a true measure of exposure

A True Measure of Exposure

234

Los Alamos Science Number 23 1995

The human tissue analysis pro-gram, a 35-year-long researchprogram at Los Alamos, has

been scrutinized by the local and na-tional news media and, more recently,by the President's Advisory Committeeon Human Radiation Experiments. Al-though this program does not technical-ly fall under the description of "humanexperimentation," as defined by Secre-tary of Energy Hazel O'Leary, chargesby the news media of DOE's "bodysnatching," unethical procurement ofhuman tissues and organs, and hidingor withholding resulting data from thenext-of-kin and their lawyers mandatedthat this program be included in theAdvisory Committee's investigation and that all documents and other infor-mation about the program be madeavailable.

As the leader of the Los Alamos tissueproject for 21 years, I will take this op-portunity to review the motivations, themanner of obtaining tissue samples, andthe most important findings of what thegeneral public, including my wife, seesas a very ghoulish activity. Work oncadavers has been at the heart of med-ical discovery and medical educationfor hundreds if not thousands of years.This work is no exception—our pro-gram enabled us to quantify the pluto-nium distribution in the body through

postmortem analysis of tissues from oc-cupationally exposed individuals. Be-cause the risk of cancer is highly de-pendent on not only the amount ofplutonium retained in the body, but alsothe fraction that goes to specific organs,our discoveries on plutonium distribu-tion have helped to clear away uncer-tainties about the human metabolismand potential health effects of this ra-dioactive substance.

The plutonium excretion models, whichwere the main product of the plutoniuminjection studies, provided an indirectmeans for estimating the amount ofplutonium retained in the body of a liv-ing person from the amount excreted inthe urine. Those models were crucialbecause they were the most commonlyused means for estimating the bodyburden and the ultimate risk from acci-dental plutonium exposures, but theygave no information about the distribu-tion of plutonium in the body, nor werethere any independent means to checkon their accuracy. The painstaking col-lection and analysis of tissues from de-ceased individuals over the last 35years has provided at least some of themissing information, and that informa-tion now serves as a cornerstone of thepresent models for determining thedoses and the risks from plutonium ex-posure. The early biokinetic modelsused to estimate body burdens werebased primarily on indirect measure-ments such as urinalysis, fecal analysis,external lung counting, and/or wholebody counting. In contrast, the tissuedata are direct and definitive. The tis-sue program has also provided an accu-rate measure of the general level of plu-tonium exposure of Laboratoryemployees and thus a check on the effi-cacy of industrial hygiene and health

physics measures that are meant to keep plutonium contamination to a minimum.

The author (now retired from the Labo-ratory) hopes that the tissue results pre-sented here, some of which are relative-ly recent, will inspire rejuvenation of aneffort that can continue to help elimi-nate the remaining uncertainties charac-terizing plutonium dosimetry.

Early Studies of Plutonium Metabolism

Bill Moss's article, "The Human Pluto-nium Injection Experiments," reviewsthe fact that, in 1944, when plutoniumbegan to be produced in large quanti-ties, nothing was known about humanmetabolism, retention, distribution, andexcretion of this manmade element.The leading scientists and medical doc-tors in the Manhattan Project, however,were well aware that working with plu-tonium might pose a serious health haz-ard. They had done research on usingradionuclides for medical diagnostics inthe 1930s, and they knew that long-lived radionuclides such as radium aredangerous if they are retained inside thebody because they become a constantinternal source of radiation. Biomed-ically, plutonium was assumed to bemuch like radium. Internal deposits ofradium had produced fatal anemias andbone cancers in the radium dial paintersof the 1920s, and there was great con-cern that internal exposure to plutoniumand its compounds might be at least asdangerous.

By January 29, 1944, 11 milligrams ofplutonium (a fair share of the world's


Number 23 1995 Los Alamos Science 235

A TRUE MEASURE OF EXPOSUREthe human tissue analysis program at Los Alamos

by James F. McInroy

The image at left is an autoradiograph of

a tracheobronchial lymph node from a

former worker at the Laboratory. It

shows alpha tracks radiating in a typical

star pattern from tiny alpha-active

clumps of matierial. Chemical analyses

of the radioisotopes in this individual’s

lungs and lymph nodes indicated that

those clumps most likely consisted of an

aggregate of plutonium particles.

total supply at that time) had been allo-cated for animal metabolic studies. Theresults indicated that the skeleton wasthe major deposition site, the retentiontime was long, and the liver had thehighest concentration among the softtissues, followed by the kidneys and thespleen. How appropriate were thoseanimal data for quantifying the distribu-tion and retention of plutonium in hu-mans—and thus for determining thedoses and the risks of plutonium exposure?

The human injection experiments were,in part, an effort to answer that ques-tion. Excretion data were collectedfrom all subjects following injection ofplutonium into the bloodstream, andsmall tissue specimens from those sub-jects who were terminally ill were ana-lyzed for plutonium following theirdeath. A number of important observa-tions followed: 1) there were no majordifferences between humans and thecommon laboratory animals in the dis-tribution in tissues with the exception ofliver; 2) the liver of humans contained20 to 40 per cent of the total amount re-tained versus 10 per cent or less for ratswhen both received the same plutoni-um-citrate complex; 3) the retentionhalf-time in liver was greater in hu-mans; 4) the retention half-time forwhole body in humans was much longerthan in laboratory animals; and 5) theexcretion pattern in humans was differ-ent, especially that a much lower frac-tion was eliminated in human fecescompared to animal feces.

Wright Langham, a radiobiologist in theHealth Group at Los Alamos who hadplanned the analytical protocols for thehuman injection experiments, used theexcretion data to create a model relatingthe amount of plutonium injected intothe bloodstream to the amount excretedin the urine. Thus, the Langham modelbecame the first basis for estimating theamount of plutonium retained in thebody as a function of time following anaccidental intake of an unknown quanti-ty. By the late 1950s, James N. P.

Lawrence of Los Alamos had modifiedthe Langham model to take into accountlong-time excretion data from a selectedgroup of Los Alamos workers who hadexperienced accidental intakes duringthe Manhattan Project and who hadbeen followed as part of an epidemio-logical study (some of those men telltheir stories in the roundtable "On theFront Lines"). But many uncertaintiesremained. Most worker exposures werethe result of inhaling tiny airborne parti-cles of plutonium into the lung. Howdid that mode of exposure compare tothe injection of plutonium directly intothe bloodstream? It was suspected thatthe patterns of retention, distribution,and excretion, and thus the dose to thebody, would change depending onwhether the intake was by inhalation,ingestion, or a cut or puncture wound,but no human data were available tocheck the conjectures. It was also ex-pected that the dose and the ultimaterisk of exposure would be affected bythe particular chemical form and particlesize of the material taken in, the timesince exposure, the duration of expo-sure, and the effects of individual bio-logical variation.

The Beginnings and the Philosophyof the Los Alamos Tissue Program

Our human tissue analysis began spon-taneously following the accidental deathof Cecil Kelley, a plutonium workerhere in Los Alamos. Kelley was expo-sure to a lethal dose of gamma andneutron radiation on December 30,1958 and died 35 hours later. The radi-ation source was a plutonium collectionvessel at DP Site that suddenly and un-expectedly went critical during theyear-end inventory (see "The Cecil Kel-ley Criticality Accident: The Origin ofthe Los Alamos Human Tissue Analy-sis Program"). As a part of the medicalautopsy, the local pathologist Dr.Clarence C. Lushbaugh collected tis-sues to examine any physical changesthat might have been caused by the ex-treme radiation exposure. Dr. Lush-

baugh, who was also a research scien-tist at the Laboratory, decided to sendseveral of the organs and bones to theLaboratory for radiochemical analysisto determine the plutonium content.

Kelley had worked with plutonium fora number of years prior to his deathand was carrying in his body a measur-able plutonium "burden," which pre-sumably had been obtained mostlythrough inhalation of moderate routineairborne contamination. The estimatedwhole-body content, based on urine ex-cretion data and the application of JimLawrence's PUQFUA (Plutonium BodyBurden (Q) From Urine Assays) code,was 18 nanocuries, a little less than halfthe maximum permissible body burdenof 40 nanocuries. The tissue samplesrepresented the first opportunity to de-termine directly the plutonium burdencarried in an individual who had beenanalyzed for plutonium content prior todeath and thus to check the predictivepower of the urine excretion modelsagainst real data. It was also an oppor-tunity to measure the real efficacy ofthe industrial hygiene and healthphysics measures that had been taken toreduce airborne plutonium contamina-tion in the work environment. Thoseresponsible for industrial hygiene atLos Alamos, including Wright Lang-ham, Donald Petersen, and Dr. Lush-baugh, felt it was incumbent on them totake advantage of the availability ofthat information, even though it result-ed from the untimely and tragic deathof a colleague.

The Kelley data offered some surprises.Although the whole-body content wasfound to be 19 nanocuries, in closeagreement with the excretion model,that result was considered by WrightLangham to be "undoubtedly fortu-itous" because the fraction in the lungand pulmonary lymph nodes was muchlarger than predicted by the biokineticmodels of the day. That surprise led tothe initiation of the tissue analysis pro-gram at Los Alamos, a conserted effortto collect and analyze tissues from


236

Los Alamos Science Number 23 1995

deceased occupationally exposed work-ers. The program also included somemembers of the general public as con-trols. The hope was to quantify all thevariables affecting the distribution andretention of plutonium and then use thedata to improve the in vivo estimates ofinternal plutonium exposures.

The most important sources of tissueswere the many workers involved withthe handling of plutonium in the 1940sand 1950s when most of the serious ex-posures occurred. Those individualswere fairly young at the time andproved to be a very healthy group. Asa result, the collection of human tissuesfrom autopsy or surgery has proceededslowly.

The plan to include unexposed peopleas controls eventually grew into a largestudy of the U.S. non-occupationallyexposed general population. The resultshave produced an accurate determina-tion of the background levels of inter-nally deposited plutonium from atmos-pheric fallout due to nuclear weaponstesting and from accidental release tothe environment from nuclear facilities.The results from the general populationstudy are presented in the last sectionof this article.

