The Work Environment Of Insulating Workers

Our plain-English summary of The Work Environment Of Insulating Workers, by J.L. Balzer, W.C. Cooper (1968).

The study

• Authors: J.L. Balzer, W.C. Cooper
• Published: American Industrial Hygiene Association Journal 29(3):222-227, May-June (1968)
• Type of article: Journal article
• Our copy: from Johns-Manville's own medical library, J-M no. 002525. The article is still under copyright, so we describe it here rather than post it.

In plain English

This was a preliminary report from a University of California study of insulating workers. It mainly described working conditions; the authors' study of lung disease and cancers in these workers was still under way. It covered the roughly 500-member San Francisco local (No. 16) of the insulators' union. Of these members, 401 were active in March 1967, in commercial, heavy industrial, and marine work. Asbestos-containing and fibrous glass materials made up 90% of the materials applied. Amosite and chrysotile were the asbestos types most used in insulation products. A review of the union's chest X-rays had found changes strongly supporting asbestosis in about 25% of members. The dust results reported came only from work with asbestos-containing materials. These exceeded the threshold limit then in force, 5 million particles per cubic foot, during prefabrication, tearing out, and mixing. However, those samples did not cover long periods. Breathing-zone dust levels in the dustiest operations were lower than the amount of pneumoconiosis had led the authors to expect. The authors suggested the asbestos limit was too high. They said their studies were not yet complete enough for a final conclusion.

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: Preliminary report of a workplace environmental survey (materials used, work methods, dust and fiber air sampling) within an ongoing study of insulating workers' health
• Who was studied: Insulating workers in San Francisco Local No. 16 of the asbestos workers' union (Northern California and Northern Nevada), about 500 members. Of the 401 active members working as of March 31, 1967, 100 were in commercial building, 236 in heavy industrial building and 65 in marine construction and repair.
• Exposure: Insulation materials, mainly asbestos-containing products (amosite and chrysotile, in calcium silicate, magnesia and other products), fibrous glass, cork, plastics and adhesives. The air sampling results discussed in this paper were limited to operations using only asbestos-containing materials.
• Main results:
  • Fibrous asbestos and glass materials accounted for 90% of the insulation materials applied in the San Francisco Bay Area.
  • Chrysotile (Canadian) and amosite (South African) were the asbestos types most often used in manufacturing insulation materials in the United States.
  • A review of the union's voluntary chest X-ray program found that about 25% of members had changes strongly supporting a diagnosis of asbestosis. An equal percentage had suggestive changes. The OCR prints the figure as '254'; the phrase 'equal percentage' shows it is a percentage.
  • Impinger dust samples were compared with the threshold limit value then in force, 5 million particles per cubic foot.
  • Impinger dust samples exceeded that limit in three job categories: prefabrication, tearing out, and mixing.
  • The authors applied Timbrell's criterion for respirable fibers (diameter smaller than 3.5 microns). By that criterion, 98% plus or minus 2% of the fibers counted on membrane filters were respirable.
  • Breathing-zone dust levels in the dustiest operations observed were not as high as the incidence of pneumoconiosis had led the authors to expect.
  • Glass fibers of respirable size were found in fibrous glass insulation materials used in the area.
• The authors' conclusion: The authors pointed to the pneumoconiosis seen in insulating workers exposed only intermittently. They suggested this means the threshold limit value for asbestos is too high, but said their studies were not yet complete enough to warrant a final conclusion.
• Limitations the authors state:
  • Obtaining a true time-weighted exposure for insulating workers was impossible under their changing working conditions.
  • Past exposures could not be reconstructed.
  • Manufacturers' and contractors' practices made it impossible to identify a group of workers exposed to only one type of asbestos fiber.
  • Asbestos fibrils are too small to count with ordinary light microscopy, which makes true fiber exposure hard to assess.
  • The samples that exceeded the threshold limit value did not cover extended periods of time.
  • The time percentages given for each job category vary and are only rough guidelines.
  • Fibrous glass exposure data were being collected but were not analyzed in this paper.
  • The authors could not rule out that other components of the insulating materials may be synergistic.

Topics

Medical terms in this study, explained in our Lexicon: Insulator, Amosite, Chrysotile, Chest X-Ray, Asbestos-Containing Material (ACM), Million Particles per Cubic Foot (mppcf), Pneumoconiosis.

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