PART I Introduction, Summaries, and Conclusions Chapter 1 Introduction Chapter 1 Realizing that for the convenience of all types of serious readers it would he desirable to simplify language. condense chapters and bring opinions to the forefront. the Committee offers Part I as'surh a presentation. This Part includes: (a) an introduction comprising. amon? other items. a chro- nology especiallv pertinent to the subject of this study and to the establish- ment and activities of the Committee. (b ) a short account of how the study was conducted, cc) the chief criteria used in making judgments. and td t a brief overview of the entire Report. HISTORICAL NOTES AND CHRONOLOGY In the early part of the 16th century. soon after the introduction of tobacco into Spain and England by explorers returning from the New World. controversy developed from differin g opinions as to the effects of the human use of the leaf and products derived from it by combustion or other means. Pipe-smoking, chewing, and snuffing of tobacco were praised for pleasura- ble and reputed medicinal actions. At the same time, smoking was con- demned as a foul-smelling, loathsome custom. harmful to the brain and lungs. The chief question was then as it is now: is the use of tobacco bad or good for health, or devoid of effects on health? Parallel with the increas- ing production and use of tobacco, especially with the constantly increasing smoking of cigarettes, the controversy has become more and more intense. Scientific attack upon the problems has increased proportionatelv. The design, scope and penetration of studies have improved, and the yield of significant results has been abundant. The modern period of investigation of smoking and health is included within the past sixtv-three years. In 1900 an increase in cancer of the lung was noted particularly by vital statisticians. and their data are usually taken as the starting point for studies on the possible relationship of smoking and other uses of tobacco to cancer of the lung and of certain other organs. to diseases of the heart and blood vessels I cardiovascular diseases in pen- eral; coronary artery disease in particular) ~ and to the non-cancerous 1 non- neoplasticl diseases of the lower respiratory tract ( especially chronic bronchitis and emphysema 1, The next important basic date for starting comparisons is 1930. when the definite trends in mortality and disease-inci- dence considered in this Report became more conspicuous. Since then a great variety of investigations have heen carried out. Many of the chem- ical compounds in tobacco and in tobacco smoke have been isolated and tested. Numerous experimental studies in lower animals have been made by exposing them to smoke and to tars. gases and various constituents in tobacco and tobacco smoke. It is not feasible to submit human beings to 5 experiments that might produce ranters or other serious damage, or to expose them to possibly noxious agents over the prolonged periods under strictly controlled conditions that \vould be necessary for a valid test. Therefore. the main evidence of the effects of smoking and other uses of tobacco upon the health of human beings has been secured through clinical and pathological observations of conditions occurring in men, women and children in the course of their lives. and by the application of epidemio- logical and statistical methods by which a vast array of information has been assembled and analyzed. Amon? the epidemiological methods which have been used in attempts to determine whether smoking and other uses of tobacco affect the health of man: two types have been particularly useful and have furnished information of the greatest \-alue for the work of this Committee. These are (1 i retro- spective studies which deal with data from the personal histories and medical and mortality records of human individuals in groups: and I 2) prospective studies, in which men and w-omen are chosen randomly or from some special group. such as a profession, and are follo\ced from the time of their entrv into the study for an indefinite period. or until thev die or are lost on account of other events. Since 1939 there ha\-e been 29 retrospective studies of lung cancer alone which ha1.e varying degrees of completeness and validity. Following the publication of several notable retrospective studies in the years 1952-1956. the medical evidence tending to link cigarette smoking to cancer of the lung received particularly widespread attention. .4t this time, also. the critical counterattack upon retrospective studies and upon conclusions drawn from tllem was launched by unconvinced individuals and groups. The same types of criticism and skepticism have been. and are. marshalled against the meth- ods. findings, and conclusions of the later prospective studies. They will he discussed further in Chapter 3. Criteria for Judgment. and in other chapters, especially Chapter Z. Mortality. and Chapter 9. Cancer. During the decade 1950-1960. at various dates. statements based upon the accumulated evidence were issued by a number of organizations. These included the Rritish I\ledical Research Council: the cancer societies of Den- mark. Norwal. Sweden. Finland. and the Netherlands: the American Cancer Society: the .4merican Heart Association: the Joint Tuberculosis Council of Great Rritain : and the Canadian Yational Department of Health and Welfare. Th e consensus. publici!