H. M. Jackson to R. B. Frandsen on Threshold Limits for Asbestos-Cement Products at Waukegan (1959)

A one-page memo of September 29, 1959, from H. M. Jackson at Johns-Manville's General Headquarters to R. B. Frandsen at the Waukegan plant, answering Frandsen's letter of September 18 on threshold limit values. Jackson wrote that it was "quite in order to establish the applicable threshold limit on the basis of estimating contaminant in the proportion of the substance in the product raw material mix," and that Frandsen's use of this principle for the asbestos-cement products was "quite correct," although at some spots in manufacturing the exposure would be to a single substance rather than a mix. A handwritten note on the memo directs that the new principle be applied to all dust samples from October 1, 1959.

In Johns-Manville's chronology

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

Jackson writes R.B. Frandsen (Waukegan) on 9/29/59, stating that it is appropriate to establish an applicable TLV on the basis of estimating the proportion of the contaminant in the substance of raw material mix when there is not already an established TLV. Jackson approves the following TLV for asbestos cement products: 5 mppcf for dust and 1 mfpcf for fiber. This TLV is based on the fact that these products contain over 25% fiber. This TLV is to apply to all stations where these products are either being manufactured or handled in a finished goods state.

Editor's note: J-M's description says Jackson approved limits of 5 mppcf for dust and 1 million fibers per cubic foot, based on the products containing over 25% fiber. Those figures are not in this memo, which approves the method Frandsen had used; his letter of September 18 is not in this file.