Asbestos in Relation to the Type of Fibre and Dose in the Insulation Industry

Our plain-English summary of Asbestos in Relation to the Type of Fibre and Dose in the Insulation Industry, by W.C. Cooper, J. Miedema (1972).

The study

• Authors: W.C. Cooper, J. Miedema
• Published: Biological Effects f Asbestos Lyon, October 2-5, 1972. Paper 27.
• Type of article: Conference paper
• Our copy: from Johns-Manville's own medical library. The article is still under copyright, so we describe it here rather than post it.

In plain English

This paper, prepared for a 1972 meeting in Lyon, reviewed studies of asbestosis in people who apply or manufacture asbestos insulation. The authors described how products changed over time. U.S. calcium silicate insulation contained 11% amosite in the 1940-50 period but 7% chrysotile in 1965. They summarized other investigators' studies of deaths, compensation cases, chest X-rays and autopsies. They stated that studies of insulation application consistently showed a high potential for asbestosis in persons exposed to materials containing chrysotile, amosite or crocidolite. They noted that there was no agreement on criteria for diagnosing asbestosis, and that brief high exposures alternated with low ones. One cited study found no dependable ratio for converting older dust counts to fiber counts in the insulation trade. The authors concluded that these uncertainties made comparisons between asbestos types and products uncertain. They added that studies of insulation manufacture were more likely to reveal significant differences, but that no published information permitted evaluation of relative hazards in terms of asbestosis. They also recommended considering magnesium carbonate, calcium silicate and diatomaceous earth as possible modifiers of the fibrotic response.

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• Design: Review of published and unpublished studies, prepared for presentation at a meeting of a working group on the biological effects of asbestos
• Who was studied: Workers who apply insulation (insulators, laggers) and workers who manufacture insulation materials, as described in studies from the U.S.A., the United Kingdom, Finland and elsewhere
• Exposure: Insulating materials containing chrysotile, amosite or crocidolite, with changing product formulations, along with accompanying materials such as magnesium carbonate, calcium silicate and diatomaceous earth
• Main results:
  • Studies of insulation application consistently showed a high potential for producing asbestosis in persons exposed to insulating materials containing chrysotile, amosite or crocidolite
  • Average dust concentrations associated with the production of disease were not reliable, because products changed and brief high exposures alternated with periods of relatively low exposure
  • In the U.S., calcium silicate insulation contained 11% amosite in the 1940-50 period and 7% chrysotile in 1965
  • The quantity of asbestos used in U.S. insulation materials remained about constant over forty years: 16,500 short tons in 1930 and 16,100 short tons in 1965
  • A cited study (Cooper and Balzer, 1968) found no dependable ratio between older dust counts and fiber counts in the insulation trade. Ratios corresponding to 1 million particles per cubic foot ranged from 0.2 to over 20 fibers/cc.
  • In data cited from the National Institute of Occupational Safety and Health (1972), some insulation manufacturing plants had mean dust concentrations of 16 to 75 fibers/cc. Other plants reported concentrations below 1 fiber/cc for similar operations.
  • Cited unpublished data (Cooper and Gaffey, 1972) showed a standardized mortality ratio for respiratory diseases of 571.4 for San Francisco insulating workers who began employment before 1946
  • A cited study (Enterline, 1971) found a standardized mortality ratio for asbestosis of 375.7 in 173 production workers manufacturing asbestos insulation products, with 5 deaths charged to asbestosis
  • The authors recommended that both epidemiologic and animal studies consider the contribution of accompanying materials (magnesium carbonate, calcium silicate, diatomaceous earth) as modifiers of the fibrotic response
• The authors' conclusion: The authors concluded that uncertainties about exposure make comparisons between asbestos types and products uncertain. Studies of insulation manufacture were more likely to reveal significant differences, but no published information permitted evaluation of relative hazards in terms of asbestosis.
• Limitations the authors state:
  • There is no agreement on criteria for diagnosing asbestosis, so comparisons between studies are difficult
  • Mortality attributed to asbestosis, cor pulmonale or chronic respiratory disease is subject to both positive and negative biases
  • It was practically impossible to classify insulation exposures cleanly by type of asbestos or by the presence of other materials
  • Peak concentrations may be high for brief periods, while time-weighted averages are often deceptively low

Topics

Medical terms in this study, explained in our Lexicon: Calcium Silicate Insulation, Amosite, Chrysotile, Chest X-Ray, Crocidolite, Silicate.

Browse return to medical research.