Dr. Kenneth W. Smith to A. B. Cummins on Asbestos Fiber for Animal Experiments (1955)

A one-page memo of February 21, 1955, from Dr. Kenneth W. Smith, J-M's medical director, to A. B. Cummins of J-M Research. Smith writes that "For many years we have believed" that longer asbestos fibers were the chief cause of lung damage, but that recent pilot studies and clinical experience indicated the shorter fibers might also cause scarring of the lungs when inhaled. To test this in animal experiments he asks Cummins to send chrysotile fiber from J-M's Jeffrey Mine in Quebec, pieces of raw fiber and samples of serpentine rock and brucite to Dr. Paul Gross at the Industrial Hygiene Foundation of America in Pittsburgh.

What it shows

J-M's fiber limit, adopted in 1954, counted only fibers 10 microns and longer, on the strength of the Saranac research (Jackson to R. C. Smith). Less than a year later the company's medical director was arranging experiments because shorter fibers might also scar the lungs.

In Johns-Manville's chronology

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

K.W. Smith wrote to A.B. Cummins of R & D, 2/21/55, that very recent data brought into doubt the long-standing belief that it was fibers between 10 and 50 microns that were the chief cause of pulmonary damage. The recent data suggested that shorter fibers might also be involved in scarring.