H. M. Jackson to J. E. Morrison on Respirators (1948)

A two-page letter of December 8, 1948, from H. M. Jackson, Johns-Manville's safety engineer in New York, to J. E. Morrison at Asbestos, Quebec, on when respirators should be required. At best, Jackson writes, respirators are "a 'last resort' for protection," but where toxic dust remains after engineering controls they are "a desirable and necessary means of protection." He names silica, asbestos, litharge and toluol among the "toxic materials which must be kept in control" in J-M's processes, and says that once the need is established "there should be no question of 'getting' them worn; they should be worn."

What it shows

Jackson explained that looking at dust "is not necessarily a reliable means of determining contamination," since the invisible particles do the harm, and that the hazard of "an almost invisible, slow acting toxic material" was hard to get across to workers. He recommended respirators approved by the U.S. Bureau of Mines for toxic exposures, referred to Maximum Allowable Concentration standards, and suggested assigning each man two or more respirators of his own. Dr. Kenneth Smith and N. P. deValois at Asbestos were to judge where they were needed.

In Johns-Manville's chronology

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

Letter from H. Jackson to J.E. Morrison (Asbestos), dated 12/8/48, responding to Morrison's inquiry regarding J-M respirator requirements and practices. States it "sometimes is necessary to require the wearing of personal protective equipment" at J-M operations. Jackson says that while he is not familiar with the method of respirator maintenance at Asbestos, he recommends assigning at least two respirators to each employee individually. Dr. Smith and N.F. DeValois are mentioned as two persons who can assist in determining the necessity for a recommendation of "suitable protective devices."

Jackson discusses the problem of enforcing respirator use, recognizes comfort problems and remarks that once the necessity of respirators is established, "there should be no question of getting them work. Mentions that he feels respirators are a "last resort" for protection and that efforts should be geared toward trying to control dust through engineering methods first. Discusses establishment of certain TLVs. Comments that visual examination is not necessarily a reliable means of determining contamination.