Relative importance of cigarette smoking in occupational lung disease

Our plain-English summary of Relative importance of cigarette smoking in occupational lung disease, by P.C. Elmes (British Journal of Industrial Medicine, 1981).

The study

• Author: P.C. Elmes
• Journal: British Journal of Industrial Medicine
• Published: 1981;38(1):1-13
• Cited by: 38 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 000733).

Abstract

Since 1900 respiratory disease has remained a constant serious cause of chronic ill health and premature death in Britain. The falling importance of tuberculosis and pneumonia has been off-set by the rise in lung cancer. Bronchitis morbidity and mortality have fallen only slightly since 1935. To produce any real improvement in the future existing information as to cause must be studied. The relative contribution of occupational exposure is compared with the importance of cigarette smoking. Relevant information is scanty and has been produced to emphasise the existence of occupational diseases rather than assess their importance to the community as whole. In Britain the evidence is that within the coal mining and iron and steel industries conditions are now such that dust exposure contributes little to the morbidity or mortality compared with the workers' smoking habits. Similar results have been shown by a cross-sectional survey of many dusty occupations in Western Germany. Only in the disappearing Welsh slate industry has dust disease been at least as important as smoking. Until the current regulations were introduced conditions existed among asbestos workers such that the combined effect of cigarette smoking and dust exposure led to a loss of life expectation of over 10 years in moderate smokers. Since the new regulations were introduced the risk for asbestos workers should approximate to that for other industrial workers. While control of occupational exposure to respiratory hazards remains important, a far greater improvement to respiratory health would be produced by controlling tobacco smoking.

In plain English

This article is the text of a 1979 lecture in which the author reviewed evidence on whether workplace dust or cigarette smoking contributed more to lung disease in coal miners, iron and steel workers, slate workers and asbestos workers. In a cohort of 162 Belfast insulation workers, half of the comparison population had died by age 72 but half of the insulators by 61, an average loss of 11 years. The loss was 19 years for the heaviest smokers, 11 for moderate smokers and 10 for light smokers, while non-, ex- and pipe smokers roughly matched the comparison population. From an American study of insulation workers, the author read the figures as about a 10-fold lung cancer risk for smoking alone, about five-fold for asbestos in non-smokers, and 53-fold for both. The author concluded that in some of the most heavily exposed asbestos groups before current regulations, asbestos and smoking carried about equal overall risk. Outside the slate industry, the author concluded, smoking was the dominant cause of respiratory disability and premature death. The author called the evidence scanty and often unreliable.

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, given as a named lecture, of published and unpublished studies comparing occupational dust exposure with cigarette smoking as causes of lung disease
• Who was studied: Mainly British working populations as reported in other studies: coal miners, iron and steel (foundry) workers, North Wales slate workers and asbestos workers. Asbestos groups included Belfast insulation workers, American insulation workers, an English asbestos textile factory, Plymouth dockyard workers, and about 500 asbestos workers in a German cross-sectional survey.
• Exposure: Workplace dusts (coal, foundry/steel, slate and asbestos dust) compared with cigarette smoking. The asbestos section also notes crocidolite and amosite in connection with mesothelioma, as background from other work.
• Main results:
  • Belfast insulation workers (162 men, compared with men of the same age and social class in Northern Ireland): the age by which half had died was 72 for the comparison population and 61 for all the insulators, an average loss of life expectation of 11 years.
  • Belfast insulation workers by smoking habit: the age by which half had died was 53 for the heaviest smokers (loss of 19 years), 61 for moderate smokers (loss of 11 years), 62 for light smokers (loss of 10 years) and 66 for non-, ex- and pipe smokers.
  • Over the whole survival curve, the author found that the non-, ex- and pipe smokers among the Belfast insulators roughly matched the comparison population. The author took this to indicate that asbestos alone carried about the same risk to life expectancy as smoking in Belfast. By indirect calculation, the author estimated a loss of three to four years of life expectation for each alone.
  • In the Belfast cohort, the ratio of observed to expected primary lung cancer deaths fell from 20:1 to less than 3:1 between 1950-4 and 1970-4. Over the same period the mean age at death rose from 55 to 66.
  • American insulation workers compared with a selected control group (study by Hammond, Selikoff and Seidman): the author read the figures as about a 10-fold lung cancer risk for smoking alone and about five-fold for asbestos in non-smokers. The combined risk was 53-fold (mortality ratio 53.24 in the table). The author judged that smoking was likely twice as important as asbestos for lung cancer in this group.
  • In other researchers' analyses of an asbestos textile mill and Plymouth dockyard workers, early signs of asbestosis were more common in smokers than in non-smokers. Advanced (certifiable) asbestosis was also more common in smokers. In the textile factory table, certified asbestosis was found in 0% of 55 non/light smokers, 7% of 116 medium/heavy smokers and 8% of 24 ex-smokers.
  • In the German study of about 500 asbestos workers, bronchitic symptoms were seen in smokers with high dust exposure but not in non-smokers.
  • The author stated that smoking contributes to asbestos-related lung cancer and lung fibrosis but not to mesothelioma.
• The authors' conclusion: The author concluded that in some groups most heavily exposed before the current regulations, the overall risk from asbestos was approximately equal to the overall risk from smoking. Only in the slate industry did dust exceed smoking in importance. In all the other situations reviewed, smoking was the dominant cause of respiratory symptoms, disability and premature death.
• Limitations the authors state:
  • The author described the evidence reviewed as scanty and in many instances unreliable.
  • Measurements of past asbestos exposure were not very meaningful, which made it difficult to compare the risks of asbestos with those of smoking.
  • The Belfast cohort was small, and smoking history was not available for all of its members.
  • Too few non-smokers in the British asbestos worker data meant that the fit to a multiplicative model for lung cancer could only be tentative.

Topics

Medical terms in this study, explained in our Lexicon: Occupational Lung Disease, Lung Cancer, Occupational Exposure, Occupational Disease, Habit.

Related studies

• Cigarette smoking and small irregular opacities — W. Weiss (1991)
• The effect of cigarette smoking on the detection of small radiographic opacities in inorganic dust diseases — P.D. Blanc, G. Gamsu (1988)
• Asbestos exposure, cigarette smoking and death rates — E.C. Hammond, I.J. Selikoff, et al. (1979)
• Influence of cigarette smoking on bronchoalveolar lavage cellularity in asbestos-induced lung disease — D.A. Schwartz, J.R. Galvin, et al. (1992)
• Association of cigarette smoking and asbestos exposure with location and histology of lung cancer — B.W. Lee, J.C. Wain, et al. (1998)
• Cigarette smoking, asbestos, and pulmonary fibrosis — W. Weiss (1971)

Browse more research in British Journal of Industrial Medicine, or return to medical research.