The tissue program has also includedthe study of americium, uranium, thori-um, and neptunium, however, the vastmajority of the analyses performed ontissues at Los Alamos were for plutoni-um and americium. As mentionedabove, plutonium in the bloodstreamwas found to be deposited preferentiallyin the liver and skeleton. If the expo-sure was from inhalation, the lung andassociated lymph nodes would also re-tain deposited plutonium. If the expo-sure was through ingestion, the conse-quences would be reduced because thegastrointestinal tract allows only aboutone plutonium atom out of ten thousandto pass through the intestinal walls andenter the blood stream. That knowl-edge of the primary deposition sites ledthe early researchers to collect tissue

specimens from the lung, tracheo-bronchial lymph nodes, liver, kidneyand bone specimens. Later, interest inminor deposition sites and possible con-sequences, such as potential genetic ef-fects if the radioactive elements were todeposit in gonadal tissue, led to the col-lection of several additional tissues.

The ethics of our tissue collectionprocess has commanded the most atten-tion during the recent re-examination ofthe tissue program by the President'sAdvisory Committee. Our own exami-nation of procedures has shown that forall normal deaths (that is, not involvingaccidents, suicide, homicide, and soforth), tissue collection was done onlyafter obtaining appropriate authoritythrough a written consent form. Forexample, during the 1950s and 1960sconsent for autopsy and tissue collec-tion were obtained in writing from thenext of kin by the floor nursing supervi-sor or attending physician at the LosAlamos Medical Center.*

Then in 1968 the Atomic Energy Com-mission (AEC) sponsored the formationof a formal registry to collect medical,exposure, and work histories of plutoni-um workers on a voluntary basis and torequest authority from the registrantsfor autopsy and tissue analysis at thetime of death. Originally called theNational Plutonium Registry, it waseventually expanded into two registries,the U.S. Transuranium Registry and theU.S. Uranium Registry. The two arenow combined and referred to as theUSTUR. They are administered atWashington State University under thesponsorship of the DOE's Office ofHealth and Environmental Research.The accompanying box "Authority andCollection of Tissues" outlines the pro-cedures followed at Los Alamos in theearly days and by the Registries inmore recent times to obtain consent andto collect tissues.

Studies of Occupationally Exposed Workers

Los Alamos Donors. From 1959 to1978 tissues from 116 former employ-ees of the Laboratory were analyzed.Not all had been exposed to plutonium;many were support personnel such assecretaries, janitors, firemen, truck dri-vers, and others who had volunteered tobe part of the program.

Since our association with the USTURin 1971, tissues from 60 additional LosAlamos workers with known or sus-pected exposure to plutonium havebeen analyzed, including six wholebodies. As of October 1995, there are42 living members of the Registry fromLos Alamos who have given their con-sent for radiochemical analyses follow-ing death; seven of them are whole-body donors. A total of 25 highlyexposed workers from all over thecountry are currently enrolled with theUSTUR as whole-body donors follow-ing death.

What has tissue analysis revealed aboutthe effectiveness of the Laboratory's ef-forts to protect its workers from expo-sure to plutonium? During the earlydays of the Laboratory's operation, par-ticularly during the war years, we knowthat the containment and filtering sys-tems were not available or were notused as efficiently as they are today.The higher levels of contamination pre-sent at that time were clearly reflectedin the tissues we analyzed from a secre-tary who worked in the original pluto-nium processing building known as "D"building. Although she probably neverworked in a plutonium laboratory, herlungs, liver, and skeleton containedlarger concentrations of plutonium thanthe general public, undoubtedly frominhalation of airborne plutonium duringher work hours.

To evaluate the overall exposure of theLaboratory work force, a comparison ofconcentrations of plutonium in the liverwas made between the worker popula-



* The Los Alamos Medical Center was operatedby the AEC until 1964, after which it was pur-chased by the Lutheran Health Systems of Fargo,North Dakota.

continued on page 241


238 Los Alamos Science Number 23 1995

Authorization and Collection of Tissues

The charge of “body snatching” by the news media opens up the issue of whereand how the Los Alamos tissue analysis program obtained samples for study.

During the first twelve years of the program, from 1959 to 1971, all samples wereobtained from individuals who had died and/or were given autopsies at the LosAlamos Medical Center. As described in the main text, the first case was CecilKelley, who had worked with plutonium and died as a result of a criticality accident.His autopsy was authorized by the Los Alamos coroner, and then the pathologist atthe Los Alamos Medical Center, Dr. Clarence C. Lushbaugh, decided to collect tis-sue samples from Kelley and have them analyzed for plutonium content by the bio-medical research group at the Laboratory (Lushbaugh had a joint appointment withthat group). After the Kelley incident, Lushbaugh decided to make the collection oftissue specimens for plutonium analyses a routine part of all autopsies performedat the Medical Center. That practice was quite acceptable since, in those days, au-topsies were considered a learning tool. They were used to confirm the accuracyof the physician’s diagnosis, to determine the effectiveness of certain medical treat-ments, and, of course, to determine the cause of death, especially in the cases ofunattended deaths. Also, autopsy programs measuring plutonium in human tissueswere being conducted at other sites in the U.S. and in foreign countries.

Perhaps the more unusual practice was Lushbaugh’s attempt to get permission toperform an autopsy on every person who died at the Los Alamos Medical Center—Laboratory employees, members of the general population from Los Alamos andsurrounding areas, and transient visitors from other parts of the country. Of courseautopsies had to be perfomed on a certain percentage of persons dying in the hos-pital each year in order to maintain the accreditation of the hospital and hospitalstaff. Also the members of the Los Alamos community were typically very interest-ed in the science that could be learned from the autopsies and were willing tomake this final contribution of themselves in the interest of science.

For routine deaths, the floor nursing supervisor or the attending physician wouldask the next of kin to sign the Medical Center's "Authority for Autopsy" form, whichstated that the next of kin "authorize(d) a postmortem examination of the decedent,including removal and retention of such specimens and tissues, as the examiningphysician deems proper for therapeutic or scientific purposes". Few refused con-sent. Non-routine deaths (accidents, unattended deaths, suicides, homicides, andso on) fell under the authority of the coroner, and so the coroner was asked andwould grant consent for the retention and analysis of tissues. In all the cases men-tioned above, the next of kin were not necessarily made aware that tissues werebeing retained specifically for the analysis of plutonium content

Formal consent from occupationally exposed workers. Procedures for obtainingconsent became more formal and more explicit in 1968 when the United StatesAtomic Energy Commission (AEC) established the National Plutonium Registry tofunction as a national center for the collection of medical, exposure, and work histo-ries for the workers in the AEC nuclear complex. The Registry was an outgrowth ofthe postmortem tissue sampling program that had begun in 1949 at the AEC's Han-ford site near Richland, Washington and continued to collect tissues at autopsy pro-vided permission was given in advance by the occupationally exposed individual. Inthe original request for funds, the primary purpose of the Registry was stated as "theprotection of the interests of the workers, employees, and public by serving as a na-tional focus for acquisition and dissemination of the newest and best information



relative to the effects of the transuranium elements on people." In 1970, the nameof the Registry was changed to the United States Transuranium Registry (USTR)but the mission did not change, and by June 1974, 5843 transuranium workers hadbeen identified, of whom 3880 had signed release forms for their medical andhealth physics records and 819 had given authority for autopsy.

Initially, all tissues collected by the Registry, with the exception of cases originat-ing at Rocky Flats, were analyzed at the Battelle, Pacific Northwest Laboratories,in Richland, Washington. In 1971, the Los Alamos Laboratory was added to thelist of "approved" laboratories. The Battelle and Los Alamos laboratories submit-ted their own research proposals and were funded independently by the AEC forradiochemical analysis of the Registry tissues. In 1978, the Energy Research andDevelopment Agency (ERDA), successor to the AEC, directed that the Los Alam-os tissue analyses laboratory become the lead laboratory for analysis of humantissues for the United States Transuranium Registry (USTR).*

Once the Registry was established, physicians in the Industrial Medicine Group atLos Alamos would use the periodic employee medical examinations as a time tointroduce the Registry and its purpose to those Laboratory employees who wereeither known to have, or suspected of having, internal exposure to the transurani-um elements. Individuals willing to release their medical, exposure, and work his-tories to the Registry and to donate tissues following their death were providedadditional detailed information and appropriate consent forms. Those forms weregenerally signed prior to death by the donor, his spouse or nearest next of kin,and a non-related witness. The forms were kept on file and had to be renewedevery five years to be valid. Also the next of kin could withdraw the consent fortissue donation at the time of death if they desired to do so.

Potential donors were provided with identification cards to carry on their personthat notified the attending physician or hospital staff at the time of death of the in-dividual's desire to donate tissues to the U.S. Transuranium Registry. The cardgave a telephone number to be called if death was imminent or had occurred.Once the Registry was notified, they alerted our tissue analysis laboratory, and wesent instructions and shipping containers to the hospital where the autopsy was totake place. Following the autopsy, tissue specimens were individually packagedin plastic bags, frozen, packed in Dry Ice, and shipped to Los Alamos by overnightdelivery.

In recent years, the Registry instituted a whole-body donation program in which allinternal organs were removed, packaged as described above, and sent directly toLos Alamos, and the cadaver was shipped to Richland for complete dissection.The skin, muscle, and bones were then shipped to Los Alamos for analyses. Be-cause identification cards in wallets were sometimes overlooked, whole-bodydonors had the additional option of carrying Medic Alert bracelets or medallions sothat there would be no delay in notifying the Registry of their death. The fact thatthe Registry often knew of an individual's death within a matter of minutes follow-ing the event, or sometimes prior to death, has led some people to conclude thatthe Registry was in collusion with the pathologists or contractors for the DOE toobtain tissue specimens. Thus, the charge of "body snatching.”

■

*In 1978, the Energy Research and Development Agency funded the establishment of theUnited States Uranium Registry (USUR). In 1992, the USTR and USUR were combined toform the United States Transuranium and Uranium Registries (USTUR). An excellent sum-mary of the history of the USTUR is given by R. L. Kathren et al in reference 12.



Layman’s View of An Autopsy

The author, during the course of his 21 years in the Tissue Analysis Pro-gram at Los Alamos, attended numerous autopsies. He is aware thatmany people do not know what happens at an autopsy, and thought itwould be interesting to offer the following lay description.

