session I I I

THE SIGh'IFICANCE OF RADIONUCLIDE CORTAMINATION IN RUMINANTS'

Ruiiiinants inay become contaminated by radionuclides released a t the tiiiie of :I nucleui. detonation and to I r.ery limited extent by radio- nucliclcs i ~ l e n ~ c d by reactor accidents or by nuclear industry opera- tion. I n o i d c r to evaluate tlic contaiiiination, we must consider the -pecific radioactive eleiiients invol\.ctl, their characteristics and be- li:ivior, :ind tlieir probable route o i en t ry into the aniiiial and their tr:tnsfer vin :iniili:il products to inan.

Thr pi.iiiiary and secondary fission products include more than 200 i.:irlion~icliclcs. In addition. there are sonie radionuclides produced by ncutron :tcti!.ation, such as carbon" from nitrogen in the atmosphere ancl zinc';" il,oln stable zinc". A list of sonle of the more important rnclionucliclc~. togcstlici. v . i t I i their cliaracteristics, is presented in Tntle 1. T1ic.i~ are. of cour-e. iii;iny sliort-lii-ed nuclides of liigti fission yield o i >ignificnnce iiiiiiietliately af ter release, but they were omitted imm t l i t i tiihle lor tlie sake of siiiiplicity. Furthermore, only single isotoiws o r tiiothcr-daughter nuclides are shown; they are generally iiiciiit)i-i,.+ o i rittlier coinplex decay schemes. For i l lustrative purposes, tlic t lvc;iy :c l ic i i ic for I1:{I is shown in Table 11.

In Fiyrrrr 1 :\rv A o n n the pcrcent:ige contributions of se\.eral iin- 1)ort:int i~:t~lionucli(lvs to the total fission procluct radioactivity fol- lou.ing slou. nc-utron fi?.\ion.:'" During early tinit.5;. of cot1r.e. the totnl fi.-:ion j ) i m l i i r t r:itlio:icti\.ity r l v c r c ; 1 ~ ~ ~ r:ti)i(iIy bccnusc of the rndio- : i c . t i \ x b (ltv,:t>.. Tllis olttain:: ::inel> 1L:irly f : t l lo~~t contains ninny short- li\.c,Il i-otoli(.-. .\.. :I i ~ i I ( ~ oi ~ I I ~ I I I I ~ ~ . t l i ~ ix(lioact1vity decreases by a l':i(,roi, ot' I O I'(JI. (. \ 'cry 7-t'olll int.rv:i.-cb in tillie : if tcr dctonntion or re- l( . : i , - (* : t l t ; i t i.., i f ' t 1 1 t ~ r . c ~ \ \ . ( ~ I I * 1000 unit.. : i t 1 tiour, t lp re \~.oultl be 100 ( i i i l t - : i t i I i o i i r . - . 10 unit.. : i t 2 (l:~!..., : i i i ( I 1 i l l l i t : \ f t c r 2 wceks.

REPOSITORY

COLLECTION

FOLDER

i I

PHYSIOLOGY O F D I G E s T I O S I l i THE R L X I S . 4 N T

fId,f.lijt

9 d 51 d " 9 y, 64 11

12 .9 d. 40 h 65 d , 35 d

285 d . 1 7 . 5 niin

30 y , 2.0 rnin

P r i m d r y o r l a n or organs irradiutrd

thyroid gland bone bone bone whole body and gna-

trointentioal t rac t gastrointestinal trnct

and ¶ k i n wliole body

SO,',<C Fdl iou I / rom n u c i r u

rrplorion

local ic IC

. s s s s

s s x s

x x s

S

lropo- st lato- spher- sphcr-

Rrarinr aftrr

ncwly opcr- Iuclcd a1100

s s s s

S s s

s

S

S

T.%BLE I1 DEC.<Y %HEVE1O FOR I O D I S E 131 (Thermal neutron fission of U'll)

d h m i c nirmbcr and element 49 50 51 52 53 54

Indium Tin Antimony Tellurium Iodine Xenon'

Q5% (1 '2% 1 sec -+ 3 sec - 23 niin - 25 niin 4 8 OJ days -- stable

------) 30 hrs 5%

ko 7 12 day

* Two iaonieric a tn*a -one stnble.

1

m 0 - - 0

c 0 3

._

n ._ L - C U - c u

L W a

I

Time af ter fission (days)

F i g , 1 .-Relative contributionn of some important radionucliclrs l o tot31 fission product activity following slow neutron h i o n of U1".