- declared. \$-a< that smoking is an important health hazard. particularlv I\ ith respect to lunc cancer and cardiovascular disease. Early in 195-l. the Tnl)acco lndustrv Research Committee rT.1.R.C.i was established br representatives of tobacco manufacturers. growers. and srare- housemen to sponsor a program of research into questions of tobacco use and health. Since then. under a Scientific Director and a Scientific .4d\-isory Board composed of nine scientists \vho maintain their respective institutional affiliations. the Tobacco Industry Research Committee has conducted a grants-in-aid program. collected information. and issued reports. The I!.S. Public Health Service first became officially engaged in an appraisal of the available data on smoking and health in June. 19.36. when. under the instigation of the Surgeon General. a scientific Study Group on 6 the subject was established joint]\- hv the Sational Cancer Institute. the National Heart Institute. the American Cancer Societ!-. and the American Heart Association. .4fter appraising 16 independent itudies carried on in five countries over a period of 18 l-ears. this group concluded that there is a causal relationship between excessive smokin, CT of cirrarettrs and lung cancer. I Impressed b!- the report of the Study Committee and h\- other new evi- dence. Surgeon General Leroy E. Rurnev issued a statement on Jul\ 12. 1937. reviewing the matter and declaring that: "The Public Health service feels the weight of the e\-idenw is incwasin=l!- pointing in one dirrction: that excessive smoking is one of the ,rausative factors in lung cancer." `AFain. in a special article entitled "Smoking and I,ung Cancer--\ Statement of the Public Health Service." publi~hrd in the Jourrlal of the dnwrican Medical Association on IVovemher 2:;. 19.50. Surgeon General Rurne\- referred to his statement issued in 19.7; and reitrrated the brlief of the Public Health Service that: "The weight of e\-idence at l)resrtlt iml)lic,ates smoking as the principal factor in the increased incidence of lung ranwr." and that: "Ciga- rette smoking particular]\ is associated w-ith an irlcreasrd chance of de- veloping lung cancer." These quotations state the position of the Public Health Service taken in 19.57 and 19.59 on the qur>tion of fmokinp and health. That position has not chanFed in the succeeding years. during which several units of thr Serlire conducted rstensiw investigations on smoking and air pollution. and the Sewice maintairlrd a constant scrutinv of reports and ljuhlications in this field. ESTABLISHMENT OF THE CO~IMITTEE The immediate antecedents of the establichmrnt of the Surgeon Gen- eral's Advisory Committee on Smoking and Health began in mid-1901. On June 1 of that year. a letter was sent to the President of the I'nited States, signed by the presidents of the American Cancer Societv. the American public Health Association. the American Heart Association. and the Na- tional Tuberculosis Association. It urged the formation of a Presidential commission to study the "widespread implications of the tobacco problem." On January 4. 1962. representatives of the various organizations met with Surgeon. General Luther L. Terra-. \+ho short]\ thereafter proposed to the Secretary of Health. Education. and Welfare the formation of an advi- sory committee composed of "outstanding experts who would assess avail- able knowledge in this area [smokin g 1s. health] and make al)propriate rec- ommendations . . ." On April 16. the Surgeon General sent a more detailed proposal to the Secretary for the formation of the ad{-isor\- _ group. calling for re-evaluation of the Public Health Service position taken I~\- Dr. Rurnr! in the Journal of the American Medical Association. IId at the Se Dr. Tkrry felt the nerd for a new r\ice's position in the light of a number of si=nifirant dr\-elol)- `nents since 1939 which emphasized the need for further actiorl. He listed he as: 1. New studies indicating that smoking has maior adverse health effects. 2. Representations from national voluntary health agencies for action on the part of the Service. 3. The recent study and report of the Royal College of Physicians of London. 4. Action of the Italian Government to forbid cigarette and tobacco ad- vertising: curtailed advertising of cigarettes by Britain's major tobacco companies on TV; and a similar decision on the part of the Danish tobacco industry. 5. A proposal by Senator Maurine Neuberger that Congress create a com- mission to investigate the health effects of smoking. 6. A request for technical guidance by the Service from the Federal Trade Commission on labeling and advertising of tobacco products. 