Vandiver Brown to C. B. Martin of General Electric on Dust from Spintex Mineral Wool (1951)

A one-page letter of September 25, 1951, from Vandiver Brown, Johns-Manville's secretary and attorney, to C. B. Martin of General Electric's Freezer Division in Erie, Pennsylvania. Martin had asked whether dust from J-M's #302 Spintex mineral wool refrigerator insulation might be a hazard, and Brown answered that "this is definitely NOT the case." Mineral wool, he wrote, contains silica only as a silicate and "no free silica, which is an important consideration since it is only free silica which can produce silicosis." He cited an old Metropolitan Life Insurance Company survey of nearly 400 workers at a J-M mineral wool plant that found no silicosis, and its advice that mineral wool dust was "innocuous from the viewpoint of lung fibroses."

What it shows

The letter is one of many J-M answers to customer questions in these years that turned on whether a product contained "free silica." Brown's reply concerned mineral wool, not asbestos, and addressed only silicosis. J-M gave similar assurances about rock wool to the Chesapeake and Ohio Railway in 1952.

In Johns-Manville's chronology

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

Vandiver Brown in letter dated 9/25/51 responds to inquiry on 302 Spintex from General Electric Co., Freezer Division. "It contains no free silica . . . which can produce silicosis."