132

S I G S I F I C A S C E O F R.4DIOSUCLIDE COST.43I IXATION 13 RUMIN.kNTS

Certainly, all of the 200 fission products are not of equal biological significance. I n selecting those to be discussed, we took cognizance of the amounts present in various kinds of fallout, their physical half- lives, their metabolic behavior, their biological significance, the avail- able da t a , and the tissue or organ involved. Regarding the latter c a t e g o v , n e chose to discuss radionuclides t h a t would be representa- tive of poorly absorbed p - y emitters t h a t would irradiate principally t.he gastrointestinal t ract and the skin, the bone-seekers, those that concentrate principally in a single organ such as the thyroid, and ?-emitters that. irradiate the total body. Alpha-emitting isotopes are not included because they are generally poorly absorbed and are not concentrated in the milki2. 5o Although many of the radionuclides have not been studied in ruminants, general metabolic d a t a are avail- able in other species and have been recently reviewed.58

T h e effects of t he various important radionuclides on ruminants will be discussed first and categorized according to the area of the body irradiated. This Kill be followed by a discussion of the significance of contaminated ruminants as a source of food for man and then esamination of various methods of reducing the hazard to both ani- mals and man.

GASTROINTESTINAL TRACT IRRADIATION

-1 grazing nniiiial could recei\.e a substantial dose of radiation to the mucosa of tlic digestive tract , primarily p-radiation from unab- sorbed p - y emitters such as Ce1'4-Pr"4. The results of radionuclide feeding studies have shown tha t the lower large intestine usually re- ceives the highest radiation dose.40 An exception is suggested by the recent n o r k of Bell' in which he fed high levels (20 mCi/day) of Cel" to sheep. (Less than 0.05 per cent of an orally administered dose of Celi4 is absorbed.) H e found t h a t gross damage to the gastrointestinal t ract was liniited to the omasum and abomasum in most of the sheep. Yellow fibrous and necrotic infiltration was present in the ornasal folds, some of which appeared to be sloughing. In one wether, seven months a f t e r the cessation of Ce"' feeding, the omasa1 folds were completely absent, the reticulo-rumen orifice was distended and the rumen appeared impacted.

In both the oiiiasuiii and the lower large intestine the contents have a rc lat iwly long transient tiiiie and are quite concentrated,20 both of lvhich result i n a high radintion dose from the contents. I n addition, the high ..ui.i:ice-to-T.oIiil1ie ratio in the o l i m u m is probably a con- tributing f:irtor in explaining the pattern of lesions observed. The p~~ysiological ..t:itc of the g:i.>trointcztinnl tract , of course, could alter the intestinal tloze ti!, a t least an order of magnitude (for example, if diarrhea O F con- t i pat ion owti rrc.cI\ , 4 G I rrndi:i t ion! t oo. could iiiodi ry :tti-orl)ticin of iii:Lt(.ri:il iroiii t I i ( . ~ : i - r t . c l i n t c , - t i n n I trnct. : ;

Some e>tiiii:ittaz ivere niatle I)y S o l d and his collengues'" 4 6 on the effects of the p-emitter YuO on the gastrointestinal t ract of a goat and.

133

'

1 1 8 3 4 1 3

PHYSIOLOGY OF DIGE-TIOS 1S THE RC>lIS . \ST

I,? rstrapoi;ition. t h o cffcct.; on n c o ~ . They tstiiiifitcti tll:it ~ n c h iiiillicuric. 01’ Y”” irigc..tc~iI t)!. t h e ~ o : i t rv>tiltc(i in ;i do2c ut I T r : i l i t o the Ion.er ILirge inte>tinc+. 5ingie 01x1 cIo>cb> of iiiore than 200 iiiCi

wliich rleli\.crt~cl \wtn.een 3000 :inti 4000 r:i& to tlie :o-callrd rritic:tl or- gan I tlic lon.er large intc-tines I , fnilcci to producc any c)\.icIt.ncc o t 1irrnoi.rh~gic cntcriri-. Doses in (’sccss o f 5MK) rads \vcrc’ cztiiii:itr.(l to I)c required to 1)rovokt tlic l:i t ter ?ynriroiiie,

i-nder niost circuii1-t:inces involving ;i higii-le\el iallout ficicl. the contribution o i t he p dose to the gut would be relatively in$ignificant compared with the dose to \\.hole body froin y-emitters on the grotinrl and in and on the animal. So ld niade estirnates of the dose to tlie nhole body and to the gastrointestinal tract for a 90-day period following a detonation t h a t resulted in :i fallout field that had dosc It.vcls of 100 r/‘lir at one hour (Tab le 111).