Generally, a medical assistant for the pathologist prepares the body by cut-ting a "Y" shaped incision in the skin and muscle covering the chest and ab-domen. The skin is cut back to reveal the muscles and ribs of the thorax(chest) and the opening the abdomen. The cartilage connecting the ribs tothe sternum (breastbone) is easily cut with a scalpel, and the sternum alongwith the connected costal cartilage from the ribs are removed to reveal thelungs and heart. The opening in the abdomen accesses the visceral organs,the liver, stomach, kidneys, small and large intestine, bladder, and so forth.

Pathologists generally remove each of these organs one at a time, begin-ning with the heart and lungs, and grossly examine them for obvious abnor-malities. They then remove small sections of tissue from suspicious areasand preserve them in a special fixative so that the tissues can later be ex-amined microscopically. To observe the interior of large organs such asthe lungs and liver, they often "bread-board" them. That is, they make par-allel slices about 1/2 inch thick throughout the organ and continually lookfor abnormalities. Any suspected areas are snipped out and preserved formicroscopic examination. In this manner, all internal organs are removedfrom the body and weighed, and appropriate sections are removed andpreserved when, based on training and experience, the pathologist deemsit necessary.

While the body cavity lies empty, a piece of the vertebrae is sliced off theinterior side of the vetebral column with a special bone saw. This bonespecimen, called a "vertebral wedge," consists of several vertebral bodiesand associated disks. It protrudes into the cavity and is easily removedwithout destroying the continuity of the vertebral column. Likewise, at thistime, a rib and/or piece of sternum can also be removed for examination.

At some hospitals, the organs that have been removed are placed in plasticbags and incinerated. Other hospitals return the organs to the body cavity.In either case, they surgically sew the skin of the abdomen and chest to-gether to restore the body to its' "normal" shape so that the mortician canprepare the body for viewing and burial. When prepared by a competentmortician, persons viewing the body are completely unaware that an autop-sy has been performed on the deceased.

When special circumstances require, the brain is removed by first cuttingthe scalp from ear to ear and turning back the skin and hair to reveal thetop of the skull. A special bone saw cuts through the skull bone to removethe skull cap, without cutting into the brain, itself. The brain is then re-moved intact, and the bony skull cap placed back into position at the top ofthe head. The scalp is sutured together, and the sutures are seldom no-ticeable when the body is prepared for the funeral. The body is then re-leased to the funeral home for embalming or cremation, as the family hasdirected. ■

Lungs from an occupationally exposed

worker inflated with dry nitrogen to ap-

proximately normal size found in the

human chest. The ratio of plutonium to

americium was measured in the Los

Alamos lung counter and compared with

measurements made before death.

A cross section of a lung that had been

inflated with nitrogen and frozen to retain

its natural shape. The dark area in the

center is an enlarged pulmonary lymph

node.

tion and the general population (seeFigure 1). The liver was selected be-cause it is a major deposition site forplutonium once plutonium has enteredthe blood stream and because all or amajor portion of the liver could be easi-ly obtained for analysis. Large tissuesamples were especially important forevaluating the extremely low levels ofplutonium in the general population.Two-thirds of the workers had liverconcentrations that did not differ signif-icantly from the general population,who were exposed only to environmen-tal sources of plutonium such as atmos-pheric fallout from weapons testing.The remaining third fell naturally intothree distinct groups. The two groupswith the highest liver concentrations(above 80 disintegrations per minuteper kilogram) had well documented ex-posures and consisted mostly ofchemists, physicists, and laboratorytechnicians. Almost without exception,the persons with those high exposureshad received them during the earliestdays of the Laboratory's existence. Thegroup with intermediate liver concentra-tions was made up of the same profes-sions as above but also included fire-men, health physics monitors, healthphysics laborers, plumbers, and so on.The latter were probably exposed whilepassing through or working in a conta-minated area for short times. Overall,it is evident that the majority of Labo-ratory workers have been adequatelyprotected from exposure to plutonium.

One might wonder whether there havebeen any Laboratory personnel who re-ceived really high plutonium exposures,and, if so, whether the exposures haveaffected their lives or been life threat-ening. These are questions frequentlyasked by concerned workers and thegeneral public, alike. (For a discussionof plutonium exposures and their ef-fects see “On the Front Lines.”)

Our study was not designed to answerall these questions. It was not an epi-demiology study where frequency ofdisease, causes of death, and life short-

ening are evaluated. However, we cananswer some of the questions and referto other related studies carried out atLos Alamos for answers to some of theothers.

Until recently, radiation protection stan-dards for internal exposures were givenin terms of the recommended maximumpermissible body burden (MPBB) spec-ified in terms of mass (micrograms) oractivity (nanocuries). [1 nanocurie =2,220 disintegrations per minute (dpm)]For plutonium, the MPBB for nuclearindustry workers was 0.65 microgramor 40 nanocuries. The MPBB foramericium is also 40 nanocuries. Thehighest depositions measured at thetime of death by our program wasabout 85 nanocuries of plutonium in aformer Los Alamos worker, 120nanocuries of americium in a worker atthe Lawrence Livermore Laboratory(the latter is thought to have receivedhis exposure while working as a gradu-ate student at the University of Califor-nia at Berkeley) and 15 microcuries(more exactly 14,600 nanocuries) ofamericium in a Hanford Site worker.Did the exposures contribute to theirdeaths? The Los Alamos worker diedat the age of 78 from a heart attack.The Livermore worker died at age 49of a malignant melanoma. However, itis not believed that americium exposureresults in melanoma. The individualfrom the Hanford Site died at age 76


70

50

40

30

Pe

rce

nt

of

Lo

s A

lam

os

Wo

rke

rs

20

10

0<5.1 5.3 - 80.1 215 - 702 2664 - 9835

60

Pu-239 Concentrations in Liver (dpm/kg)

Fig 1 (Tissue)

Workers in range of general population

Figure 1. Plutonium in Workersversus the General PopulationThis bar chart shows the liver concentra-

tions of former employees of the Los

Alamos National Laboratory. Approxi-

mately two-thirds of all those employees

measured had liver concentrations below

5.1 disintegrations per minute per kilo-

gram (dpm/kg), which is within the range

observed in the U.S. general population

exposed only to fallout. Individuals hav-

ing liver concentrations ranging from 5.3

to 80.1 dpm/kg included mainly support

personnel (firemen, custodians, health

physics monitors, security guards, and

so forth) that may have received minor

exposures incidental to their job assign-

ments. Individuals with liver concentra-

tions greater than 80 dpm/kg were physi-

cists, chemists, health physics monitors,

and metallurgists, all of whom had well

documented plutonium exposures.

continued from page 237

from cardiovascular disease. Of all thecases analyzed by this program and/orfollowed by the Los Alamos plutoniumepidemiology studies, only one isthought to possibly have died from theeffects of their plutonium exposure.That individual, a chemist at Los Alam-os during the Manhattan Project, diedin 1990 at age 66 of an osteosarcoma(bone cancer). The primary site of thecancer was the sacrum. Osteosarcomasof the sacrum are not common in manbut have been observed in animals(beagle dogs) exposed to plutonium.Keep in mind, however, that this is asingle case and must be evaluated cau-tiously. There seems to be scant hardevidence that exposure to plutoniumand/or americium at the levels reportedabove has caused any significant lifeshortening or disease.

Quantitative results on plutonium de-position and distribution. The dataobtained from deceased occupationallyexposed workers by the tissue analysisprogram has been used in many ways.One of the primary objectives of thisstudy was to measure quantitatively thetotal body burden, or deposition, of plu-tonium in a person so that models pre-dicting this deposition from urineanalyses could be validated and im-proved. This can be accomplished by

chemically measuring the plutoniumcontent in the major deposition sites,that is, the lungs and associated lymphnodes, the liver, and the skeleton.These three organs contain about 90 percent or more of the retained plutonium.Determining the lung, and liver contentis straight forward, since these organsare easily obtained at autopsy and aresmall enough to be analyzed in total.

The skeletal content is much more diffi-cult to determine, but is a critical mea-surement since about half of the sys-temic burden (internal to the body andexclusive of the lungs) is in the skele-ton. Obviously, the entire skeleton isnot easily obtained at autopsy. A rib, avertebral wedge (a block of one to threevertebral bodies removed from withinthe body cavity), and the sternum werethe bones most often removed by thepathologist for our study. That choicewas dictated in part by aesthetics—re-moval of these specimens does not dis-figure the body when it is prepared fora funeral and burial. In the early partof the study, the bone specimens wereanalyzed for plutonium, and the resultswere extrapolated to represent thewhole skeleton under the assumptionthat plutonium is uniformly distributedin all bones. The average weight of theskeleton in a young (25 to 35 yearsold), caucasian male weighing 70 kilo-grams is 10 kilograms, or about 14 percent of their body weight. The donorsto our program were much older men intheir sixth or seventh decades. In thecurrent enrollment of the USTUR, 69per cent of the donors are age 65 orolder. (Eighty-five percent are olderthan age 55.) Body weight proportionschange significantly with age. The as-sumption of a 10-kilogram skeleton, oreven a skeletal weight based upon 14per cent of the body weight, is there-fore very uncertain.

An even more important complicationin estimating the skeletal content of plu-tonium was the discovery that, unlikeradium, which is distributed somewhatuniformly throughout the bone mineral,



Figure 2. Spongy versus CompactBoneThis drawing shows a portion of a bone

from which the marrow has been re-

moved. Bone is composed of two kinds

of tissue. One is dense in texture like

ivory and is termed compact bone; the

other consists of slender spicules, tra-

beculae, and lamellae joined into a

spongy structure, which is called cancel-

lous, or spongy, bone. The compact

bone is always on the exterior of the

bone, the spongy bone on the interior.

The relative quantity of the two kinds of

tissue varies in different bones and in

different parts of the same bone, accord-

ing to functional requirements (see

Gray's Anatomy, page 282).

Endosteal layer

Compact bone

Trabecula

Periosteal layer

Blood vessel

Spongy bone

plutonium is deposited on the bone sur-face. Autoradiographs made from ani-mals given large injections of plutoniumcitrate demonstrate that phenomenonquite clearly. That means that the con-centration of plutonium is greatestwhere there is a large amount of bonesurface compared to bone volume.

