H. M. Jackson to Schilling on the Travelers Dust Survey of the Manville Pipe Department (1956)

A two-page memo of December 1956 from H. M. Jackson, manager of J-M's industrial health program, to Schilling at the Manville plant on a survey of the pipe department in "P" Building made by the Travelers insurance company's laboratory. Jackson writes that the counts "in general" showed adequate control, with exceptions. At the swing saw both dust and fiber counts were excessive: with about 25 percent each of silica and asbestos, he puts the limit at 20 million particles per cubic foot and 1.0 million fibers, and recommends approved respirators "be required job apparel during the sawing operation" until better control is in place. Counts were also high at a bagging station, a walkway above the No. 4 machine and in a box car where fiber was unloaded, where he urged respirators for all workers.

What it shows

The memo shows J-M measuring both dust and asbestos fibers in its own pipe plant in 1956 and finding excessive levels at several jobs. Where control was lacking, the answer was respirators until ventilation could be improved, the same approach Jackson recommended to customers in his Colorlith letter.

In Johns-Manville's chronology

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

Travelers Dust Data Memorandum from Jackson to Schilling (Manville), 12/18/56 re industrial hygiene survey of Pipe Department. This letter attaches the dust count analysis of thirteen samples of which two are reported in excess of the 5 mppcf TLV. The Travelers data is also expressed in terms of a fiber count. Jackson's memorandum describes the stations that were surveyed. These include sample station 1021, swingsaw. Notes excessive concentrations of dust and fiber at swingsaw, bagging operation, raw material unloading, and walkway above operation; respirator use in an area within "MAC" (or TLV). Both the dust and fiber concentration are excessive at this operation.

With approximately 25% each of silica and asbestos in this dust, Jackson states that the applicable maximum acceptable concentration would be 20 million particles per cubic foot. The m.a.c. for the fiber count is 1.0 million fibers per cubic foot. "Since this is the first survey made at this location, it would be well to determine whether this represents typical operating conditions by taking a series of at least three samples. Until more adequate control is established, however, I would recommend that approved-type respirators be required job apparel during the sawing operation."

Related documents

• H. M. Jackson to Dr. R. E. Joyner of Carbide and Carbon Chemicals on Superex and Thermobestos Insulation (1956)