Asbestos exposure, cigarette smoking and death rates

Our plain-English summary of Asbestos exposure, cigarette smoking and death rates, by E.C. Hammond, I.J. Selikoff, H. Seidman (Annals of the New York Academy of Sciences, 1979).

The study

• Authors: E.C. Hammond, I.J. Selikoff, H. Seidman
• Journal: Annals of the New York Academy of Sciences
• Published: 1979;330:473-90
• Cited by: 275 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 001027).

Summary of the article

The study examined the combined effects of cigarette smoking and occupational asbestos exposure on death rates. Members of the insulation workers' union in the United States and Canada answered smoking questionnaires in 1966, and 17,800 men alive on January 1, 1967 were traced through December 31, 1976. The analysis was confined to 12,051 men observed 20 or more years after entering the trade (77,391 man-years, 1,946 deaths). Causes of death were coded from death certificates and from the best available medical evidence, including review of histologic slides and x-rays. Expected deaths were based on U.S. white male rates and on age- and smoking-specific rates of 73,763 comparable men from an American Cancer Society prospective study. All-cause mortality ratios were 1.70 and 1.41. Lung cancer ratios ranged from 4.24 to 5.51. Best evidence identified 170 mesothelioma deaths (61 pleural, 109 peritoneal) and 160 asbestosis deaths. Age-standardized lung cancer death rates per 100,000 man-years were 11.3 for unexposed nonsmokers, 58.4 for asbestos-exposed nonsmokers, 122.6 for unexposed smokers and 601.6 for asbestos-exposed smokers. The authors concluded that asbestos and smoking acted synergistically on lung cancer risk. They also concluded that smoking increased asbestosis deaths, that ex-smokers had lower death rates than continuing smokers, and that asbestos increased deaths from colorectal and esophageal cancer.

PubMed has no abstract for this study, and the article doesn't print one. We wrote this summary from the full article with the help of AI. It is not the authors' wording.

In plain English

This study followed 17,800 members of the International Association of Heat and Frost Insulators and Asbestos Workers in the United States and Canada from 1967 through 1976. The report covered 12,051 men observed 20 or more years after entering the trade, among whom 1,946 died. Expected deaths were based on age- and smoking-specific death rates of control-group men from an American Cancer Society study, and on U.S. white male death rates. Total death rates were raised in the workers (mortality ratio 1.70 against the control group, 1.41 against U.S. white males). Lung cancer mortality ratios ranged from 4.24 to 5.51. Based on the best available medical evidence, 61 men died of pleural mesothelioma, 109 of peritoneal mesothelioma and 160 of asbestosis. Compared with control-group men without asbestos exposure who had never smoked regularly, lung cancer death rates were 5.17 times as high in insulation workers who had never smoked regularly; the authors cautioned that a closely related estimate rested on small numbers. They were 53.24 times as high in insulation workers who smoked cigarettes. The authors concluded that asbestos dust and cigarette smoking had a strong synergistic effect on lung cancer risk.

