H. M. Jackson to G. S. Smith on J-M's Own Threshold Limit for Asbestos (1954)

A one-page memo of April 6, 1954, from H. M. Jackson at Johns-Manville headquarters to G. S. Smith of General Engineering at Manville, attaching the 1953 threshold limits of the American Conference of Governmental Industrial Hygienists as the standards J-M should apply. The one exception was asbestos: "We have tentatively established 1 Million Fibers Per Cubic Foot instead of" the Conference's limit of 5 million particles per cubic foot. The standard rested on the Saranac Laboratory's animal research and its conclusion that "the long fibers (10 microns and longer) not the dust particles per se, are the fibrosis-producing element."

What it shows

Jackson wrote that New Jersey was expected to adopt J-M's standard and that the data had gone to the Conference for consideration. A handwritten note asks that copies go to all dust engineers. J-M had asked Saranac for a fiber count standard three years earlier (Jackson to Vorwald, 1951); the Conference's limit dated from 1947. See Threshold Limit Value (TLV).

In Johns-Manville's chronology

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

Jackson Memorandum to G.S. Smith, General Engineering Manville, 4/6/54, Re: Threshold Limits, J-M adopts 1953 ACGIH except for asbestos, since J-M has "tentatively established 1 million fibers per cubic foot instead . . . ." due to Saranac data.

Related documents

• Asbestos Textile Institute Hygiene Committee Minutes on Fiber Sampling and Two Standards (June 1953)