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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 such a presentation. This Part includes: (a) an introduction comprising, among other items, a chronology especially pertinent to the subject of this study and to the establishment and activities of the Committee, (b) a short account of how the study was conducted. (c) the chief criteria used in making judgments, and (d) a brief overview of the entire Report.

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 differing 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 pleasurable and reputed medicinal actions. At the same time, smoking was condemned 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 increasing 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 proportionately. 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 sixty-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 cardiovascular diseases in general; coronary artery disease in particular), and to the non-cancerous (non-neoplastic) diseases of the lower respiratory tract especially chronic bronchitis and emphysema), The next important basic date for starting comparisons is 1930, when the definite trends in mortality and disease-incidence considered in this Report became more conspicuous. Since then a great variety of investigations have been carried out. Many of the chemical 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 Rh