DO-day whole body diiue 90-day g u t dose

4 0 0 r 130 r 100 r 30 r

It was assumed t h a t the animals t h a t did not begin grazing until after two weeks u-ere kept in a barn tha t provided a shielding factor of thrce, and during their confinement their ration was not contami- nated. I t should be noted in Table I11 tha t with a nhole 1)ody dose tha t ~ o u l d be acutely lethal to most i f not all of the COWS (1000 r ) , the dose to the gut would only be about 10-15 pe r cent 1250 r i of the dose required to produce iiiininial injury. This latter figure is h ~ s v d on the assuniption t h a t approsiinately 1 per cent of the significant radionucljdes is retained on the grass and thus available for ingestion by the grazing aniiual. I f the retention of the raclionuclidcs on the forage consuiued is greater than 1 per cent, thcn the dose to the gastrointcstinal t rac t rvould be increased accordingly.

SKIN IRRADIATION

SIGSIFIC. \SCE O F R.ADIOSUCLIDE COST.iSIIX.%TIOS IX RUSIIXAXTS

as olie niiglit espect due to the similarity of the p energies of P3? and the Y g o datlghter. Short-term and long-term results of exposing sheep to P3? plaques are summarized in Table IV.2e The reader is referred to the nork o i 1,ushbaugh and associates who have summarized well the early reaction of sheep skin to P - i r r a d i a t i ~ n , ~ ~ as well as reports by Tesmer-6 and T r u m and

Lethality in ruminants due to P-irradiation of the s h n is unlikely because the levels of 7-irradiation would be limiting before overwhelm- ing doses of p-irradiation would be received. Extensive "beta burns" of the skin have been seen in animals grazing near a nuclear test site, however, n i thout their manifesting damage from excessive exposure to 7-irradiation.lO T h e subject animals were Hereford cattle which were accidentally exposed to radioactive fallout from the first nuclear weapon test. The dose of radiation received by these animals was estimated to be I50r of penetrating ( 7 ) radiation and 40,000rads from p and (I emitters to the skin. The area of skin affected was principally the back region where dust easily settles. -4 number of these exposed animals were shipped to Oak Ridge and

later transferred t o the University of Tennessee for a s tudy of the effects caused by irradiation.

Plccording to Brown,lo the most significant and consistent damage associated n.ith these cattle has been lesions on the skin, especially o i w the hack and upper par ts of the head and neck. These changes

F q . 2.-5liecp +hotr.iny wool loss following exposure to 20,000 rads from a Pc plaque.

P H Y S I O L O G Y O F DIGE>TIOS IS THE RL'.MIS,lST

i v c r e p r e w ii i :i 1) I y c :iiisot\ t )y /j - I,:\( I i ; i ti o n fro 111 r:i( i i o:!c t i vc. f i\ I IO 11 t . T 1 I C Y r on >i.<t o f ix,l :i t i \ .( ,I y 1 i1.0 I I I i n c j n t . i r t q t i I :I 1.1 y l I i.. t ri t ) t i t c( I 1 I 0 ~ i ! . 1 ltv - jcctions o r p l : ~ ( \ ~ i c ~ > . Tliiw :!niiti;lla \ v i i i c l i i t i t t i (one i n 19M). [ n . ~ in 1962, hat1 r:inc('roiis growths in tlic 3rc:l o f these skin lesion$. One animal succuiiilwcl to c;\nccr \ \-hich h g a n in a "beta h r n " lcsion on the skin and sprcnd to otl icr tissues."; Perhaps the cause o f death in this nninial iniglit t)c consitlered a n csception to the coliinion C ~ U X of death in c:ittlc. This form of cancer is, however, coltinion in the Hereford b r e d . Ysually i t de\.ixlol)s about the eyes (.cancer eye) hu t inay occur in other areas of the hody. There appeared to be no deleterious effect on the reproductive performance over a 14-year period. T h e overall conception rate was 94 per cent and one reiiiLiining cow has given birth t o 16 calves in 16 years.

