ML19331B259

Testimony of Ej Sternglass (Univ of Pittsburgh) on 720614 Re Synergism

ML19331B259
Person / Time
Site:	Midland
Issue date:	06/06/1972
From:	Sternglass E PITTSBURGH, UNIV. OF, PITTSBURGH, PA
To:
Shared Package
ML19331B256	List: ML19331B255 ML19331B259
References
NUDOCS 8007280853
Download: ML19331B259 (12)

Text

-

k, * /}'y huu. . wi.

'A

,,g 6( )P f,:)}(,

'??.

• l l'?

,.n- ,sN

/

.N*

Tho Rnlo o f ""nerr-i: n in'the Bi ol o r-i c.1 Ef fect of Environ ont al Rn.dic. tion E. J. S ternglann Department of Radiology Univornity of Pittsburgh School of Medicine '

Pittc$urgh, Pa.15213

/

June 6,1972 k

Tontirdny cubmitted at the Hearingc for the Conctruction '

Licers ;c of the Eidinnd Nucloe.r Power Plant, AEC Docket r

oc. 50-329 cnd.50-330, Juno l'4, 1972 1

80072,80 f

I. .Illlrd.l lis:

e Until recently, nuclent powor' plants have been located in relatively remote arca far from urban or induntrial arcan with their heavy chemical air pollutante. Thuc, the plant at Midland, Michigan, being propoccd for constntetion in close proximity to a large chemical plant and urbcn area introducen the potentially corious complication of pocnibic synergictic effects betueen the chomieni cminnione and the radioactive gance dincharged from

ucicar plantn in the normal courso of operation uhich could incroacc the effect on the hon 1th of the population well beyond that produced by either .

the chemical or the radioactive air-pollutants alonc.

It is the purponc of the present paper to cunnarize the latest evidence curgentin.; that ::rch multiplying offectc of ordinary chemicals and radioactive air-pol?ution have in fact a3 ready been observed not only for animals in laboratory ctudice, but alFo for large human populations.

II. Ih t u t<d_.E; rpf_ .y + i e !!c e h r,r.jm ilrorully unce::ing, there arc two principal ucyc in which ordinary aid pollut,ntn cuch an nog, durt and chenicals can act co as to increene the hon 1th effect of radioactivity in the air, an'd vice verna.

The firnt in a purely physical effect largely independent of chemieni con-ponition, in which the air-pollutant in the forp of dust or liquid droplets acte no an to increase the concentration of radioactivity above the levcin that would c eint if the air were free from dunt or smog. IIere, the caall particles in the air ninply act to tr. p and thun concentrate both the natural radioactivity in the nir, and an: nnn-nnde redioactive effluent cuch ac in produced either by unnpun tert:: or omincient. from nuclear facilitien.(1)

One innortnnt illuntrntion is the fact that fallout fron uennonn tettn 10 Intrely brou$t down frca the attocphere by precipitation.(2) Thuo, arens of bervier rainfall chou the 1crcer derocition nnd concentration in mill:.(3)

- !!cre, U:e watex!ropletn act to trap the airborne radioactive n terial, uhich woult' o th e n.' inn h: vo p .n: ed over a civen area.

Th5n "unn:.r.ut" actiin of water <1ropletn han been found to be particularly n '! <g ? i f <. fo r U.<: e. o r r. o f*

ic,l i n<: dj ::cht.rt:0 freso proct;un-pl an te uhnre the enount

2 trepped wn noncured to be 10 times greater than expected for soluble naces.

Another illurtration of the trapping action of airborne contaminnnts is the well-knmin fact that dust partic1cc tacd to abcorb radioactivo cac mole-cules,(51 thstr, raising tho total amount of airborno netivity in dry, dusty crenn above that in arcan of low dust concentration.(6)'

The net effect of cither liquid or dry acrosolo in therefore to raico the ambient radioactivity, and thus the amount inheled por unit time. Thuc, uithout eny rer ard to the chemical nature or poccibic carcinogenic proportico ,

of the nerocoln, their acre presence will increase the done to the lung and other bod.y or.cnnn above that which would recult from the inhalation of cican air in the ereconce of a source of gascoun radioactive offluent.