Figure 2 shows that the bone is com-posed of two general types of structure:a very dense structure like ivory on theoutside, termed "compact" bone; and aspongy stucture on the inside consistingof slender spicules, trabeculae, andlamellae. The cavities of the bone arefilled with bone marrow. Yellow mar-row is found in the large cavities of thelong bones. It consists, for the mostpart, of fat cells and a few primitive

blood cells. Red marrow is the site forthe production of the red blood cellsand the granular leukocytes. It is foundin the spongy portions of the flat andshort bones, the ends of the long bones,the ribs, sternum, and vertebral bodies.

The relative quantity of compact versusspongy bone varies among differentbones, and in different parts of the samebone, according to functional require-ments. Because plutonium deposits onthe bone surfaces, and spongy bone hasa high surface area, the distribution ofplutonium within a bone is proportionalto the distribution of the spongy bone.Figure 3, showing the distribution ofplutonium in the large thigh bone calledthe femur, illustrates this very well.Most of the plutonium is located at the

two ends of the femur, which containmost of the spongy tissue.

Given this pattern of deposition, the pri-mary carcinogenic risk from plutoniumin the skeleton is associated with thehematopoietic stem cells (blood-formingcells) of the bone marrow, which fillsthe spongy structure, and osteoblasts(bone-forming cells) close to the bonesurfaces. Plutonium in or near the bonemarrow might lead to leukemia, where-as plutonium on the bone surface mightlead to osteosarcoma.

Returning to the problem of estimatingthe amount deposited in the skeletonfrom the samples taken during autopsy,we note that the ribs, sternum, and ver-tebral bodies usually sampled at autop-



Figure 3. Deposition of Plutonium in a Thigh BoneThe bar chart shows the plutonium-239 content of different sections of a thigh bone (femur) in two ways, the total activity of each

section and the concentration, or activity per gram. Plutonium deposits on the bone surface, and therefore, the concentration in-

creases with the amount of surface area. Since the interior of the end sections of the femur contain spongy bone with a high de-

gree of trabecularity and therefore a large surface area, the concentration of plutonium is higher at those ends.

0

Activity per section (dpm)

Concentration (dpm/gram ash)

0

10

0.520

1.

30

1.5

40

2.

50

Act

ivity

(dp

m p

er s

ampl

e)

Con

cent

ratio

n (d

pm/g

ram

ash

)

2.5

60

70

80

90

100

Plutonium content of sections of the femur

Fig 3 Tissue

Proximal end Proximal shaft Middle shaft Distal shaft Distal end

Compact boneCancellous bone

sy have relatively high proportions ofspongy bone and therefore have a rela-tively higher concentration of plutoni-um than the entire skeleton. Thereforeearly estimates of skeletal content de-rived from analyses of those bone typescould easily have overestimated theskeletal content if uniform distributionhad been assumed.

Wisely, the USTUR instituted a whole-body donor program in 1979 so that thedistribution of the actinides could bedetermined for the entire skeleton andalso for the less frequently sampled softtissues. As of October 1995, 47 indi-viduals have since consented to becomewhole body donors. To date, 23 ofthose individuals have died. Twelvewhole bodies have been analyzed in our

laboratory at Los Alamos for one ormore of the following elements: pluto-nium, americium, uranium, and thori-um. Six of the twelve analyzed hadworked and received their exposures atLos Alamos. Twenty-four donors arestill living, and ten bodies are awaitinganalyses at the Registries' newly estab-lished laboratory at Washington StateUniversity in Pullman,WA. One bodywas not analyzed because the persontested positive for hepatitus-B at thetime of death, and we did not wantto expose our analysts to that deadlydisease.

Detailed data from six whole bodieshave been published. Figure 4 showsthe relative distributions of plutoniumand americium in four of the bodies.

For the inhalation cases, greater propor-tions of plutonium-239 and americium-241 are found in the respiratory tractthan are predicted by the InternationalCommission on Radiological Protection(ICRP publications 30 and 48). Earlymodels based upon animal data hadproposed a 500-day half-time for theretention of plutonium in the lungs.The data in Figure 4, derived from indi-viduals who died approximately 30years following their exposure, showvery clearly that the half-time in thelungs of humans is much longer. An-other finding is that americium iscleared much more rapidly from theliver than is plutonium, whereas earlymodels used the same clearance timefor both elements. The liver-clearancehalf-time for americium is two to threeyears whereas the liver-clearance half-time for plutonium is 20 years (ICRPpublication 48). After long-term expo-sure, significant fractions of the sys-temic plutonium-239 and americium-241 are found in muscle and other softtissue, which suggests that those tissuesfunction as a long-term depot for thosenuclides.

How do the body burdens measuredfrom our radiochemical analyses ofwhole-bodies compare to the body bur-dens predicted by applying biokineticmodels to excretion data? Table 1 pre-sents a comparison that Ron Kathrenand I published in 1991. Measurementsof the systemic deposition (all organsexcept the lung) and the whole-bodydeposition of plutonium-239 in fourwhole bodies are shown in red. Alsolisted are 13 different theoretical esti-mates of the deposition. Each theoreti-cal estimate was calculated by applyinga different biokinetic model to the uri-nary excretion data obtained during thelives of those four individuals.

Table 1 shows that the plutonium bur-dens estimated from the older biokinet-ic models were many times greater thanthe measured values. The results oftwo models are within a factor of twoof the tissue analysis results for all four



Figure 4. Whole-body Distibution of Plutonium and AmericiumThe bar chart shows the mean distributions of plutonium-239 and americium-241 in

four whole bodies donated to the U.S. Transuranium Registry. All were exposed pri-

marily by inhalation approximately 30 years prior to death. The error bars represent

one standard deviation from the mean. The two elements differ most in the liver re-

tention time (plutonium has a residence half-time of 20 years compared to 2 to 3

years for americium). Also the fraction of americium found in the skeleton and mus-

cle is higher than that of plutonium. The large error bars are indicative of individual

biological variation and possible variation in exposure parameters.

Respiratory Tract

0

10

20

30

40

Per

cent

Who

le B

ody

Con

tent

50

60

70

80

Liver Skeleton Muscle Other

239Pu

241Am

Fig. 4 Tissue

cases: the Langham power functionmodel as modified by Leggert and Eck-erman and the two component exponen-tial model proposed in ICRP publica-tions 19 and 30. In all four cases inTable 1, exposure was primarily by in-halation. Jim Lawrence’s PUQFUAcode is also a modification of the Lang-ham equation and was used at LosAlamos for many years. The code esti-mated the whole-body deposition in-cluding the lung, and therefore, thePUQFUA results should be comparedwith the radiochemical estimate ofwhole-body contents shown in paren-theses. Lawrence continuously usedthe tissue analysis estimates of plutoni-um deposition in deceased workers overthe years to verify and improve hismodel.

One of the other new studies done on

the whole bodies was an investigationof the amount of plutonium in the bonemarrow. Animal studies had shownthat myeloid leukemia as well as os-teosarcomas (bone cancer) can be in-duced in laboratory animals by plutoni-um in bone given appropriate exposureconditions. As a result, there was someconcern that a high bone marrow con-centration might increase the risk ofleukemia above that calculated by theICRP bone model.

We attempted to evaluate the leukemiarisk from plutonium exposure in hu-mans by separating the bone marrowfrom mineral bone. The separationwas accomplished by washing the mar-row out of the bone cavities with a jetof water and then measuring the pluto-nium in the bone-mineral and bone-marrow components. As expected,

most of the skeletal plutonium was as-sociated with the mineralized bone.Concentrations of plutonium weremore than ten times greater in the min-eralized portions than in the organicfraction. Approximately 3 per cent ofthe total skeletal plutonium was esti-mated to be resident in the marrow,with the concentration in the red mar-row several times greater than the con-centration in the yellow marrow. Ourresult suggests that the radiation doseto the mineralized portion of the boneand to osteoblasts in the periosteal lay-ers andendosteal layers of the bone(see Figure 2) may be an order of mag-nitude or more than the dose to the redmarrow. The implication of these find-ings is that the risk of bone tumors isseveral times greater risk than the riskof leukemia.



Table 1. Tissue Results on Whole Bodies Compared with Estimates of Biokinetic Models

Systemic Burden of Plutonium-239* (nanocuries)

Biokinetic Model Date Case 193 Case 208 Case 213 Case 242

Langham 1950 27.0 56.5 55.9 94.6

Healy 1956 23.2 40.0 43.0 80.0

Durbin 1972 13.0 30.5 61.1 47.8

Rundo et. al. 1976 3.0 10.0 5.9 15.1

Parkinson & Henley 1981 8.9 31.6 17.8 42.4

Leggett 1984 3.8 4.0 11.6 29.7

Jones 1985 5.7 11.9 8.1 20.0

Leggett & Eckerman 1987 4.9 8.4 6.8 11.6

Revised Langham perLegett & Eckerman 1987 3.2 5.9 8.1 16.2

PUQFUA (7.3) (15.5) (13.5) (23.3)

Tissue Analysis 1988 3.1 3.8 6.7 24.3

Tissue Analysis (whole body) (6.6) (6.1) (8.2) (75.7)

*Systemic burdens refer to the content of all organs excluding the lungs, whereas whole-body burdens include the lung content.

General Population Studies

Origin and procedures. From the be-ginning in 1959 the tissue program in-cluded non-occupationally exposed in-dividuals who died at the Los AlamosMedical Center. At first the collectionand analysis of tissues from that gener-al-population sample was meant to de-termine background levels for compari-son with the levels found in plutoniumworkers. The community and the Lab-oratory were also interested in deter-mining whether or not any plutoniumhad been released from the Laboratoryand was causing internal exposure ofpeople living in Los Alamos and near-by communities.

A more global concern was the impactof the more than 320 kilocuries (ap-proximately 5,000 kilograms or 11,000pounds) of plutonium-239 that had beendistributed worldwide, mostly in thenorthern hemisphere, from atmospherictesting of nuclear weapons. Reliabledata were not available on how muchhad been deposited and retained in tis-sues of the general population, norwhether there were significant differ-ences in exposure depending on wherea person lived. It was obvious even atthe start of the tissue study that answer-ing those questions would be a naturaland important extension of the researcheffort if and when the opportunityarose.

