Relation Of Cigarette Smoking To Risk Of Death Of Asbestos-Associated Disease Among Insulation Workers In The United States

Our plain-English summary of Relation Of Cigarette Smoking To Risk Of Death Of Asbestos-Associated Disease Among Insulation Workers In The United States, by E.C. Hammond, I.J. Selikoff (1973).

The study

• Authors: E.C. Hammond, I.J. Selikoff
• Published: Biological Effects Of Asbestos (J.C. Wagner, Editor), Lyon: Iarc Scientific Publications, Volume 8, Pp. 312-317 (1973)
• Type of article: Conference paper
• Our copy: from Johns-Manville's own medical library, J-M no. 001304. The article is still under copyright, so we describe it here rather than post it.

In plain English

Hammond and Selikoff followed two groups of asbestos insulation workers to examine smoking and asbestos-associated deaths. Among 370 New York-area union members followed 1963 to 1971, 41 of 283 regular cigarette smokers died of lung cancer, versus 1 of 87 non-cigarette smokers. Among 17,800 US and Canadian members followed 1967 to 1971, 213 of 1,092 deaths were from lung cancer. Only 44.4 were expected from US white male rates, which ignored smoking because smoking-specific rates were unavailable. Among 9,590 cigarette smokers, 134 of 596 deaths were from lung cancer; among 2,066 non-cigarette smokers, 2 of 73 deaths were. Asbestosis caused 45 of the smokers' deaths and 4 of the non-smokers'. Expected asbestosis deaths were computed from the study population's own rates. On that basis the observed-to-expected ratio was almost three times higher in smokers, of borderline statistical significance. The authors concluded that insulation work greatly increases smokers' lung cancer risk and that any effect in non-smokers is uncertain. They added that dust exposure would still need reducing below concentrations associated with asbestosis even if workers stopped smoking.

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: Prospective follow-up (cohort) study of two groups of insulation workers, comparing observed deaths with expected numbers
• Who was studied: Cohort 1: 370 insulation workers from New York-area union locals, followed from 1 January 1963 to 31 December 1971 (283 regular cigarette smokers, 87 not). Cohort 2: 17,800 members of the insulation workers' union in the United States and Canada on 1 January 1967, followed through 31 December 1971. Of these, 9,590 had a history of regular cigarette smoking and 2,066 had no history of cigarette smoking (including 609 pipe or cigar smokers). Smoking history was not known for 6,144.
• Exposure: Asbestos dust exposure through work as asbestos insulation workers (union membership), together with cigarette smoking history from a questionnaire. The article does not name specific fiber types.
• Main results:
  • Cohort 1 (370 New York-area men), 1963 to 1971: 41 of 283 regular cigarette smokers died of lung cancer. Of the 87 men who did not smoke cigarettes regularly, 1 died of lung cancer, and he was a cigar smoker.
  • Cohort 2 (17,800 men), 1967 to 1971: there were 1,092 deaths in total, 213 of them from lung cancer. Only 44.4 were expected from US white male rates.
  • Cohort 2, 9,590 men with a history of regular cigarette smoking: 596 deaths, 134 of them from lung cancer
  • Cohort 2, 2,066 non-cigarette smokers: 73 deaths, 2 of them from lung cancer (one a cigar and pipe smoker, one who never smoked regularly)
  • Cohort 2: 26 deaths from pleural mesothelioma. Of these men, 17 had a history of regular cigarette smoking, 1 was a pipe smoker, 1 never smoked regularly, and 7 had unknown smoking habits.
  • Cohort 2: 51 deaths from peritoneal mesothelioma. Of these, 9 were among the 2,066 non-cigarette smokers, 29 among the 9,590 cigarette smokers, and 13 among the 6,144 with unknown smoking history. The authors said this suggests cigarette smoking does not increase the already high risk of peritoneal mesothelioma.
  • Cohort 2, asbestosis: 4 of the 73 deaths among non-smokers and 45 of the 596 deaths among smokers. Expected asbestosis deaths were computed from age-specific death rates for the total study population, disregarding smoking.
  • Cohort 2: the ratio of observed to expected asbestosis deaths was almost three times as high for men with a history of cigarette smoking as for men without one. The authors described this as of borderline statistical significance.
  • Cohort 2, all men: 16 observed versus 6.62 expected deaths from stomach cancer, 26 observed versus 17.51 expected from colon-rectum cancer, and 13 observed versus 3.21 expected from oesophageal cancer
• The authors' conclusion: The authors concluded that asbestos insulation work greatly increases the lung cancer risk of cigarette smokers, and that it is uncertain whether it increases lung cancer risk among non-smokers. They concluded that smoking may also increase the risk of death from asbestosis, to a much lesser extent. Because non-smoking insulation workers had a greater risk of death from asbestosis than from lung cancer, the authors said dust exposure would still need to be reduced below concentrations associated with asbestosis even if workers stopped smoking.
• Limitations the authors state:
  • Smoking-specific expected and observed rates could not be calculated, because smoking-related death rates for individuals were not yet available for the period. The comparisons with US white male rates therefore disregard smoking.
  • The numbers of pleural mesothelioma deaths were too small for definite conclusions about smoking
  • There were too few stomach, colon-rectum and oesophageal cancer deaths among non-smokers to draw conclusions about interaction between smoking and asbestos
  • Asbestosis deaths in smokers likely reflect a mixture of effects, including smoking-related emphysema, bronchitis and fibrosis

Topics

Medical terms in this study, explained in our Lexicon: Insulator, Lung Cancer, Statistical Significance.

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