Ash of Bikini and Its Effects on Human Body (Fishermen of the Fukuryu Maru)

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ASH OF BIKINIAND ITS EFFEJ'@O_N_'JlflJMANBODI_ Accordingto the report of the'fisherineno i began to come down about3 hours after the hydrogenbomb explosion. It continuedto fall about 5 hours at varying rates and coveredthe boat like the light snow that footprintswere left on the deck as they The ash consistsof light and white grainsof varioussize less than 1 mm in diameter. Microscopicexaminationshows that they are amorphousand porous. It might be the fragmentof the corallinesubstance.(Fig.1) Its radioactivitywas surprisinglystrong and even a few grainsof ash showedten-thousandscountsper minuteon March 16. The thicknessof the absorberto reduce the intensityof radiationto of theFray from the ash is shown in Pig. 2. The half-life-wasabout 8 dqs at first,but it is in these days (aboutApril 5) of the order of 18 dqs. Kxtrapolatingthe dampingcurve of radioactivityobservedafter March 17, the intensityof thee- ray on the next day of the explosion(March2) is estimatedto be about50 times larger than that of March 17. Similar resultq be obtainedfor theI- ray too. The chemicalanalysisof the ash has been performedat Kimura lablishedso far is shown in Table 1. There are severaldefinitionsof the half-lifeaccordingto the purpose as is shown below. The half-lifegiven in Table 1 is the pwsical half-lifedefined as the periodof time during which the munt of a particularradioactiveisotopeis reducedto half its initialvalue. The biologicalhalf-lifeis the time duringwhich the amountof elementsdepositedin some part of the body decreasesto half The effectivehalf-lifeis the time duringwhich the radioactivityof the depositedradioisotopeis reducedto half as a resultof combination of the two effectsmentionedabove. This is the quantitywhich must be taken accountof in discussingthe injuryproducedby the radioactive *Printedin Journalof Japan PhysiciansSociety,Vol. 31, NO. 9 (Mq 1, 1954)

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In Table 2 the physical, biological, and effective half-lives of the main elements which are supposed to deposit in the human body are given together with the organs in which they tend to deposit. As is evident from this, these elements have a tendency to deposit in the bone, thyroid, kidney and liver. There may be some rare earths which have not been detected yet. If they exist, they will also deposit in these organs. In the animal experiments, the Bikini ash was given to the animals with the food and also by the hypodermic injection and then their autoradiograph was taken. The result is the same as that of Table 2. Especially, the deposit is found to be the largest in the bone. This , is very important in connection with the problem of prognosis of the The result up to Uarch 26 of quantitative analysis mating use of the radioactivity of these elements is shown in Table 3. (Kimura Lab.) To our slight relief in this unfortunate accident, mre than 50% of the radioactivity is found in the rare earths while the amount of Srm is only of the order of 0.02%. The radioactive elements are absorbed in various ways through the digestive organ, respiratory organ, skin, etc. The rate of absorption of course depends on the elements and the chemical compounds which they form. Injury of patients of the Bikini accident has been caused by the radiation of the fallout in contrast to the atomic bomb injury at Hiroshima and Nagasaki. In the former, the injury is caused either by ~et~;ra$;~no;f~- andr - rays of fission products located outside or e body or by the irradiation of special organs such as the bone, thyroid, kidney, and liver in which the fission products are deposited by means of absorption through the respiratory organ, digestive organ, skin, etc. In the latter, the main cause of the (radiation) injury is the exposure to the initial nuclear radiation though there may be some effects of the induced radiation from inside and outside of the body. Thus the characteristic danger of the Bikini ash lies in the fact that the fission products deposit in such organs as the bone, thyroid, kidney, and liver; irradiate them, and moreover, are difficult to take out of these organs. To understand better the effect of radiation on the living'body, we shall first see what reaction will happen.when the energy of the B- or{- ray is absorbed by a cell, which is a unit of the life. In general the living body contains a lot of.water which will be ionized by the radiation yielding the free radicals like ti and OIT or the harmful molecules like H202. If this happens, the function of cells is damaged and such a biological change follows as the destruction of

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chromosome,the change of permeabilityof the cell membrane,the of the boil, death, etc. . One of the most importantfacts about the biologicaleffect of radiationis known as the law of Tribondeau-Bergonywhich assertsthat the cell is mst sensitiveto the radiationwhen it is young and has producingorgans (bone,spleen,lymphatic,etc.) and genitalcells are IIlostlikely to be injuredby radiation. The injury of radiation from outsideof the body may be classified into two categories. One is causedby thep- ragrof fissionproducts adheredto the skin. In this case, the skin turns to black, gives rise to bleb or fester,and the hair may be lost from the head. In fact, hands and faces of two patientswho enteredthe Tokyo UniversityHospital on March 1s were black'andhad festers at some places. It was found by a Geiger counterthat the radioactivitywas strongat the head, ears, neck, armpits,abdomen,sole, parts of hands or feet between the fingers or toes.' The result of measurementby the miliroentgenometer(distance 5 cm) is given in Table 4. The radioautographof the hair is shown in The other is causedby the r- rays of radioactivesubstances adheredto the deck, cabin,fishingimplements,clothes,etc. Since the ’ Y- ray has a large penetratingpower, itwillirradiate the whole body ani cause the change of blood (decreaseof leucocyte),recurrentanem%a, As is well-known,we are incessantlyexposedto the cosmic-rayfrom the sky and the radiationof naturalradioactivesubstanceslike radium and radon from the earth. Nevertheless,we are not injuredby these radiations,not to a visibleextent at least. This is due to the fact that even the exposureon successivedays has no damageif the amount of irradiationis less than a certainlimit. The maximummunt which the human body can tolerateis calledthe permissibledose. The internationalsocietyof radiologydeterminedthat the permissibledose is 300 miliroentgenper week. People living on a boat are exposedto the radiationat any time so that the permissibledose is 1.8 mr per hour. The intensityof radiationon the A&uryu Maru measuredat Yaieu on March 17 was 10~100 mr per hour which was 540 times the permissible In Table 5, it is shown how the intensityof radiationchangesfrom place to place in the boat and how it changeswith time. It is seen that on the averagethe intensitydecreasedto about 20-30 % of the value of :_)inr>h17 during the period of a month. If one estimatesthe intensity ;of radiationon March 2 from the dampingcurve, it is about 50 times larger than that of March 17. Severalhours after the ash began to come down many fishermenfelt sick and some vomited. This is the so-called