The reverse action is alco pocrible, nancly where the presence of rcAio--

active enroc incr?ncen the fornation of liquid aerosol droplets by virtue of the fact th 't the rndienctivo ntoma emit cicetrically charged partic1ce, thus providinn condonnation nucici uhcro moicture can condonne. Thuc , radioactive ,

etmorpheric eninnion can contritt,tto to the formation of lirIuid droplate, uhich in turn enrve to c ,11 cet ntill further redioc.ctive moleculen.

Turnin~ ne::t to the second croup of mechanisms, thoco include all those in uhich pc.rticulnte, chemical and radioactive pollutants facilitate the bio 3nticn1 nction of the other acerit...

Here it ic useful to dintinguich two categorico, namely the direct intets actionn of the different,agente, and indirect action: where one pollutent nets to produce n pathole.~ical coniition or dincace which in turn enhences the cr.%ctivero.- of the othr:r acent in inducing cancerouc or other pc.thologic I con lition :.

In t'u: forne.r irnet internction, four iypco of proconnec hnvo teen connirlerc' and invertir ated czperimentally:

(1) Frono tinnni nction- b.y " inert" duct particloc actint; to carry the chemicr1 or rMionctive carcinogen into the body (2) Ir,itant rction by :ennn of which the nornal barriern to the entrance of c .rcivo-one are tro':en doun. IIere, either the chenien1 or the rn 'in r:t vn contnuinnat can act an irritant.

(3) A* i r. t f. 'u .i n ta r .% : .- itith or inhibit thr mra-'1 ni chat.irna of

~

c1 mi: tica of '.l." cr rcinogan.

t

'(/) *e..in c - !c-1 co-enrcinorenic nctions on the cc11ulnr 1, vol, uhore the t% <e, i< a n .t u re: of the unterini pron"> ten or rotnrein the indiract

action of the r dioactive enrcinogen.

iiith regard to the more indirect promotionel action of ordinar/ nnd radioactive polletonto, at loact throc such actions have been exenined:

(1) The lotenrint of resistance to viral infections, which in turn reatice the ability of the body to climinate the radioactivo na-terini, thuc increa.ning the radiation dance from a given amount of activity introduced into the body.

(2) The pronotion of bacterial infectione trith the cato result on the ,

ability of the body to climinate the radio-carcinocen.

(3) The indirect action of one or more aconte on the ability of the body to produce certain key hormones,11hich in turn influences the carcinogenic crrect of a given amount of radioactivo natoric1.

The above t: foes of nochanienc have so far been most c tencively studied for thn cano of cancer induction, particularly rocpirato / cancern, both by Inboratore ntudieu on anionic and by epidomiological ciudien of huacn popu-Intione.(7)(B) .

The cyncrcintic proceroco havo cico bocn invecticated in the caco of chronic dircenen such an enphyccma,(9) and nore recently for the action of rndinnetivo c ticcionn on 'the embryo, no in t! e cacc of infant nortalit; ,(10) uhcro indications of syncrcintic actions have alco been found.(II) -

I. En.c.<mt E U.in- r,L 3- nn&'ic 3rfee%

Turning to tSc avniinblo data on biologioni effectn of the direct typo, the firnt of t'rene involvoc the action of otherwine " inert" dunt part.icien.

The b,-' .'ni c role k u(, no dont in producing lung cancer han ment recently boo duct freed fran inrn in proiucing lun'; cancer in nico. Sirnifice.ntly, nnphalt inh Intion by itrelf failr.d to inrince lunc c s.ncerc, illuntrating the cracici role piryod h:* i:uet in n-onoting d:e action of carcinoconn.