On the basis of the obserr.ations made on these cattle and other studies cited ahove, i t is unlikely t h a t p b u m s of ruminants will detract significantly froin their food value or contributc to m y sub- stantial increase in the effects of accoinpanying external lVhole-hod\v irradiation. Furthermore, the latency of neoplasms of the skin prob- ably exceeds the econoniic life o f most ruminants. The principal hazard from particles on the backs of ruminants niay well be to herdsmen and abattoir eitiployees handling the contaminated ani- i n a I s.

T.\BLE I \ - C R O S S P.4THOLOClC CHASCES FoLLowtsc BETA ~ R R A D I . ~ T I O S O F S H E E P SKIS"

Strclf i n g None Onset iitintediate. severe. a n d diffuse. Dura t ion about four da, a .

Reddncrr Sone Obrioua b u t no1 severe

Scnsiltr.tlr Very slight Ooaet immediate. Dura t ion a b o u t four daya .

Pipmcnlation Very alight. b u t Firat noted dur ing s e m n d perslated reek. persisted.

W'ml changer S o msmtion of Slight censation o f y.wd grou t h urn1 growth. during first SIX week8 fol- S o wool 1-8. luu-ed b y noriiialgrou-th. N o

w o o l l o s a .

Onset i n i n i d l a t e . very severe. diffuse (eyteoding 1 ctti. b r y o n d the b+rder of the ir- radiated a res i . Duration four d W 3 .

Severe initially. Durs l inn abiDut lour d a l e .

Onset i tnniediate s n d I ery severe. Uuration sbout S I X

days. Very dense black piantentation

in the irradhated a r m . Firs t noted during s m n d post- radiation week. peramled.

H'uol loss occurred during s m m l and th i rd ~ t - r a d i a t i ~ ~ n week. vmriablc in extent und cw118- pltteneaa. s o rmruu.ll i until a f t e r the f o u r t h n i o n t h . SCU- a-wl fibers did nut ~ 1 l a i n the fu l l l ength norilia1 U ~ W ~ I fibers.

.% I G S I F I C 4 S C' E 0 F R.4 D 10 S LC L 1 DE C 0 ST . A N I S .AT I 0 S 1 S R I' 11 1 S .\ST.-

g;i-ti.ointc?tin;iI tract (5-15 pcr cent in adults and u p to 70 per cent in 1 1 1 ~ ' y o u n g i , is concentrated rcadily in bone I -99 per cent 1 , has a slo\\- ttirnoi.er in bone c > 5 years for 50 per cent1 and a 28-year physical lialf-life. Bariuiii 140 and S P are also bone-seeking isotopes, but the Iinznrd is not as great since the physical half-li\.es a re only t x o weeks and 51 dn\.s. rcspecti\.ely. (There could, hoxever, be circunistances when sliortcr-lived nuclides may assunie a position of iniportance 1)ccausc of their [or their precursors'] greater fission yield.)

Only liiirited 5tudies have been perfonned on the effects of bone- seeking radionuclides in ruininants.lO, 3. 34. s ~ . 55 I n n study a t Oak Ridge'" tlvo groups of sheep, one administered Srno intravenously ant1 the othcr Razzti, ha1.e txcn obscri.ed since 1954. T h e original csperiruent consisted of 16 aniinals dosed with Sreol 9 animals dosed iVith Ra226. and 6 controls. (RazJ6 \vas utilized in these studies be- cause considerable d a t a is available on i ts toxicity in man.I) Cur- rently, 5 aniinals are surviving, including l control. Some pertinent data on these animals a re summarized in Table V. Early deaths Kere

TABLE I' S C . M M . 4 R Y O F 1 1 . 4 ~ ~ ON SHEEP I N T R A V E N O V S L Y . \DMISISTERED EITHER Sr90 OR

R U r i s IS 1 9 s AT UT-AEC ACRICCLTCRE RESEARCH L A B O R . t T O R Y ' p

T r c d n t c n t p o t i p

Sr90 0.11 pCi/kg

5 . G pCi/kg

5 5 . 5 rC i /kg

'178 pCi /kg

( ' o n lrol s

Siiinbcr of animals i n

grotrp

4

4

4

4

3 R

3

6

A'rrinbcr and t y p c o j lumors a1 nccrops?. Rcmorks

osteogenic sarcoma a t 102 months post -injec- t ion

osteogenic sarcoma suspected in surviving animal rhabdomyosarcoma at 55 months post-injec- t ion osteogenic sarcnma a t 93 months post-injec- t ion

