Massachusetts Department of Labor and Industries, Recommended Safe Practices: Asbestos (1949)

A one-page "Recommended Safe Practices" sheet, Mineral Data Sheet No. 2, issued in February 1949 by the Division of Occupational Hygiene of the Massachusetts Department of Labor and Industries. It classifies asbestos dust as "very harmful" because it may cause asbestosis, says death "is usually the result of infection of the lungs, such as tuberculosis, or from congestive heart disease," and sets a maximum allowable concentration of 5 million particles of asbestos dust per cubic foot of air (see Threshold Limit Value (TLV)). It calls for controlling dust at its source, with approved respirators "only as a last resort," and for a chest X-ray before hiring and at least once a year for everyone in dusty asbestos work.

In Johns-Manville's chronology

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

Massachusetts Dept. of Labor and Industries Bulletin No. 492, (February, 1949). Recommended Safe Practices re Asbestos. Notes risk of asbestosis, death due complicating infections such as TB, or congestive heart failure. TLV is 5 mppcf, recommends dust control, respirators as "last resort". Annual x-rays should be required.