Dr. Kenneth W. Smith to H. O. Blackburn of Pine Bluff Arsenal on 85% Magnesia (1959)

A one-page letter of September 25, 1959, from Dr. Kenneth W. Smith, Johns-Manville's medical director, to H. O. Blackburn, safety director of the Pine Bluff Arsenal in Arkansas, who had asked about possible health hazards in handling 85% Magnesia products and foam glass insulation. Smith declined to comment on the foam glass, another company's product, and wrote that the magnesia insulation contained about 12% asbestos fiber and that "a minimal amount of asbestos fiber might become airborne" if the block and pipe insulation was cut or handled carelessly; he advised exhaust ventilation, proper handling and approved respirators. He said he had no records of injuries among installers, because "People who use this material are employees of subcontractors and not this company," and that after reviewing the literature and consulting insurers that year he "could find no record or report indicating that there was a pulmonary health hazard associated with this occupation."

What it shows

Smith judged the potential health hazard of 85% magnesia "minimal." That summer H. M. Jackson had told a Navy shipyard hygienist that he knew of only two cases of asbestosis among insulation installers (Jackson to Marr), and two years earlier Jackson had given a similar answer about the same product (Jackson to Black, Sivalls & Bryson).

In Johns-Manville's chronology

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

Letter from Kenneth Smith to H.O. Blackburn, Pine Bluff Arsenal, 9/25/59, responding to an inquiry concerning the possible health hazards posed by the handling of 85% magnesia products. Smith acknowledges the 12% asbestos content of the products and notes: "It is possible that a minimal amount of asbestos fiber might become airborne if the magnesia block and pipe insulating material was cut or otherwise handled carelessly."

He advocates ventilation, proper handling, and respirators. He reports that he is unable to furnish information concerning "disabling injuries resulting from installation of this insulating product. People who use this material are employees of subcontractors and not this company. Therefore, I have no records concerning possible injuries. I believe that the potential health hazard is minimal. Earlier this year I reviewed available health literature and consulted with insurance companies and numerous other people. I could find no record or report indicating that there was a pulmonary health hazard associated with this occupation."

Related documents

• H. M. Jackson to George Finley of Black, Sivalls & Bryson on 85% Magnesia (1957)
• Armstrong Cork, Travelers and Alexander & Alexander on E. O. McCarrell's Asbestosis Claim (1956–1957)