7. Evidence that medical opinion has shifted significantly against smoking. The recent study and report cited by Surgeon General Terry was the highly important volume: "Smoking and Health-Summary and Report of the Royal College of Physicians of London on Smoking in Relation to Cancer of the Lung and Other Diseases." The Committee of the Royal College of Physicians dealing with these matters had been at its work of appraisal of data since April 1959. Its main conclusions, issued early in 1962, were: "Cigarette smoking is a cause of lung cancer and bronchitis, and probably contributes to the development of coronary heart disease and various other less common diseases. It delays healing of gastric and duodenal ulcers." On June 7, 1962, the Surgeon General announced that he was establishing an expert committee to undertake a comprehensive review of all data on smok- ing and health. The President later in the same day at his press conference acknowledged the Surgeon General's action and approved it. On July 24. 1962. the Surgeon General met with representatives of the American Cancer Society. the American College of Chest Physicians, the .imerican Heart Association, the American Medical Association, the Tobacco Institute. Inc.. the Food and Drug Administration. the National Tuberculosis Association. the Federal Trade Commission, and the President's Office of Science and Technology. At this meeting, it was agreed that the proposed work should be undertaken in two consecutive phases, as follows: Phase I-An objective assessment of the nature and magnitude of the health hazard. to be made by an expert scientific advisory committee which would review critically all available data but would not conduct new research. This committee would produce and submit to the Surgeon General a technical report containing evaluations and conclusions. Phase II-Recommendations for actions were not to be a part of the Phase I committee's responsibility. No decisions on how Phase II would be conducted were to be made until the Phase I report was available. It was recognized that different competencies would be needed in the second phase and that many possible recommendations for action would extend beyond the health field and into the purview and competence of other Federal agencies. The participants in the meeting of July 27 compiled a list of more than 150 scientists and physicians workin, 0 in the fields of biology and medicine. 8 rvith interests and competence in the broad range of medical sciences and with capacity to evaluate the element. = and factors in the complex relation- ship between tobacco smoking and health. During the next month. these lists were screened by the representatil-es of organizations present at the July 27 meetin?. Any organization could \-et0 any of the names on the list. no reasons being required. Particular care was taken to eliminate the names of any persons \vho had taken a public position on the questions at issue. From the final list of names the Surgeon General selected ten men who agreed to serve on the Phase I committee. which was named Tlrc Surgeon General's Advisory Committee on Smoking and Health. The com- mittee members. their positions. and their fields of competence are: Stanhope Bayne-Jones. M.D.. LL.d.. I Retired 1. Former Dean. Yale School of Medicine i 193.5-40 I _ former President. Joint Administrative Board. Cor- rlell University. New York Hospital Medical Center (1947-52 I : former president. Socjetv of Ameriran Bacteriologi$ts I 1929 \. and American Societ! of Pathologv and Bacteriolog! I 19401. Field: Nature and Causation of N-ease in Human Populations. Dr. Bayne-Jones served also as a special consultant to the Committee staff. Walter J. Burdette. M.D.. Ph. D.. Head of Deljartment of Surgery. Uni- \rrsitv of Itah School of Medicine. Salt Lake Cit\-. Fields: Clinical 8 f:uperimental Surgery; Genetics. William G. Cochran. M.A.. Professor of Statistics. Harvard University. Field: Mathematical Statistics. lcith Special .4pplication to Biological I'rohlems. Emmanuel Farber. M.D.. Ph. D.. Chairman. Department of Pathology. t-rliversity of Pittsburgh. Field: E. p . Y el imental and Clinical Pathology. Louis F. Fieser. Ph. D.. Sheldon Emory. Professor of Organic Chemistry. II arvard University. Field: Ch emistry of Carcinogenic Hydrocarbons. Jacob Furth, M.D.. Professor of Pathology. Columbia University. and ljirector of Pathology Laboratories, Francis Delafield Hospital, skew York. u.Y. Field: Cancer Biology. John B. Hickam, M.D.. Chairman, Deljartment of Internal Medicine. Uni- `c'rsity of Indiana, Indianapolis. Fields: Internal Medicine. Physiology of "ardiopulmonary Disease. Charles LeMaistre. M.D.. Professor of Internal Medicine, The IIniversit) "I Texas Southwestern Medical School. and Medical Director. Woodla\l n Hos- Vital. Dallas, Texas. Fields: Internal Medicine. Pulmonary Diseases, I'rt.\.entive Medicine. Leonard M. Schuman, M.D.. Professor of Epidemiology. I-niversity of "ilsnesota School of Public Health. Minneapolis. Field: Health and its ti ' d Ionship to the Total Environment. 1. t' \hrice H. Seevers. M.D., Ph. D.. Ch `.lliversity of Michigan, Ann Arbor. airman. Department of Pharmacology. Field: PharmacoloFy of Anesthesia "11(1 Habit-Forming Drugs. (`hairman: Luther L. Terry, 1,f.D.. Surgeon General of the United States Public Health Service. 