H. M. Jackson to William T. Marr of the Long Beach Naval Shipyard on Asbestos Dust Standards (1959)

A two-page letter of June 22, 1959, from H. M. Jackson, manager of Johns-Manville's Industrial Health Program, to William T. Marr, industrial hygienist in the Medical Department of the Long Beach Naval Shipyard in California, answering Marr's letter of May 5. Jackson agreed that Marr's doubts about the methods used to measure asbestos dust were "well founded," since "There is still much to be learned about the etiology of asbestosis itself." He explained that J-M applied limits of five million dust particles and one million fibers per cubic foot, the fiber limit resting on the Saranac Laboratory's "Experimental Studies of Asbestosis," and that J-M's "clinical experience tends to confirm this arbitrarily selected standard."

What it shows

Asked whether insulation work caused asbestosis, Jackson wrote that he knew of "only two cases of asbestosis" arising from installing asbestos insulation, and that insulators also breathed other dusts (diatomite, magnesia, refractory cements) that could complicate the picture. He added that little was known about "short duration massive exposures," and assumed that on ships part of the work "would be performed in confined spaces which might result in heavy concentrations for short periods of time." The 1946 survey of Navy pipe coverers had reported three cases (the Fleischer-Drinker study). The attachments Jackson mentions (J-M's counting procedure, the Saranac study and reprints) are not in the file.

In Johns-Manville's chronology

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

Jackson letter to William T. Marr, Industrial Hygienist, Long Beach Naval Shipyard, Medical Department, Long Beach, CA dated 6/22/59. Jackson responds to Marr's inquiry concerning the validity of present techniques for evaluating asbestos contamination. Jackson states that at Johns-Manville, sampling is made on both dust and fiber. By dust Jackson says he means the spherical particles less than 10 microns in size and by fiber he means the elongated particles greater than 10 microns in length. Threshold limits of five million particles per cubic foot for the dust and one million fibers per cubic foot for the fiber are applied. Jackson states that Johns-Manville's procedure for dust and fiber counting is attached. (No attachments.)

Jackson explains that the one million fiber threshold limit is based on the experimental work done at Saranac and Johns Manville's clinical experience tends to confirm the "arbitrarily selected standard."
Jackson responds to Marr's inquiry regarding whether asbestosis arises out of insulation operations. Jackson is aware of only two cases of asbestosis arising from exposures involving the installation of asbestos insulations. (Jackson has testified he was referring to the Dreessen data - actually 3 cases). Usually the fellows in the insulation field are exposed to a variety of dusts (e.g., diatomite, magnesia, refractory cements) which might contribute to and complicate the pulmonary picture.

Jackson states in addition, that there is a lack of knowledge about the import of short duration massive exposures, which Jackson believes occurs on ships. Johns-Manville's approach to control utilizes the standard techniques, that is, ventilation control of the dust at its source, vacuum cleaning of settled dust, and use of respirators in areas incapable of being otherwise controlled. Jackson states that "Johns-Manville's Health Maintenance program is tied into the other [sic] preventative measures" and the periodic physical examination results are used as an additional evaluation of the work environment. Jackson asks Marr to contact him if Marr has any other questions.

Editor's note: J-M's description says Jackson defined a fiber as a particle longer than 10 microns; on this faint copy the letter appears to read "greater than 5 microns in length." The description's note about Jackson's later testimony on the Dreessen data refers to testimony that is not in this file.

Related documents

• Bergit A. Swartout v. Mundet Cork Corp. and Others, California Asbestosis Death Claim (1956–1958)