Document jBq1wJvo0NyebrOnvdv7mnO9p

lisa* re^*k -iA !-3t-- .ffik Us m .3 >a ^TO M :f GENEPAL OVNAMICS C ORPO R AT ! ON <: \.O u< o 3. 3 + > n ; i . : . .;; /, m / , - o t? r-: a :>. > .2 June 6, 1967 Dr. Robert A. Kehoe Kettering Laboratory Eden and Bethesda Avenues Cincinnati, Ohio ^5210 Dear Dr. Kehoe: I am enclosing a brief technical discussion concerning the use of radioactive Fb203 as a tracer for experiments with humans. As you will recall, during your visit here we suggested this technique as a means for studying the clearance of lead from the lungs. We think it is quite feasible to make Fb203 using our accelerator and to label lead tetraethyl with the Fb203 . We estimate that the specific activity of the labeled lead tetraethyl will be sufficiently great to follow the lead using a conventional radiographic scanning technique as the lead is cleared from the lungs. We do not know exactly how to do the labelling at the moment but feel confident that we can do so after a modest amount of research on the subject. If you should be interested in using the tracer technique, we would be pleased to discuss the labelling problem in greater detail. We have also calculated the radiation dose a person would absorb in an experiment utilizing Pb203 . The dose is far below the presently accepted tolerance level. Therefore, we do not feel that the use of this particular radioactive isotope should be of concern from a health point of view. We are most anxious to continue discussions with you as to ways we can contribute to your studies. If you have questions concerning our suggestions, please feel free to call or write. Zi 1 V / S 1 O N OF: Sincerely yours. N15303 David F. Herring ETHYL CORPORATION INTER-OFFICE To Dr. A. S. Hawkes Fr o m Gary Ter Haar Su b j e c t Lead Inhalation Studies Ad d r e s s Ad d r e s s Da t e Detroit Detroit August 23, 1967 In regard to the use of 210 Pb or 203 Pb for use in inhalation studies on humans, the following model could be considered as a working base. Assume a person breathed in l80-ug of lead, about 53% or 100 jug would be deposited in his system. Each box shows the amount of lead deposited and as a total of 100 g is present each number is the percentage of total lead deposited. Figure I rnin. lJO-Ug 80 jug back to air Naso-Pharynge al j rnin. V Blood /A A ii i 1.5 -g 15 ,,ug ! 11.7 jug 4 min. 1.4 jig Tracheo-Bronchial | 14 jug 4 min. 12.6 ,,ug G. I. Tract A "A 90 days 15 -Mg Pulmonary 73-Mg 24 hours 29 -Mg 90 days 29 Jig 10% of that in G. I. tract is absorbed, into blood Using the model one can calculate the number of counts to be found in a given sample if a known dose of radioactive lead were administered. The I.C.R.P. report in Health Physics, Volume 5, i960, page 75, shows that 90 microcuries of 203 Pb and 4 microcuries of 210 Fb is the maximum permissible dose to the whole body. If we administered l/lOO of the permissible dose and assumed 50% counting efficiency for 210 Pb (^) and 10% for 203 Pb (&) the samples deposited would have a total count of about 5 X 104 c/min for the 210 Pb and 2 X ICc'C/min for 203 PB. What counts should be expected from samples of blood urine and feces. HZ 0012929 N15303.01 To: Dr. A. S. Hawkes August 23, 1967 2- - I. Blood A. One hour In the first hour 2.7$ should reach the blood. If a 10 ml sample of blood were taken and a man has about 8-000 ml of blood the following is true: 10 1. 210 Pb - 5 X 104 X 0.027 X 8000 ' = 1.7 C/min 2 . 203 Pb - 2 X 105 X 0.027 X = 7 C/min B. Twenty four hours At the end of 24 hours an additional amount will enter the blood stream.from the gut. If 10$ is absorbed from the gut [29 + 12.6 + 11.f] (o.l) = 5.3$ 4. 10 / 1. 210 Pb - 5 X 104 X 0.033 X ~8ooS = 5-3 c/min 2. 