H. M. Jackson to Western Gold and Platinum Company on the Health Hazards of Colorlith (1956)

A two-page letter of September 18, 1956, from H. M. Jackson, manager of J-M's industrial health program, to Western Gold and Platinum Company of San Francisco, with a cover memo sending it through R. V. Lohse. Asked about the health hazard of dust from Colorlith board, Jackson writes that "both silica and asbestos fiber" are in it and are "potentially hazardous if exposure to sufficient quantities over long periods of time is involved," since "silicosis and asbestosis may result from excessive exposure." He cites the 1956 threshold limits of the American Conference of Governmental Industrial Hygienists, including five million particles per cubic foot for asbestos, and says dust can be judged only by industrial hygiene sampling, not by eye.

What it shows

Jackson closes that in J-M's own plants "we have developed satisfactory dust control" by hooding cutting and grinding equipment, and that where control was incomplete, "U. S. Bureau of Mines approved type respirators will provide protection." Three months later a survey of J-M's own Manville pipe department found excessive asbestos fiber at the saws. Colorlith was asbestos-cement board, "really steam cured Transite."

In Johns-Manville's chronology

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

Correspondence from Hugh Jackson to Western Gold Platinum Company dated 9/18/56 concerning possible health hazards associated with the fabrication of Colorlith. Jackson points out that both silica and asbestos fiber are contained in the product and that both are potentially hazardous if exposures exceed certain levels and certain durations. Absent state standards, Jackson refers the customer to the ACGIH standards. Jackson cites the standards for both silica and asbestos and recommends the use of industrial hygiene sampling rather than relying on efforts at visual estimation. He closes: "In our own operations, we have developed satisfactory dust control through the hooding of cutting and grinding equipment at the point of operation. At points at which the operation is intermittent and complete control has not been effected, the use of U.S. Bureau of Mines approved-type respirators will provide protection."

Related documents

• S. E. Williams to H. M. Jackson on a Customer's Question About Colorlith Dust (1956)
• H. M. Jackson to Dr. R. E. Joyner of Carbide and Carbon Chemicals on Superex and Thermobestos Insulation (1956)