Document em3eXgnyqGZwpOo50MvNbwYLy

July 5, 1967 Dp. Harriet L. Hardy Assistant Medical Director In Charge of Occupational Medicine Service Room 20B-238 Massachusetts Institute of Technology Cambridge, Massachusetts 02139 Dear Dr. Hardy: In common with many persons in industries using substantial quantities of asbestos, we are frequently asked for guidance in setting industrial hygiene ' standards for this mineral. A recent conversation with Dr. Dixon of Pisons (England) suggested that there may be a real difference between the various forms of asbestos in regard to their ability to cause mesothellomata. My first question would then be, is there such a difference? and does it apply to the . other less specific tumors of the lung and gastro intestinal tract also associated with asbestos? Secondly, If there is such a difference In tumorigenlcity between the various forms of asbestos, is it of a suffi cient degree to be the basis for a recommendation to management on asbestos handling? Yours sincerely, . ORIGINAL SIGNED BY ' O. J. 8T0PP3 Q* J. Stopps, M.B.,B.S. Chief, Physiology Section QJS/dyb 091 - DUP 0900838 SC-DP-01895