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TIME (years)|i.--Times New Romanh- .-P%&;)dy /X$Mu Aj  j6^ #*S | --- "- $ f-- $23; E3f-- $[dpnf-- $f-- $f-- $f-- $f-- $&/9f-- $OXbf-- $xf-- $f-- $f-- $   f-- $$.f-- $D MW f-- $l u f-- $f-- $f-- $!!f-- $"f-- $8AKf-- $a'jt'f-- $ f-- $%%f-- $**f-- $t atf-- $-%6@%f-- $U^hf-- $~**f-- $((f-- $))f-- $- -f-- $!* 4f-- $JS]f-- $s!|!f-- $f-- $((f-- $##f- "-P%&;d4/&X8_$Mu)9AUj} 6^*S|-- "- f--E2f--n[f-->+f--f--f--f--09&f--Bb/Of--iVxf--zf--f--f--.f--WDf-- lf--!f-- f--3 f--C"0f--_KL8f--ttaf--f--f--f--f--@-f--hUf--~f--f--f-- f--4!f--]Jf--sf--f--f--f- "-P%&;d/X@$ M(u) B6AjI@GM k6F^"MKLQ*>S1|B1KE--- "- f--E2f--n[f--"f--f--f--f--9&f--b Of--xf--f-- f--J7f--.f--2WDf--3 lf--f--*f--L9f--@"-f--K8f--St@af--J7f--Q>f--WDf--ubf--P@=-f--,hUf--WD~f--UBf--VCf--[ Hf--H45!f--;](Jf--L9sf--;(f--UBf--O<f--- "-Y--Times New Romanh- ..- "-LLLz--- $BVKCUVf!Fallout (Bqm-)--L/L/L---VfCSf ! Milk (Bqm-)--L@L@L--VwCdf!Fit Milk (Bqm-)----       l    G       Level 1 Level 2 Level 3 Level 4 Level 5(;3$2#  0  .3  0  ($ (    ) , .#M << deUU w X Figure1.0  90Srfalloutandmilkactivitiesandmodeledmilkactivitiesusingequation/1/.  #  ==a=#==a:#=XX=/3/#=X=X|##=#< Level 1Level 2Level 3Level 4Level 5Level 1Level 2Level 3Level 4Level 5  #  a#a#XX/5/#XX]# PALIGNL  ~H~=~C~int~SIGMAfromk~Dsubcf(k)Asubk(t)dt Level 1 Level 2 Level 3 Level 4 Level 5($     8 9#A<< c XXoHXXWXX'CXXZLXX$7kXXD8cfXX(XXkXX4)XXxAkXX5(XXytXX)XXdtWPC ! =ƚ aW {P  "System-Times New Romanh- .--Times New Romanh- .--Times New Romanh- .--Times New Romanh- .-- .--Times New Romanh- .--Times New Romanh- .-- .--Times New Romanh- .--"Ariali- .--Times New Romanh- .-- . - "-  - "- "-- "-- "- --Times New Romanh- .----Times New Romanh- .-- .--Times New Romanh- .-- .--Times New Romanh- .--Times New Romanh- .--Times New Romanh- .--Times New Romanh- .-- .--Times New Romanh- .--Times New Romanh- .-- .--Times New Romanh- .--"Ariali- .--Times New Romanh- .-- .-- "-*c-- "-&&&\&\\\-Times New Romanh- .- "-.- "-&&&- "-!0 - "-ttt- "-ttt\- "-!200 U- "-- "-\- "-!400 - "-- "-\- "-!600 - "-]]]- "-]]]\- "-!800 >- "-- "-\- "- !1000 - "-- "-\- "- !1200 - "-FFF- "-FFF\- "- !1400 '- "-- "- !1600 u..--Times New Romanh- . !ACTIVITY..--"Ariali- ..- "---Times New Romanh- ..==&!1961==;=;&;=d=d&d==&==&!1965===&==&=/=/&/=X=X&X!1969=X==&==&==&==&!1973==$=$&$=M=M&M=u=u&u==&!1977===&==&==&=A=A&A!1981=A=j=j&j==&==&==&!1985== = & =6=6&6=^=^&^==&!1989===&==&==&=*=*&*!1993=*=S=S&S=|=|&|==&==&!1997===&==&=G=G&G..--Times New Romanh- . ! TIME (years)|i.--Times New Romanh- .-P%&;)dy /X$Mu Aj  j6^ #*S | --- "- $ R-- $23; E3R-- $[dpnR-- $R-- $R-- $R-- $R-- $&/9R-- $OXbR-- $xR-- $R-- $R-- $   R-- $$.R-- $D MW R-- $l u R-- $R-- $R-- $!!R-- $"R-- $8AKR-- $a'jt'R-- $   R-- $%%R-- $**R-- $t atR-- $-%6@%R-- $U^hR-- $~**R-- $((R-- $))R-- $- -R-- $!