Asbestos exposure, smoking habits, and cancer incidence among production and maintenance workers in an electrochemical plant

Our plain-English summary of Asbestos exposure, smoking habits, and cancer incidence among production and maintenance workers in an electrochemical plant, by B. Hilt, S. Langård, A. Andersen, et al (American Journal of Industrial Medicine, 1985).

The study

• Authors: B. Hilt, S. Langård, A. Andersen, J. Rosenberg
• Journal: American Journal of Industrial Medicine
• Published: 1985;8(6):565-77
• Cited by: 39 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. 000481).

Abstract

The incidence of cancer was studied in a cohort of 287 men who were exposed to asbestos at a nitric acid production plant from 1928 onwards. During the observation period from 1953 through 1980 all cancer cases among the cohort members were identified in The Cancer Registry. For the whole cohort 42 cases of cancer were observed versus 30.6 expected. The figures for cancer of the lungs and pleura combined were 17 observed versus 3.7 expected. The corresponding figures for a heavily exposed subcohort were 11 observed and 1.2 expected. In that group there was also an increased incidence of colon cancer with 3 cases observed against 0.8 cases expected. Within the whole cohort four cases of pleural and one case of peritoneal malignant mesothelioma were found. There was also an increased incidence of malignant melanoma of the skin with 3 cases observed against 0.6 expected. For cancer cases that were registered as of unknown origin there were 7 cases observed and 1.4 expected. There was no increased rate ratio for cancer at any site before 20 years after the first asbestos exposure. The smoking habits of all cohort members were recorded and the relative rates for lung cancer were calculated in relation to smoking habits. In common with previous studies the results indicate a multiplicative model for the interaction between asbestos exposure and smoking in regard to lung cancer risk.

In plain English

This Norwegian cohort study tracked cancer from 1953 through 1980 in 287 men exposed to asbestos at a nitric acid plant. Crocidolite was mostly used early on; from the 1940s, both amphiboles and serpentines were used. Among 97 heavily exposed men, 11 lung and pleural cancers occurred against 1.2 expected. Among 190 lightly exposed men, there were 6 against 2.5, of borderline statistical significance. Five malignant mesotheliomas were found: four pleural, and one peritoneal that was the most probable diagnosis on review of a tumor registered as stomach cancer. The whole cohort also had more malignant melanoma of the skin (3 observed, 0.6 expected) and cancer of unknown origin (7 observed, 1.4 expected). A colon cancer increase in heavily exposed men was not statistically significant. No cancer increase appeared within 20 years of first exposure. The authors concluded that most of the lung cancer excess reflected a real difference in risk independent of smoking. They noted that, with no lung cancers among 33 non-smokers during 1966 to 1977, their data gave no straight answer on how asbestos and smoking interact.