203 Pb - 2 X 105 X 0.053 X " 13*2 C/min C. Seven days The situation in the blood at the end of the first week would be one in which nearly all of the activity is coming from absorption from the gut and the lungs. As about 90 days are needed to clear the dose from the lungs to the blood (15 ,ug in the model), about 1$ of this 15$ or 0.15$ will be cleared per day. As 29$ is cleared to the G. I. tract from the lungs in 90 days of which 10$ is absorbed to the blood, an additional 0.029$ will come from this source. 29$ X 1$ X 10$ = 0.029$ Total 0.15$ + 0.03$ = 0.18$ The half life of 203 Pb (52 hours) of course, reduces its activity by about a factor of 8. 210 Pb with a half life of 22 years is not affected. 1. 210 Pb - 5 X 104 X 0.0018 X 3555 = 0.1 C/min 2. 203 Pb - 2 X 105 X 1/8 X 0.018 X = 0.1 C/min Examination of blood is of no use for 203 Pb at the end of a week; however, 210 Pb could readily be continued for the first month. He 0012330 To: Dr. A. S. Hawkes August 23, 1967 -> II. Urine A. One-two hours About 90io of the lead in the blood is very rapidly passed to the urine. Therefore, collecting the total sample after about 1-2 hours should show the 2.7$ that had passed to the blood. Thus for 210 Pb 1. 210 Pb - 0.9 X 5 X 104 X 0.027 = 1.2 X 103 C/min for 2. 203 Pb - 0.9 X 2 X 105 X 0.027 = 4.9 X 103 C/min B. Twenty-four hours At the end of 24 hours an additional 5*3% will be found in the urine or about twice the above counts C. One week At the end of a week the blood will be near equilibrium with the urine and about 0.18fo should be found in one daily sample 1. 210 Pb - 0.0017 X 5 X 104 = 91 C/min 2. 203 Pb - 0.0018 X 2 X 105 X 1/8 = 45 C/min Lead-210 in the urine could be run for at least the 90-day period and lead-203 through the first 8 days III. Feces A. Twenty-Four Hours During the first 24 hours about 11.7$ + 12.656 + 29$ or about ^Ofo should be found in the feces 1. 210 Pb - 5 X 104 X 0.5 =*2.5 X 104 C/min 2. 203 Pb - 2 X 105 X 0.5 = 105 C/min B. Seven Days After a week, about ifo of the 295 remaining in the 3.ungs should pass through the G. I. tract and into the feces 1. 210 Pb - 0.29 X 0.01 X 5 X 104 = 1.5 X 102 C/min 2. 203 Pb - 0.29 X 0.01 X 2 X 105 X 1/8 - 100 c/min HS 0012331 To: Dr. A. So Hawkes August 23, 1967 -k Lead-210 could be measured In the feces for many more days while lead-203 could be measured to about 12 days. Lead-210 would best be measured by isolating it in Po-210 daughter which would require two separations of Po-210. The lead-203> being a gamma emitter could be measured simply by placing the unprocessed sample in a counter. In addition an estimate could be made of the concentration of lead-203 in the lungs, liver and spleen by using external body counters. The advantage of Pb 203 is the ease of counting. The disadvantages are its short half life, making rapid manipulation necessary and preventing a complete long-term metabolic balance, and its preparation which in volves use of a cyclatron and separation of a very hot sample from a lot of other undesirable isotopes. The advantages of lead-210 are ready availability, long half life, permitting complete study, and alpha dis integration which permits use of very low background counters. (0.02 c/min). Lead-210 has the added advantage that the early counts in the blood are sufficiently above background to determine very accurately the percent in the blood. One important disadvantage is that at least three months are needed to allow the 210 Po to grow in order to analyze the samples. According to the I.C.R.P report one hundredth of the maximum dose of either isotope should be equally safe. GTH:die cc: D. E. Cooper J. E. Faggan M. E. Gluckstein E,, B. Rifkin K? 0012.332