The Los Alamos general populationstudy expanded its borders somewhataccidentally when, in 1968, tissuesfrom 36 individuals from New YorkCity (unclaimed bodies) were sent toLos Alamos and, at the request of theAEC's Health and Safety Laboratory,analyzed for fallout plutonium. In1970, the Colorado Department ofHealth wanted to evaluate the extent ofoff-site plutonium contamination thatwas suspected to have occurred as theresult of a major fire in 1969 at theRocky Flats plutonium processing andfabrication facility. They requested that

Los Alamos analyze tissues from indi-viduals living in the Denver-Boulderarea. Local hospitals collected the tis-sues, which were then picked up andsent to Los Alamos by personnel fromthe Colorado Department of Health.Tissue collection from the Denver-Boulder area continued until 1985.

With the cooperation of the MedicalDirector at the plutonium productionplant at Savannah River Plant, contactwas made with local pathologists andtissues were collected, from 1972 to1979, from the areas around Augusta,Georgia and Aiken, South Carolina toestablish the background levels of envi-ronmental plutonium and evaluate thepossible release of plutonium from theSavannah River Plant. Realizing thesamples collected from the Los Alam-os, Rocky Flats, and Savannah Riverareas may have been contaminated bylocal releases from these nuclear facili-ties, we sought control populationsfrom areas far away from existing nu-clear facilities. As a result, we addedthe Illinois-area residents to the study

in 1973 and the Pennsylvania-area in1974.

Before setting up those programs, weinvestigated the legality of havingpathologists send tissues to Los Alamosand found it to be within the limitationsincluded in the autopsy consent formused by most hospitals. Although con-sent forms vary from hospital to hospi-tal, they are all similar. In particular,the "Authorization for Autopsy" formpublished by the American Medical As-sociation states in part, "I (we) autho-rize the removal and retention or usefor diagnostic, scientific, or therapeuticpurposes of such organs, tissues, andparts as such physicians and surgeonsdeem proper."* This authority wasgranted subject to any special restric-tions by the next of kin, but it generallyprovides for the release of tissues for ascientific study such as ours. With afew exceptions, individuals whose tis-sues were sent to us were not identified



237

338

1

1

1

1

12

2

22

2

2

18

40

309

149

4

458

3

1

4

10

4

Distribution of U.S. general population cases

Figure 5. Geographic Distribution of General Population StudyThe map shows the states of origin of the 1187 individuals from the general population

from whom tissues were collected and analyzed over the course of the Los Alamos tis-

sue analysis project. Major collection sites were near the DOE nuclear facilities at Los

Alamos, the Rocky Flats Facility in Colorado, the Savannah River Facility, and the Han-

ford Facility in Washington State. Control populations were collected from areas not

near nuclear facilities in Pennsylvania, Illinois, and New York. A few other individuals

from other states died in one of the participating hospitals and were included in the

sampling process.

*Form 44 in "Medico-legal Forms with LegalAnalysis" (American Medical Association,Chicago, Illinois, 1961).

by name, only by hospital identificationnumber or autopsy number. We be-lieved that the standard autopsy clausewas adequate to release tissues for ourplutonium study, and we left it to thediscretion of the pathologist or theirrepresentative to do whatever additionalexplaining to the next of kin theydeemed necessary and appropriate.(That means we did not follow up to

determine if the next of kin were toldspecifically about our plutonium analy-ses of the donated tissues.) Patholo-gists were generally reimbursed a smallamount ($25 to $100) to cover theircost of collecting the tissues, packagingeach tissue individually, freezing themfor storage, packing them in Dry Ice,and finally arranging to have themshipped to us. (We also paid the ship-

ping charges for sending the tissues tous by air freight).

Between 1959 to 1985 samples werecollected in that manner from 1848 in-dividuals in seven geographic areasthroughout the United States. Figure 5shows the number of individuals fromwhom we analyzed tissue for each ofthe 27 contributing states.



Table 2. Results of Hypothesis Testing for Geographic Differences

1974-75

Kidney PA LA CO GA NM(0.114) (0.108) (0.081) (0.075) (0.063)

Liver LA NM GA IL PA CO(2.399) (2.123) (1.942) (1.461) (1.398) (1.276)

Lung NM LA GA CO PA IL

(0.535) (0.447) (0.316) (0.301) (0.271) (0.104)

Lymph Node LA NM CO PA(6.553) (6.500) (2.917) (1.923)

Rib LA NM PA(1.125) (0.966) (0.460)

Vertebrae NM CO GA PA LA(0.673) (0.631) (0.400) (0.363) (0.213)

Female Gonad CO PA LA(2.769) (1.000) (0.667)

Male Gonad LA PA CO NM GA(0.568) (0.319) (0.063) (0.053) (0.042)

Spleen LA PA GA NM CO(0.350) (0.164) (0.160) (0.147) (0.101)

Thyroid LA PA CO IL NM GA(1.303) (0.749) (0.363) (0.286) (0.00) (-0.194)

1967-68

Liver LA NM NY(1.823) (1.730) (1.500)

Lung LA NM NY(1.272) (1.165) (0.668)

Vertebrae NM NY LA(4.557) (1.539) (0.769)

The table summarizes the results of sta-tistical testing for geograhic differencesin the plutonium content of different tis-sues. The two-letter abbrevations standfor states, except for LA, which standsfor Los Alamos. For each tissue listed,the distribution from those states under-lined with the same line do not differsignificantly. Median values in units ofdisintegrations per minute (dpm) perkilogram are given in parentheses. Evenwhere statistically significant differencesexist from one state to the next (inwhich case the states fall on two differ-ent lines), the differences in median arequite small, on the order of 1 dpm perkilogram of tissue, so that the measureddifferences probably have no practicalconsequence.

In the analysis, we tried to eliminate thedependence on age at death and year ofdeath by considering only very shorttime segments, namely, the year ofdeath, and subtracting out the agetrends found during those time periods.The two time periods chosen (1974-75and 1967-68) were selected because theyincluded the major portion of the dataand because they were the only periodswhere data was available from certaingeographical locations. A Kruskal-Wal-lis non-parametric test of significance ofamong-region differences at the a = 0.05level was used. If this test indicatedoverall significance, Mann-Whitney testswere performed for all pairwise compar-isons of the geographic regions (at thea = 0.05 level). If the Kruskal-Wallis testwas not significant, then all pairwisecomparisons were declared not significant.

In 1978 Los Alamos was named thelead laboratory for analyzing tissues do-nated by occupationally exposed work-ers to the U.S. Transuranium and Ura-nium Registries. At that time ourgeneral population study had to be dis-continued because of funding con-straints. By then, one or more tissueshad been analyzed from 1,254 of theindividuals who had contributed autop-sy specimens. Results from approxi-mately 900 individuals (approximately4,400 tissues) were reported in the openliterature through three major reports.Unfortunately, in 1990, a freezer failureresulted in the loss of the unanalyzedtissues and they had to be destroyed bycremation.

What has been learned? Most impor-tantly, the data showed that levels ofplutonium in the U.S. general popula-tion are small and that populations liv-ing near major nuclear facilities did nothave significantly higher plutonium lev-els than those living far from such facil-ities. The analyses also confirmed thatmajor deposition sites of fallout plutoni-um were the respiratory tract, the liverand the skeleton. The measured deposi-tion patterns and retention factors arecritical for identifying the level of haz-ard to the general population.

The data also show that liver concentra-tions increase slightly with age andskeletal concentrations decrease. Evi-dently, as time passes a remobilizationof the bone mineral releases plutoniumfrom the skeleton, which then depositsin the liver.

No significant differences in tissue de-position of plutonium between malesand females were evident.

The data were also examined for geo-graphic differences (see Table 2). Toeliminate any influence of the year ofdeath, we examined tissues from indi-viduals who died during a certain shorttime period and we subtracted out theage trends found in that time period.For the time span 1967-68, the data

showed no geographic differences inany of the tissue concentrations of plu-tonium. For the time span 1974-75, thedata showed no regional differences inplutonium concentrations in the verte-brae, kidney, spleen, and female go-nads, but, as shown, there were smallregional differences in all other tissues(liver, lung, lymph node, rib, malegonad and thyroid).

How have the data been used? The1981 report "Deposition and Retentionof Plutonium in the United States Gen-eral Population" evaluated the data as afunction of time and compared the re-sults with the predicted organ concentra-tions estimated using the ICRP lungmodel and the annual air concentrationsof fallout plutonium measured by DOE'sEnvironmental Measurements Laborato-ry in New York City (formerly AEC’sHealth and Safety Laboratory). Accord-ing to the ICRP Publication 48, "TheMetabolism of Plutonium and RelatedElements," those data showed "reason-able agreement between computed andmeasured values for lung. Computedvalues for skeleton were about threetimes lower than measured values invertebrae and rib. . . .The computed val-ues for liver were also somewhat lowerthan the measured values. . . .The com-puted content of fallout plutonium-239in lung-associated lymph nodes is anorder of magnitude higher than the mea-sured content. The half-time valuesused in the [ICRP] model were basedupon data from beagles; monkeys, androdents accumulated less plutonium thanbeagles in their lymph nodes, and aremore consistent with human data.These findings emphasize the need forcareful extrapolation of animal data topredict human metabolism."

Based to a large extent on the LosAlamos general population tissue studyprogram (the ICRP referenced fourmajor Los Alamos reports and one per-sonal communication from me in theirPublication 48), the ICRP has recom-mended changes in their lung modelthat reduce the retention parameters for

plutonium in lung and liver. In thegeneral conclusions of the above refer-ence, they stated "...there is consider-able evidence to suggest that both the40-year half-time for plutonium in liverand the 100-year half-time for plutoni-um in the skeleton recommended inICRP Publication 19 (ICRP72) and em-ployed in ICRP Publication 30 (Part 1),(ICRP79), are too long. Values of 20-and 50-years for retention times in liverand skeleton, respectively, now seemmore reasonable." The ICRP reportstated further: "The more recent infor-mation on the behavior of inhaled plu-tonium, or other actinide compounds, inanimals, and on the behavior of inhaledparticles in man [from the Los AlamosTissue Study], is not always consistentwith the assumptions of the ICRP LungModel. These discrepancies are beingconsidered by the Task Group on Res-piratory Tract Models."

