C. M. McGaw to H. K. Sherry on Gardner's Interim Report (1940)

A two-page confidential memo of February 6, 1940, from C. M. McGaw of the Industrial Relations Department at Asbestos, Quebec, to H. K. Sherry, a vice-president of Canadian Johns-Manville, on Leroy Gardner's "Interim Report on Experimental Asbestosis at the Saranac Laboratory." McGaw called it "a very revealing document" and read it as showing "a definite hazard to exposure to asbestos dust," though one "much less in the case of fine dust," and that "the hazards are very much less than commonly supposed." On contacts with K. D. S. Robertson of the Workmen's Compensation Commission and others, he thought it advisable to discuss the report at the next Q.A.M.A. meeting "in a confidential manner and give it no further publicity whatsoever."

What it shows

McGaw noted that Gardner's second experiment "definitely showed that fibrosis developed" in guinea pigs, white mice and rats after one year's exposure to fairly long fibres, and that a report by Mr. Binder had found "a heavy concentration of fine dust in our mills." On Gardner's observation that asbestosis does not progress after exposure ends, he wrote: "Our policy to place mill men in outside jobs when possible when their lungs appear to show symptoms of fibrosis." He asked whether there might be "individual human susceptibility as our physical examinations here would indicate," and advised waiting for the final report before any definite statement. The report itself is described in its own entry.

In Johns-Manville's chronology

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

C.M. McGaw writes to H.K. Sherry (2/6/40) regarding Dr. L. Gardner's "interim report on experimental asbestosis at the Saranac Laboratory". McGaw comments that the report indicates there is a definite hazard from exposure to asbestos dust but it is "much less in the case of fine dust" (two microns or less) and that the "hazards are much less than commonly supposed." McGaw mentions that the report indicates asbestosis does not progress after cessation of exposure although he states this has not been proven conclusively. He ponders whether certain individuals may be more susceptible to asbestos-related disease than others. Regarding K.D.S. Robertson, Workers' Compensation Commission, McGaw advises discussion of the report at the next QAMA meeting "in a confidential manner and give it no further publicity whatsoever." He advises waiting until Gardner's final report before making a statement since the conclusions drawn on the interim report are not yet "sufficiently positive to form the basis of a definitive statement." Copy of the report is attached which generally describes the methodology used and mentions that the fibers used were two microns or less in maximum diameter. Tables indicating the period of time exposed are included. Report suggests that irritation from asbestos is mechanical rather chemical in nature. Report states that proof now seems conclusive that grinding asbestos to a degree of fineness of two microns or less destroys its capability to irritate the lungs.

Editor's note: J-M's description goes on to describe Gardner's interim report as attached to McGaw's memo. The report is not in this file; see the interim report.

Related documents

• Leroy Gardner, Interim Report on Experimental Asbestosis at the Saranac Laboratory (1939)