9 Vice-Chairman : James M. Hundley. X'I.D.. Assistant Surgeon General for Operations, United States Public Health Service. Staff Director Medical Coordinator Eugene H. Guthrie. M.D., M.P.H. Peter V. V. Hamill, M.D., M.P.H. Public Health Service Public Health Service 10 Chapter 2 Conduct of the Study Chapter 2 CONDUCT OF THE STUDY The work of the Surgeon General's Advisory Committee on Smoking and Health was undertaken. organized. and pursued with independence. a deep sense of responsibilitv. and with full appreciation of the national importance of the task. The Committee's constant desire was to carrl. out in its own way. with the best obtainable advice and cooperation from experts outside its membership. a thorough and objectit-e review and evaluation of available information about the effects of the use of various forms of tobacco upon the health of human beings. It d esired that the Report of its studies and judp- ments should be unquestionably the product of its labors and its authorship. With an enormous amount of assistance from 155 consultants. from members and associates of the supportin, c staff. and from several organizations and institutions. the Committee feels that a document of adequate scope. integrity. and individuality has been produced. It is emphasized. however. that the content and judgments of the Report are the sole responsibility of the Committee. At the outset, the Surgeon General emphasized his respect for the freedom of the Committee to proceed with the study and to report as it saw fit, and he pledged all support possible from the United States Public Health Service. The Service, represented chiefly by his office. the National Institutes of Health, the National Library of Medicine. the Bureau of State Services, and the Na- tional Center for Health Statistics, furnished the able and devoted personnel that constituted the staff at the Committee's headquarters in Washington, and provided an extraordinary variety and volume of supplies, facilities and re- sources. In addition, the necessary financial support was made available by the Service. It is the purpose of this section to present an outline of the important features of the manner in which the Committee conducted its study and com- posed this Report. A retrospective outline of procedures and events tends to convey an appearance of orderliness that did not pertain at all times. A plan was adopted at the first meeting of the Committee on November g-10, 1962, but this had to b e modified from time to time as new lines of inquiry led into unanticipated explorations. At first an encyclopedic approach was con- sidered to deal with all aspects of the use of tobacco and the resulting effects, with all relevant aspects of air pollution, and all pertinent characteristics of the external and internal environments and make-up of human beings. It was soon found to be impracticable to attempt to do all of this in any reason- able length of time, and certainly not under the urgencies of the existing situation. The final plan was to give particular attention to the cores of prob- lems of the relationship of uses of tobacco, especially the smoking of ciga- rettes, to the health of men and women, primarily in the United States, and 13 to deal with the material from both a general viewpoint and on the basis of d' isease categories. As may be seen in a glance at the Table of Contents of this Report, the main topical divisions of the study were: o Tobacco and tobacco smoke, chemical and physical characteristics (Chapter 6 ) . o Nicotine: pharmacology and toxicology (.Chapter 7). o Mortality, general and specific, according to age, sex, disease, and smok. ing habits. and other factors (Chapter 8). o Cancer of the lungs and other organs; carcinogenesis; pathology, aud epidemiology (Chapter 9). o Non-neoplastic diseases of the respiratory tract, particularly chronic bronchitis and emphysema. with some consideration of the effects of air pollution (Chapter 10). o Cardiovascular diseases. particularlv coronary artery diseases iChapter 11 I. o Other conditions. a miscellany including gastric and duodenal ulcer, perinatal disorders. tobacco amblyopia, accidents (Chapter 12). o Characterization of the tobacco habit and beneficial effects of tobacco i Chapter 13'1. o Psy-cho-social aspects of smoking i Chapter 14`). o Morphological constitution of smokers (Chapter 15). As the primary duty of the Committee was to assess information about smoking and health. a major general requirement was that of making the information available. That requirement was met in three ways. The first and most important was the bibliographic service provided by the National Library- of Medicine. .