The ICRP further stated that "Since theappearance of ICRP Publication 19,much more information on the tissuecontents and retention of plutonium andamericium in humans has becomeavailable. Much additional informationcan be obtained from continuing themeasurements of fall-out plutonium inautopsy material. . . .” ■

Further Reading

Wright H. Langham. 1961. Special supplement:acute radiation death resulting from an accidentalnuclear critical excursion. Journal of Occupa-tional Medicine 3, no. 3 Special Studies: 169-177.

B. G. Bennett. 1974. Quarterly Summary Re-port, HASL-278, January 1974. New York:Fallout Program Health and Safety Laboratory.

I. C. Nelson, K. R. Heid, P. A. Fuqua, and T. D.Mohony. 1971. Plutonium in Autopsy TissueSamples. Battelle-Northwest Pacific Laboratoryreport BNWL-SA-4077.

Y. Takizawa. 1970. Japanese hygienists pointsout increase in plutonium in human body. JapanSociety of Public Hygiene. Nagoya, Japan. Oc-tober 28, 1970.



P. W. Krey, D. Bogen, and E. French. 1962.Plutonium in man and his environment. Nature195: 263-265.

C. R. Lagerquist, S. F. Hammond, D. L. Bokows-ki, and D. B. Hylton. 1973. Distribution of plu-tonium and americium in occupationally exposedhumans as found from autopsy samples. HealthPhysics 25: 581-564.

E. E. Campbell, M. F. Milligan, W. D. Moss, H.F. Schulte, and J. F. McInroy. 1973. Plutoniumin autopsy tissue. Los Alamos Scientific Labora-tory report, LA-4875.

J. F McInroy. 1975. The Los Alamos ScientificLaboratory's human autopsy tissue analysis study(Los Alamos Scientific Laboratory report LA-UR-85-2322). In The Health Effects of Plutoni-um and Radium: Proceedings of the University ofUtah's Workshop on the Biological Effects andToxicity of 239Plutonium and 226Ra, Sun Valley,Idaho, October 6-9, edited by W. S. S. Jee, 249-270.

J. F. McInroy, E. E. Campbell, W. D. Moss, G.L. Tietjen, B. C. Eutsler and H. A. Boyd. 1979.Plutonium in autopsy tissue: a revision and up-dating of data reported in LA-4875. HealthPhysics 37: 1-136.

J. F. McInroy, H. A. Boyd ,and B. C. Eutsler.1981. Deposition and retention of plutonium inthe United States general population. In Ac-tinides in Man and Animals, edited by M. E.Wrenn. Salt Lake City, Utah: RD Press, 161-179.

Wendy Hoffman to J. F. McInroy. 1994. LosAlamos Medical Center Authority for Autopsyform. Los Alamos Medical Center, Los Alamos,New Mexico.

R. L. Kathren, L. A. Harwick, R. E. Toohey, J. J.Russell, R. E. Filipy, S. E. Dietert, M. M. Hu-nacek, and C. A. Hall. 1994. Annual report ofthe United States transuranium and Uranium Reg-istries: April 1992 - September 1993. Washing-ton State University report USTR-0015-94.

J. N. Stannard. 1988. Radioactivity and Health:A History, edited by R. W. Baalman, Jr. Officeof Scientific and Technical Information, BattelleMemorial Institute.

G. T. Seaborg to R. S. Stone. January 5, 1944.Physiological Hazards of Working with Plutoni-um. MUC-GTS-384.

J. F. McInroy, H. A. Boyd, B. C. Eutsler, and D.Romero. 1985. Part IV: Preparation and analysisof the tissues and bone. Health Physics Journal49, no. 4: 587-621.

J. F. McInroy, R. L. Kathren, and M. J. Swint.1989. Distribution of plutonium and americium

in whole bodies donated to the United StatesTransuranium Registry. Radiation ProtectionDosimetry, 26, no. 1/4: 151-158.

J. F. McInroy, R. L. Kathren, G. L. Voelz, andM. J. Swint. 1991. U.S. Transuranium registryreport on the 239plutonium distribution in ahuman body. Health Physics Journal 60, no. 3:307-333.

J. F. McInroy, E. R. Gonzales, and J. J. Miglio.1992. Measurement of thorium isotopes and228Ra in soft tissues and bones of a deceasedthorotrast patient. Health Physics Journal 63,no. 1: 54-71.

R. L. Kathren, and J. F. McInroy. 1991. Com-parison of systemic plutonium deposition esti-mates from urinalysis and autopsy data in fivewhole-body donors. Health Physics Journal 60,no. 4: 481-488.

J. N. P. Lawrence. 1978. A History of PUQ-FUA—plutonium body burden (Q) from urinaly-sis Los Alamos, NM. Los Alamos National Lab-oratory report LA-7403-H.

E. R. Humphreys, J. F. Loutit, and V. A. Stones.1985. The induction by 239plutonium ofmyeloid leukemia and osteosarcoma in femaleCBA mice (interim results). In Metals in Bone,edited by N. D. Priest, 342-352. Lancaster MTPPress.

International Commission on Radiological Protec-tion. 1979. Limits for Intakes of Radionuclidesby Workers: ICRP Publication 30. Oxford:Pergammon Press.

J. F. McInroy and R. L. Kathren. 1990. Plutoni-um content in marrow and mineralized bone in anoccupationally exposed person. Radiation Pro-tection Dosimetry 32, no. 4: 245-252.



James F. McInroy earned a M.Ed. in physicalscience from Pennsylvania State University in1959. He taught chemistry and physics for tenyears in the public school system in Pennsylva-nia and New York with an additional five yearsat Slippery Rock University, Slippery Rock, PA.McInroy earned a M.S. in 1969 and a Ph.D in1973 from Colorado State University in healthphysics and radiobiology. His doctoral researchinvolved evaluation of possible exposures to thegeneral population via the food chain, shouldthere be an accidental release of polonium-210during the launch of satellites containing nuclearpowered electronic sources (SNAP devices).McInroy joined the Health Research Division ofthe Laboratory as project leader in 1972 follow-ing funding by the Atomic Energy Commissionof the human tissue analysis program and re-mained in that position until his retirement in1993. From 1979 to 1984 he was deputy groupleader of Health Division’s EpidemiologyGroup. McInroy was instrumental in the organi-zation and establishment of the InternationalConference on Low Level Measurements of Ac-tinides and Long-Lived Radionuclides in Biolog-ical and Environmental Samples, and was Chair-man of the Technical Planning Committee fortheir meetings in Sweden, Japan, India, andBrazil. He also played an instrumental role inthe development of the National Bureau of Stan-dards (now NIST) natural matrix reference mate-rials containing metabolized actinide elements inhuman tissues (lungs, liver, and bone). McInroyhas been a member of Sigma XI, the HealthPhysics Society, the Radiation Standards Com-mittee of the Health Physics Society, and theBioassay, Analytical and Environmental Chem-istry Conference. McInroy became a member ofthe Human Studies Project in December 1993and was responsible for making available alldocuments associated with the Human TissueStudy Project.

On December 30, 1958, an acci-dent occurred in the Los Alam-os plutonium-processing facili-

ty, where plutonium was chemicallyseparated, or “recovered,” from variouscompounds. In this facility, plutoniumcompounds were dissolved and mixedin a large tank with chemical reagentsto concentrate and purify the plutonium.On the day of the accident, Cecil Kel-ley, an experienced chemical operator,was working with the large mixing tank.The solution in the tank was supposedto be “lean,” typically less than 0.1grams of plutonium per liter, but theconcentration on that day was actually200 times higher. In fact, the tank con-tained enough plutonium (3.27 kilo-grams) in an upper layer of organic sol-vent to be very close to criticality—thatis, capable of sustaining a chain reac-tion. When Kelley switched on the stir-rer, the liquid in the tank formed a vor-tex, or whirlpool. The lower, aqueouslayer was pushed outward and up thewalls of the tank, as if forming a bowl;the upper, plutonium-containing layerflowed into the center of this “bowl,”which increased the thickness of thelayer. In this new configuration, theplutonium went critical, releasing ahuge burst of neutrons and gamma radi-ation in a pulse that lasted a mere 200microseconds.

Kelley, who had been standing on a footladder peering into the tank through aviewing window, fell or was knocked tothe floor. Confused and disoriented, heapparently turned the stirrer off and onagain, then ran out of the building. Thetwo other operators on duty at the timesaw a bright flash of light, like that of aflash bulb, and heard a dull thud.Quickly, they rushed to help, and foundKelley outdoors. He was ataxic (lack-ing muscular coordination). All hecould say to the operators was, “I’mburning up! I’m burning up!” Assum-ing he’d had a chemical accident, the

two operators led Kelley to a shower.One operator turned the stirrer off asthey went by.

Within five or ten minutes, a nurse, su-pervisors, and radiation monitoring staffwere all on the scene. Kelley was evi-dently in shock and virtually uncon-scious, but rather innocently, the nursenoted that Kelley had “a nice pinkskin.” Because the nature of the acci-dent was unknown at the time, it wasnot understood until later that Kelley’spink skin was erythema (a redness ofthe skin, like that from a sunburn)caused by his radiation exposure.

The possibility of a criticality accidenthad been considered so remote that theradiation monitoring staff began theirinvestigation by searching for plutoniumin the work environment with alpha de-tectors. They found no widespread ac-tivity. It was only as Kelley was leav-ing in an ambulance, eighteen minutes after the accident, that the cir-cumstances of his accident becameclear. The monitoring staff had justbegun gamma radiation measurements.When they saw the high level of gammaradiation in the vicinity of the largemixing tank (tens of rad per hour), theinvestigators quickly realized what hadhappened.

