Document a1qm3mL2EjwVYVM9VyQee0GNy

Ctatsig uf H00 . Smiif! W t p Mi m m i BBS&ToriijSpring#imi 7m Augj?ka12,(Ealiforuta May 20, 19U8 Robert A, Kehoe, M.D. Kettering Laboratory of Applied Physiology College of Medicine - Eden Avenue University of Cincinnati Cincinnati 19> Ohio Dear Dr. Kehoet Many thanks for your letter of May 5, 19U8, answering my inquiry regarding M.A.C.'s. Practically all of the dozen or so persons ad dressed on this question have written thoughtful and com plete replies; yours has been especially valuable. Our group here realizes that the situation re garding M.A.C.'s is far from simple; we have no thought of attempting to settle the problems involved. Our purpose rather is merely to formulate the working defini tion of the term, M.A.C., to be used in our day to day work. You realize, of course, that the field engineer or chemist often in his activities meets persons who sometimes ask rather embarrassing questions. Good policy calls for the former to have answers, that, while possibly not air tight, do not admit confusion. Again, thank you for your courtesy and trouble. Sincerely yours, Roy 0. Gilbert, M.D. Health Officer PGBiMP KE 0020006 Paul G. Brown Industrial Hygiene Engineer Division of Industrial Hygiene