R. F. Winkworth to Dr. T. H. Davison on the Meaning of a "No Dust" Work Restriction (1970)

A confidential one-page memo of November 20, 1970, from R. F. Winkworth at J-M's Toronto plant to Dr. T. H. Davison, the corporate medical director, on the standard procedure for work restrictions and counseling of pneumoconiosis cases. As Winkworth read it, the company physician would recommend that a worker with pneumoconiosis not work where dust was over 12 fibers per cubic centimeter or 5 million particles per cubic foot unless he wore a respirator, yet his understanding of company policy was that "no employee, whether or not he is a pneumoconiosis case or clear, should be exposed to these levels of dust." C. L. Sheckler had given him the impression that the plant physician was setting much tighter restrictions, which Winkworth took to mean any significant dust over 1 fiber per cubic centimeter.

What it shows

Handwritten notes on the copy, initialed "C.L.S." (Sheckler), say the "Basic problem is the dual stds" of the ACGIH and J-M limits, and that the plant physician had advised "no dust" restrictions in some pneumoconiosis cases, "far less than even the 6.0 f/cc limit that I suggested." What a "no dust" restriction meant had come up before, with the Manville plant's "no dust" list in the 1950s. Davison's answer is not in the file.

In Johns-Manville's chronology

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

Davison (HW) - R. Winkworth (Toronto) on 11/20/70. CLS correspondence re: meaning of a medical "no dust" restriction. Does it mean exposure below 12 f/cc, exposure below 6 f/cc (J-M internal respirator breakpoint) or no exposure at all? Davison says that it means cannot exceed 12 f/cc.

Editor's note: J-M's description says Davison answered that the restriction meant exposure could not exceed 12 f/cc. No reply from Davison is in this file, which holds only Winkworth's memo.