An poin'e*1 ont by hfiotti,(13) the duct partic1ce pencir sto the unlin r.r ' re ::tii r ..y brr.9<W.1 < n :.nd ni veoli, nn 1 the colui,1 c cercinor:enn enter t h e- Li c.e,1 n '.ro- . .,ml : r.

r.~ ri ntl to tothcr t>ti::uu:.

then.the carcinnecn ir innoinb]c, the bic Ir,cical de:w;c in fotuel to occur t d. r. a tbc .hi ' . .rti ci r; in fjnra ]y lodt.ed , t:hich an - bo in one of the lung 3 y.u n n a ar:: . .

Vory racently, rmall particles of iron oxido (hematito) adninintered to the lunr:c of hamsters were foun'd not to be carcinogenic by themcolven, but when conbined uith the radioactive element polonium-210, malirnant tunors ucro readily induced. Furthermore, as compared to adninictration of poloniun without hematito particles, the tunor incidence was potentiated. It trac found that one effect of the hematite particles was to clow down the removal of the radioactivity from the long so that the total radiation dose for a given amount of activity wac more than doubled.

Duct in also believed to be an inportant factor in the hi incidence of .

of lunc cancer'anong the uranium miners. As reviewed by Dair, early attemptc to induce lunc car.ccr in experimental animale through the inhalation of radio-active radon alone failed to produce lung cancers, although cuch tu'nors ucro readily inr:nced by the inhalation of ficsion product icotopcc cuch as Cc-144, P-32, Fc-59, 0-35, P.u-103, Cc-60 and Sr-90 of the type releaced by nucicar pi nnte. Iloucvor, then in rec'ent experimento reported by Stuart end his coll cacucc at the Datelle Northuent Laboratorico, dunt from uranium ore was added in relatively low concentrations of 15 mcm/m 3, comparabic to. the concon-trationc of inorgrnic ducts emitted by the Dow Chemical Plant at Ilidland, animals developed a variety of chronic lung disenecc, including emphysema, hyperplasia and cctaplania of the broschial ticcuc.

Thun, er:ain the addition of a relatively inert dust promoted dramatically the effectivenenn of radioactive gases in producing cerious biological dosaago.

Furthernore, an reported by Bairk4) in hic revicu article of the uraniu:n miner lun<: cancer incidence, nome of the excess lung cancero occurred at very low tot I cleorbed <ionen, comparabic to thoce permitted for rariiation vorhcrc unlcr the pronent 10CP.120 limita adopted by the AEC. Thuc, excecn cancorc ucrc o%crved at only 40 " working 1cyc1 monthc" of exponuro. Cince one "uor): inn l evel nonth" reprocont:: anywhere from 1 to 7 rade to the lung,16) cignificant c:: conn rink occur ~ red at cumulativo donce an low as 40 rado in the relatively rmall nonulation of conc 4,000 minero exponed. Thin in only 3 ti:en an 1.rre an the pernicnibic nnnuni donc to the lung of 15 rede according to prewnt MC re ulationo, and nnaller than the 10 year permincible done of l 'O rrA- tr> lune tir ve.

~

It  :.wil , r, " c , tvre ,1+ r.,!.ed that thoro in n t.rt.ag evidence for the crintenen or rtill renoi.her :.ym:rgintic factor among the uranium minern bouirien

5 duct, neticly the effect of cinnrette nnoko. Ac pointed out by Dair, the L'a-tional Acadeny of Sciences hne concluded that there is otrong ovidence for the hypothecia that those who emoke are particularly cueceptibic to lung cancer.

Thus, baned on the data up to 1967, Lundin concludoc that for a population of 100,000, 700 lung cancer deathe por year uould occur among cigarette enoking uranium ninere, compared with only 4 among noncmoking mincrc. This illuctrates the enor.nouc cir.c of poccible cyncrC i stic effecto,'in thic caso increasin's the rick from radiation niono by no much no 175 times, ecpecic11y when cuch other f actorc an duct and ploynucicar hydrocarbons from diesel exhaunt arc. cico precon't.

