H. M. Jackson to T. R. Turnbull on Fiber Counts Above J-M's Limit at Waukegan (1954)

A one-page memo of April 1, 1954, from H. M. Jackson at Johns-Manville headquarters to T. R. Turnbull, manager of the Waukegan, Illinois, plant, on the industrial hygiene survey of the Cement and Magnesia departments, March 10 to 15, with the Travelers laboratory's analysis attached. Dust counts generally showed good control, but at several stations, mostly feeding and loading operations, fiber concentrations exceeded "our standard of 1 million (1,000 thousand) fibers per cubic foot." Because the work was intermittent, Jackson recommended that approved respirators be required during charging, feeding and loading until ventilation could reduce the dust.

What it shows

Jackson added: "Our clinical experience elsewhere leads us to believe that the amosite fiber is capable of producing fibrosis more rapidly than the chrysotile." Five days later he explained J-M's own fiber limit to the company's engineers (Jackson to G. S. Smith). See Amosite and Threshold Limit Value (TLV).

In Johns-Manville's chronology

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

H.M. Jackson memorandum to T.R. Turnbull (Waukegan) dated 4/1/54, regarding the industrial hygiene survey at the Waukegan plant - Cement and Magnesia Departments, March 10-15. Jackson attaches copies of Travelers' analysis report. While in general the dust counts indicated good control, there are several sampling stations, particularly at the feeding operations, in which the fiber concentrations are above the TLV for asbestos fibers. Since each of these is an "intermittent operation," Jackson recommends that "approved type" respirators be required during the charging, feeding or loading process of the work cycle until such time as ventilation or process control can be effected to reduce the degree of contamination. "Clinical experience elsewhere leads us to believe that the amosite fiber is capable of producing fibrosis more rapidly than the chrysotile. This further emphasizes the need of operator protection during the above portions of their work."