A case control study of lung cancer and exposure to chrysotile and amphibole at a slovenian asbestos-cement plant

Our plain-English summary of A case control study of lung cancer and exposure to chrysotile and amphibole at a slovenian asbestos-cement plant, by M. Dodic Fikfak, D. Kriebel, M.M. Quinn, et al (The Annals of Occupational Hygiene, 2007).

The study

• Authors: M. Dodic Fikfak, D. Kriebel, M.M. Quinn, E.A. Eisen, D.H. Wegman
• Journal: The Annals of Occupational Hygiene
• Published: 2007;51(3):261-8
• Cited by: 17 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

A lung cancer case-control study was conducted in a Slovenian asbestos-cement factory for which unusually good records of asbestos exposures were available. The cohort consisted of all 6714 workers employed at the Salonit Anhovo factory after 31 December 1946 who worked there for at least one day between 1964 and 1994. Fifty-eight histologically confirmed cases of primary lung cancer and 290 controls were selected from the cohort. Working life exposure histories to amphibole and chrysotile forms of asbestos were estimated separately. Airborne asbestos concentrations were low. For example, the arithmetic mean exposure to all forms of asbestos in the highest exposure period (1947-1971) was 1.2 f/cm(3). Chrysotile asbestos made up about 90% of this exposure (mean 1.1 f/cm(3)), whereas amphibole accounted for 10% (0.1 f/cm(3)). Comparing those above and below the 90 percentile of cumulative exposure, the odds ratios for all asbestos, chrysotile and amphibole were 1.5, 1.6 and 2.0, respectively, but confidence intervals were wide. There are only a few asbestos-lung cancer studies with high-quality exposure data and exposures in this low range. Though imprecise, the findings are important to the ongoing debate about asbestos risks.

In plain English

This case-control study drew on 6714 workers at Slovenia's Salonit Anhovo asbestos-cement factory who were hired after 31 December 1946 and employed at least one day in 1964–1994. It included 58 lung cancer cases from the Slovenian cancer register, plus matched controls. From more than 1000 air measurements and work records, the authors estimated chrysotile and amphibole exposure separately. In 1947–1971, mean intensity was 3.16 f/cm3 for chrysotile and 0.17 f/cm3 for amphibole. For exposure more than 15 years before diagnosis, ever-exposed versus never-exposed workers had odds ratios of 0.8 (95% CI 0.4–1.6) for total asbestos and chrysotile and 0.9 (0.5–1.6) for amphibole, which the authors called close to null. In the same window, workers above versus below the 90th percentile of cumulative exposure had odds ratios of 1.5 for total asbestos (95% CI 0.6–3.9), 1.6 for chrysotile (0.6–4.1) and 2.0 for amphibole (0.9–4.7). Ever-smokers versus never-smokers had an odds ratio of 3.9 (95% CI 1.6–9.3). The authors reported somewhat higher lung cancer risk for amphibole than chrysotile, with limited precision. They named low statistical power as the main limitation.

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: Case-control study nested in a factory worker cohort; controls matched on date of birth, gender and year of hire
• Who was studied: 6714 workers at the Salonit Anhovo asbestos-cement factory, Slovenia, hired after 31 December 1946 and employed at least one day between 1964 and 1994. Of 67 lung cancer cases in the cohort, 58 hired after 1947 were analysed, with five controls per case.
• Exposure: Chrysotile and amphibole asbestos, estimated separately for each worker from air measurements and work histories in asbestos-cement pipe and sheet production. Mean chrysotile intensity in 1947–1971 was 3.16 f/cm3. Duration of exposure to silica and cement (chromium) dust was also examined.
• Main results:
  • Ever versus never exposed, for exposure more than 15 years before diagnosis: the authors described associations with lung cancer as close to null. Odds ratios were 0.8 (95% CI 0.4–1.6) for total asbestos, 0.8 (0.4–1.6) for chrysotile and 0.9 (0.5–1.6) for amphibole.
  • Above versus below the median cumulative exposure (more than 15 years before diagnosis): odds ratios were 0.9 (95% CI 0.5–1.7) for total asbestos, 1.1 (0.6–2.1) for chrysotile and 0.8 (0.4–1.5) for amphibole.
  • Above versus below the 90th percentile of cumulative exposure (more than 15 years before diagnosis): odds ratios were 1.5 (95% CI 0.6–3.9) for total asbestos, 1.6 (0.6–4.1) for chrysotile and 2.0 (0.9–4.7) for amphibole.
  • Among smokers above the 90th percentile, the odds ratio was 1.8 (95% CI 0.7–4.7) for chrysotile and 2.2 (95% CI 0.9–5.5) for amphibole.
  • Any exposure more than 35 years before the risk date, a period before amphiboles were used in the factory (8 cases, 34 controls): odds ratio 2.2 (95% CI 0.4–11.9).
  • Ever-smokers compared with never-smokers (conditional logistic regression): odds ratio for lung cancer 3.9 (95% CI 1.6–9.3).
  • No evidence that duration of exposure to cement or silica dust was associated with lung cancer risk.
• The authors' conclusion: The authors concluded that their risk estimates were close to the null at these low exposures. They also concluded that the study observed a somewhat higher lung cancer risk for amphibole than for chrysotile asbestos, with limited precision.
• Limitations the authors state:
  • Low statistical power: confidence intervals for the separate fiber-type estimates were wide.
  • The fiber-type comparison may have been biased by cross contamination between the separate parts of the factory.
  • Smoking data came from next-of-kin for cases but by postal questionnaire for living controls, which might have introduced recall bias.
  • Only six cases were non-smokers, so models of risk among non-smokers were very unstable.
  • There was probably not enough time since the peak production years (1971–1986) for them to affect lung cancer incidence in this study.

Topics

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

Medical terms in this study, explained in our Lexicon: Lung Cancer, Chrysotile, Amphibole Group, Asbestos-Cement, Case-Control Study, Asbestos Exposure, Cumulative Exposure, Odds Ratio.

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• Comparison of Calidria chrysotile asbestos to pure tremolite: final results of the inhalation biopersistence and histopathology examination following short-term exposure — D.M. Bernstein, J. Chevalier, et al. (2005)
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• Asbestos fiber concentrations in the lungs of brake repair workers: commercial amphiboles levels are predictive of chrysotile levels — G.M. Marsh, A.O. Youk, et al. (2011)

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