Ac reported by Falk,0.0 carbon dunt particle have alco boon found to cauce II02 to change from a natorial that did not produce lung cancor in mico into a ctrong carcinogenic nnterial producing covere lung damage.(14 Oxidcc of nitror:en ronrecent a major component of the emissionc from the Dou Chemical Picat in Midinnd. Thuc, both . radioactive cubstances and various chemienic nornnily relatively leen abic to induce cancers can beconc highly toxic when inhaled in the precence of fine duct or cmoke.

Thun, anido from any poncible' organic carcinogens,' cigarette enoke pro-videc rnall particien on uhich radionctive caccc con be adcorbed and held in the lun.r, greatly incrennintf the toxicity of cigarettes well beyond the 1cvel knoun before the cd'ition of radioactivity to the pollutants in the atnonphere.

Thin recult, obnorved for the uraniuci miners, is conconnnt uith the foot recently reported ( 8) that respiration and lung en: cer ratco both in Japan and the United Staten ucre criNentially conctant for cone 10 yonre prior to 1948, and rore rharpi: only 4 to 6 years af ter the onnot of heavy nucicar tecting by the U.">. and the Soviet Union greatly increnced the icycle of airborne railo.*ctivity in tSene countries. Furthernore, the creatent rointive ricon tool: pit.cc in the dry, dunty oronn of Japan end' the United Utaten, uhcre air-borno ect.ivity r: voll nn lu t-count nro generally highent.

The recond t~no of direct nyncrrictic effect, ncncly the bren':doun of

.. ecitulnr h .rriern by irritante an ronrcrented b:t the cacc of SO is revicued 2e b; I!ci ron. (18) Ho pointe out that uherenc the inhelation of polynt:cicar hydro-enrhonr nlone hr.n not ininec4 lunr* concer in ratn, in conbinntion uith the irri-t ni ':0,, thnep4 t irinir. did r r.ul.t' in cancern. Yet at n11 but very hi~h docco, -

Pt.1':(i i) "p<>inin m t th st UO p in not eble to induce lung cancer.

i'e r:nn n r.r .i t r abil i '.:l Lo dentroy onmhru:< n on the collul ar end rubcollular 1 r.w 1, Pnt h(19 #

r w.!r. ?.O p . a n:.1 : 1. ninrl/ treic irrit. m:, of iuport nr.<r in ci re.1 to r:tn': . Itn nrr::meco ur.'ild thurofore br- expects 1 to bc tethr r fnetor

.6 -

that enucen radioactive raccc nuch ne redon in the uranium nincrc to becone co nuch nore effective in producing both cnnbysena and lung cancdr.

It in cleo poccibic to regard the radionctive partic1ce emittinr- hig;ily ionizing alrhn r.nd beta rrws as a acvoro irritant which hol st to breck down the cellular defencen so that other carcinoronc such c.c the polynuclonr hydro-carbonc can enter the eclic of the lung. Econuce of the very 15.rgo enorcy depocition by theco particles por unit volunc, coverc local demaco to cellu-Inr nombrnnen cc.n take picco even if the averngo doco calculated for the whole lung in quite small. ~

And thic effcot is onhancod uhon the radionctivity is concentrated on the curface of rub-micron duct particles.

Other irritanto in cigarette onoke listed by Falk(18 are acetic acid e.nd emonia, neither of which by itccif is a carcinogen.

The third t po of direct synergistic effect can teho place in cituations where the chemical ceta so an to reduce the rate of clininntion of a carc51 ogen.

Ac Fn1h pointo out,(18 in the caco of the bronchici pasnagoc, thoro are two unyc the.t the rate of climination of carcinononn een be influenced. One in throuch r.4verno ef fr>ct; on th'c nucun flou or rato' o'r itc cocrotion. The other in through cn effect' on the cilia, the fine haire uhoco motion puchoc out the mucun together trith any particlos trr.pped on it.

