokers. The cytologic studies included in this table (182, 198, 222) ali noted an increased percentage of sputum specimens showing meta- plasia among smokers as compared with nonsmokers. PULMONARYCAFLCINOGENESIS General Aspects of Carcinogenesis Agents found in cigarette smoke which have been identified as, or are suspected of being carcinogenic, are listed in table 11. The list includes certain compounds which most probably contribute to the pathogenesis of the various cancers discussed in the other sec- tions of this chapter. Many other agents have been identified in tobacco and tobacco smoke. At the present time, they do not appear to bear a direct relationship to carcinogenesis. Stedman (262) and Wynder and Hoffmann (S19) provide detailed listings and discus- sions concerning these materials. 284 1068, &uLopslcd mt Nonsmokom . . . :, , . , . , , . . , , . . . , , . . .-. . . . ,y. ,:. , . Norwn~ 84.0. (89) cludo tbas Cnde Institute Pl9e . . * , . , *, , , * . . . . * , , , , . . . . . . . , , . . . . , , , . . , . , . , , , , , 80.6 (20) amoklng Inn trio). on whom All cigarette . . sg . . . . . . . . . . an..., . . . . . . . . . . . . . ..t...... . . . . 78.0 (88) than or equal Lo smoking data Clgsrdtps per day: 6 gram. per dry. was available. 6-14 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70.0 (23) ) 16-26 ..1...............III.....,I.....I........,....I....1. 90.0 (10) X6 ,.....,,,.,,.............,.,,,I..,,...,........,..,,..,. 100.0 (6) Knudtson, 100 D,ci-eOna 1960. Pncmt 01 colu with: AlVgLXl Age. occuuntlon. 23-86 yesrd No. of NO U.S.A. Baaal cell Squomour g+olilc+aliuo and site or of age PCWXl4 (147). change hvrm&da WWt&WiG mct4ula8ia rcaldencs were autwsied at Nonsmokers . . , , , . . . . . ,, . (21) 47.6 26.6 14.8 9.6 senwc Clgarettea/drr: found to hevr DO Veterans rDprccl&lls l-9 . . . , . * * . . . . , . . , . , (9) 77.0 11.1 11.1 Hospital on lo-16 eflcct. .*.*..*,......... (11) . . 18.2 18.2 64.6 9.1 whom 16-20 .*.*..*,,..,,.,,. (44) 20.4 29.6 28.6 20.6 amoklng >21 , . . . *. . . . ,. ,. ., ,. , (9) 11.1 88.8 data WLI 44.4 11.1 Pipe or clgw I....I`.,,,. (6) . . 100.0 ~Vllll~!Jl`Z. . . . . TABLE IO.-Pathologic and cytologic findings in the traclreo-bronchial tree of smokers and nonsmokers (cont.) (Actual number of cues ahown in psrenthna) Author, Y-r. NE%f countrY, method of RcauPd C0mfTlentd rofernee aelretion Auerbach 339 pcreons Number oj Percent rectionr Pcrcmt secfiow The authora noted. et al.. 22-88 ye.m Numbrr rcctimu with cilia ablent with some dcdcrrsvonse lx- 1961, U.S.A. (If). of age mJtopalcd nt Enst Orange Veterans HOSDitAl (excludes lung CUtCW), Nonamokcn: ot perswu 01 bronchial and entirclu cpithelium atypical cell4 atypical cella and cilia absent <40 yean of .ge . .*. . . . . . . . . . . a 4&69 ,.. ., ., ., . . .I .., . . ., , . . ,. 11 6049 . . . , .a . . . ,. . . . , , ., . 28 >70 .,..........,.,..,,*.,,...... 18 Smokera 70 . . . , . . . . . . . , . . . , , ., 22 Smokers >l pack/day: 70 .,..,.,`.........,. ,,.,, ,,.., 16 383 660 1,463 918 . 0.3 0.1 0.6 121 0.1 4.1 1,240 1.0 16.9 1,772 0.6 10.8 1,101 0.6 9.4 lath of smoking Lo: a, lose al clllr., b. lncrearc In number of atypical ceh. c. carcinoma in ailu. Averbgc number of aectiona per oil0 e~uald 62.3. am 1.6 12.6 3.027 4.6 11.4 4.186 6.3 20.6 766 9.8 23.7 CKW 140 personr Pcrcnlt rectiou showing chunpta in bronchi& rpilhclium (number 01 mcctionr) t The nuthOr8 noted et al.. autopeicd at S.Jl`flt?lOW AlVpicd Carcinoma that thr diflcra lP61, Iowa City Normal Ilyvcrp,liuia mct,lvla4ia rnCt4Vhlia in aitv Crrrcitwmo ence bclxccn U.S.A. VpterU!I~ Nonamoken (al) ..II,..I.. Gl(GC2) X(131) a (33) tl6(68) . . . . .a.. smokers and non. (64). iioaplt.1 Smokera (109) .,,,......... 