none acute rndiation syn- dronie-average survival 25 dsy3

1 3 i 1 1 8 3 4 1 1

P H Y 5 I O L O G Y OF DIGESTIOS IS THE RC>IIS.\ST

asaociatcd with parasitism, infection, cardiac failure, traumatic peri- carditis, and tuinors.1° Tlie skeletal burden of SrD0 a t death was about 5 per cent o f t he intravenously administered dose. On the basis o f these data , the LD,, dose of SrYo administered intrsvenously would be About 0.3 mCi;kg in s1ieep.l" -\ some\vh:lt higher figure 11.3 mc'i. k g ~ was reported5s fo r the goat using SrBD.

Relative to strontium in milk , abuut 1-2 per cent of an orally ad- ministered dose mill be secreted in the 21 while 10-27 per cent o i an intravenous dose may be secreted in the iuilk in 5-8 tlays.'"~ "I

We estimate that i f enough SrD0 is given to a pregnant cow or sheep in doses large enough to seriously injure the fetus, the dam will al:o be seriously injured or will succumb. Furthermore, since the economic lifespan of most farm animals is relatively short , i t may be tentatively concluded tha t i f a n animal survives the acute phase, any long-term effects can probably be ignored.

WHOLE BODY IRRADIATION

T h e passage of a radioactive cloud or the accumulation of early or local fallout containing a large assortment of y-emitters results in an exposure of the whole body to penetrating radiation from both the external and internal containination. Our present s ta te of knowledge indicates t h a t the n.hole-body dose from 7-emitting radionuclides will be the limiting exposure from the standpoint of survival.

Gamma-emitt ing radionuclides which are readily absorbed from the gastrointestinal t ract and distributed throughout the body may con- tr ibute significantly to the whole-body radiation dose. Of these radio- nuclides, Cs13; is the doniinant one because i t is readily absorbed from the gastrointestinal t ract , has a relatively long biological half- life, and a 30-year half-life. Since i t is metabolized in a manner re- sembling t h a t for potassium, it, too, is distributed throughout the body.

TABLE VI R E L ~ T I V E TISSGE COSCESTRATIOSS O F RADIOCESIUM FOLLOWISG DAILY O R - ~ L

ADMINISTRATION TO SHEEP .ISD GOATS ('20-30 days feeding)

Cesium cunccnlrdions (yo daily dose/!ig tissue)

Sheep" Goat6o

11uscle Kidney ,

Liver Hear t Brain Ovary Testis Bl i~c~d pl3smn Femur

8 10 6 8

9 0.5 1

30 36 19

138

1 1 8 3 4 1 8

Rtiniiiiants n1)sorb from 50 to 100 per cent of the Cs''7 ingested and cscr~qc i~vl:tti\.cly i i ioi~* in fccvs t l i x n i n urinc. altliougli tlrc fccal iii.in;iry twrvt iun ratio is liigher in non-ruininant:.

Tile rate of loss of Ca137 from the body can be described niathe- ninticnlly by a series of exponential functions. Hood and ComarS1 0l15erved that i 5 per cent o l an intravenously adnniniatered dose was excreted in the first month after administration. I n shccp more than 50 per cent of a single adininistered ciosc is excreted within 10 days :liter adiiii nij tra tion.'3

I n Table 1'1 are shown the relative tissuc concentrations of ratlio- ceiiuru follon-ing rlailg oral administration to sheep and goats. Unpub- lislictl work in our laboratory with sheep has s h o n n that body burdens 10-20 tinies the daily intake are renchcd af ter about three months of dnily Cs':'; fcetling. Relative CsI3; concentration in the muscle of tlicse latter aniiiiiils is I'rohably a t least a factor of 2 higher than t h a t obscrved in the Acep fed

, 31. :A : { , 1.5. 1 4 , 4 4 , 43. I10

for 20 days.

1.2 I

/ IC) Continuous intake f rom

pHP5IOLOGY OF DICEaTIOS IS THE RYXIS.\ST

Extrapolation of da ta from .ingle do5e studies to continuous daily intake indic:lres tha t t h e percentage of the daily dose found in the milk each day is 6-25 per cent and 6-11 per cent in the goat and C O W ,

In Figure Y are shown the changes in CsI3' concentration in milk respectively.31. 33. 13- 14

with time iolloning various esposure regimen.