Thuc, nucue can be doctroyed 'by various cinple, acide. Ciliary cotivity can be inpaired by such enento an 30 g and by citsretto enoko, thun multiplying.

the dono roccived by the "'

bronchic1 lining for a given amount of radior.ctivity

,deponited. '

A lint of po11utente known to inpair cilia movenont is given by A. .in and Wynder,(1() noot of ubich are found both in cigaretto cooko and urh ac co rdinr* to theco authorn. Out of the five groupc of r,uch sub0tancen licted, four are niro found among the offluents of a inrgo chemical p1'ent cuch ac that at l'.idlend nant the rito of .the propocod reac tor. The table lintn the follouing nsterinin:

(1) Volatile aldchydes (2) liydrn en cycniv.o (3) lii',roven oxiica (4) Vol stile acidn .

(5) 701 - ti!c nhermin

-[

Only hydrocen cyanido 1:: not licted an an offluent from the Mid1 cad P1nnt of the Dow Chenical Company.

The fourth type of promoting effect in that of a truo chenieni in ter. c lion where one acent enhanecc the offect of another.  !!cny carcinocenc , tucor initiators and tunor promoters are known as for instance licted in the recent articloc by lioffnan and Wynder.(19) Among the mont important commonly encountered carcinogens licted is bcnco[a3pyrono and related materials (Tablo I of Ref.(19).)

since it in proditcod durint; the inefficient burning of dicac1 fuel.

Among the tumor promoters, thece authern lict phenoic and nincollancoun polynors an encountered in urban air. Theco two materials are alco onitted in cienificant concentratione by many chemical plante cuch ac that in Midicnd.

Clearly a civen acent can act in variouc roles, for inctance cc both an irritant,' a carcinoren or as a ciliary motion derpressant is in the cacc of SO . The full cynergintic effects are therefore highly conplex and peorly predictabic, and only through large scalc statistical ctudies of human popu-Intionc such cc the uraniun miners can the full potentiating effects be deter-nined for the case of man. .

To complice.tc nattern further, recent cfxperimental studice have revenled the larco mn?titude of yet another more indirect clanc of effectc of a bio-nodical characta . .

~Thus Falk cunmcrices the evidence that the incidence of both viral cad bacterial infectionn is increased by ordinary air pollutanto in man ac ucll an in laboratory aninnlc,,. 13ut recent studien of the effect of rcepiratory

, infections on the eliminntion rate of inhaled radioactive clonento carried out

- ..by Creacin, !!cttechein end Hannonc show that cuch infectionc in turn greatly increanc the retention of radioactivits in tho lung.

The effect of the increceed renidence tinc of the radioactivity in the lu,nn van to incroace by nearly 10 timon t'ho total radi stion done by rndionctive -

chrouina oxide particles in the lung. Ac the cuthorn point out, the infection nr.rkedly c::tonded the time npeut by the materici in the lung uhon the activity w; n nominintered before, during or up to 91:cchn after infection uith the viruc took place.

Thun, it in nott clear that a renunonia attack con result in a rently ire rer ned hnznrd to en individuni fron any inhaled rrdiocctivo particlon, to thnt ordin .ry air poll u !.cnto Dird merely tr ',no the chnt.co of . re cpiratory in rection niro incren e the ch.anen of deveJoWng lont -m;c chinnic lung dinernen

. 1 nuch as cephycena, bronch'itic and cancer. In effect, there indirect effcets of ordinary c.ir pollutina incronco the rink fron rndioactive- coinnionn rne beyond th '.t eniculated eccording to procent AEC ctend. rdn tha t do u.i t tak si there neuly diacnvered effecto into account.

At the ranc nectinc uhere the effects of lung infectionc on redir. tion doce were reported, ctill another unruspoeted nubtle biological potentinting factor l was described by Nilscon.(29 In a series of execrinents with both male and female nice, it uas found that when estrogenic hornones were adminictored together with strontium-90, the nunber of bonc tunore produced by a given dose wac alcont doubled, and i

the tino of their appearance was cut by about one third.