* 4R-- $JS]R-- $s!|!R-- $R-- $((R-- $##R- "-P%&;d4/&X8_$Mu)9Aj} 6^*S|-- "- R--E2R--n[R-->+R--R--R--R--09&R--Bb/OR--iVxR--zR--R--R--.R--WDR-- lR--!R-- R--3 R--C"0R--K8R--ttaR--R--R--R--R--@-R--hUR--~R--R--R-- R--4!R--]JR--sR--R--R--R- "-L%$d/Xm$FMXuwrAj 6j^*S|--- "-n[R--R--(R--R--R--9y&R-- bOR--wdxR--R--R--R--P.=R--bWODR--nlR--~R--|iR--R--"R--K8R--taR--R--R--R--R--t@a-R--hUR--~R--R--R-- R--4!R--]JR--sR--R--R--R--- "-Y--Times New Romanh- ..- "-LLLz--- $BVKCUVR!Fallout (Bqm-)--L/L/L---VfCSR ! Milk (Bqm-)--L@L@L--VwCdR!Fit Milk (Bqm-)----       l    G      (9 Z6Times New Roman Regular y X Figure2.0  90Srfalloutandmilkactivitiesandmodelledmilkactivitiesusingequation/2/. ALIGNL  ~Psub{23}={INTfrom0to{~INF}Asubk(t)dt}over{INT from0to{~INF}Udotsubk(t)dt} XXoPp23XXoYXXXLN70XXAkXX[(XXtXX)XXdtXXLD?-70XXrXXBU)kXXeB(XXBtXXB)XX%Bdt kALIGNL  ~Psub{23}~=~bsub1~+~bsub2~+~bsub3{esup{mu}}over{1~~esup{mu}} XXoP23XXXXb1XXXXgb2XXgXX7b3X5XXve@XXG1XXGXXGe V   #  aJaa#JJa#JXXJ/4/#JXJX|##J:#(9 Z6Times New Roman Regular !  _  ____________ _ _ _ _ @  XXRadiostrontiumContaminationofMilkintheRepublicofCroatia#XXL#   @Z.Franic,N.LokobauerandG.Marovic@ InstituteforMedicalResearchandOccupationalHealth@  Ksaverskacesta2,POBox291,HR-10001Zagreb,Croatia@ E-mail:franic@imi.hrXXINTRODUCTION#XX#  ,    ThedominantroutefortheintroductionofartificialradionuclidesintotheenvironmentuntilthenuclearaccidentinChernobyl,Ukraine,on26April1986hasbeentheradioactivefalloutresultingfromtheatmosphericnuclearweapontests.Atmosphericnuclearexplosionshavebeenconductedsince1945andwerespeciallyintensivein1960s,i.e.,beforeanuclearmoratoriumbecameeffective.However,similar,butsmallertestswereperformedbytheChineseandFrenchalsointhe1970sandafterwards.Therefore,radioactivityofmostenvironmentalsamples,includingthosethatenterhumanfoodchaincouldbeexpectedtobeincorrelationwithfalloutactivity(i.e.,surfacedepositinBqm-2).Amongtheanthropotropicradionuclidespresentinglobalfallout,137Csand90Srhavebeenregarded x  asthefissionproductsofamajorpotentialhazardtolivingbeingsduetotheuniquecombinationoftheirrelativelylonghalf-lifes,andtheirchemicalandmetabolicpropertiesresemblingthoseofthepotassiumandcalciumrespectively.Milk,containingbothpotassiumandcalciumisthereforethesensitiveindicatorforpresenceoffissionproductsintheenvironment.Inaddition,milkastheveryimportantfoodstuffindietaryhabits,ispotentiallyamajorsourceofradioactivecontamination.Consequently,intheprogramofmonitoringofradioactivecontaminationofhumanenvironmentinCroatia(1,2,3,4)investigationsofradiostrontiumandradiocaesiumindairymilktakesignificantpart.Inthispaperaresummarizedtheresultsoflong-termsystematicmeasurementsofradiostrontiumactivitiesinmilk.XXMATERIALANDMETHODS#XX # `   FalloutsampleswerecollectedmonthlyatthelocationoftheInstituteforMedicalResearchandOccupationalHealth(4550'07.3"N,1558'58.7"E).Thefunnelsusedforfalloutcollectionhad1m2area.Theprecipitation  amountwasmeasuredbyHellmanpluviometer.  