RADIOIODINE AND THE THYROID GLAND

Radioiodine is considered one of tlie ruost biologically significant radionuclides because of: (1) its abundance in early fallout and i n the gaseous effluent of certain nuclear facilities; (2) its high inventory in reactors; and (3) because i t is so readily absorbed and concen- trated in the thyroid gland and in the milk of ruminants. T h e thyroid uptake of radioiodine is dependent on the level of stable iodine and other constituents in the diet, as well as upon the age of the animal. Reported peak thyroid uptakes in ruminants on the second d a y follow- ing a single oral administration vary from 5 to more than 50 per

T h e most practical case to consider when dealing with radioiodine is the situation in which animals ingest iodine from a decaying source as they would following a single contamination event. Several ex- perimental studies have been performed in dairy cows in which a single contamination event was simulated.21. 38. An idealized pres- entation of the results of such a n experiment is s h o s n in Figure 4 . I n

cent.8, 54, lB, I?. 21, 25, i, B

( I O g c ON FIRST D A Y )

>- c a d a a

w a

k6

X Y U P

0

w o

- L

c

0

2 ; LL 0

u c

COWS THYROID lqooo

I A V G . - ~ ANIMALS)

I l l ' FED/DAY

1,000: DISCONTINUED '

i I I I I I 1 I I I

,I~~~/LITER OF MILK ( A V G . - ~ C O W S ) so ,-.

DAYS FOLLOWING INITIATION OF llsl FEEDING TO OAIRY CATTLE

F i g . $.-I'm in milk and in thyroid of cattle and man in a simulated contaniinalion event s tudy (feed pellets fed morning and evening

were all spiked wi th 5 pCi/day on day one).

1-10

S I C S I F I C I S C E OF R.1 D I O S L C L I DE COST.UI. I S.4T IO S 1 S RCM I ShS T S

this experiment, cows and sheep were fed, morning and evening, one pellet that had been spiked with 5 pCi each on day one. The approxi- mate thyroid uptake curve for man drinking milk from these is also included. If cows were eating contaminated vegetation, the uptake values would probably be about 70 per cent or less of those shown because the effective half-life of fallout radioiodine on vegetation is closer to 5 days40 than the %day half-life provided by physical decay alone in the s tudy illustrated in Figure 4.

a t apparent equilibrium in vari- ous tissues, excretions, and secretions of catt le are shown in Table VII. Sheep usually show higher concentrations than cattle.s-

The relati1.e concentrations of

TABLE VI1 C O S C E S T R . % T I O S S O F 1"' FOLLOWSC DAILY O R . 4 L . k D M I S I S T R I T I O N T O C O W S

(expressed as per cent of dai ly dose/g t issue, excretion or secretion X 10')

Organ, tisstu, s c c r e h n , or cxrrcfion

Blood l lusc le Spleen, pancreas Kidney, l iver Ovary , sal ivary glands Feces, milk Thyroid

oJdosc/g X 1@

1.7 0 .2 0.8 1 .? 1 .o 5 .O

32 ,ooo

A cow niny secrete in its milk about 0.5-1 per cent of the daily :idministered II3* dose per liter of G 3 q 37 Unlike the monogastric animals, considerable quantit ies of

.I\ thyroid dose of several thousand rads appears to be necessary bcfore any thyroid damage c3n be readily observed. Doses in excess of 50,000rads appcar to be requircd for ablation in sheep, and more than 100.000 rads are required in cattle. T h e effects of IL31 in animals have been recently reviewed and a re only suminarized here.'O T h e most spectacular effcct is in the young animals which will fail to grow if the thyroid has been destroyed. Adul t animals m a y appear fairly nor- mal folloning thyroid ablat ion; however, lethargy, constipation, flatu- lence. and a d ry skin dcvclop. Such animals, however, may continue to concei1.e :ind rcproduce, but they m a y encounter difficulties a t parturition. The fetal thyroid is quite subject to damage since it con- ccntrntes u p to ttirce times a i niucli a; thc rive's and six times as much :is thc c u u . * ~ . ~ . 27 T f ;I thyroid at)l:\ti\.e dosc is rccei\.ed by the fetus, thci aninul ivi l l not w r v i v c heyond the first ncek of life unlcss therapy i:: i n i t i n t c d .

