H. M. Jackson to the Los Angeles Division of Occupational Health on Marinite, Colorlith, Asbestocite and Transite (1960)

A one-page letter of July 11, 1960, from H. M. Jackson, manager of J-M's Industrial Health Program, to Mr. G. E. Terry of the City of Los Angeles Division of Occupational Health, answering a request about Marinite products. Asking that the information be kept confidential and used only for environmental evaluation, Jackson discloses that Marinite, Colorlith, Asbestocite and Transite contain 25% to 50% asbestos fiber, and that Colorlith and Transite also contain about 20% quartz silica. "Both silica and asbestos fibres are potentially hazardous if exposure to sufficient quantities over long periods of time is involved," he writes, citing the 1959 threshold limits of 20 million particles per cubic foot for such silica-bearing dusts and 5 for asbestos.

What it shows

Jackson gives the same advice J-M gave customers that summer (Jackson to R. J. Reynolds, July 8): proper handling, good housekeeping and ventilation at the dust source "will remove any health hazards that might exist," and where engineering control is impossible a Bureau of Mines approved respirator should be "used and made a requirement of the job." The same summer, J-M's own Manville factory decided not to make respirators a job requirement for its overexposed workers (the 1960 respirator memos).

In Johns-Manville's chronology

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

Correspondence from H.M. Jackson to G.E. Terry at the City of Los Angeles Division of Occupational Health, dated 7/11/60. Jackson reveals in confidence the asbestos and silica composition of J-M's Marinite, Colorlith, Asbestosite and Transite. He cites the 1959 ACGIH threshold limits for silica and asbestos. Jackson advises that: "We believe that proper material handling methods, good housekeeping practice, and adequate ventilation at the dust source will remove any health hazards that might exist. If engineering control of the dust is impossible, we recommend that a U.S. Bureau of Mines approved respirator for pneumoconiosis-producing dust be used and made a requirement of the job."