MilksamplesfromZagrebdairy,1Leveryday,wereobtainedcommercially.  In1960s90Srwasdeterminedbytheconventionalradiochemicalanalysiswithfumingnitricacidseparation. l  From1970topresent,90Srwasdeterminedbyextractionwithtributylphosphate,exceptintheyearoftheChernobyl 4! nuclearaccident,whenfumingnitricacidwasalsoused.  Aftertheradiochemicaltreatmentoffalloutandmilksamples,theradioactivityof90Srwasdeterminedbybeta t # countingitsdecayproduct,90Y,inalow-levelanti-coincidenceshieldedGMcounter.Countingtimedependedon90Sr     ` ExxeeLv   v'@0,p>    ` ExxeeLv (#(#                               (#(#   Thephysicalmeaningoftermsinmodel     /2/isasfollows:thefirstterm(ratefactor)describesdirect   depositionandtransfer,thesecondterm(lagfactor)describescontaminationthroughfalloutfrompreviousyear,and x! thethirdterm(landfactor)reflectsthecontaminationfromfalloutdepositionaccumulatedfromallprecedingyears, @" theexponentialdescribingthecombinedphysicaldecayandanyotherdecreaseinavailabilityofconsideredradionuclideduetovariousotherprocesses(likepenetrationindeepersoillayers,dilutionetc.).  Regressionanalysisgivesthefollowingvalues:b1=1.00,b2=0.09,b3=0.97Bqykg-1/(Bqm-2)and=0.32 !% yr-1,thecoefficientofcorrelationbetweenactualdataanddatapredictedbymodelbeing0.91.Theeffectivemeanlife `"& of90Srinmilkdefinedas1/is3.12years.The90Sractivityconcentrationsinmilkandthefitobtainedbyequation (#x' /2/areshowninFigure2.  Thetransferbetweensuccessivestepsinthepathwaychainsisdescribedbytransfercoefficients,whichrelateinfinitetimeintegralsofactivityconcentrationintherelevantcompartments.Thus,P23,thetransfercoefficientfrom % * falloutdeposition(compartment2)todiet(compartment3)isgivenbythefollowingequation:/D E2]MIz , @ pX @Xdddddddd@E'xj d(L'@ ####(#(# ######## ######## ######## ######## ######## ######## ######## ######## (#(##### .h)5 Ї  n'3:*&`>  ` E  ee n   n'3:*&`>    ` Exxeepn   v'3>@0,p>    ` ExxeeLv (#(#                               (#(#  Figure2.0 ` 90Srfalloutandmilkactivitiesandmodelledmilkactivitiesusingequation/2/.   where:Ak(t)0  istheactivityconcentrationofradionuclidekinfood,i.e.,milk(Bqkg-1)andx!(#(# Uk(t)0  isthefalloutdepositionrateofradionuclide(Bqm-2y-1).@"(#(#   AsforvaluesofAk(t)andUk(t)assessedontheyearlybasistheintegrationcanbereplacedbysummation,the  $ combinationofequations/2/and/3/leadsto:/F GH]MIz ,  pX @Xdddddddd@E`"x^ d N(L`"@z ####(#(# ######## ######## ######## ######## (#(#####  P23for90Srinmilkwasassessedtobe2.72'10-3Bqykg-1/(Bqm-2).ThatmeansthatwitheachBecquerel H&!