\s th e annotated monograph by Larson, Haag, and Silvette-compiled from more than 6.000 articles published in some 1,200 journals up to and largely into 1959-was available as a basic reference source. the National Library of Medicine was requested to compile a bibliog raphy thy author and by subject) covering the world literature from 1958 to the present. In compliance with this request, the National Library of Medicine furnished the Committee bibliographies containing approximately 1100 titles. Fortunately. the Committee staff was housed in the National Library of Medicine on the grounds of the National Institutes of Health, and through this location had ready access to books and periodicals, as well as to scientists working in its field of interests. Modern apparatus for photo-reproduction of articles was used constantly to provide copies needed for studv by members of the Committee. In addition, the members drew upon the libraries and bibliographic services of those institutions in which thev held academir positions. A considerable volume of copies of reports and a number of special articles were received from a variety of additional sources. All of the major companies manufacturin, u cigarettes and other tobacco products were invited to submit statements and any- information pertinent to the inquiry. The replies vvhich were received were taken into consideration by the Committee. Through a system of contracts with individuals competent in certain fields, special reports were prepared for the use of the Committee. Through these 14 sources much valuable information was obtained: some of it new and hitherto unpublished. In addition to the special reports prepared under rontracts. many con- ferences, seminar-like meetings. consultations, visits and correst,ondence made available to the Committee a large amount of material and a consider- able amount of well-informed and well-reasoned opinion and advice. To deal in depth and discrimination with the topics listed aho\-e. the Com- mittee at its first meeting formed subcommittees with much overlapping in membership. These subcommittees were the main forces engaged in collec- tion. analysis. and evaluation of data from published reports. contractual reports. discussions at conferences. and from some new prospective studies reprogrammed and carried out generousll- at the request of the Committee. These will be acknowledged more fullv elsewhere in this Report. The first formulations of conclusions \qere made by these subcommittees. and these were submitted to the full Committee for revision and adoption after debate. At the beginning. and until the Committee began to meet routinely- in Pxesutive session, it had the advantage of attendance at its meetings of ob- servers from other Federal agencies. There were representatives from the following agencies: Executive Office of the President of the United States. Federal Trade Commission, Department of Commerce. Department of Agri- culture. and the Food and Drug Administration. Ser\-ing as more than ob- servers and reporters to their agencies. \$hen they were present or by written communication, the)- supplied the Committee with much useful information. There were an uncounted number of meetings of subcommittees and other lesser gatherings. Between November 1962 and December 1063. the full Committee held nine sessions each lasting from two to four days in Washing- ton or Bethesda. The main matters considered at the meetings in October, November, and December 1963 were the review and revision of chapters. critical scrutiny of conclusions, and the innumerable details of the composi- tion and editing of this comprehensive Report. 714-422 O-64-3 15 Chapter 3 Criteria for Judgment Chapter 3 CRITERIA FOR JUDGMENT In making critical appraisals of data and interpretations and in formulat- ing its own conclusions, the Surgeon General's Advisory Committee on Smoking and Health-its individual members and its subcommittees and the Committee as a whole-made decisions or judgments at three levels. These levels were: I. Judgment as to the validity of a publication or report. Entering into the making of this judgment were such elements as estimates of the com- petence and training of the investigator, the degree of freedom from bias, design and scope of the investigation, adequacy of facilities and resources, adequacy of controls. II. Judgment as to the validity of the interpretations placed by investigators upon their observations and data, and as to the logic and justification of their conclusions. III. Judgments necessary for the formulation of conclusions within the Committee. The primary reviews, analyses and evaluations Of publications and unpub- lished reports containing data, interpretations and conclusions of authors were made by individual members of the Committee and, in some instances, by consultants. Their statements were next reviewed and evaluated by a subcommittee. This was followed at an appropriate time by the Committee's critical consideration of a subcommittee's report, and by decisions as to the selection of material for inclusion in the drafts of the Report, together with drafts of the conclusions submitted by subcommittees. Finally, after re- peated critical reviews of drafts of chapters, conclusions were formulated and adopted by the whole Committee, settin g forth the considered judgment of the Committee. It is not the intention of this section to present an essay on decision-making. Nor does it seem necessary to describe in detail the criteria used for making scientific judgments at each of the three levels mentioned above. All mem- bers Of the Committee were schooled in the high standards and criteria im- Illicit in making scientific assessments; if any member lacked even a small Part of