Document vVXZy6ZEoYJy6jeDQ5kZXvpmm

MlIETAIL PROGRESS P U B L IS H E D BY THE A M E R IC A N S O C IE T Y TOR M E TA LS 7016 EUCLID AVENUE CLEVELAND, OHIO December 20, 1958 Dr. Robert A. Kehoe College of Medicine University of Cincinnati Eden Avenue Cincinnati, Ohio Dear Dr. Kehoe: I find that I have so far failed to acknowledge with thanks the very fine letter you wrote me on December 6 concerning threshold value for lead poisoning in its mildest form. Rest assured that I will use this material with dis cretion. Very truly yours, E. E. Thura Editor - Metal Progress N7924 December 6* 193 Mr. E. E. Thum Editor Metal Progress 7016 Euclid Avenue Cleveland* Ohio Dear Mr. Thum:- Since our exchange of corres pondence of some weeks ago* I have had some information about the problem of lead in steel which leads me to believe that your vtorst fears are likely to be realized. My information Is confidential and to some degree it is also hearsay* but I have reason to believe that in some of the plants the lead fume In the atmosphere is grossly in excess of the most optimistic estimates of safe ex posure . The expression "threshold value" as employed in your letter* is an entirely correct one. It means in effect the level of exposure which Is just short of a magnitude which will produce lead poisoning in its mildest fora, This magnitude has been somewhat variably expressed, but the figures given in your letter must either be incorrect with respect to the decimal point or else there is something wrong with my mathematics. In any case the figure is not customarily expressed in the manner in which you have given it. The first valid expression of this threshold, so far as I know* was given by Legg and Goadby in their book on lead poisoning and lead absorp tion* Their statement is to the effect that if the atmosphere in a plant does not contain particulate lead in excess of* 5 milligrams per 10 cubic meters, cases of lead poisoning would not occur at all* or would be very mild. Since their time measurements of lead in the atmosphere have been carried -out by somewhat different methods than they used. The figure for the threshold in terms of present standard methods of analysis is somewhat lower than their figure. In astanlteiaosntedonteheoffitghuerestoafte1s.,5 medico-le&al practice has milligrams of lead per 10 Cubic meters of ai when determined by standard lmpinger methods. I believe this figure is a little low though it is certainly a good one to shoot at. My own experience leads me to believe that the presence in the atmosphere of quantities not in excess of 2 milligrams per 10 cubic meters is safe. This value is equivalent to .0057 milligrams per cubic foot, or .00009 grains per cubic foot. Very truly your3, RAKs is Robert Aw Kehoe, M.D.