Thomas J. Weeks and Allan F. Burns, "Performance of Dust Respirators Against a Fibrous Dust" (1970)

A four-page technical note by Thomas J. Weeks and Allan F. Burns of the Johns-Manville Research and Engineering Center, published in the May–June 1970 American Industrial Hygiene Association Journal. Noting that "no data are available" on how respirators perform against fibrous dusts, the authors made a fine test dust by grinding Canadian chrysotile from J-M's Jeffrey Mine and tested three U.S. Bureau of Mines approved and five unapproved respirators against it at the Bureau's Pittsburgh laboratory. With one exception, all let through less than 1% of the fiber.

What it shows

The authors caution that chrysotile is "a soft, flexible asbestos fiber" and that their results "may not be valid for a harsh, brittle fiber such as amosite, crocidolite, a harsh chrysotile, or glass fiber." One aim was to help the Bureau of Mines develop approval tests for respirators against fibrous dust, and J-M offered the same test dust to other investigators. It followed J-M's work with Dr. Irving Selikoff on a fibrous dust respirator workers would accept; a month earlier, J-M's Asbestos, Quebec, plant was still relying on the uncomfortable Dustfoe 77.

In Johns-Manville's chronology

Johns-Manville's own chronology of what the company knew describes this document as follows:

An article entitled "Performance of Dust Respirators Against A Fibrous Dust," authored by Thomas Weeks and Allan Burns (J-M R&D Center} is published in the American Industrial Hygiene Association Journal in the May-June, 1970 issue. The authors state that prior to their study, no data was available on the performance of respirators against fibrous dust. In view of the exposure of a great many workers to various fibrous dusts, the authors note that it is important to have this information.

A primary obstacle to obtaining this necessary information has been the difficulty in generating a reproducible easily dispersed, fibrous dust of respirable size. Such a dust was prepared by J-M from Canadian chrysotile asbestos from the Jeffrey mine. The article describes the preparation of such a dust and the performance of different types of respirators against it. (All except one respirator tested offered considerable protection against chrysotile asbestos.)

One objective of the study was to assist the Bureau of Mines in developing possible requirements and tests for approving respirators to be used for protection against fibrous dust. The authors emphasize that additional work is needed to establish a standard test for evaluating respirators against fibrous dust. The authors state that J-M will provide samples of the same fibrous test dust to investigators as was used in their study.