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: Historical cohort study of cancer incidence, with cases identified by record linkage to the Norwegian Cancer Registry and compared with expected numbers from national rates
• Who was studied: 287 men regularly exposed to asbestos at a nitric acid production plant in an electrochemical complex in southern Norway (Telemark county). All were first exposed between 1928 and 1961 and alive on January 1, 1953. There were 190 men in the lightly exposed group and 97 in the heavily exposed group. Observation ran from 1953 through 1980.
• Exposure: Asbestos used as jointing material in granite nitric acid towers and as gasket material. Crocidolite was mostly used in the earliest years; from the 1940s both amphiboles and serpentines were used. The heavily exposed group was workers in the 'fiber hut' mixing asbestos with waterglass, and men placing the jointing material in the tower grooves. The lightly exposed group was maintenance workers (mechanics, plumbers, welders) and production workers with mostly indirect exposure. Workers were also exposed to nitrous gases, nitric acid vapors and ammonia.
• Main results:
  • Whole cohort, all cancers: 42 observed versus 30.6 expected (Table III gives an observed-to-expected ratio of 1.4, 95% CI 1.0-1.9).
  • Heavily exposed group, cancer of lung and pleura: 11 observed versus 1.2 expected, observed-to-expected ratio 8.9 (95% CI 4.6-16.4).
  • Lightly exposed group, cancer of lung and pleura: 6 observed versus 2.5 expected, observed-to-expected ratio 2.4 (95% CI 0.92-5.44, p = 0.084). The authors described this as of borderline statistical significance.
  • Five malignant mesotheliomas in the cohort. Four were histologically verified pleural cases, three of which had been registered as lung cancer. One was peritoneal: histological review of an abdominal cancer registered as stomach cancer assigned malignant mesothelioma of peritoneum as the most probable diagnosis.
  • Whole cohort, malignant melanoma of the skin: 3 observed versus 0.6 expected, observed-to-expected ratio 5.1 (95% CI 1.03-14.61, p = 0.046).
  • Whole cohort, cancer of unknown origin: 7 observed versus 1.4 expected.
  • Heavily exposed group, colon cancer: 3 observed versus 0.8 expected, observed-to-expected ratio 3.9 (95% CI 0.77-10.96, p = 0.095), not statistically significant.
  • Maintenance workers within the lightly exposed group, all cancers: 11 observed versus 5.1 expected (observed-to-expected ratio 2.2, 95% CI 1.1-3.9).
  • Whole cohort: no increased incidence of any cancer until 20 years after first exposure.
  • Smokers in the cohort (182 men) had an age-adjusted lung cancer rate of 47.8 per 1,000 for 1966-1977, compared with 11.1 among smokers in a general Norwegian population sample. The authors calculated a ratio of 4.3.
  • The cohort had more smokers than the national sample. Taking the asbestos-smoking interaction into account, the authors estimated this higher smoking rate would raise lung cancer rates in the study population by a factor of 1.87.
• The authors' conclusion: The authors concluded that most of the observed increase in lung cancer represented a real difference in risk between the study and reference populations, independent of smoking habits. Their abstract states that the results indicate a multiplicative interaction between asbestos exposure and smoking for lung cancer risk.
• Limitations the authors state:
  • No lung cancer cases occurred among the 33 non-smoking cohort members during the 1966-1977 smoking analysis follow-up. As a result, the data could not show whether the asbestos-smoking interaction was additive or multiplicative.
  • Because of very small numbers, the study could not show a reduction in lung cancer rates among exposed workers who had stopped smoking.
  • There was no exact measure of the degree of asbestos dust exposure in the heavily and lightly exposed groups.
  • The prior work history, including possible earlier asbestos exposure, of deceased cohort members was not known.
  • No tissue samples were available to review the cancers of unknown origin. The authors note that some may have been undiagnosed malignant mesotheliomas.
  • Only workers with at least 1 year of exposure were included in the lightly exposed group, because short-term workers were hard to identify.

Topics

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

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, Habit, Cancer Registry, Pleura, Colorectal Cancer, Malignant Mesothelioma, rate ratio, Lung Cancer.

Related studies

• Pulmonary function, smoking habits, and high resolution computed tomography (HRCT) early abnormalities of lung and pleural fibrosis in shipyard workers exposed to asbestos — S. Neri, P. Boraschi, et al. (1996)
• Insulation, asbestos, smoking habits, and lung cancer cell types — J.E. Muscat, S.D. Stellman, et al. (1995)
• A mortality cohort study among workers in a graphite electrode production plant in Italy — D.F. Merlo, S. Garattini, et al. (2004)
• Cancer incidence among asbestos-exposed chemical industry workers: an extended observation period — B. Hilt, A. Andersen, et al. (1991)
• Mortality among maintenance employees potentially exposed to asbestos in a refinery and petrochemical plant — S.P. Tsai, L.C. Waddell, et al. (1996)
• Digestive cancers and occupational asbestos exposure: incidence study in a cohort of asbestos plant workers — M. Boulanger, F. Morlais, et al. (2015)

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