Association of asbestos and bronchogenic carcinoma in a population with low asbestos exposure

Our plain-English summary of Association of asbestos and bronchogenic carcinoma in a population with low asbestos exposure, by M.L. Warnock, A.M. Churg (Cancer, 1975).

The study

• Authors: M.L. Warnock, A.M. Churg
• Journal: Cancer
• Published: 1975;35(4):1236-42
• Cited by: 54 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. 002339).

Abstract

Quantitative counts of ferruginous bodies were performed on digests of lungs from 100 control and 30 lung cancer patients. It was found that the lung cancer group had significantly higher levels, although only 1 patient was known to be occupationally exposed to asbestos. It is suggested that even extremely low levels of asbestos exposure may have a carcinogenic effect.

In plain English

This autopsy study from the Department of Pathology at the University of Chicago counted ferruginous bodies in digested lung tissue. Ferruginous bodies are coated fibers seen under a light microscope, and the authors noted that not all of them necessarily have an asbestos core. The authors compared 100 adults who died without lung cancer with 30 lung cancer patients. Only one of the cancer patients had a known history of occupational asbestos exposure. Among the controls, 5 of 100 had more than 50 bodies per gram of lung, including two arc welders and a cement finisher. Among the cancer patients, 8 (27%) had more than 50 per gram. This difference was statistically significant. It remained significant when only patients aged 50 and over were compared: 4 of 64 controls versus 8 of 26 cancer patients. Electron microscopy found fibers with the appearance of chrysotile in every cancer case above 50 bodies per gram, and none in five low-count cases. The authors suggested that even extremely low asbestos exposure may have a carcinogenic effect. They cautioned that their data were limited and the 50-per-gram cutoff was arbitrary.

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: Autopsy study comparing lung ferruginous body counts in controls (collected prospectively) and lung cancer patients (partly prospective, partly retrospective from autopsy files), with electron microscopy on selected cases
• Who was studied: 100 autopsied adults over 20 without lung cancer (51 females, 49 males) and 30 autopsied lung cancer patients (9 from the prospective series, 21 retrieved retrospectively from autopsy files), University of Chicago local autopsy population; study years not stated
• Exposure: Asbestos in the lung, measured as ferruginous bodies per gram of wet lung tissue by light microscopy; fiber type examined by electron microscopy and electron diffraction (chrysotile found). Only one cancer patient had known occupational asbestos exposure.
• Main results:
  • Controls: 61% had fewer than 10 bodies/g; 5 of 100 had more than 50 bodies/g (range 64-3800)
  • Of the 5 high-count controls, two were arc welders (3800 and 2200 bodies/g) and one a cement finisher (2400 bodies/g); the authors considered these three occupationally exposed
  • Lung cancer patients: 8 of 30 (27%; 1 female, 7 males) had more than 50 bodies/g
  • Comparing 27% of cancer patients with 5% of controls above 50 bodies/g gave a chi-square of 9.75, significant at the 0.005 level
  • Among patients aged 50 and over, 4 of 64 controls and 8 of 26 cancer patients had counts greater than 50/g (corrected chi-square 7.61, significant at the 0.01 level)
  • Fibers with the typical appearance of chrysotile were identified in every cancer case with more than 50 bodies/g; none were found in five patients with 0-10 bodies/g or in blank filters; fibers large enough for diffraction showed the chrysotile pattern
  • The one cancer patient with known occupational asbestos exposure (shipyards during World War II) was in the intermediate 11-50 bodies/g group
  • Of the 8 high-count cancer patients, half were known smokers, one was a nonsmoker, and smoking history was unknown in 3
  • 38% of cancers in high-count patients were in the lower lobes, versus 17% in low-count patients
• The authors' conclusion: The authors suggested that even extremely low levels of asbestos exposure may have a carcinogenic effect, while noting their impression that body counts in the high-count cancer group were far smaller than in most occupationally exposed workers
• Limitations the authors state:
  • The results are based on limited data
  • The comparison was chosen after examining the data, so the p value must be interpreted with caution
  • The 50 bodies/g cutoff is arbitrary
  • The counting method probably recovers only a minimal fraction of fibers (uncoated fibers are likely missed)
  • Not all ferruginous bodies may have an asbestos core, and other dusts such as cosmetic talc or fiberglass cannot be ruled out
  • Differences between laboratory techniques make comparison of counts with other studies unreliable

Topics

Medical terms in this study, explained in our Lexicon: Bronchogenic Carcinoma, Asbestos Exposure, Ferruginous Bodies, Lung Cancer, Carcinogenic.

Related studies

• Asbestosis associated with bronchogenic carcinoma — R. Stoll, R. Bass, et al. (1951)
• Asbestos, an extrinsic factor in the pathogenesis of bronchogenic carcinoma and mesothelioma — W.M. O'Donnell, R.H. Mann, et al. (1966)
• Occupational and environmental causes of bronchogenic carcinoma — B.M. Haus, H. Razavi, et al. (2001)
• Morphology of bronchogenic carcinoma in workers formerly exposed to crocidolite at Wittenoom Gorge in Western Australia — J.E. Baker, D.C. Reutens, et al. (1986)
• Biomarker assessments in asbestos-exposed workers as indicators for selective prevention of mesothelioma or bronchogenic carcinoma: rationale and practical implementations — E. Pluygers, P. Baldewyns, et al. (1992)
• Biomarker assessments in asbestos-exposed workers as indicators for selective prevention of mesothelioma or bronchogenic carcinoma: rationale and practical implementations — E. Pluygers, P. Baldewyns, et al. (1991)

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