C. J. O'Neill to Union Oil Company of California on Handling Hyflo Super-Cel (1952)

A two-page letter of July 2, 1952, from C. J. O'Neill, merchandise manager of Johns-Manville's Celite Division, to H. R. Morrison, purchasing agent of Union Oil Company of California, answering a question about the caution needed in handling Hyflo Super-Cel filter aid. O'Neill explained that Celite powders are diatomaceous silica which, when calcined (heated), contains "a substantial percentage of crystalline silica," and that Hyflo Super-Cel is calcined. "The full story of the exact nature and extent of the occupational disease hazard" was not yet known, but J-M knew "enough to warrant our advising customers (a) to minimize so far as possible the dust" and (b) to require protective devices where dust could not be reduced to safe levels.

What it shows

O'Neill recommended careful bag handling, vacuuming instead of sweeping, and respirators approved by the U.S. Bureau of Mines for pneumoconiosis dusts, especially in confined areas such as car loading. He closed: "Our best information is that Hyflo may contain from 20 to 50 percent crystobolite," a crystalline form of silica. The advice repeats almost word for word the guidance in Jackson's May 1952 memo on Celite caution labels, and became the form answer for customers in O'Neill's October bulletin to salesmen.

In Johns-Manville's chronology

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

Correspondence to Union Oil Company of California from C.J. O'Neill of J-M, 7/2/52, in response to its inquiry concerning the safe handling of J-M's Hyflo Super-Cel (Celite). J-M advised that the full story concerning the nature and extent of the occupational disease risk posed by diatomaceous earth dust was not yet fully comprehended but stated: "However, we know enough to warrant our advising customers (a) to minimize so far as possible the dust created by the use of the materials and (b) if the nature of the use will not permit the reduction of the dust concentration to safe levels, to require the use of protective devices." J-M gave some specific suggestions, including the establishment of appropriate bag handling procedures and the use of vacuum cleaners rather than sweeping to remove spilled or accumulated dust, and urged the use of respirators while handling bags. J-M advised that Hyflo might contain between 20% and 50% crystobalite (i.e., free crystalline silica).

Related documents

• H. M. Jackson to All Plant Managers on Caution Labels for Celite (1952)
• Frederick M. Kriete of the California Department of Public Health to Dr. A. J. Lanza Enclosing the Bulletin on Diatomaceous Earth Pneumoconiosis (1952)