The symptoms Kelley displayed at theplutonium-processing facility, character-ized by collapse and mental incapacita-tion, were the first stage of his clinicalcourse (what is now know as the mostsevere form of acute radiation syn-drome). The second stage began whenhe arrived in the emergency room of theLos Alamos Medical Center. It wasdire. Kelley was semiconscious, retch-ing, vomiting, and hyperventilating. Hisskin was cold and dusky reddish-violet,and his lips had a bluish color that indi-cated poorly oxygenated blood. He wasimmediately wrapped in blankets and

surrounded by hot water bottles. Hisblood pressure and pulse were at firstunobtainable. He had shaking chills,and the uncontroled movement of hisextremities and torso necessitated re-straint by the nursing staff. Kelley’sanxiety and restlessness were eased onlyby Demerol. After about ten minutes,the nurses were able to measure Kel-ley’s pulse (160 beats per minute) andhis blood pressure (80/40). His bodyemitted a small but measureable amountof gamma rays, and his vomit and feceswere sufficiently radioactive to give apositive reading on the detector.

One hour and forty minutes after the ac-cident, Kelley entered the third stage,which was both the longest and mostencouraging. Kelley regained coher-ence, and although he complained of se-vere abdominal cramps and occasionallyretched and vomited, he seemed consid-erably improved overall. He was trans-ferred from the emergency room to aprivate room, placed in a bed that wason “shock blocks,” and enclosed in anoxygen tent. Kelley’s first blood sam-ples were drawn at this time. BecauseKelley had been irradiated with neu-trons, the sodium and other light metalsin his blood were “activated,” or trans-formed into radioisotopes such as sodi-um-24. His average whole-body dosewas first estimated by measuring the ra-dioactivity of his blood. It appeared tohave been massive—in the range of 900rad from fast neutrons and 2,700 radfrom gamma rays, giving a total of3,600 rad—and certainly lethal.1

Six hours after the accident, the lym-phocytes virtually disappeared fromKelley’s peripheral circulation, which



The Cecil Kelley Criticality Accident The origin of the Los Alamos Human Tissue Analysis Program

1 After his death, Kelley’s radiation dose was bet-ter estimated, again using biological indicators ofthe neutron dose and inferring the gamma dose.The results were somewhat greater than the esti-mate made during Kelley’s period at the hospital:900 rad from fast neutrons and 3,000 to 4,000 radfrom gamma rays, giving 3,900 to 4,900 rad.

was taken as a grave sign. Twenty-fourhours after the accident, a sternal bonemarrow biopsy was performed. Themarrow appeared watery, rather thanbloody, and no excessive bleeding oc-curred. The marrow was almost com-pletely acellular, edematous, hemorrhag-ic fatty tissue. From that observation,along with the rapid onset of lymphope-nia (depression of the lymphocytes inthe bloodstream overall), it was clearthat Kelley would not survive long.

During the second evening after the ac-cident, Kelley entered the fourth stage.The pain in his abdomen became diffi-cult to control. He became increasinglyrestless despite medication—so much sothat the intravenous infusions were inad-vertantly interrupted. He began tosweat profusely, his color becameashen, and his pulse irregular. About35 hours after the accident, Kelley died.

Kelley had spent about half of his 11.5years at Los Alamos as a plutonium-processing operator (from 1946 to 1949and, again, from 1955 through 1958).During that time, he underwent severalminor exposures to plutonium, includingregular exposure to moderate levels ofairborne plutonium in various chemicalforms. Therefore, his tragic death be-came an opportunity to determine cer-tain factors crucial to the protection ofworkers. By analyzing the tissues of hisbody, researchers could determine Kel-ley’s total plutonium body burden andcompare it with the result obtained fromperiodic urine assays during his life.Furthermore, they could determine thedistribution of the plutonium in Kelley’sbody. Because certain tissues are moresensitive to radioactivity than others, thedistribution of the plutonium was im-portant in determining the effectivedose. That result could be appliedbroadly to other individuals who wereexposed to plutonium largely by inhala-tion over a prolonged period.

Kelley’s exposure record included 18instances of high nose-swipe counts and10 instances of minor exposures, suchas being involved in the cleanup of aplutonium spill or getting a slight lacer-ation. Urine assays taken during thatperiod usually showed slight amounts ofplutonium. Analysis of those assays in-dicated that Kelley’s plutonium bodyburden was 19 nanocuries (see “TheHuman Plutonium Injection Experi-ments”). Kelley’s records showed thatall of his exposures occurred during hisearly plutonium work (1946-1949) andit was very likely that most of his pluto-nium burden was accumulated duringthis period from chronic inhalation ex-posure to low-level airborne plutonium.

Autopsy samples were taken fromthroughout Kelley’s body to measureplutonium concentrations. (The acci-dent itself, an exposure to neutrons andgamma rays, had no impact on theamount or distribution of plutonium inhis body.) The tissue analysis showedthat Kelley’s total plutonium body bur-den was 18 nanocuries. This comparedextremely well with the value of 19nanocuries determined from urinalysis.Wright Langham stated that the aboveagreement “was so very satisfactory thatit is undoubtedly fortuitous.” In addi-tion, it was found that about 50 per centof the plutonium was in the liver, 36 percent in the skeleton, 10 per cent in thelungs, and 3 per cent in the respiratorylymph nodes. Plutonium Injection Ex-periments in humans had shown asomewhat different distribution: 65 percent in the skeleton and 22 per cent inthe liver, for example, most likely theresult of differences in the chemical andphysical nature of the plutonium (theexperiments used a soluble salt of pluto-nium whereas Kelley inhaled plutoniumdust particles).

Another interesting factor in Kelley’sanalysis was that they were able to de-

termine relative timescales for the move-ment of plutonium through the body andwithin organs. This was possible be-cause changes in plutonium productionmethods between Kelley’s first and sec-ond stints as a plutonium worker hadconsiderably increased the ratio of pluto-nium-238 to plutonium-239 in the mater-ial being handled. This fact, coupledwith the record of nose counts and expo-sures, enabled them to distinguish the“early” plutonium from the “late” pluto-nium and, thus, to trace qualitatively themovement of plutonium from the lungsto other organs. They found that pluto-nium cleared relatively rapidly from thelungs compared with the clearance fromthe bone and lymph nodes. Much of theplutonium in the lungs migrated to theliver whereas only a small percentagemigrated to the bone and lymph nodes.Finally, the rate of clearance from thelungs to the liver must be relatively fastand the retention time in the liver mustbe longer than in the lungs.

A memorandum written by Jean Mc-Clelland and Bill Moss, chemists in theHealth Division, presented the results ofKelley’s tissue analysis. Those resultsshowed that plutonium was retained inthe lungs and pulmonary lymph nodesmuch, much longer than contemporarymodels had predicted. Because this wasunexpected, it was decided to collect tis-sues from other exposed individuals toconfirm this phenomenon. They alsostated that tissues from non-occupation-ally exposed individuals would be col-lected as controls. Thus, the Los Alam-os tissue analysis program was begun. ■

Further Readings

T. L. Shipman, C. C. Lushbaugh, D. F. Petersen,W. H. Langham, P. S. Harris, and J. N. P.Lawrence. 1961. Acute radiation death resultingfrom an accidental nuclear critical excursion.Journal of Occupational Medicine: Special Sup-plement. (March 1961): 145-192.



The origin of the Los Alamos Human Tissue Analysis Program



The Karen Silkwood Story what we know at Los Alamos

After her death,organs from Silkwood’sbody were analysed aspart of the Los Alamos

Tissue Analysis Program. Silkwood’s case was

important to the programbecause it was one of

very few cases involvingrecent exposure to pluto-nium. It also served to

confirm the contemporarytechniques for the mea-surement of plutoniumbody burdens and lung

burdens.

Karen Silkwood died on November 13, 1974 in a fatal one-car crash. Sincethen, her story has acheived worldwide fame as the subject of manybooks, magazine and newspaper articles, and even a major motion picture.

Silkwood was a chemical technician at the Kerr-McGee’s plutonium fuels produc-tion plant in Crescent, Oklahoma, and a member of the Oil, Chemical, and Atom-ic Workers’ Union. She was also an activist who was critical of plant safety.During the week prior to her death, Silkwood was reportedly gathering evidencefor the Union to support her claim that Kerr-McGee was negligent in maintainingplant safety, and at the same time, was involved in a number of unexplained ex-posures to plutonium. The circumstances of her death have been the subject ofgreat speculation.

After her death, organs from Silkwood’s body were analysed as part of the LosAlamos Tissue Analysis Program at the request of the Atomic Energy Commis-sion (AEC) and the Oklahoma City Medical Examiner. Silkwood’s case was im-portant to the program because it was one of very few cases involving recent ex-posure to plutonium. It also served to confirm the contemporary techniques forthe measurement of plutonium body burdens and lung burdens. The following ac-count is a summary of Silkwood’s exposure to plutonium at the Kerr-McGee plantand the subsequent analysis of her tissues at Los Alamos.

In the evening of November 5, plutonium-239 was found on Karen Silkwood’shands. Silkwood had been working in a glovebox in the metallography laboratorywhere she was grinding and polishing plutonium pellets that would be used in fuelrods. At 6:30 P.M., she decided to monitor herself for alpha activity with the de-tector that was mounted on the glove box. The right side of her body read 20,000disintegrations per minute, or about 9 nanocuries,1 mostly on the right sleeve andshoulder of her coveralls. She was taken to the plant's Health Physics Officewhere she was given a test called a “nasal swipe.” This test measures a person’sexposure to airborne plutonium, but might also measure plutonium that got on theperson’s nose from their hands. The swipe showed an activity of 160 disintegra-tions per minute, a modest positive result.

The two gloves in the glovebox Silkwood had been using were replaced. Strange-ly, the gloves were found to have plutonium on the “outside” surfaces that were incontact with Silkwood’s hands; no leaks were found in the gloves. No plutoniumwas found on the surfaces in the room where she had been working and filter pa-pers from the two air monitors in the room showed that there was no significantplutonium in the air. By 9:00 P.M., Silkwood's cleanup had been completed, andas a precautionary measure, Silkwood was put on a program in which her totalurine and feces were collected for five days for plutonium measurements. She re-turned to the laboratory and worked until 1:10 A.M., but did no further work inthe glove boxes. As she left the plant, she monitored herself and found nothing.