Thus, rubtic notabolic effcets produced by vr.rious chemicale can produce far creater effects on cancer production by a given amount of radioactivity entering the body than had been cupposed when procent radiation stenderds ucre set even for the extrencly well-ctudied case of atrontium-93 in bone.

Similarly uncuspected hormonal effects are believed to be involved in the .

. obrervation that for infants born in the county containing the Drondon nucienr reactor, the rises and falle of the gnscous radioactivo enicsionc ucre ecsocin-ted uith corronnondinc rises and falls in tho number of premature or undor-weicht babies born.(10) The accompanying changcc of infant mortality rater, nou independently confirned by DeGroot(28 and Tseng,ON are therefore likely to rr'orecent another enne uherc' hormonal effects are involved in Creatly nnplifying the action of-rniioisotopen in the body.

Thic in nuccetted by the obeervation that a largo fraction of premature infanin die due to respiratory dictrons and hyaline nenbrane diccane known to be nrnoeinted uith the Inch of a key chemical or curfc.etant in the lung that prevente collnenc of the air-cacc, and that t50 production of thin vital rub-ntence ic controlled by hornonen oricinating in the pituitary glano. 3 And it in thic canter-cit _nd of the b'ody unich is involved in the control of entro:en it-vale nou rhoun by Niinnon's =tuely to be crucin) to the notabolina of ctron-t in a-9') in the body. .

IV. Cn,nt d n3 The cro rin evidence for hich')y offectivo and of ten compicx crnorgirtie ef fect n he ttean cheuf c'.1, nart5cultto and rnlionctivo cir-pollutr..:n indic f e" th t o n c- : tin ~ cnti '.cc or the lihr ly hara th effectn of rr.dier ciive ux N

_9_

relcanon havo been cronnly underentimated.

Alone the tracic oracrience with the unexpectedly larco incidence of lung cancor noong the uranium mincrc far beyond that anticipated on the basic of the action of radiation alono chould cerve ac a warning that wo do not. yot adequately understand the full complexity of biolonical effecto of rediatiAn on human henith to rink the relcaco of growing amounto of radioactivo vactoc into the environment. .

This warning applico particularly in an area cuch as Midland where very Inrge quantitics of particulatec, vnporc and chemicals are conntantly being diccharged which have aircady been shown to increcce the biological effect of a given amount of radioactivityg though many of thene cubstances produce no detectabic rices in cancer at all uhen acting alone.

He cro now becoming aware of the meny unanticipated complex biological prococccc that anplify the effcetc of radioactivity releasco into the environ-i nont. It scene that theccpan expInin the serious ricoc in mortality rates for all ance accociated with levoln of.ctrontium-90 and cecium-137 in the milk at a feu percent of the present perniscibic concentration recently reported

- by Lave for 61 metropolitan aronn of the United States.D4) And it ic through

~

the action of such syncrcietic and cencitizing effecte reculting from viruc dincene and hormonal cetion ac have been recently dincovered that it becomon ponnibic to underntand hou incroaccc in rndiation Icycle of only 10 milliradn por year appear to havo renulted in leuhenia and cancer risec of 2 to Sfs in large hunan populationc.( a)

" - . - What no have apnarently fciled to anticipate adequatoly in the pact ic the fact that uhon radionctivity in rolcaned into the environment, it will be thore who happen to be mont cennitivo ne a recult of varieuc biological fno-torn and nyncrqictic ofrectn who uill be nont coverely affected. And unlcre we cre uilling to lot.rn from our past mictskes, uc uill c poco ourec1vec and our children to continued ricec in ennecre end chronic diceaccc in the yearc t o C o'.1c .

1 l

l l

J

Ecrerences

. (1) "Heteoro' log nnd Atomic b'ncr,v," edited by D. H. Slade, U. S. Atomic Encrg/ Conienion, Divinion of Tech. Infdra. (July 1963), Chap. V.