44(670) 43(662) 16(197) 20(263) l(12) 2.6(34) amokera W~I on whom ,t~llC,liC~lllY smohinr algnlncsl~t. data WBI available. TADLE 10.~Pntlrologic and cytologic findings in the traclreo-bronchial tree of smokers and nomnokcrs (cmt.) (Aclual nurnbcr uf cose4 ahown in vnrcnttwn) Author. Numbrr of Year, CQ~ES nnd c""ntlY. method of ncsulta Commcnls reference selcclion AUCrbaCh 72 sulopsicd Nurnbcr of Pcrccnt scctim~ Pnccnt scclims Percent rrctiow Each cx-smoker et al., former ciga- acctiona Of with cilia obacnt tuitJ~ smncalvpi- with 60 gerccnt matched with a 1962. rette smokers brmtcAia1 and cnlircly U.S.A. cd ecu4 and atypical cell4 CUI~C~L smoker who had been Number epill~clium alvpical cella (II). cilia abrent and ciiia grerrnt vlua never-smoker smoking for Nonsmokers . , , , . . , 72 3,156 0.0 0.1 0.6 for ape, oceuvn- 210 years EIxx-amokerr . , , . 12 3.436 0.2 0.9 2.6 tion. and rcsl- and had Current amoken . . . 72 3,537 8.0 18.0 80.8 dcnce. There wu ceased *n llb'ernge of 26 yetll-8 .*o. GO.3 e.CCtlDna vcr subject nnd none had leas than 18 sections. TABLE lo.-Pathologic and cytologic findings in the trachea-bronchial tree of smokers and nonsmokers (cant,) (Acluul number ol CLI(CB ahown In pnrenthraca) AUthW. Number of Year. CLSCB and CO"l-htCJ. mcthnd of Ihulta Cummcnld rctcrcnce sclrclian Auerbrch 466 male and Prreed #cc- Percc?d ,CC. Percent ICC. Major llndlnrs ct al.. 302 fcmnle Number of tionr utith tion.4 with lion4 wit.4 50 lW1d: 1962, amokera rnd rccliotu 01 cilia abacnt U.S.A. 80md afypi- prtccd alylricnl Urbun nonamokcrn nonsmoken brachial and nltircly cd cell1 and (13). cdl, and ghowrd more ~u~opaled nnd Number epithetturn ulvpicol cell8 cilia abrmt cilia prrrmt lesion than rure.l. mntched for blslea: Both lmlona and we. OCC". Nonemokcrs 1. ,. . ,,`.. . 41 2,346 0.1 0.1 ._LY9iCII nuclei DatiOn, and Cigarette amokera . . . , . 1 76 3.303 62 21.2 78.6 were much lrw residence. Females: ,, 2reQucnt In nan- Nonamokcn . . . . . . , . . . . 41 2.919 . 0.1 0.6 nmokem and lcae Cisarettc smokera , , , . , 76 3,607 2.6 13.8 62.6 Ireclucnt In plvc Mlll~: snd cigar amokera Nonsmokers . .s,, , , . . . . 36 1,106 . . 0.2 0.5 thnn In clgareltc Cimr smokers , , , . , ,. , . 86 1,133 0.8 10.0 10.7 smokera. Clsaretteamokera . . . . . . 36 1,62t 12.6 27.8 89.1 K'I.I$`O of e.ara h&d 6b66 sectiona al.ayfo of cuea had 40-40 arclions 7.370 01 CBBNI had 30-s asctiona 4.6% of cn~rtl hrd 16-20 scctlwls Robbina, 103 students -^_ Percent in rwh evtolollio ctddr Smokora drilncd LLI 1ICC. 11-24 years U.S.A. Slightly Modrratclv Strongly those hnvlnu con- of aze who NOWWl (PPO. afvpicd l7!YPiCOl 4tupical #urned 210 ciye- underwent Nonamokera (46) . . . . * .*,.. ~ ..,.... 86.1 4.4 a.9 aerosol Smokers (68) rsttn n dw for I. *.* . . *.,,.......,,, 66.2 32.8 10.8 1.7 21 Ye*?. sputum induction. I Aulhar. Number of year. COHPI~ nnd cowltrY. method of rcfcrcnce srlrctlon Results Commcnla Number Pcrcmt rhmuinn mrlolrla#ia 234 41.16 189 41.09 886 61.43 93 6 I .29 38 CO.29 Nasiell. 60 nanamoklng Sputum cvlologic ehanpca Pcrcrnt ruilh t RlKilrdiYl by 19G8. wtpnlicnt~. l'crcL71t Percent with alvpicd author a8 "rcrl Sweden 398 smukera Number nra1c1 Airan aye mclnphrio mclapluriat vrcmnliununt (ISA). parMpr.ting Nonsmokers . , . . . , 60 42 67.1 18 4 chsnyc." In wneral Smokers . . . , , . . , . . 398 73 kG.6 62 27 health exam- lnation who underwent suutum induction. Spnin 167 males and Number Prrccnt with mc(apkuia The authors found et PI., 78 femsles AldeB: no evidcnrc of 1970. autopsied foL Nonamokera . ., . . . . . . . . . . . . . . . . . . . . . ., a.. , . ., , 36 60.0 carcinoma in rilu U.S.A. lowing sudden Ex-smokers . . . . . . . . . . (. . . . . . . . . . . ,. . . , . . . . . . . . , , (. . . ,. . . . 