Document DMwL5KOvEp9E6BwwnRMZGoGm4

The tubjrot of *noraal load* has boon ein tensively investigated by Kehoe and hi a associates (1333*1933) Jour, of Xnd* Hyg.1933 - A rticl* ready for publication 1939 - Citation to bo providsd later* probably in Jour* Biol, Chao* -who have found that the normal American adult excretes lead at the rate of 0.25 to 0,^0 nm^u per day* Host of thia lead le present In the feces* the urinary output amounting only to 0-02 to 0,10 aga, per day* (0,02 to D.OS ags, per liter). The normal concentration of lead in the feoee la from 0*03 to 0 ,11 a, per gran of feoal aeh* Analysis of duplicate 2& hour aanple# of the food of a series of normal individual# revealed that 0,22 to 0,35 mgs, of lead per day was obtained from this source, A portion of 1 the lead content of the food was found to be of natural origin* frombut additional quantities were derived a variety of artificial sources, Those food# which were found most eoastonly above an ataverage lead content were* in order inore&alng Importance* bread-stuffs* meats* processed neats* ins cream, candy* leafy green vegetables* and certain fruits, tfubse^uuuiliy C133J1) piece investi gators In essential agreement with Willoughby and Wilkins (1238) -- it-- -- -- -- ---------- ---------- Willoughby* C,S. and Wilkins* F, 3, Jour, Biol, Che* lgfri (>39*(193S) and Kaplan and McDonald (193-) obtained a mean value of approximately 0,030 fflgja, per 100 gratae of the whole blood of normal individuals and showed that their earlier results owed their variability and their higher and less stabile mean value (1935) to certain sources atof contamination in the collection blood samples. They also showed (1973* 1939) that the blood of Mexican Indiana* living on natural vegetable and animal products of their own cultivate, m* N24624 *2 contained lead to tlie scan extent of 0*02 mgo. per 100 grama, The identification of lead la the blood, urine, end faces, therefore, is not indicative of lead poisoning, However, when exposure to lead hae boon excessive, and the system* of peleonlog occur, normal value* are greatly exceeded* Xehoe and hie associates (1933**939) hove studied groups of workmen under a variety of condition of occupational lead exposure* Depending upon the occupation, they found that the mean daily feoal lead output of group* of men varied frost 0.^7 to 7*6t> mgra., (0.09 to 0.57 per gram of fee&l ash) * The mean lead concentration in the urine of the corresponding groupa ranged from 0,05 to 0,3*1 mgjs, per liter. Case* of lead poisoning were found among oertaia group* of the&* workmen| and from the oorrelatlon of the analytical ith the clinical findings over considerable period* of tine, Xehoe and hi# ooliabrator# drew the following pertinent and practical conclusion*. Occupational lead exposure la safe if It doe# not give a mean lead output of more than 0.6o ngs. per day la the fee* or a seen urinary concentre tion above 0.10 tagm. per liter. Poisoning any be expected to occur under conditions in which lead occurs In the-feces of workmen In excess of a aeon level of 1.1 sign, per day, and In which the mean urinary lead concentration exceed* 0* 15 ngn, per liter, The higher the values go above these levels, the greater will be the frequency of occurrence end the severity of lead poisoning among the workmen. The threshold concentration of approximately 0.10 apps. of lead per liner in the urine, corresponds genrally, under condition# of maintained lead exposure, to a blood concentration of 0.06 to 0.07 ffigm. In acute lead intoxlcati *i, reacting from vefy severe exposure, the blood concentration m y rise as high as 0.30 mg, par 100 gram# 3 of whole blood, but under more usual condition# .-,f hasardou# exposure, it 1# found between 0*06 and 0* 15 sag* per 100 grnai of whole blood* Kaplan and McDonald found lead le ve ls in the blood ranging from 0*6 to 0*10 go* per 100 ee in t h e ir ease# of lead poisoning* Ho doubt In a number of t h e ir eases, some Oppor t unity had been given for a low ering of the blood concentrations below those present at the time of t h e ir exposure* (This ie doubtless true because of the t ine elapsing between the onset of Illn e ss and the t lae of taking the s&nplss* Our own result s on hospit al and in d ust r ial compensation eases, seen seme days or weeks af t e r the cessation of exposure# f ir e values consider rbly lower than those found among workers at the onset of their illness, RAK.) Additional Qttsent# on certain phases of tills matter* - 1* The expression *fecal output* has been used instead of "fecal excretion* because moot of the alimentary lead 1#. not excreted in the physiologic sense but merely traverses the tract unabsorbed* 2m Reference Is made to "the dai'y intake by ingestion and from the upper respiratory tract* because this lend in the feces is a rough but practical measure of the intake by inhalation, which, of course, is much more Important than that swallowed* In the following paragraph on the toxio level of industrial lead exposure, the significance of the fecal lead output is expressed on this basis. There is no reference here, therefore, to the threshold of toxicity of purely ingested lead, since the latter is -now to be off a very different order of magnitude, for this reason, I have inserted the word *ocoup.':tional* before *lead exposure* in the sentence beginning "Lead exposure is safe if * * , . etc", I har also ohangd the following sentono e that it refers spesiflsally to "wor`jen#. 3 Th quoted paragraph presents my present opinion quite oouraely. ^0, I 003