Lois Gaul's Manville Memo on the Bureau of Mines Circular Mineral Wool (1985)

A one-page Manville internal memo of April 3, 1985, from Lois Gaul to eight colleagues, on Mineral Wool, a U.S. Bureau of Mines information circular by J. R. Thoenen published in June 1939. Manville had only the circular's pages on mineral wool as a health hazard, which describe experiments at the Harvard School of Public Health and quote a letter from Dr. R. R. Sayers of the U.S. Public Health Service: mineral-wool fibers produced "an inert foreign body reaction similar to that of asbestos," and the Service had been "considering dust from mineral wool as potentially harmful."

What it shows

Gaul records the circular's own conclusion: "there is a definite danger from inhaled mineral-wool dust, but its action is mechanical rather than pathological." Mineral wool was used in place of asbestos in some insulation, and the 1939 circular shows a federal health official comparing the two dusts. The memo is one of a series written at Manville in the mid-1980s, while the company was defending asbestos lawsuits, recording what older publications said.