Document KRjL5gzYxzoyzdYaxvRX5K7oN

i August 22, 1960 Mr. Vilbux L. Thomas, Jr. Center for ths Biology ol Natural Systsaa Washington University St. Louis, Missouri 63130 Dear Mr. Thomas: I aa, of course, interested in your approach to the problea of lead poisoning in children in St. Louis, this problea is of long standing in the older cities of tho United States, and if I may say so, there is little need of new information in dealing with this problea. It will be a decade, at least, I should say, before the information concerning the lead content of hair, in its relation to the recognition of hazardous exposure to lead, and to the diagnosis and therapy of lead poisoning, can compete with the presently available knowledge of the significance of lead in the blood (and urine). In ay view, this source of information is unlikely ever to be ns useful as that of the blood, for the reason that the basic physiology of the hair in this relationship is essentially unknown. In consequence of this situation, I would not waste my time and the facilities of the laboratory (for that is what I believe it would be) in testing out the hair as a present source of environmental information, but would undertake to learn the facts as to the basic rastabollc activities of the hair in relation to lead. I am being brutally frank in speaking thus, but I hardly think it is understood that three or more decades of clinical, epidemiological and physiological investigation, cm a large scale, in the community, generally, and in industry have gone into the establishment of the relationships which obtain between various types and degrees of human exposure to lead and the rates of absorption, excretion and distribution of lead in the various tissues of the body. The relationships of lead in the skin and hair have not been included in these investigations, partially, at least, for the reason that it is difficult (and will continue to be) to be sure of the extent of the external contamination of the integument and its appendages. There is, of course, a large body of information on the physiology (including the biochemistry) of the hair, and this I think should be explored minutely before embarking upon any investigation relating to the mineral (including the trace metal) metabolism. So far as I know from the literature, none of the fairly large number of people in this and other countries, have undertaken this type of survey of the available information. I recommend this to you as a preliminary to your work on this tissue. As to the case of which you have spoken, there is one serious obstacle to my venturing any opinion of this case. Tour reference to such a value as 413 mg. % of lead in the blood stops me cold. I presume that this is a typographical error and that the figure is 413 micrograms per 100 grams of whole blood. This value, while in the highly dangerous range, is not necessarily associated with illness of any type. I aa surprised, therefore, that Dr. Lattimer finds it difficult to understand why no neurological manifestations of intoxication were found. There is in fact no level of lead concentration in the blood or any other tissue (with the possible exception of the central nervous system) which, of itself, is indicative of lead intoxication. High concentratlona, above a certain level, are clearly i 00490 Mr. Wilbur L. Thoi > Jr Pa S August 2B, I B M indicative of unusual and potentially dangerous degrees of absorption within comparatively recent periods of ties, and under such conditions the onset of symptoms nay occur at any tise, but M y not be inferred. We have seen such higher concentrations of lead in the blood than that which I believe to have been found in this instance without any concurrent evidenoe of intoxication. Ibis is eore common in adults than in children, but the fact remains, which many inexperienced people sieply cannot bring themselves to believe, that the diagnosis of lead intoxication is made, sot on the basis of the findings of the laboratory, but on strictly clinical grounds. The question to be asked by the clinician is, "is this person, child or adult, ill, and if so what is the nature of the illness?** Those of us, who have had wide experience with lead poisoning in industry and in the community have been reiterating this fact for many years, but it seems not to have made any Impression on any but the wisest and most experienced clinicians. X emphasize this fact in writing to you, for the reason that you speak of investigating the effects of low levels of exposure to lead upon people. This is, undoubtedly, the most difficult problem in the entire scope of the occurrence of lead in the human environment. There has been an almost Infinite amount of confused thinking on this subject, especially by people who are not familiar with the facts. Lead poisoning has been known (in varying degrees of completeness) for oenturdes, and some of the best and most thorough clinical observations known to medical experience (those, for example, of Tanquerel Des Planches) have been made and described in this relationship. And yet, the cllnloal novices apeak pseudolearnedly of "subclinical effects'* of lead intoxication, without realising that a subclinical effect of this much studied disease is one which no clinician can recognize, identify or describe. What does one mean by this term, if not that "there may be injurious effects of a very subtle type (presumably disturbances of the cellular metabolism Induced by enzymatic impairment) of which, at present, physicians have no knowledge." Since such a statement aan be made in relation to any disease known to man, I cannot but wonder why it is so seemingly impressive when made about the effects of lead upon the human body. You will forgive me, 1 trust, for my emphasis upon a point of view which 1 believe to be founded entirely upon baseless apprehension concerning matters which we do not understand fully. Our problem as investigators is, of course, to use our imagination in the design of investigations of unknown phenomena. This, X believe, Is not a reason for playing upon the apprehensions of people, generally, including our own, in the field of the public health. Having lived and worked for a long time, and so being full of years and some, X hope, profitable experience, X am fully aware of some of the uncertainties of the medical sciences in particular, and of life generally. However, they rarely keep me awake at night, or in a state of apprehension in the daytime. 81ncerely yours, RAK:wp Robert A. Xehoe, M.D. Professor Emeritus of Occupational Medicine 00491