H. M. Jackson to All Plant Managers on Caution Labels for Celite (1952)

A two-page memorandum of May 14, 1952, from Hugh M. Jackson at Johns-Manville's headquarters to all plant managers, headed "Industrial Hygiene, Diatomaceous Earth." It opens: "Recent research and medical studies indicate that there is a potential health hazard in the use of Diatomaceous Earth under conditions of prolonged exposure at high concentrations." Bagged products from Lompoc were therefore being labeled "CAUTION," with one wording for natural products and another for calcined (heat-treated) products, the latter described as "almost pure silica, partly amorphous and partly crystalline." Both labels said that inhaling silica dust "over long periods may be harmful" and that workers should have "adequate protective devices" if dust could not be avoided.

What it shows

Jackson told the plants to handle bags so they did not break, to vacuum spills instead of sweeping, and to have workers wear respirators approved by the U.S. Bureau of Mines when handling bags, especially in confined areas such as car loading. "While we do not yet know what concentrations of the diatomaceous earth dust may be harmful," he wrote, "experience indicates that respiratory protection should be used." The labeling followed the state laws described in Woodard's January 1952 letter to Vorwald, and its wording matches the asbestos label debated in the 1952 Illinois labeling memos.

In Johns-Manville's chronology

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

Hugh Jackson memorandum dated 5/14/52 to plant managers regarding caution label for Celite bags. Document is contrary to Jackson's prior testimony.

Editor's note: J-M's description says the memo is contrary to Jackson's prior testimony. That testimony is not in this file, so the comparison cannot be checked here.

Related documents

• J. P. Woodard to Arthur J. Vorwald on Labeling Diatomaceous Earth and the Delayed Saranac Studies (1952)