Tremolite/chrysotile ratios

Our plain-English summary of Tremolite/chrysotile ratios, by G. Scansetti, G. Piolatto (American Journal of Industrial Medicine, 1987).

The study

• Authors: G. Scansetti, G. Piolatto
• Journal: American Journal of Industrial Medicine
• Published: 1987;12(1):117-8
• Type of article: Letter
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 000997).

In plain English

This was a letter to the editor by two University of Turin researchers, followed by a reply from the authors it criticized. It analyzed no new lung samples; it recalculated figures from published tables. The letter re-examined a 1986 paper by Churg and Wiggs on lung fibers in processed-chrysotile workers, chrysotile miners, and the general population. That paper had reported a tremolite-to-chrysotile ratio of 9.7 for processed-ore workers. The letter writers said the paper's own tables did not support this figure. Recalculating for the 21 workers gave a value close to 3.4. They argued that a geometric mean was the better average and reported geometric means from 0.05 (textile) to 1.04 (shipyard), with 0.57 for all categories. They noted that such ratios depend strongly on when each worker was exposed. They concluded that amphibole contamination of chrysotile may not be as large a problem as the original paper suggested. In reply, Churg and Wiggs gave geometric means of 1.8 for chrysotile miners and millers and 0.6 for processed-product workers. They interpreted this as implying that tremolite is lost in milling.

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: Letter to the editor recalculating published data from another paper (Churg and Wiggs, 1986), with the original authors' reply. No new lung samples were analyzed.
• Who was studied: No new subjects. The letter recalculated data from the 21 exposed cases reported in Churg and Wiggs (1986). These were processed-chrysotile workers in shipyard, insulation, brake, textile and manufacturing jobs. That paper also included chrysotile miners and a general-population control group.
• Exposure: Tremolite (an amphibole) contamination of chrysotile asbestos, measured as the ratio of tremolite to chrysotile fiber concentrations in lung tissue
• Main results:
  • The letter writers said the Churg and Wiggs tables gave no evidence for the reported mean tremolite-to-chrysotile ratio of 9.7 in processed-ore workers.
  • The letter writers recalculated the mean ratio for the 21 workers from the published tables, using the method they believed the original authors had used. This gave a value close to 3.4.
  • The letter writers noted an apparent typing error: the values for manufacturing and textile workers seemed to be exchanged in Table VI of the original paper.
  • Using geometric means, the letter writers reported tremolite-to-chrysotile ratios by occupation: shipyard 1.04, insulation 1.00, brake 0.21, textile 0.05, manufacturing 0.45, and all categories 0.57. The ratios were close to or substantially below 1.
  • In their reply, Churg and Wiggs said they had averaged over every fiber in each group, which explained the different values.
  • Using the letter writers' geometric-mean method, Churg and Wiggs reported ratios of 1.8 for chrysotile miners and millers and 0.6 for workers exposed to processed products.
  • Churg and Wiggs said the higher ratio in miners implied to them that tremolite is lost in milling, probably because the tremolite fibers are short.
• The authors' conclusion: The letter writers concluded that the extent of amphibole contamination of chrysotile may be smaller than the conclusions of Churg and Wiggs implied. In reply, Churg and Wiggs concluded that processed chrysotile products are probably much less dangerous than chrysotile ore, to the extent that the amount of tremolite matters in causing mesothelioma.
• Limitations the authors state:
  • The letter writers stated that tremolite-to-chrysotile ratios depend very strongly on each worker's exposure time history. People analyzed long after exposure ended would tend to have proportionately more tremolite.
  • The letter writers stated that data were not available to calculate geometric means for the control group and miners. Their figures for those groups were only estimates from the original paper's table.

Topics

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

Medical terms in this study, explained in our Lexicon: Tremolite, Chrysotile.

Related studies

• Malignant mesothelioma caused by childhood exposure to long-fiber low aspect ratio tremolite — F. Magee, J.L. Wright, et al. (1986)
• Chrysotile, tremolite, and malignant mesothelioma in man — A. Churg (1988)
• Inhalation studies on the effects of tremolite and brucite dust in rats — J.M. Davis, J. Addison, et al. (1985)
• Mesothelioma in Cyprus: the role of tremolite — K. McConnochie, L. Simonato, et al. (1987)
• Radiological survey of past and present vermiculite miners exposed to tremolite — J.C. McDonald, P. Sebastien, et al. (1986)
• Environmental pleural plaques in residents of a Quebec chrysotile mining town — A. Churg, L. DePaoli (1988)

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