Lung cancer among asbestos cement workers. A Swedish cohort study and a review

Our plain-English summary of Lung cancer among asbestos cement workers. A Swedish cohort study and a review, by C.G. Ohlson, C. Hogstedt (British Journal of Industrial Medicine, 1985).

The study

• Authors: C.G. Ohlson, C. Hogstedt
• Journal: British Journal of Industrial Medicine
• Published: 1985;42(6):397-402
• Cited by: 67 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 000499).

Abstract

A cohort study of 1176 Swedish asbestos cement workers did not indicate any asbestos related excess mortality. Possible explanations of the negative outcome are relatively low exposure levels and the predominant use of chrysotile in production. Such a tentative conclusion is supported by a review of five mortality studies of workers exposed to asbestos cement that report considerable differences in relative risks for lung cancer. These differences could be explained by various degrees of cumulative exposure, the amount of amphiboles in the production, and methodological shortcomings. A median exposure of 10-20 fibre-years does not seem to cause an increased risk of lung cancer, particularly when only chrysotile is used.

In plain English

This article combined a Swedish cohort study with a review of other studies. The authors followed 1,176 men employed more than three months between 1943 and 1976 at a Swedish asbestos cement plant, comparing their deaths (1951-82) and cancers (1958-79) with national rates. Mostly chrysotile was used; amosite and crocidolite made up under 1%. There were 220 deaths against 214 expected, and 11 lung cancer deaths against 9 expected. Counting only deaths 20 or more years after first employment, there were 9 lung cancer deaths against 5.7 expected, which was not statistically significant. The excess fell among short-term workers; men employed over five years had 1 lung cancer death against 2.6 expected. No mesothelioma was reported. A review of five other asbestos cement studies (New Orleans, Ontario, Wales, Belgium, Austria) found widely differing lung cancer risks. The authors tentatively concluded that a median exposure of about 10-20 fibre-years did not seem to increase lung cancer risk, especially with chrysotile only, while long-term exposure of around 70-100 fibre-years did. Smoking was not known for the whole cohort.

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 study of mortality and cancer incidence, compared with national rates, combined with a review of other mortality studies of asbestos cement workers
• Who was studied: 1,176 men who had worked more than three months between 1943 and 1976 at a Swedish asbestos cement plant. The starting group was 1,216 men; 36 who had emigrated were excluded and 4 who died before 1951 did not enter the study. Deaths were followed from 1951 to 1982 (26 931 person-years), and cancer cases from 1958 to 1979 through the National Cancer Registry.
• Exposure: Asbestos cement manufacture using mostly chrysotile. Amosite (630 tons, 1949-1951) and crocidolite (400 tons, 1962) were estimated at less than 1% of all asbestos used. Fibre concentrations averaged 1 fibre/ml in 1970-1976 and were estimated at 2 fibre/ml in earlier decades. The highest value was 8 fibres/ml over 45 minutes in 1970 in the asbestos bag barn. For a subcohort of 125 workers with at least 10 years of employment, average cumulative exposure was estimated at about 18 fibre-years. The authors estimated the median exposure of the whole cohort at 10 fibre-years at most.
• Main results:
  • Whole cohort, deaths before age 80: 220 observed against 214 expected (SMR 103)
  • Whole cohort, no latency requirement: 11 lung cancer deaths against 9 expected (SMR 123); malignant tumours 44 against 50 expected (SMR 88)
  • With a 20-year latency requirement: lung cancer SMR 158 (9 observed against 5.7 expected), which was not statistically significant
  • Lung cancer deaths by employment time, with 20-year latency: under 2 years, 5 observed against 1.8 expected; 2 to under 5 years, 3 against 1.3; over five years, 1 against 2.6
  • Short-term employees had higher mortality from various causes, whatever latency time was used
  • Overall cancer incidence in the cohort was similar to the national average. With 20-year latency, men employed under 2 years had 13 tumours against 10 expected, and men employed 2 years or more had 15 against 24 expected.
  • No case of mesothelioma was reported in the Swedish cohort
  • Two of the lung cancer deaths among short-term employees had previously worked on the docks unloading sacks of asbestos bound for the plant
  • Review finding, Ontario study (not this cohort): production workers at an Ontario asbestos cement plant had a lung cancer SMR of 8.5 (17 observed against 2.0 expected) with 20-year latency
  • Review finding, Welsh study (not this cohort): 1970 male and female asbestos cement workers in Wales, where only chrysotile was reported used, showed no increased mortality from any type of cancer
• The authors' conclusion: The authors found no work-related excess mortality in the Swedish cohort. They suggested this could be explained by relatively low exposure and the predominant use of chrysotile. From the review they tentatively concluded that a median cumulative exposure of about 10-20 fibre-years does not seem to increase lung cancer risk, whereas long-term high exposure with a median of 70-100 fibre-years does. They added that lung cancer risk seems relatively low when only chrysotile is used.
• Limitations the authors state:
  • Smoking habits were not known for the whole cohort. Smoking was recorded only in a voluntary health examination subsample, which may not be representative.
  • National death rates may be a deficient comparison. County death rates were not available, although county lung cancer incidence averaged 108% of national rates.
  • Exposure data were scanty for the 1950s and 1960s, and personal exposure estimates were not available for all cohort members
  • The cohort's median exposure is not known and was only crudely estimated
  • The cancer registry was incomplete: at least one lung cancer death was not found in it
  • The reduced lung cancer mortality among men employed longer than five years remained unexplained, and further follow-up was needed

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: Lung Cancer, Asbestos-Cement, Cohort Study, Chrysotile, Relative Risk, Cumulative Exposure, Amphibole Group.

Related studies

• Cancer incidence among Swedish pulp and paper mill workers: a cohort study of sulphate and sulphite mills — E. Andersson, H. Westberg, et al. (2013)
• Mortality and cancer morbidity in cohorts of asbestos cement workers and referents — M. Albin, K. Jakobsson, et al. (1990)
• Ventilatory decrements in former asbestos cement workers: a four year follow up — C.G. Ohlson, L. Bodin, et al. (1985)
• Survival in cohorts of asbestos cement workers and controls — M. Albin, V. Horstmann, et al. (1996)
• Cancer risk after cessation of asbestos exposure: a cohort study of Italian asbestos cement workers — C. Magnani, D. Ferrante, et al. (2008)
• Absence of radiographic asbestosis and the risk of lung cancer among asbestos-cement workers: Extended follow-up of a cohort — M.M. Finkelstein (2010)

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