+ depositedbyfalloutonanareaof1m2ofsoil,theactivityconcentrationof1m3milkincreasesby2.72Bq.For '`", comparison,thetransfercoefficientP23fortotaldietwasestimatedtobe4'10-3Bqykg-1/(Bqm-2)(10). '(#- Radiostrontiumdosesincurredbymilkconsumption 0*%0   IntheRepublicofCroatia,consumptionofmilkanddiaryproductsbeingapproximately100Lperyearperperson(12,13)canpotentiallyleadtosignificantradiationdoses.Theequivalentdoseincurredduetomilkconsumptionovercertainperiod,dependsontheactivityofradionuclidesthatarepresentinmilkandonthequantityofmilkconsumed.Thedosecanbeexpressedas: .h)5 Ї/7;6]MIz ,  pX @Xdddddddd@Ex d(L@ ####(#(# ######## ######## ######## (#(#####where:H0  isthetotalequivalentdoseinSv,(#(# C0  totalannualpercaputconsumptionofmilk(100ly-1),` (#(# Dcf(k)  thedoseconversionfactorforradionuclidekand ( x Ak  themeanactivityconcentrationofradionuclidekinmilk(Bqkg-1).  @   Dcf(k),i.e.,theequivalentdoseperunitinput,whichconvertstheingestedactivitytotheequivalentdose(for    agegreaterthan17years)for90Sris2.8'10-8SvBq-1(14). H     Forequaltimeincrementsofonemonth,integralfromequation/5/canbereplacedbytherespectivesumsofaveragemonthlyactivityconcentrations.Neglectingotherisotopesapartfrom90Sr,thetotaldoseduetothat (  radionuclidein1998wasapproximately0.2Sv.Forcomparison,in1994thetotaldosedueto134Csand137Cswas   aboutthesame,i.e.,0.3Sv,94.4%beingdueto137Cs(15).Thesameyear,theannualdosereceivedby90Srintake h  viafoodwasestimatedtobeabout3Sv(16).  _ _ AssumingsimilarradiostrontiummilkactivityconcentrationsinotherCroatianregions,thecollectiveeffectivedoseforCroatianpopulation(4.8millioninhabitants)dueto90Sringestionbymilkconsumptionin1998can  beestimatedtobe1.1manSv,whiletheannualcollectivedoseintheyearofChernobylwas5.5manSv.XXCONCLUSIONS#XXJ# 0   The90Sractivityinmilkdecreasesexponentiallyeversince1960s.Peakvalueswererecordedin1964,  followingthemostintensivenuclearweapontests.Consequently,the90SractivitiesinmilkinCroatiaarelog-normally  distributed,reflectingthatexponentialdecrease.  Dosesduetoradiostrontiumfrommilkconsumptionaresmall,inspiteofrelativelylargeconsumptionofmilkbytheCroatianpopulation,thecollectiveeffectivedoseforCroatianpopulationin1998being1.1Sv.  ItshouldbenotedthatalthoughradiocaesiumlevelsintheenvironmentintheyearofChernobylaccidentweremuchhigherthanthoseofradiostrontium,since90Srtransferfromsoiltothefoodchainisconsiderablymoreefficient, | thanfor137Cs,inthefollowingyearsthedosesthatCroatianpopulationreceivedfrom137Csand90Srwere D approximatelythesame.  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