2~ 67.7 Or DrenCOVh8lk (258). or accidental <1 wck .I. . . . . . . ..t I... . . . . . . . . . . . . . . . . . ,, . . . . . . . . . . . . . 32 62.6 &LYpicnl ctinngca. dcnth for >I pack . . . . . . . . . . . . . . . . . . . . ,.....I... . . . . ,..,..,,..,,,..,,, , 68 13.6 whom smok- Females: ing data were Nonsmokera . . . . . . . . . . . . , . . . . . . . . . +. . , , , , , . 34 34.1 available (ex. l pndc . . , ,, ,. . , . . . . ., . . . ., ..~. . . . . . . . . .., 46.1 eluded 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 is 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 maI%- 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 pIay 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[a]anthracene, chrysene, benzo[a]pyrene, and benzo- [blfluoranthene 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 tobacco 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-ai-e 7,12-dimethylbenz[a]anthracene and 3-methylcholanthrene and have been frequently used as tumor initiators or complete carcino- gens, parCcuIarly in skin painting and tracheal impIantation experiments. The nitrosamine compounds listed are potent carcinogens affect- ing many organ systems, including the respiratory tract (188, 189). hlagee 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 IL-Identified or suspected tumorigenic agents in cigarette smoke' I. Complete urcioantna and tumor initiators: I'olynuclar mromatic hydrocarbons ........ 1. Bcnw(~)p9rene .................... 2. Dibcnrlr.h)snthmcene .............. 3. Bcnu,(b)fluaranthene ............... 4. Bcnw( j)fluoranthenc ............... S.Dibenzo(a.i)pyrene ................. 6. Benz(a)anthracene ................. 7. Chrvsene ........................... 8. Indena(l.2.3.cd)pyrene .............. 9. Ben7.o(c)pheoanthrcne~ ............. 10. ~cthylbenra(.)pyrc"es ............. 11. MethylcblTsenea .................... X0-30 UP 3.3 0.4 0.3 0.6 Trace 0.3 2.0 0.6 TTllCC 0.1 2.0 N-heterocyclic hydrocarbons .............. 1. Dibenrls.h)acridine ................ Z.Dibenr(a.j)ncridine ................. 3.7Hdlb~zo(c.z)carbarole ........... N-nitrossmio~a ......................... 1-2 0.01 1.0 0.07 l-10 1. Dimetb~lnitrosnmine ................ 0.4 2. Diethylnicroae.mine ................. TlTLC-2 3. ~lethpl-n-butylnitro.aminc ........... TWlCTZ 4. Nitraopyrrolidine .................. 0.4 5. Nitrosopipcridine ................... T0TC.Z Epoxidea. perory compound% and lactones: 1. Eporides ........................... 2. Peroxides .......................... 3.Lkctones ........................... L. ,-Levantenolide ................ b. p-Levantenolide ................ No data Present . 20.0 2.0 N-alkyl-hcterocyclics: 1. I-methylindole ...................... Paticidn and fungicides:' l.TDE ............................... Z-c,.;-DDD ........................... 3.DDT ............................... 4. Malcic bydrrzide .................... BeLwnsphthylamine ...................... Present Possible initiator. No essential contribution sus9eetcd. 10-100 10.100 10-100 10-100 2-3 Tumor initiators. Tumor initial-am. ~uspcrted carcinonens of possible im~artance (presence in fresh smoke possible). Certain of these compounds are known carcinogens; presence in smoke condensate not established. Suspected bladder carcinosen: of doubtful significance at reported Iev&. Polonium 210 _. . . _. . . . . . . ..-- 1.60 Of .90me importance only in the gicocuriea caz.e of relatively high conix~n- trslion. but not impo&nt at reported levch. TABLE Il.