Dr. Kenneth Smith to Patrick A. Christel of Hamilton Manufacturing on Colorlith Dust (1958)

A one-page letter of January 6, 1958, from Dr. Kenneth W. Smith, Johns-Manville's medical director, to Patrick A. Christel, safety director of the Hamilton Manufacturing Company of Two Rivers, Wisconsin, about the hazard of dust from Colorlith, a J-M board. Smith wrote that "both silica and asbestos fiber are used in the formation of Colorlith" and that these materials "are potentially hazardous if exposure to sufficient quantities over long periods of time is involved." He cited the American Conference of Governmental Industrial Hygienists' 1957 limits, saying in J-M's experience the 20 million particle limit for 5 to 50 percent quartz would apply to sawing and grinding dust, and that the asbestos limit was 5 million particles per cubic foot.

In Johns-Manville's chronology

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

Letter to P.A. Christel from Dr. Smith dated 1/6/58, responding to Hamilton Manufacturing inquiry re potential health hazards of Colorlith dust. Advises that product contains silica and asbestos and that these materials are potentially hazardous if exposure to sufficient quantities over long periods of time is involved. Suggests that the more lenient standard for silica (20 mppcf) and the ACGIH asbestos standard (5 mppcf) would apply to dusts arising from sanding and grinding Colorlith.

Related documents

• H. M. Jackson to Western Gold and Platinum Company on the Health Hazards of Colorlith (1956)
• S. E. Williams to H. M. Jackson on a Customer's Question About Colorlith Dust (1956)