Ti. i n :t p:t.<tiii.e coiit:iiiiin:ition c!vc.nt G L I ~ I I ;ts t l l : t t rlcscrihecl : i l ) o ~ ~ , t 1 1 1 . i r i i t i n i c~c~ncc~nti .~~t ion i.G 1 p( ' i o i I ( : ' ' [)tar g1,:tiii of 11i.y i.tbgc>t;ttion c':itcii (20 1 ) t ~ r cc-nt of this on >ucculvnt p:i.itur:igc), tlie infinity thyroid tlo>e will cscced 100,000 rads. .-2nimnls grazing such a pasture for 30

are excreted via the feces.54*

1 1 8 3 4 2 1 141

INHALATION HAZARD

Aniiiials csposed to lethal doses of estcrnal 7-irradiation froin close- in fallout tha t originiited f r o m surface and untlerground shots liad only insignificant aiiiounts of fission products in their .\[ens- urenients iiinde on aniiiials exposed in the 3Iarihall Islnnris and o:i indigenous :iniiiials a t the Sevada Test Site sho\\-cd very little con- taiiiination in the resi)iratory iystctn. I n addition to tlicse field oh- aervations, it \\-as estiiiintetl tha t a factor of IOG \\-auld ha1.e to be ;il)plied to t l i r inhaled dose of radiation to place it in tlic ~ii i i ic order of iiiagnitudc as that resulting iroiii csternal -1-irrndi:ttion in :i id lout

I t would a])l)car th:it in iiiost cases the I i a z : \ i d of inhalctl radioactivc iii;ttcri;tls can iw ignorcd lor ruininants.

COMBINED EFFECT

I n ordcr to evaluate tlie acutc c fcc t s froin a coml)incrl d0.r of tlie iiiiportant radionuclides, it has hccn assuuicd tha t tlir etTect5 rlrc additive and tha t the u.liolc body dose is a sum of t l w tloses for enclt inclividual radionuclide. Tlie cstiniatc of this dosc is Ixiscrl upon tlie tonccntration of W" in thc blood :inti iwnc inarrow. r:itlioiotline in tlic blood, CS'"' in the muscle. and Ce'44 in the g:\sti.ointcstin:tl tract. Estitnates o f t he \\-hole-body dose are gii,cn in Table 1.111. Thc Ic t l i i i l a n d datnaging oral tloecs for adults and fetuses arc $ho\vn in TtiI~lc.5 I S and S, rcspectivcly.

ThBLE \ . I11

SINGLE ISCESTIOS OF Sr90, I"'. Cs"' W H O L E - B O D Y DOSE TU A SHEEP OR COH. DcRisc T H E F I R ~ T N'EEI; . ~ F T E R

I183522

3 I G S I F I C . X S C E OF R . i D I O S C C L I D E C O S T . i . \ I I S . \ T I O S IS R C M I S . I S T S

T.XBLE IS ESTIXIXTED O R A L DOSE TO .XDULT SHEEP O F I l l L , SrgO, CsI37, ASD

C C ' " THAT TVOULD C A V S E s E R i O r S [ X J U R Y O R DEATH

O r d l Dose ( m C i / k g body i t t ) Radionirclidc Lethal (LDwm) Causing serious injury

15 10

8 5

0 . 2 1 0 . 5 4

T,\BLE S

THAT H A Y RESULT IS FETAL ISJCRY O R DEATH ESTIMATED OR.4L DOSE TO A D C L T S H E E P O F IL", SrQa, CS13', AND Ce"'

Oral Dose ( m C i / k g body u.1) R d i o n w l i d c Dailx administration Single administration

1 1 3 1 0.002 0.1. SrQO 0.015 t Csln 0.020 0.2 Ce*" 0.5 4

* 11 administered in latter abgea of pregnancy. t Death of letua i n unlikely at doaea that rill not ki l l the darn.

CO3TA.MINATED RUMINANTS AS A SOURCE OF FOOD FOR MAN

I n evaluating the effects of fallout or nuclear accidents o r controlling them, i t is the human population tha t must receive priority. One of the major routes of contamination for man, and particularly children, is the con5uniption of fresh milk. If acceptable limits are set, for milk for n u n , the animal will be well protected. A comparative value for II3' will i l lustrate this point. -4 cow nould have to ingest 70,000 times :is much to cause economic damage (-1.5 mCi/day) as n.ould give milk-drinking man a per inis~ible level of the Ruclide in the milk (100 pCi j l in m i l k ) . Similar factors for SrDo and CS'~' would be about 10,ooO and 1,OOO; therefore, we n s u n i e there is no danger to grazing stock as long ns the limits applied to the human population are met.