-Zdentified or suspcctcd tumorigenic agents in cigorettc smoke' (cont.) II. Tumor promotinp nnenta: Neutral pmmotur (polmera) (unboan ,tructuren.) No data Of pwsible importance. VoLtilc pbm& . . . . . . . . . . . . . . . . . . . . . . . . . 20.30 my. Of porGble immxtance. 1. Phenol 2. cresc.1 Nonvolatile fatty s&da . _. . _. . . _. . . . 20-100 mu. Of minor importance. 1. St.sric acid 2. Oleic acid N-dkyl heterocfdics: Of possible imwrtancc. 1. S-mstbylcrrbarole . . . . . . . . . . . . . . . . Present 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 (38,138,155,319). 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 (1 II, 128). A recent, extensive review by Guthrie (111) provides more detailed informa- tion concerning these agents. Radioactive isotopes can be found in tobacco and tobacco smoke (205). Potassium-40, while present in tobacco leaf, is not trans- mitted in any substantial amount to mainstream smoke (230). Polonium-210 ( PoZID) , however, is transmitted into the mainstream smoke (94, 123, 142,145, 215,217). A number of autopsy studies (table AI2) have shown that the bronchial epithelium of smokers contains significantly more Po~,~ than that of nonsmokers. Littie, 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 (12.3, 217) have not observed this excess at bifurcations, and in a recent discussion Wynder and Hoff- mann (320) concluded that it appears unlikely that Poz10 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 volatiIe aldehydes, hydrogen cyanide, nitrogen oxides, volatile phenols, and certain volatile acids such as formic and acetic (129). Expen`mental 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 In.jection 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 animal skin. A seIected number of these studies is presented in table A13. Numerous other studies, performed prior to and following 1953, are reviewed by Wnder 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. Tiss-ue 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 Al4 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 (233,2.3:) Laskin, et al. (159). and hiontesano, 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 benzo[a]pyrene (B[a]P) is 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 (2%). 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 Al& 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 (II, ff9) 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 H3-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 anima!s 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 listed 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 bronchiole-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 bronchiole-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 invasivee bronchiole-alveolar tumors which did not extend into the pleura, one dog had an invasive bronchiole-alveolar tumor which extended to the pleura, and four had invasive bronchiolo- alveolar tumors extending into the pieura beyond the pleural- pulmonary junctions. In addition, two bronchogenic squamous cell carcinomas \r-ere 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 lvere of a bronchiole-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 TILE 17.