Document V3yJz1R2XJv8jVkGxV8j4x5jj

t July 22, 1937 Dr* W* H* Whitman Norfolk and western Railroad Company Roanoke, Virginia Dear Doctor Whitman* Proa what you have told me in your letters concerning cases of illness in men engaged in osy-aeetylene cutting operations, I am in no position to say that you were dealing with lead poisoning* However, that lead poisoning of the most severe types may occur from the cutting or burning of metal coated with lead paints is so well known in certain trades, especially in bridge building and ship breaking, as to require no proof from me* The chemical department of your company is taking a very vulnerable position in constructing their very original hypothesis concerning the impossibility of the inhalation of lead under these conditions* Indeed, no hypothesis is required here at all, since the facts are well known* However, just a,little discussion of the theoretical issues at stake may be justified* You quote some technical person as stating that, "To be inhaled into the system through the respiratory organs it would be necessary for the lead to be converted into a gaseous state, and we have never known of lead being converted into such a form." Perhaps you should chide your infor mant for iris naivete in physiological matters, but we can let that pass* He should know the facts in his own field better than to doubt that lead is volatilized at the temperatures occurring in the oxy-acetylene flame* The temperatures here are compounds begin to be avpoplraotxiliemaattelyte2m7p0e0ratuC,reswhailreoumnadny50l0e,ad lead oxide bolls at "white heat" (about lfj00oC, and metallic lead bolls at about 1525C* Thus the lead oxide literally bolls off from the melting surface, and is thrown into the air in the form of the oxide in a finely divided state* These particles may be inhaled and are fairly readily absorbed from the pulmonary surface* (That lead must exist as a gas to be absorbed by the lung is indeed a new and delightful hypothesis* I could wish it were true, for if it were, industrial lead poisoning would be largely non existent* It is well known that finely divided metallic lead, lead oxide, lead carbonate, and indeed, praotially any other lead compound suspended in the air will cause lead intoxication in men and animals permitted to breathe such atmospheres* It is also generally accepted that lead 00G75oY - 2- poisoning 111 occur among human beings exposed to atmos pheres containing lead compounds in particulate fora In excess of 1*5 to 5.0 mg* Pb per 10 cu* m. of air.) The test mentioned In your letter, If carried out as described* as a rather crude and Inadequate one* The air stream from the hood should have been taken through a solution that would dissolve lead oxide promptly* and at the same time prevent the escape of particles, through the solvent l.e. using an impingerj or the stream should have gone through a strong electro-magnetic field l.e* a Cottrell precipitator* After collecting the material and getting It In solution* a precipitation with H2S could then be done at the proper reaction* I can assure you that if the air stream from a lead-oxide-coated plate which is being cut by an oxy-acetylene torch la properly examined* It will be found to have considerable -quantities of lead in it. The diagnosis In cases of exposure of this type can usually be made from the clinical picture alone* However* in doubtful cases one can determine the approximate magnitude of the exposure and absorption by the analysis of the blood and the excreta* if samples are ob tained shortly after the cessation of exposure* The lead content of the blood and also the urine vary with the severity of the exposure* In severe cases the blood and excretory lead remain at abnormal levels for months* In less severe cases* and particularly those with short periods of exposure* definitely and significantly high lead levels remain for only a few weeks* If you would care to send me all the available information on the cases at issue* I should be glad to give you my opinion about them* Cordially yours* RAKjls Robert A* Kehoe, MD* 0* 00075d