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: Cohort mortality study of union members traced from 1967 through 1976. Observed deaths were compared with expected numbers based on age- and smoking-specific death rates of a control group from an American Cancer Society prospective study, and on death rates of all U.S. white males.
• Who was studied: Members of the International Association of Heat and Frost Insulators and Asbestos Workers in the United States and Canada. 17,800 men were alive on January 1, 1967. The analysis was confined to the 12,051 men who were, or became, 20 or more years past entering the trade during 1967 to 1976 (77,391 man-years, 1,946 deaths). The control group was 73,763 white, non-farmer men with no more than a high school education and a history of occupational exposure to dust, fumes, vapors, gases, chemicals or radiation, from the American Cancer Society prospective study.
• Exposure: Insulation work with materials that mostly contained asbestos; the article does not name fiber types. Cigarette, pipe and cigar smoking were recorded by questionnaire in 1966.
• Main results:
  • Deaths from all causes among the workers: mortality ratio 1.70 compared with the control group and 1.41 compared with U.S. white males.
  • Lung cancer among the workers: mortality ratios ranged from 4.24 (versus U.S. white males, death certificate causes) to 5.51 (versus the control group, best-evidence causes).
  • By best available evidence, 61 workers died of pleural mesothelioma and 109 of peritoneal mesothelioma. Death certificates recorded 101 mesothelioma deaths.
  • Asbestosis was the underlying cause of death for 76 workers according to death certificates and 160 according to best evidence.
  • Of 46 deaths attributed on death certificates to cancer of the pancreas, review found 15 were actually due to peritoneal mesothelioma.
  • Using better evidence, the authors said pancreatic cancer death rates may be slightly elevated in the workers, but this was far from certain.
  • Cancer of the esophagus among the workers: mortality ratios ranged from 2.64 to 3.34. The mortality differences were reported as statistically significant.
  • Colon-rectum cancer among the workers: mortality ratios ranged from 1.59 to 1.81. The differences were statistically significant (p less than 0.05).
  • Kidney cancer among the workers: mortality ratios ranged from 1.76 (versus the control group, death certificates) to 2.30 (versus U.S. white males, best evidence). Two of the four mortality differences were statistically significant.
  • Stomach cancer among the workers: mortality ratios ranged from 1.42 to 1.68. The differences were not statistically significant.
  • Bladder cancer: very few workers died of it, and the authors saw no indication of increased risk.
  • Of 8,220 workers who answered the 1966 questionnaire, 6,841 (83%) were current or former cigarette smokers.
  • Within the workers, current smokers of 20 or more cigarettes a day had a lung cancer mortality ratio of 10.40 relative to workers who never smoked regularly.
  • Within the workers, for all causes of death relative to men who never smoked regularly, the ratio was 1.98 for current smokers of 20 or more cigarettes a day. Former heavy smokers who had quit for 10 or more years had a ratio of 1.38.
  • Within the workers, the asbestosis death rate of current smokers of 20 or more cigarettes a day was 2.8 times that of workers who never smoked regularly.
  • Among workers who never smoked cigarettes regularly, there were 8 observed and 8 expected deaths from pleural mesothelioma. The authors judged that cigarette smoking had little or no effect on pleural mesothelioma death rates.
  • Lung cancer by death certificate, compared with control-group men who never smoked regularly: workers who never smoked regularly had a mortality ratio of 5.33 (4 observed versus 0.7 expected). Workers currently smoking 20 or more cigarettes a day had 87.36 (152 observed versus 1.7 expected).
  • Age-standardized lung cancer death rates per 100,000 man-years were 11.3 for control-group men who never smoked regularly. Mortality ratios relative to that group were 5.17 for workers who never smoked regularly and 10.85 for control-group cigarette smokers. In this comparison, never smoked regularly meant no regular smoking, and pipe- or cigar-only smokers were excluded.
  • Workers with a history of cigarette smoking had a lung cancer death rate of 601.6 per 100,000 man-years (mortality ratio 53.24). The authors estimated about 169.7 would be expected if the two exposures acted independently.
• The authors' conclusion: The authors concluded that the study's evidence indicates a strong synergistic effect of asbestos dust and cigarette smoking on lung cancer risk.
• Limitations the authors state:
  • Only one group of asbestos workers, members of the insulation workers union, was studied.
  • For the control group, additional medical information on cause of death could not be requested after 1965 because of the large number of deaths.
  • Control group death rates were known only through September 1972 and were extrapolated to cover the workers' follow-up through 1976.
  • Using death certificate causes overestimates the association with pancreatic cancer and underestimates the impact of mesothelioma and asbestosis.
  • Mesothelioma death rates were not available for the control group or U.S. white males, so mortality ratios could not be computed.
  • The lung cancer mortality ratio of 5.33 for workers who never smoked regularly was based on small numbers. The authors said it is subject to considerable sampling variation and could be as high as 12.00 or a little higher.
  • Small numbers prevented identifying which, if any, other specific cancer sites were involved.
  • The authors did not expect the exact figures to be duplicated in other groups of asbestos workers, which differ in smoking, time since exposure and dust inhaled.

Topics

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, Insulator, Death Certificate, Lung Cancer, Mesothelioma, Esophageal Cancer.

Related studies

• Effects of asbestos and smoking on the levels and rates of change of lung function in a crocidolite exposed cohort in Western Australia — H.S. Alfonso, L. Fritschi, et al. (2004)
• Relative importance of cigarette smoking in occupational lung disease — P.C. Elmes (1981)
• Cigarette smoking and small irregular opacities — W. Weiss (1991)
• Spirometric impairments in long-term insulators. Relationships to duration of exposure, smoking, and radiographic abnormalities — A. Miller, R. Lilis, et al. (1994)
• Asbestosis: interstitial pulmonary fibrosis and pleural fibrosis in a cohort of asbestos insulation workers: influence of cigarette smoking — R. Lilis, I.J. Selikoff, et al. (1986)
• Clinical findings among asbestos workers in U.S.: influence of cigarette smoking — Y. Lerman, I.J. Selikoff, et al. (1986)

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