Interaction of asbestos, age, and cigarette smoking in producing radiographic evidence of diffuse pulmonary fibrosis

Our plain-English summary of Interaction of asbestos, age, and cigarette smoking in producing radiographic evidence of diffuse pulmonary fibrosis, by K.H. Kilburn, R. Lilis, H.A. Anderson, et al (The American Journal of Medicine, 1986).

The study

• Authors: K.H. Kilburn, R. Lilis, H.A. Anderson, A. Miller, R.H. Warshaw
• Journal: The American Journal of Medicine
• Published: 1986;80(3):377-81
• Cited by: 66 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. 000408).

Abstract

The study of 3,472 chest x-rays from four populations with different levels of exposure to asbestos and with different cigarette smoking histories shows that smoking in the general population does not produce pulmonary fibrosis recognizable on chest radiography. In the general population of Michigan, the prevalence of a radiographic pattern of fibrosis was 0.5 percent in men and 0.0 percent in women. In a Long Beach, California census tract population, the prevalences were 3.7 percent for men and 0.6 percent for women. Similarly, cigarette smoking does not enhance fibrosis when the exposure to asbestos has been as light as that in households of shipyard workers. Asbestosis was recognized in 6.6 percent of 137 shipyard workers' wives who have never smoked and 7.6 percent of 132 who had ever smoked. Cigarette smoking and asbestos appear to be synergistic in those occupationally exposed to asbestos (as insulators), since 7.2 percent of 97 nonsmokers and 20.5 percent of 316 ever-smokers showed fibrosis. This apparent synergy was also found in shipyard workers up to age 70 with 31 percent of nonsmokers and 43.3 percent of ever-smokers having fibrosis. There were increases of approximately 10 percent in the prevalence of fibrosis in cigarette smokers and nonsmokers for each decade after age 40.

In plain English

This study compared chest X-rays of 3,472 adults in four U.S. groups to see how asbestos exposure, smoking and age related to signs of diffuse lung scarring (pulmonary fibrosis). Among randomly sampled Michigan residents, 0.5 percent of men and none of 583 women had fibrosis. A Long Beach, California census tract showed 3.7 percent in men and 0.6 percent in women. Among 269 shipyard workers' wives, exposed only at home, 6.6 percent of never-smokers and 7.6 percent of ever-smokers had fibrosis, not a significant difference. Among 419 insulators, fibrosis appeared in 7.2 percent of nonsmokers, 22.1 percent of ex-smokers and 19.4 percent of current smokers, though smokers were older. Among 260 shipyard workers, 31 percent of nonsmokers versus 40.5 percent of ever-smokers (43.3 percent in the article's table) had fibrosis, a significant difference. In shipyard workers of both smoking groups, prevalence rose about 10 percent per decade, which the authors linked to longer time since first exposure plus accumulated exposure. The authors concluded that smoking alone did not produce detectable fibrosis in a general population, nor enhance it after light household asbestos exposure.

