Document a4dbq0wV8Grvxq6oOm301VaNy

The subject of *normal load* has boor* ein tensively Investigated by Kehoc and his associates (1333*1939) * Jour. of Xnd. Hyg.1933 A rtiel* ready for publication 1939 Citation to be provided later* probably la Jour* Biol, Chao* -who have found that the normal American adult excretes lead at the rate of 0*2$ to 0.40 Mm* per day* Host of this lead le present In the feces* the urinary output amounting only to 0*02 to 0.10 agn* per day* (0*02 to 0*06 mm* Pr liter)* the normal concentration of lead in the feoes is from 0*03 to 0.11 age. per gran of feeal ash* Analysis of dupliest# 24 hour samples of the food of a series of normal individuals 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* but additional quantities were derived from & variety of artificial sources* Those foods which were found most eoastonly above an average le&d content were* in order of increasing Importance* bread-stuffs* meats* proesseed meats* ioc cream* candy* leafy green vegetables* and certain fruits. 0ubcc^uuuitiy UJ39)'"jkheie investi gators in essential agreement with Willoughby and Wilkins (1238) -- ---- ---- ---------- ------------ -- -- Willoughby* C.S. and Wilkins* F*. 3Jour* Biol. Chem* 124i 639*(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) certain courses of contamination in the collection of blood samples. They also showed (1973* 1939) that the blood of Mexican Indiana* living on N 24624 *2 containad load to the aean extent of 0*02 mgm* per 100 grama* fha i&entifioatlon of lead la the blood, urine# and feces* thm*efore* la not indicative of load poisoning, However* when exposure to lead hae been excessive* and the aya^toraa of poisoning occur* normal values era greatly exceeded* Kehoe and hit associates (1933**939) have studied groups of worfen under a variety of conditions of occupat ional lead exposure* Depending upon the occupation* they found that the mean dally feoal lead output of groups of men varied from 0*%7 to 7.60 egra.* (0.09 to 0.57 **g, per gras of feoal ash) The mean lead concentration in the urine of the corresponding groups ranged from 0*05 to 0*3% m$s per liter. Case* of lead poisoning were found among certain groups of the&a workmen} and from the correlation of the analytical Jlth the clinical findings over oonel&emblo period# of tis&e* Kehoe and hi# oollabratora drew the following pertinent and practical conclusion#. Occupational lead exposure la safe if it dose not give a mean lead output of more than O.60 sign, per day in the feces or a mean urinary eonoentra* tlon above 0*10 mgm. per liter. Poisoning nay be expected to occur under conditions in which lead occurs in the feoea of workmen in excess of a mens level of 1*1 mg. per day* and la which the mean urinary lead concentration exceeds 0*15 g* per liter, the higher the value# go above these levels* the greater will be the frequency of "ocurrenoe and the severity of lead poisoning among the workmen. The threshold concentration of approximately 0.10 ngs*. of lead per liter in the urine* correspond# generally* under condition# of maintained lead exposure* to a blood concentration of 0.6 to 0*07 rngrn. In acute lead intoxicati m* resulting from vefy sever exposure* the blood concentration may rise aa high as 0.30 mgm* per 100 grams j^r I 00366 3 of whole blood# bat under more ustud condition* of hazardous exposure# it i# found between 0,06 and 0*15 per 100 gram* of whole blood* Kaplan and McDonald found lend level* in the blood ranging from 0*6 to 0*10 mga* per 100 eo in their ease* of lead poisoning, Ho doubt in a number of their ease*# eoae djtpofv tunlty had been given for a lowering of the blood concentrations below those present at th* time of their exposure* (This ie doubtless tro* because of the time elapsing between the onset of illness and the time of taking the samples* Our own results on hospital and industrial compensation oaaee# seen some days or weeks after the cessation of exposure* give values considerably lower than those found among workers at the onset of their illness, RAK.) Additional ooanente on certain phases of this matter, 1* The egression * fecal output* has been used instead of "fecal excretion* because noet of the alimentary lead ie not excreted in the physiologic sense but merely traverses the tract unabsorbed* 3, Reference is mads to "the daily 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 toxic level of industrial lead exposure* the significance of the feoal 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 / ie known to be of a very different order of magnitude, for this reason# X have ins rted the word "occupational* before "lead exposure" In the sentence beginning "Lead expos-are is safe if " , , . etc", Lgp /3 0XC7 -4~ I hav Alao hanged the following sent once eo that it refers epeslfloally to *vror`uen#, 3. *h# quoted porseraph presents sr present opinion quite eoouroely* 00368