E. M. Fenner to All Plant, Mill and Mine Managers on the Membrane Filter Technique (1969)

A two-page confidential memo of February 10, 1969, from E. M. Fenner of J-M's Environmental Control Department to all plant, mill, mine, production and division general managers, announcing that J-M would begin measuring asbestos dust by the membrane filter technique. "The British asbestos industry has used this method for many years," Fenner writes; the U.S. Public Health Service recommended it, and it was "a truer method than our present technique" because it sampled the air the worker breathed "as he moves about on his job" and counted fibers more accurately. Each worker sampled would wear a small battery-powered personal air sampler for 1½ to 3 hours, and the four area industrial hygiene laboratories would start the new surveys at Marshville, Waukegan, Reeves Mill and Coalinga between February and July 1969.

What it shows

Until 1969 J-M measured asbestos dust with the impinger, which counted all particles at fixed stations. Fenner's memo records the switch to counting fibers in the breathing zone, a method the company acknowledged British producers had used for years. The first results under the new method were worse than the old counts had shown (Environmental Control Subcommittee, May 1969). The difference between British and American dust counting had been discussed in industry meetings earlier in the decade (Asbestos Textile Institute Air Hygiene Committee minutes).

In Johns-Manville's chronology

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

E.M. Fenner memorandum to all Plant, Mill and Mine Managers of 2/10/69 informs J-M's adoption of the membrane filter sampling method. Counts fibers not particles.

Related documents

• Asbestos Textile Institute Air Hygiene and Manufacturing Committee Minutes on Selikoff's Study and British Fiber Counting (1963)