Dr. Kenneth W. Smith to N. J. O'Brien on Health Hazards of Expanded Perlite (1954)

A one-page memo of July 28, 1954, from Dr. Kenneth W. Smith, Johns-Manville's medical director, to N. J. O'Brien at the Manville plant. Smith had "just received certain confidential information" that expanded perlite was a potential serious health hazard: the perlite producers had not published their health research, but "confidential sources have warned us" that inhaling it would predispose workers to a rapidly progressing tuberculosis and aggravate healed lesions. Until more was known, he ordered a list of every employee exposed, chest X-rays every six months, no work with perlite for anyone with present or past lung disease, and dust held below 5 million particles per cubic foot.

What it shows

J-M had been watching perlite since at least 1949, when H. M. Jackson found heavy dust where it was used in pipe covering (Jackson's 1949 memo). Smith's precautions were for J-M's own workers on the new Fibrocel line. Whether to warn the men who would install the finished product came up a week later (DuBow and Smith on Fibrocel).

In Johns-Manville's chronology

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

Dr. K.W. Smith writes to N.J. O'Brien (Manville). 7/28/54, that he has just received certain confidential information which indicates that there is a potential serious health hazard when handling expanded perlite. Dr. Smith states that the perlite producers "have not seen fit to publish the results of their research in the health field," and the medical literature contains very little information on perlite. But confidential sources "have warned us" that inhalation of expanded perlite pre-disposes one to the development of TB and aggravates any existing healed TB lesion.

Therefore, until more factual information can be obtained on this material, Dr. Smith initiates the following precautionary measures: (1) A list is to be prepared of all employees (salaried and hourly) who are exposed to expanded perlite. (2) Everyone on the list should have a chest X-ray every six months. (3) Anyone who has evidence of present or past pulmonary disease (especially a healed TB lesion) should not be allowed to work in contact with expanded perlite. (4) "Once this list of employees has been established indicating that those exposed to the material are free from pulmonary disease there should be no new additions to the list and no one should be allowed to work where this material can be inhaled unless they have received approval from the Medical Department." (5) Periodic checks should be made to determine that dust control is satisfactory. Although there is no TLV for expanded perlite, Dr. Smith suggests that a level of less than 5 mppcf be maintained.