such schooling he received it in good measure from the strenuous debates that took place at consultations and at meetings of the subcommittees and the whole Committee. CRITERIA OF THE EPIDEMIOLOGIC METHOD It is advisable, however, to discuss briefly certain criteria which. although applicable to all judgments involved in this Report. were especially significant for judgments based upon the epidemiologic method. In this inquiry the 19 epidemiologic method was used extensively in the assessment of causal fac- tors in the relationship of smoking to health among human beings upon whom direct experimentation could not be imposed. Clinical, pathological and ex- perimental evidence was thoroughly considered and often served to suggest an hypothesis or confirm or contradict other findings. When coupled with the other data. results from the epidemiologic studies can provide the basis upon which judgments of causality may be made. In carrying out studies through the use of this epidemiologic method, many factors, variables, and results of investigations must be considered to deter- mine first whether an association actually exists between an attribute or agent and a disease. Judgment on this point is based upon indirect and direct measures of the suggested association. If it be shown that an asso- ciation exists, then the question is asked: "Does the association have a causal significance?" Statistical methods cannot establish proof of a causal relationship in an association. The causal significance of an association is a matter of judgment which goes beyond any statement of statistical probability. To judge or evaluate the causal significance of the association between the attribute or agent and the disease, or effect upon health, a number of criteria must be utilized. no one of which is an all-sufficient basis for judgment. These criteria include : a) The consistency of the association b) The strength of the association c) The specificity of the association d) The temporal relationship of the association e) The coherence of the association These criteria were utilized in various sections of this Report. The most extensive and illuminating account of their utilization is to be found in Chapter 9 in the section entitled "Evaluation of the Association Between Smoking and Lung Cancer". CAUSALITY Various meanings and conceptions of the term cause were discussed vigorously at a number of meetings of the Committee and its subcommit- tees. These debates took place usually after data and reports had been studied and evaluated, and at the times when critical scrutiny was being given to conclusions and to the wording of conclusive statements. In addi- tion, thoughts about causality in the realm of this inquiry were constantly and inevitably aroused in the minds of the members because they were preoccupied with the subject of their investigation-"Smoking and Health." Without summarizing the more important concepts of causality that have determined human attitudes and actions from the days even before t2ristotle, through the continuing era of observation and experiment. to the statistical certainties of the present atomic age. the point of view of the Committee with regard to causality and to the language used in this respect in this report may be stated briefly as follows: 1. The situation of smoking in relation to the health of mankind includes a host ( v-ariable man) and a complex agent (tobacco and its products, partic- 20 ularly those formed by combustion in smoking). The prohe of this inquirv is into the effect. or non-effect. of components of the agent upon the tissues. organs. and various qualities of the host which might: a\ improve his well- being. b I let him proceed normally. or c I injure his health in one way or another. To obtain information on these points the Committee did its best. with extensive aid. to examine all available sources of information in puhli- cations and reports and through consultation w-ith well informed persons. 2. When a relationship or an association between smoking. or other uses of tobacco, and some condition in the host was noted. the significance of the association was assessed. 3. The characterization of the assessment called for a specific term. The chief terms considered were "factor." "determinant." and "cause." The Committee agreed that Mhile a factor could he a source of variation. not all sources of variation are causes. It is recognized that often the coexistence of several factors is required for the occurrence of a disease. and that one of the factors may plav a determinant role. i.e.. without it the other factors I as genetic susceptibility 1 are impotent. Hormones in breast cancer can play such a determinant role. The word cause is the one in general usage in connection with matters considered in this study. and it is capable of convey- ing the notion of a significant, effectual. relationship between an agent and an associated disorder or disease in the host. 4. It should be said at once, however, that no member of this Committee used the word "cause" in an absolute sense in the area of this study. Although various disciplines and fields of scientific knowledge were repre- sented among the membership, all members shared a common conception of the multiple etiology of biological processes. No member was so naive as to insist upon mono-etiology in pathological processes or in vital phenom- ena. All were thoroughly aware of the fact that there are series of events in occurrences and developments in these fields. and that the end results are the net effect of many actions and counteractions. 