Silkwood arrived at work at 7:30 A.M. on November 6. She examined metallo-graphic prints and performed paperwork for one hour, then monitored herself asshe left the laboratory to attend a meeting. Although she had not worked at theglovebox that morning, the detector registered alpha activity on her hands. Health

1 1 nanocurie = 2,220 disintegrations per minute



what we know at Los Alamos

Dr. Voelz reassured Silkwood that, based

upon his experience withworkers that had much

larger amounts of plutoni-um in their bodies, she

should not be concernedabout developing canceror dying from radiation

poisoning. Silkwood wondered whether theplutonium would affect

her ability to have children or cause her

children to be deformed.Dr. Voelz reassured her

that she could have normal children.

physics staff members found further activity on her right forearm and the rightside of her neck and face, and proceeded to decontaminate her. At her request, atechnician checked her locker and automobile with an alpha detector, but no ac-tivity was found.

On November 7, Silkwood reported to the Health Physics Office at about 7:50 inthe morning with her bioassay kit containing four urine samples and one fecalsample. A nasal swipe was taken and significant levels of alpha activity were de-tected (about 45,000 disintegrations per minute (dpm) in each nostril and 40,000dpm on and around her nose). This was especially surprising because her leftnostril had been almost completely blocked since a childhood accident. Otherparts of her body also showed significant alpha activity (1,000 to 4,000 dpm onher hands, arm, chest, neck, and right ear). A preliminary examination of herbioassay samples showed extremely high levels of activity (30,000 to 40,000counts per minute in the fecal sample). Her locker and automobile were checkedagain, and essentially no alpha activity was found.

Following her cleanup, the Kerr-McGee health physicists accompanied her to herapartment, which she shared with another laboratory analyst, Sherri Ellis. Theapartment was surveyed. Significant levels of activity were found in the bath-room and kitchen, and lower levels of activity were found in other rooms. In thebathroom, 100,000 dpm were found on the toilet seat, 40,000 dpm on the floormat, and 20,000 dpm on the floor. In the kitchen, they found 400,000 dpm on apackage of bologna and cheese in the refrigerator, 20,000 dpm on the cabinettop, 20,000 dpm on the floor, 25,000 dpm on the stove sides, and 6,000 dpm ona package of chicken. In the bedroom, between 500 and 1000 dpm were detect-ed on the pillow cases and between 500 and 2,000 dpm on the bed sheets. How-ever, the AEC estimated that the total amount of plutonium in Silkwood’s apart-ment was no more than 300 micrograms. No plutonium was found outside theapartment. Ellis was found to have two areas of low level activity on her, soSilkwood and Ellis returned to the plant where Ellis was cleaned up.

When asked how the alpha activity got into her apartment, Silkwood said thatwhen she produced a urine sample that morning, she had spilled some of theurine. She wiped off the container and the bathroom floor with tissue and dis-posed of the tissue in the commode. Furthermore, she had taken a package ofbologna from the refrigerator, intending to make a sandwich for her lunch, butthen carried the bologna into the bathroom and laid it on the closed toilet seat.She remembered that she had part of her lunch from November 5 in the refrigera-tor at work and decided not to make the sandwich, so she returned the bologna tothe refrigerator. Between October 22 and November 6, high levels of activity hadbeen found in four of the urine samples that Silkwood had collected at home(33,000 to 1,600,000 dpm), whereas those that were collected at the Kerr-McGeeplant or Los Alamos contained very small amounts of plutonium if any at all.

The amount of plutonium at Silkwood’s apartment raised concern. Therefore,Kerr-McGee arranged for Silkwood, Ellis, and Silkwood’s boyfriend, DrewStephens, who had spent time at their apartment, to go to Los Alamos for testing.On Monday, November 11, the trio met with Dr. George Voelz, the leader of theLaboratory Health Division. He explained that all of their urine and feces would



be collected and that several whole body and lung counts would be taken. Theywould also be monitored for external activity.

The next day, Dr. Voelz informed Ellis and Stephens that their tests showed asmall but insignificant amount of plutonium in their bodies. Silkwood, on theother hand, had 0.34 nanocuries of americium-241 (a gamma-emitting daughter ofplutonium-241) in her lungs. Based on the amount of americium, Dr. Voelz esti-mated that Silkwood had about 6 or 7 nanocuries of plutonium-239 in her lungs,or less than half the maximum permissible lung burden (16 nanocuries) for work-ers. Dr. Voelz reassured Silkwood that, based upon his experience with workersthat had much larger amounts of plutonium in their bodies, she should not be con-cerned about developing cancer or dying from radiation poisoning. Silkwoodwondered whether the plutonium would affect her ability to have children orcause her children to be deformed. Dr. Voelz reassured her that she could havenormal children.

Silkwood, Ellis, and Stephens returned to the Oklahoma City on November 12.Silkwood and Ellis reported for work the next day, but they were restricted fromfurther radiation work. After work that night, Silkwood went to a union meetingin Crescent, Oklahoma. At the end of the meeting, at about 7 P.M., she left alonein her car. At 8:05, the Oklahoma State Highway Patrol was notified of a singlecar accident 7 miles south of Cresent. The driver, Karen Silkwood, was dead atthe scene from multiple injuries. An Oklahoma State Trooper who investigatedthe accident reported that Silkwood's death was the result of a classic, one-car,sleeping-driver accident. Later, blood tests performed as part of the autopsyshowed that Silkwood had 0.35 milligram of methaqualone (Quaalude) per 100milliliters of blood at the time of her death. That amount is almost twice the rec-ommended dosage for inducing drowsiness. About 50 milligrams of undissolvedmethaqualone remained in her stomach.

At the request of the AEC and the Oklahoma State Medical Examiner, Dr. A. JayChapman, who was concerned about performing an autopsy on someone reported-ly contaminated with plutonium, a team from Los Alamos was sent to make radia-tion measurements and assist in the autopsy. Dr. Voelz, Dr. Michael Stewart,Alan Valentine, and James Lawrence comprised the team. Because Silkwood’sdeath was an accident, the coroner did not legally need consent from the next ofkin to perform the autopsy. However, Silkwood’s father was contacted, and hegave permission for the autopsy over the telephone. The autopsy was performedNovember 14, 1974, at the University Hospital in Oklahoma City, Oklahoma.

Appropriate specimens were collected, preserved, and retained by Dr. Chapmanfor his pathological and toxicological examination. At the request of the coronerand the AEC, certain organs and bone specimens were removed, packaged,frozen, and brought back to Los Alamos for analysis of their plutonium content.Because Silkwood had been exposed to plutonium and had undergone in vivo plu-tonium measurements, her tissue was also used in the Los Alamos Tissue Analy-sis Program to determine her actual plutonium body burden, the distribution of theplutonium between different organs of her body, and the distribution within herlung. On November 15, small samples of the liver, lung, stomach, gastrointestinaltract, and bone were selected and analysed. The data, shown in Table 1, indicatedclearly that there were 3.2 nanocuries in the liver, 4.5 nanocuries in the lungs, anda little more than 7.7 nanocuries in her whole body. These measurements agreedwell with the in vivo measurements made before Silkwood’s death (6 or 7nanocuries in the lung and a little more than 7 nanocuries in the whole body).

At the request of the AEC and the

Oklahoma State Medical Examiner,

Dr. A. Jay Chapman,who was concerned about

performing an autopsy on someone reportedly

contaminated with plutonium, a team from

Los Alamos was sent to make radiation

measurements and assistin the autopsy.



There was no significant deposition of plutonium in any other tissues, includingthe skeleton. The highest concentrations measured were in the contents of thegastrointestinal tract (0.05 nanocurie/gram in the duodenum and 0.02nanocurie/gram in a small fecal sample taken from the large intestine). Thisdemonstrated that she had ingested plutonium prior to her death.

With the exception of the left lung, the remaining unanalyzed tissues were repack-aged and kept frozen until it was determined whether or not additional analyseswere required. The left lung was thawed, inflated with dry nitrogen until it wasapproximately the size that it would have been in the chest, and re-frozen in thatconfiguration. It was packed in an insulated shipping container in dry ice and sentto the lung counting facility at the Los Alamos Health Research Laboratory. Thedata were then compared with the in vivo measurements made prior to her death.As expected, without the ribs and asso-ciated muscle attenuating the x raysfrom the americium-241, the results forthe left lung measured postmortem wereabout 50 per cent higher, but not incon-sistent with the in vivo result.

Some of the most interesting observa-tions made during Silkwood’s tissueanalysis were: 1) the distribution of plu-tonium-239 within her lung and 2) theconcentration of plutonium in the lungrelative to that in the tracheobronchiallymph nodes (TBLN). After the frozenleft lung was returned to the TissueAnalysis Laboratory, the superior lobe was divided horizontally into sections.Those sections were further divided into two parts: the outer layer of the lung(pleura and sub-pleural tissue) and the inner soft tissue of the lung (parenchyma).The plutonium concentrations in the inner and outer parts of Silkwood’s lung wereabout equal, in stark contrast with another case examined under the Tissue Analy-sis Program in which the concentration in the outer part of the lung was 22.5times higher than that in the inner part. That difference was an indication thatSilkwood had probably been exposed within 30 days prior to her death, whereasthe other case had been exposed years prior to death. Furthermore, the concentra-tion of plutonium in Silkwood’s lung was about 6 times greater than that in thelymph nodes, whereas in typical cases that ratio would be about 0.1. Both ofthose results indicated that Silkwood had received very recent exposure and sup-ported the view that the plutonium tends to migrate from the inner part to theouter part of the lung and to the lymph nodes over time.

The saga of Karen Silkwood continued for years after her death. Her estate filed acivil suit against Kerr-McGee for alleged inadequate health and safety programthat led to Silkwood’s exposure. The first trial ended in 1979, with the juryawarding the estate of Silkwood $10.5 million for personal injury and punitivedamages. This was reversed later by the Federal Court of Appeals, Denver, Col-orado, which awarded $5000 for the personal property she lost during the cleanupof her apartment. In 1986, twelve years after Silkwood’s death, the suit was head-ed for retrial when it was finally settled out of court for $1.3 million. The Kerr-McGee nuclear fuels plant closed in 1975. ■

Table 1. Amounts of Plutonium-239 in the Organs of Silkwood

Organ Plutonium-239 Concentrations

(nanocuries) (picocuries/gram)

lung (whole) 4.5 4.6

parenchyma 4.5 4.6

pleura 0.01 0.004

liver 3.2 2.4

lymph nodes (TBLN) 0.02 0.80

bone ~ 0 ~ 0

a true measure of exposure

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