Malignant mesothelioma among employees of a Connecticut factory that manufactured friction materials using chrysotile asbestos

Our plain-English summary of Malignant mesothelioma among employees of a Connecticut factory that manufactured friction materials using chrysotile asbestos, by M.M. Finkelstein, C. Meisenkothen (The Annals of Occupational Hygiene, 2010).

The study

• Authors: M.M. Finkelstein, C. Meisenkothen
• Journal: The Annals of Occupational Hygiene
• Published: 2010;54(6):692-6
• Type of article: Case report
• Cited by: 20 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

There is ongoing argument about the potency of chrysotile asbestos to cause malignant mesothelioma. Risk assessment for chrysotile is influenced by the alleged absence of mesotheliomas among workers at the Raybestos Manhattan friction products plant in Connecticut, a plant that essentially used only chrysotile asbestos. Regrettably, the statement that there is an absence of mesothelioma deaths in the Connecticut plant is false. In this paper, we report on our review of the work histories and pathological reports of five individuals from the Connecticut plant who were diagnosed with mesothelioma. We discuss the Connecticut plant in relation to the most recent epidemiological information for chrysotile. Calculation suggests that mesothelioma rates at this plant were similar to those observed among Quebec miners and the South Carolina textile plant. We urge everyone concerned with the risk assessment of chrysotile asbestos to make use of all available data.

In plain English

The authors reviewed law-firm records of workers with mesothelioma from the Raybestos Manhattan friction-materials plant in Connecticut, which made products such as brake linings. Until 1957 the plant used only chrysotile asbestos, mainly from Canada; some anthophyllite was then added. Six workers had sought legal representation from a law firm where one author works, but one had worked at a Pennsylvania plant instead. Adding two female clerical workers identified earlier from a tumor registry, the authors counted seven cases. They excluded one man who had navy exposure and amosite in his lungs, leaving six workers, three women and three men. Using only the two cases among men eligible for an earlier cohort study, and an assumed number of deaths, they estimated mesothelioma risk at 0.002 percent of total expected mortality per fibre-year per ml (95% confidence limits 0.0002 to 0.006), versus 0.001 for Quebec miners and millers. The difference was not statistically significant. The authors concluded that claims of no mesothelioma cases at the plant are not correct, and called their count a minimum estimate.

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 series: a review of work histories and pathology reports of mesothelioma cases in a law firm's files. It is combined with a risk calculation, using the Hodgson and Darnton method, that compares the plant with other chrysotile-exposed cohorts.
• Who was studied: Six workers diagnosed with mesothelioma who sought legal representation from Early, Ludwick & Sweeney, LLC of New Haven, Connecticut. One of them was found not to have worked at the Connecticut plant. Two further cases came from earlier Connecticut Tumor Registry data. The risk calculation used the earlier McDonald cohort: workers employed a calendar month or more before 1 January 1959.
• Exposure: Work at a plant making friction materials (brake linings, automatic transmission friction materials, discs and bands). The plant used chrysotile asbestos, mainly from Canada, as its only asbestos type until 1957, when some anthophyllite was added for paper discs and bands. The mean cumulative exposure used for the cohort was 46 fibre-years per ml, taken from Hodgson and Darnton.
• Main results:
  • Of the six law-firm cases, one man (Subject 5) had worked at the Raybestos plant in Mannheim, Pennsylvania, not the Connecticut plant. This left five Connecticut-plant cases from the files.
  • Two additional cases had been identified earlier from Connecticut Tumor Registry data. Both were female clerical workers: one died of pleural mesothelioma and the other of peritoneal mesothelioma.
  • Subject 3 had a 20-year navy machinist career before working at the plant in 1983 to 1984, and amosite was found in his lungs. He was excluded as having mixed fibre exposure.
  • The authors counted seven mesothelioma cases from the plant. After excluding Subject 3, at least six workers remained, three women and three men.
  • For the Raybestos plant, the estimate used 2 mesothelioma deaths among cohort-eligible men, an estimated total expected mortality of 2800, and a mean cumulative exposure of 46 fibre-years per ml. The estimated risk was 0.002 percent of total expected mortality per fibre-year per ml (95% confidence limits 0.0002 to 0.006).
  • The comparison estimate for Quebec miners and millers was 0.001 (0.0006 to 0.0012), taken from Hodgson and Darnton. It was based on 33 mesothelioma deaths and a mean cumulative exposure of 600 fibre-years per ml.
  • The authors' calculation for the South Carolina textile plant, using data from Hein et al. (2007), gave 0.007 (0.001 to 0.021), based on 3 mesothelioma deaths.
  • The authors' calculation for four North Carolina textile plants, using data from Loomis et al. (2009), gave 0.027 (0.008 to 0.045), based on 8 mesothelioma deaths. This was substantially higher than for Quebec.
  • The Raybestos and South Carolina estimates were several-fold larger than the Quebec estimate. Because of small numbers they were not significantly different from it (P = 0.50 for Raybestos versus Quebec; P = 0.24 for South Carolina versus Quebec).
• The authors' conclusion: The authors concluded that the repeated statement that there were no mesothelioma cases from the Connecticut plant is not correct. They also concluded that their calculations suggest mesothelioma rates at the plant were similar to those among Quebec miners and at the South Carolina textile plant.
• Limitations the authors state:
  • The case count is a minimum estimate, because only cases that sought legal help from the law firm where one author works could be identified.
  • The small number of deaths made the confidence limits wide.
  • Mesothelioma deaths may be under-counted when death certificates are relied on.
  • Cumulative exposure estimates rely on sometimes scanty historic exposure measurements.
  • Total expected mortality was not directly available. The authors assumed 80% of the cohort had died by the end of 2000 and judged this error likely small compared with other uncertainties.

Topics

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

Medical terms in this study, explained in our Lexicon: Mesothelioma, Chrysotile, Friction Products.

Related studies

• Mesothelioma in a connecticut friction plant: the need for transparency and exposure information in attribution of risk — M.J. Teta (2011)
• Malignant mesothelioma, airborne asbestos, and the need for accuracy in chrysotile risk assessments — C. Meisenkothen (2013)
• Environmental history of a factory producing friction material — J.W. Skidmore, B.L. Dufficy (1983)
• Airborne asbestos exposures associated with work on asbestos fire sleeve materials — C.L. Blake, S.C. Harbison, et al. (2011)
• Mortality among employees of an Ontario factory manufacturing insulation materials from amosite asbestos — M.M. Finkelstein (1989)
• A study of airborne chrysotile concentrations associated with handling, unpacking, and repacking boxes of automobile clutch discs — G.C. Jiang, A.K. Madl, et al. (2008)

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