5. Granted that these complexities were recognized, it is to he noted clearly that the Committee's considered decision to use the words "a cause," or "a major cause," or "a significant cause," or "a causal association" in certain conclusions about smoking and health affirms their conviction. 21 Chapter 4 Summaries and Conclusions Contents A. BACKGROUND _4ND HIGHLIGHTS .......... Kinds of Evidence .................. Evidence From the Combined Results of Prospective Studies . Other Findings of the Prospective Studies ...... Excess Mortality ................. Associations and Causality ............... The Effects of Smoking: Principal Findings Lung Cancer ... .... ..... : : : : : . . Chronic Bronchitis and Emphysema ......... Cardiovascular Diseases .............. Other Cancer Sites ................ The Tobacco Habit and Nicotine ........... The Committee's Judgment in Brief .......... B. COMMENTS AND DETAILED CONCLUSIONS .... (A Guide to Part II of the Report) Chemistry and Carcinogenicity of Tobacco and Tobacco Smoke . Characteriza&t bf.th.e ,Tdbacco Habit : : : : : : : : : : Pathology and Morphology ............... Mortality. ...................... Cancer by Site .................... Lung Cancer ................... Oral Cancer. ................... Cancer of the Larynx ............... Cancer of the Esophagus .............. Cancer of the Urinary Bladder ........... Stomach Cancer .................. Non-Neoplastic Res iratory Diseases, Particularly Chronic Bronchitis and Pu monary Emphysema P ........ Cardiovascular Disease ................. Other Conditions ................... Peptic Ulcer ................... Tobacco Amblyopia ................ Cirrhosis of the Liver ........... Maternal Smoking and infant Birth Weight ..... Smoking and Accidents .............. Morphological Constitution of Smokers ......... Psycho-Social Aspects of Smoking ............ List of Tables 1. Deaths from selected disease categories, United States, 1962 . 2. Expected and observed deaths for smokers of cigarettes only and mortality ratios in seven prospective studies . . . . . 24 Page 25 26 28 2 30 33: 31 E ;"3 33 33 34 34 ;; 37 37 37 i; 38 26 29 Chapter 4 This chapter is presented in two sections. Section A contains background information, the gist of the Committee's findings and conclusions on tobacco and health, and an assessment of the nature and magnitude of the health hazard. Section B presents all formal conclusions adopted by the Committee and selected comments abridged from the detailed Summaries that appear in each chapter of Part II of the Report. The full scope and depth of the Committee's inquiry may be comprehended only by study of the complete Report. A. BACKGROUND AND HIGHLIGHTS In previous studies, the use of tobacco. especially cigarette smoking, has been causally linked to several diseases. Such use has been associated with increased deaths from lung cancer and other diseases, notably coronary artery disease, chronic bronchitis, and emphysema. These widely reported findings, which have been the cause of much public concern over the past decade, have been accepted in many countries by official health agencies, medical associations, and voluntary health organizations. The potential hazard is great because these diseases are major causes of death and disability. In 1962, over 500,000 people in the United States died of arteriosclerotic heart disease (principally coronary artery disease), 41,000 died of lung cancer, and 15,000 died of bronchitis and emphysema. The numbers of deaths in some important disease categories that have been reported to have a relationship with tobacco use are shown in Table 1. This table presents one aspect of the size of the potential hazard; the degree of association with the use of tobacco will be discussed later. Another cause for concern is that deaths from some of these diseases have been increasing with great rapidity over the past few decades. Lung cancer deaths, less than 3,000 in 1930, increased to 18,000 in 1950. In the short period since 1955, deaths from lung cancer rose from less than 27,OOO to the 1962 total of 41,000. This extraordinary rise has not been recorded for cancer of any other site. While part of the rising trend for lung cancer is attributable to improvements in diagnosis and the changing age-composition and size of the population, the evidence leaves little doubt that a true increase in lung cancer has taken place. Deaths from arteriosclerotic, coronary, and degenerative heart disease rose from 273,000 in 194.0, to 3%,000 in 1950, and to 578,000 in 1962. Reported deaths from chronic bronchitis and emphysema rose from 2,300 in 1945 to 15,000 in 1962. The changing patterns and extent of tobacco use are a pertinent aspect of the tobacco-health problem. 25