The Pathology of Smoking

Our plain-English summary of The Pathology of Smoking, by G.W.H. Schepers (1981).

The study

• Author: G.W.H. Schepers
• Published: August 28th 1981
• Our copy: from Johns-Manville's own medical library. The article is still under copyright, so we describe it here rather than post it.

In plain English

This document is a narrative review summarizing evidence on the harmful effects of smoking from vital statistics, analyses of smoke components, and experimental research. It did not report a new study, and its tables do not name their sources. The author presented mortality ratios comparing cigarette smokers with non-smokers, including 10.8 for lung cancer, 5.4 for laryngeal cancer and 6.1 for bronchitis and emphysema. A table on 1146 U.S. veterans with lung cancer gave a ratio of 15.4 for epidermoid carcinoma in cigarette smokers. The author noted that some of these figures include cancers caused by factors other than smoking. A table of environmentally induced lung cancer listed crocidolite and amosite asbestos as probable carcinogens, and chrysotile, anthophyllite and tremolite as suspected carcinogens. It noted that the table referred only to direct carcinogenesis, not to cancer caused indirectly. Asbestos was not otherwise discussed. The review also covered coronary artery disease, peptic ulcer, and animal experiments using smoking machines. The author's summary statement was that smoking, together with various environmental agents, can be a significant additional factor in cancer, emphysema, bronchitis, cardiovascular disease and upper gastrointestinal ulceration.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Narrative review of the pathology of smoking (no original study; tables given without cited sources)
• Who was studied: No study population of its own. The review drew on vital statistics, studies of smoke components, and experimental research in humans and animals. One table concerns 1146 U.S. veterans with lung cancer.
• Exposure: Tobacco smoke, especially cigarette smoke, compared with pipes and cigars. A table of environmental lung carcinogens listed crocidolite and amosite asbestos as probable carcinogens, and chrysotile, anthophyllite and tremolite asbestos as suspected carcinogens. The table refers only to direct carcinogenesis.
• Main results:
  • The mortality ratio for cigarette smokers compared with non-smokers was 10.8 for lung cancer. It was 5.4 for cancer of the larynx, 4.1 for the mouth and 3.4 for the esophagus.
  • The author estimated that, after allowing for other causes, the excess lung cancer ratio due purely to cigarette carcinogens was probably three times the background rate. For the larynx, the estimate was about twice the background rate.
  • Among 1146 U.S. veterans with lung cancer, the mortality ratios relative to non-smokers for epidermoid carcinoma were 15.4 for cigarette smokers and 2.2 for pipe or cigar smokers. For adenocarcinoma, they were 5.1 for cigarette smokers and 0.6 for pipe or cigar smokers.
  • Stopping smoking was presented as improving survival in proportion to years of abstinence. The mortality ratio was 2.28 for less than 1 year of abstinence and 1.16 for more than 10 years.
  • In a table of pulmonary impairment by occupation, prevalence was higher in smokers than in non-smokers in every group listed. For example, among steel workers it was 51.0% in smokers and 2.0% in non-smokers.
  • The mortality ratio for bronchitis and emphysema in cigarette smokers was given as 6.1.
  • Estimated annual excess deaths in the U.S.A. were about 35,700 from lung cancer. For coronary heart disease, with a mortality ratio of 1.7, the estimate was 441,000.
  • For gastric and duodenal ulcer combined, peptic ulcer deaths in smokers were 333 observed against 117 expected, a ratio of 3.8.
  • In animal smoking-machine experiments, cigarette smoke produced practically all the changes reported in human smokers except stomatitis nicotina.
• The authors' conclusion: The author concluded that the statistical evidence strongly suggests that smoking, together with various environmental agents, can be a significant additional factor in the development of cancer, emphysema, bronchitis, cardiovascular disease and upper gastrointestinal ulceration.
• Limitations the authors state:
  • The adverse effects of smoking are difficult to separate from the effects of other environmental agents and certain diseases.
  • The cancer mortality ratios include cancers caused by factors other than cigarette smoking.
  • The table classifying environmental lung carcinogens, including the asbestos fibers, refers only to direct carcinogenesis. It does not address the capacity of these substances to cause cancer indirectly.
  • Death certificates do not always list lung disease as the main cause of death, so emphysema figures may be understated.
  • The cardiovascular and digestive tract lesions seen in human smokers had not yet been satisfactorily shown in animals.

Topics

Medical terms in this study, explained in our Lexicon: Pathology, Lung Cancer, Laryngeal Cancer, Emphysema, Carcinoma, Crocidolite, Amosite, Chrysotile.

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