-4 sunimnry of the fraction of orally administered doses of the four radionuclides that appear in the iiiilk arc s1lon.n in Table SI .

T.4ULE SI

Cei" SECRETED IS S[ILK n F D . \ I R Y COWS F R A C T l O S O F O R A L L Y . k D X ! i S I . ~ T E R E D IIF SrgO, I ' J 1 , CSIa , ASD

PHY3IOLOC;Y OF DIGEhTIOS IS THE R U M 1 S . G T

I t is highly unlikely that the nicat froni 3 contaminntcil ruminant >urviving the acute [)hast> will contain enough ratlionctivity to cause any acute clcletcrious c f fe r t> upon the consuiiicr.id

T h e methods ;ipplicd in cooking !vi11 A I > O have soiiic effect and re- sult in some 102s of ratlionucliclcs. Bcll acd coworkers,'. i.i found tha t there was some leaching of Srsu froui \)one into the contiguous me:it in H roast during thc cooking proccss, but it was of little hignificnnce. (S low than 99 per ccnt of the Sr in a n aniiiial is in the hone.:, K i t h cesiuiii t h w e workcrs found tli : i t nn oven-roastcil loin rctaincd :rI,oot 80 pcr cent of its radioacti\.ity, tot) round steak >urf:tce-braised wi th a $iiiall aniount of Lvater rctaincd 57 per cent, and bottom round 5tewcd with iiiucli water rct:iined lcss than 30 per cent.

PROPHYLACTIC AND CONTROL MEASURES

I n the event of large-scale contamination, a nuinher of procedures can he initiated t h a t will rcduce the hazard both to runiinants and to illan. Vtilizing uncontaminated stored hay and grain can, of course, essentially eliminate the Contamination problem.35 There is also some n.ork indicating fertilization of pastures x i 1 1 reduce the Ii31 transferred to milk.53 Ear ly hosing down of the backs of animals t h a t have been exposed to close-in fallout will reduce significantly thc possibility of "beta burns" on the skin.18

Iodine concentration can be rcduced in a nuinber of w:iys and they have been thoroughly re1.ien.d by Lengciiiann38 recently. \\-e have found tha t increasing stable iodine content of the diet from 5 mg to 2 g,'dag reduced milk levels of by 50 per cent a n d thyroid burdens more than 90 per cent.g T h e thyroidal uptake of adul t volunteers drinking this milk was reduced by 50-80 per cent.e1 X process for removing radionuclides from milk was developed to

the pilot-plant stage a t t he Agricultural Research Center in Belts- ville, SIary land under the cooperative sponsorship of the (-. S. Depart- ment of Agriculture, the r. S. Public Health Service, and the E, S. Atomic Energy Commission. Th i s adaptation of a continuous ion exchange appara tus has been under commercial scale testing by the Producers Creaniery Couipany in Lebanon, l l issouri . I t is planned tha t about 12.500 lb of milk a re to be processed each hour. T h e basic steps in the process ini.ol1.e acidifying to p H 5.2- passage through a cation resin bed where >95 per cent of the Sr anti Cs is removed, thence to a n anion resin uhich removes the iodine (more than 90 per cent) and hydrochloric acid."!' T h e results of the commercial evaluation of thc rcrnovnl of radionuclides from milk . hon.evcr. arc not ye t completed.47

.4C'KSO\VLEDG.\IESTS

Grateful :irknowledgment is ni:itle to our :isocicltes i i t Hnniorll 1,ahor:itoiir~ :ind the . l t i t l ior i~j . Health :ind S:iftty Branch for thrir i,ontrilliition. :in(l roopcr:i- tion. Spcci:il t h a n k s are gii,rn to Drs. Carl Bell. Dan Brotvn. anti U. F. .hnsniii

144

-1.. .I .

s lGSIFIC. \SCE OF R.iDIOSCCLIDE COST.LUIS.iTIOS LY RUMISASTS

for fiirni4iing iis valunblc material, permitting us to use some of their unpublislied resillis. ant1 rliecking the manuscript. Tile senior author extends special thanks io Dr. Robert Dougherty w h o was instrumental in dircctlng my career into rescnrcli and \Tho has been a source of great encouragement to rile.

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