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: Cross-sectional comparison of chest X-ray findings (prevalence of fibrosis) across four populations. Films were read using the International Labour Organization 1980 classification. A film counted as positive when irregular opacities were graded at profusion 1/0 or greater by at least two readers.
• Who was studied: 3,472 adults in four groups: 1,177 adults in a stratified random sample of Michigan residents (1978); 1,347 adults in a Long Beach, California census tract (1976); 419 male midwestern insulators from six union locals in Ohio and Michigan (1977); and 260 white male shipyard workers plus 269 of their wives from the Los Angeles Harbor area (1981).
• Exposure: Asbestos exposure (fiber types not named) at different levels. The insulators were occupationally exposed. The shipyard workers were 20 or more years from first shipyard employment. The wives had household exposure only, from asbestos brought home by their husbands. Cigarette smoking was grouped as never versus ever smoked (and for insulators as nonsmokers, ex-smokers and current smokers). Age or birth decade was also examined. In Long Beach, 12 men and 2 women with clear occupational asbestos exposure were removed.
• Main results:
  • Michigan general population sample: 3 of 584 men (0.5 percent) and 0 of 583 women had diffuse pulmonary fibrosis. The table gives the denominator for men as 594.
  • Long Beach census tract: fibrosis prevalence was 0.6 percent in women and 3.7 percent in men (table: 4 of 674 women, 25 of 673 men).
  • Wives of shipyard workers: fibrosis in 6.6 percent of the 137 never-smokers (9 of 137) and 7.6 percent of the 132 ever-smokers (10 of 132).
  • Wives of shipyard workers: there was no significant difference in fibrosis prevalence between smokers and nonsmokers.
  • Midwestern insulators: 7 of 97 nonsmokers (7.2 percent, mean age 40) had asbestosis. So did 29 of 131 ex-smokers (22.1 percent, mean age 44, risk ratio 3.1) and 37 of 191 current smokers (19.4 percent, mean age 48.2, risk ratio 2.7).
  • Midwestern insulators: fibrosis was found in 22.1 percent of ex-smokers and 19.4 percent of current smokers; the authors described this as more than twice the prevalence in nonsmokers.
  • Male shipyard workers: the text gives fibrosis in 31 percent of nonsmokers and 40.5 percent of ever-smokers, and the difference was significant (p less than 0.05). Table III gives 14 of 45 (31.0 percent) and 93 of 215 (43.3 percent), a risk ratio of 1.4.
  • Shipyard workers by birth decade, ever-smokers compared with never-smokers: the ratio was 1.6 to 1 for those born 1911 to 1920 and 1921 to 1930. It was 2.2 to 1 for those born 1931 to 1940. It was 0.84 for the oldest group (born 1896 to 1910: 71.4 percent of never-smokers versus 60.0 percent of ever-smokers).
  • Shipyard workers: the authors linked a longer time since first exposure (together with more years of exposure) to a rise in asbestosis prevalence of about 10 percent per decade, in both smokers and nonsmokers.
• The authors' conclusion: The authors concluded that cigarette smoking by itself does not produce detectable diffuse pulmonary fibrosis in a general population. They also concluded that with relatively light household asbestos exposure, smoking does not enhance fibrosis. They further concluded that smoking insulators and smoking shipyard workers showed more fibrosis than nonsmokers, which they described as an additive effect of smoking and asbestos.
• Limitations the authors state:
  • Among insulators, ex-smokers and current smokers were older than nonsmokers and had more years since first exposure, so the risk ratios should be interpreted with caution.
  • The higher prevalence in nonsmokers in the oldest shipyard group may be due to chance because the numbers were small.
  • The oldest shipyard group may reflect survivors, because nonsmokers may be more likely to survive into that age group.
  • The evidence was inadequate to prove the idea that, given more time, nonsmokers may reach the same asbestosis prevalence as smokers.
  • Occupational histories for the Long Beach population were less detailed than those for the Michigan population.
  • Pleural disease was coded by the readers but was not considered in this report.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestosis.

Medical terms in this study, explained in our Lexicon: Pulmonary Fibrosis, Chest X-Ray, Fibrosis, Insulator.

Related studies

• 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)
• Cigarette smoking does not produce or enhance the radiologic appearance of pulmonary fibrosis — K.H. Kilburn (1981)
• Cigarette smoking, asbestos, and pulmonary fibrosis — W. Weiss (1971)
• Radiographic abnormalities in asbestos insulators: effects of duration from onset of exposure and smoking. Relationships of dyspnea with parenchymal and pleural fibrosis — R. Lilis, A. Miller, et al. (1991)
• Radiographic evidence of pulmonary fibrosis and possible etiologic factors at a nickel refinery in Norway — S.R. Berge, K. Skyberg (2003)
• Smoking-associated fibrosis and pulmonary asbestosis — J.R. Bledsoe, D.C. Christiani, et al. (2015)

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