-Data on pcdigrecd male beagle dogs of groups F, L, H, h, and N (Some of the figures (rnuly only lo doga surviving 876 dwa or longer) Filter I-E, group oroup F L 12 12 26.0 26.1 6,143 3,103 7.02 3.64 42.1 21.2 17.8 34.8 1.11 1.86 109.3 103.6 1.19 6.66 4.31 4.12 0.29 0.22 NO nikr grO"p II 2b 26.0 6.1'28 7.0 42.0 34.8 1.85 207.8 11.12 0.91 0.44 fEr Nonsmokera ETOUP YP N a0 0 al.9 SO.7 E.129 no,is 7.0 - a2.9 - 84.8 - 1.86 - 207.8 - 11.12 - 6.61 - o.aa - ' The smoking doga wetc divided Into grwDe F, L. H, and h on day No. 67. ' Dogs of gwunl L. ii, snd h amok& hltcr.tiD clgarcttcs during B training period nt the start of tbc uporlment. but amoktd nonfilter clU&retttl tbcrcaf'er. SUUHCE: Adardrd from lIammond, E. C. et hl. (110). TABLIZ l&-Summary of principal cause of death (&us No. 57 through No. 875) in dogs of groups F, L, H, h, and N (Each death clwained according to m&st scvcre condition--eome doas diad ol a combinstion uf ce,uses listed) Filter NO No tip filter nltcr n% Principal C.USC of death N~~~y;;cra Croup c TO" p C;oiuD Cr"UD Total F I, h N Pulmonwy emphysema nnd fibrosis . . . . . . . . . . . . . . . . . . . . . - 2 Cur pulmunale (pulmonary emphysema and fibrosis with - - 2 right heart enlargement) . . . . . . . . . . . . . . . . . . . . - 3 Pulmonary infarction . . . . . . . . . . , . . . . .,. - 6 8 1 1 2 Broncho~neumonla ..,.,...,..,........,......,,..,.... 6 - 9 - 3 Aauir&tion of food . . . . . . . . ., . . . . . . . . . . . . . . . . . ,... , . . - 1 - 4 1 1 VnCWtsi" - - 2 . . . . . . . . . . ..1............................... 2 Number of deatha . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . - 1 - a 2 2 12 Number surviving 876 dam 12 20 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 10 Total number of dogs 12 26 0 66 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 12 24 38 8 84 SOURCE: Hammond, E. C. et al. (111). TABLETS.- Data on dogs with lung tumors indicating type of tumor and lobe in which tile tltmor wae found CIOUD %xf N%bcr &c at Early n~u~lnou dCBlb Lubcn wiLh bmnchialo-rlv~~~~i~mo~ ccl1 bmnchlnl cignrcttcs (Years) Non-invnoive CnKIrIUma 9048 904b - 6.1 4.0 LA IU 8788 6,161 6.1 879a 6.170 4.1 8868 G.224 6.2 890a 6.269 5.4 LA LA LA LA 347 1.055 3.8 LA. LC 812 2,847 6.1 I1A 876n 3,103 6.1 LA,RA 8778 3,107 6.2 LA.LC 8R2a 3.127 1.2 LA, LD Aclria 3.lh3 6.3 I.h, l(D 8lJliu 3,I'JG 6.4 l.h 6IH 2.L l.:i4:I 3..1 3.404 47 4.6nv 6.0 s.o:io 3n G.lJKH 4.2 6.970 13 G.l'LY I.9 G. I :I" 6.1 C,l47 6.3 6,1X3 6.4 6,192 4.7 C,?IO 6.0 6.246 6.0 6.255 I.9 6.?73 6.7 6.273 6.3 G.3lX 6.2 G.3lR 4.6 IIC: I.h. RA, 1tn 1.11. IlA I(1 1.A L A . LA LC.RA ItA LC - - - - - - - - LA 1.h. Ilh, IlD -_ - LA. 1.1). IlA LA LA - LA LA, KA LA - - LA, 11A - LA - - - - - - - - - - - - -. - .- -. - - LAUII - - -- L51U -- - -. - - TABLE l&-Data on dogs with lung tumors indicating type of tumor and lobe in which the tumor was found (cont.) Number of cigarettes hKC at death (Years) CrOUD h (no filter) . . ...* . . . . . . . . . . a..... h 606 3,761 4.6 LA - h 626 3,928 4.4 LA, RI - h 649 4.143 5.0 iI LA, RA - h 794 5,400 5.1 LA, RA - - LA. left apical lobe; LC, left cardiac: LD left diaphrsgmatic; RA, risht spicnl: RC. ripbt cardiac; RI, right intermediate; RD, right dinpbragmatic; LAUD. left nuical branch bronchus; LMB. left main bronchus. start of smoking. The letter "a" or "b" follows the day of dcutb of doga sacrilicetl after day #876. For smoking dopa, the day of death indicates the number of days since SOURCE: Auerbach. 0. et al. (I!), 58.3 -- - -..--- GROUP N: NONSMOKING GROUP F: GROUP L: GROUP H: FILTER-TIP NO FILTER NO FILTER (I/Z a* many ciparrtlcs) .s Group H i i ;:i TUMORS 2 4 7 19 DOGS -ii 12 i;i Fi FIGURE 2.-Percent of smoking dogs with tumors. SOURCE: Adapted from Auerbach. O., et al. (11). 60 s 4 40 b s Y 20.8 _ s & 20 0 GROUP N: GROUP F: GROUP L: GROUP H: NONSMOKERS FILTER-TIP NO FILTER NO FILTER (`A as many cigIrstta) II Grout H TUMORS 2 4 12 35 LOBES M SC sr 1-z FIGURE J.-percent of lung lobes with tumors in smoking dogs. SOURCE: Adapted from Auerbach, 0.. et al. (11). 300