(2) "U. U. Ucinntific Con::iittee on the Effects of Radiation," I'ew York (1962), Anner. P.

(3) Pederal Rediation Council Report No. 6 (October 1964)

(4) Ref. (1), Section 5-4 9 (5) Ref. (2), Annex F, Sectionc 23-26, 47, 57 (6) See for inctance the hir:h airborno activity in th'e vectern mountain statec for the period 1953-58 reported by the National Air Sampling Network, P.H.S. Publication No. 637 (7) '"Inhnintion Carcinogenecic," U. S. Atomic Encrr,y Commiccion, Div. of Tech. Infornation, ( April 1970) Volume 18, Ax S aponium j Geries (8) E. J. Stornpinen, "Spidemiologioni Studiec of Fallout and Pattorno of Cancer Mortality," to bc ,publiched in "Radionuclido Carcinot;cnecic,"

. Proc. of the 12th Hanford Biolorg/ Symponium,!*ay 11,1972. '

(9) H. L. E,crk and D. Deitch, "Pathologion1 Effecto in the Rat after Repeti-tive Exnocure to. Europium 152-154," in Ref. (7), p.429 (10) E. J. Sternglacn, "3nvironmental Radiation and' Human Health," Proc.

6th 3cr%ely Sympocium on Math. Statictics and Probability, 3crkolcy (July 22,1971),- J. lieyman, editor, Univorcity of California Proca (1972) '

(15) John Tneng, Thecin, North Western Univornity, Evancton, Ill. , (June 1972).

(12) kl. L'. Fc1k, " Chemical Definitionn of Inhalation Hacard," in Ref. (7), p.13 (13) M. Ceriotti, "E::narimental Recniratory Tract C'arcinogenocic and it Relation to ~Inhal ation Enporuro ," in Ref. (7), p.27

'(14) U. J. Unir, "Inhalatiori of Iladionuclidos and Carcinocencin," in Ref. (7),

p.77

'(15) 11. O. St u .rt ,' D. H. Willtr-1 and E. 3. Houcrd , " Uranium Minor Air Con tnminante in Dor and Hnacterc ," in Ref. (7), p.413 (I T-) H. I'. Hr.4 fo r'1, !!c t'. (7) , p.99

(17) H. C. Eoren, " Carbon an a Carrier IIcchanica for Irritant gacoc," Arch.

Envir. ilo.41th, 6,119-132 (1964)

(18) N. Nelcon, " Inhalation Carcinogenonic in Man," in Ref. (7), p.3 (19) D. Hoffmann and 3. C. Uvndor, " Chamber Development and Acrocol Dic-percion," in Ref. (7), p.173 (20) D. A. rentin, P. Nottelshoin and A. S. IIcemonc, "Increnned Effectivo Half Life of Inhaled Radionuclido by Recniratory Infection," to be publirhed in "Rndionuclido Carcinogencein," 12th Ann. Hanford Diol. Symo. ():ay 11, 1972)

(21) A. Nilsson, " Influence of Ocetrocenic Hormonec on the Carcinogenecie of Radioctrontium," in "Radion clido Carcinogenesis," 12th Ann. Hanford Biol. Symp. (may 11, 1972)

(22) II. H. DeGroot, "St atictical Studien of the Sffect of Low Level Radiation fron Nuclear Roe.ctors on Human IIcalth," 6th Berkeley Symp. on IInth.

. Stat. and Prob. , Serhoicy (July 19, 1971)

(23) J. H. Knolnon, " Environmental Influence on Intrautorine Lung Development,"

Arch. Int. lied. 122, 421 (1971) ,

(24) L. D. Lavo , S. Loinhardt and M. B. Keye, " Low Lovel Radiation nnd U.S.

I ortality," Workinr; Papor 10-70-1, Crad. School of Ind. Adninictration, Carnecio IIollon Univorcity (July 1971), in publication.

S a

O

/

o e

8 4

e W

w.

6 9

l