D. R. Christensen to D. H. Markusson on Simulated 1960s Thermobestos Sawing and Cement Mixing (1976)

A four-page memo of September 2, 1976, from D. R. Christensen of J-M's Research and Development center to D. H. Markusson, reporting tests meant "to simulate and quantitate conditions that existed in the 1960's while sawing THERMOBESTOS pipe insulation and mixing insulating cements." On August 17, 1976, workers sawed Thermobestos on a band saw for a full day in an enclosed trailer with no mechanical ventilation. Sampled the 1960s way, with an impinger, the air held 87.8 to 139.7 million particles per cubic foot (mppcf), against a 1965 threshold limit of 5.0 mppcf; by the 1976 OSHA filter method, operators' exposures were 7.1 to 14.1 fibers per cc against a 2.0 limit. Mixing insulating cement by trough on August 18 gave 1.4 to 4.6 mppcf and 3.1 to 5.9 fibers per cc.

What it shows

Christensen, who had visited insulation warehouse operations in the late 1960s and early 1970s, judged that the tests "would represent the worst conditions that existed for sawing material and about average or slightly below average for the cement mixing operation." J-M's own description says the work was done for the asbestos litigation. W. B. Reitze later wrote that cement mixing on job sites, as he had sampled it with Dr. Selikoff's group, ran much higher (Reitze to Markusson on mixing cements). See Threshold Limit Value (TLV).

In Johns-Manville's chronology

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

Memorandum to D.H. Markusson from D.R. Christensen, dated 9/2/76, regarding Asbestos Exposure while Handling Thermobestos Insulation and Mixing Insulating Cements - Simulated 1960's Conditions. Christensen summarizes the experiments performed for the purposes of the asbestos litigation to determine the conditions users of Thermobestos and Insulating Cement may have encountered during the 1960s. The results show fiber levels ranging from 87.8 mppcf to 139.7 mppcf. The TLV for 1965 was 5.0 mppcf.