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radiationcrapulence. The estimateddose of radiationthe fishermenreceived during the followingtwo weeks is about200 r. It is thereforenot amazing that the bone and other organs sufferedconsiderableinjuries. of the radioactivityin the body. The outline of this problemwas given already when we referredto the chemicalanalysisof the ash. We shall thereforebegin here with the - survey of the animalexperiments. The radioactivedepositsin various organs of mice are measured12 hours and 48 hours after they were fed with the Bikini ash (fissionproducts)(Tables6 and 7 respectively).It is thus found that, though mst part passes by the digestiveorgans,some part is absorbedand depositsselectivelyin the bone, thyroid,kidney, and liver (Table8). Jihenthe fissionproductis given to the mice by hypodermic injection,it is found to depositin the bone, thyroid,kidney, and liver .' in the same way as above and excretedthroughthe digestiveorgans and with As to the patients,the radioactivityof the urine (15 cc) collected in a --tubeat the early dates was measuredand the number of counts was found to be severaltimes the backgroundcounting. The same resultis obtainedfor the concentratedurine. These are the evidencesfor the depositof the radioactivityin the patient'sbody. The radioactivitywas also measuredby a scintillationcounterplaced near the thyroid. In one case, the countwas 8 times that of the background on Karch 26 (see F2g. 4) and 2 times on April 13. From the half-lifeand--- the thyroid. Similar conclusionis On the basis of the fundamental it is presumedthat 1131 depositedin arrivedat for other patients,too. It is convenientto cite the followingstatementpublishedon April & by the clinicalsubcommitteeof the Councilfor the Investigationof the Atomic Bomb Sicknessof the Departmentof PublicWelfarein the names of Yoshio the Directorof Tokyo UniversityHospital,and Shigenobu Wn March 28, five of the patientsof Bikini accidententered the Tow0 UniversityHospital(sevenin all because two patients had been there already)and 16 patientsenteredthe First State Hospitalof Tokyo. Thoughthe degreeof injuryvariedfrom person to person, all of them were found to be the patientsof the acute radiationsicknessdue to the radioactiveashes. "The radioactivityinside and outsideof the body was considerably high at the time of their entranceto the hospitals. But it decreasedlater on by an appropriatetreatment. The contentof -fi

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radioactivityin the patient'surine has also been reducedvery juries to the body surfaceand the injuriesto the organs, especiallythe blood producingorgans. Ml1 patientssufferedon the head and the upper half of the pigment,inflammationof the skin, ulcer, eruptionwith abcess and scab, and blister. They are recoveringfrom these injuries by the treatmentin the hospitals. But some of them are still sufferingfrom the depilationin wide area. "The injury to blood-producingorganswas observedas the decrease of blood count of leucocyte,granulocyteand red blood corpuscles as well as the decreaseof the number of cells in the marrow. It was gettingworse sincethey were hospitalized.Especially,the blood count of leucocytefluctuatedaround1000 per cubic milimeter and the number of marrow cells has been of the order of 10,000per cubic milimeterin severalcases. It was thus hematologically diagnosedto be the generalacute sicknessof the marrow. "In these cases,in spiteof the ample blood transfusionand the use of pills for blood-production,the blood count of the leucocyte and granulocytedid not increaseand even the hemorrhagictendency appeared. Furthermore,their temperaturehad been as high as 3Y°C thoughvery effectivepills of antibiotic had been given, which has made us fear of an unfavorableprognosis. Such a dangerousconditioncontinueduntil recently andwe had to refrainfrom publishingthe facts in order to avoidundesirable effectson the treatmentof the patients. Fortunately,however, the fever began to leave the patientsvery recentlyand moreover the blood count of leucocytein some of the seriouscases began to increase. We are workinghard to cure the patientscompletely. It would be our duty and also the hope of all people to save the lives of all patients of this unfortunateaccident." Summarizingthe clinicalsymptoms,it may be said that the skin burn by thee- ray has almost been cured. There is now hardly any detectable radioactivityremainingon the skin surface. The most seriousproblemis the injuryto the marrow. Two causesmay be responsiblefor this. One is the the radioactiveelementsdepositedin the body. The clinicalsymptoms observedup to now may be mainlycausedby the former althoughsome part might have been playedby the latter too. This may be evidentin view of the fact that the estimatedradiationto which the fishermenwere exposedduring the two weeks stay on the boat amountsto 200 r, The intensityof radiation

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from the elementsdepositedin the body (especiallyin the bone) is small comparedto the externalradiation. But it may give a considerableamount of injuryduring the long period since it will continuouslyirradiatethe importantorgan, namely the marrow. It is thereforenecessaryto observe carefullythe clinicaldevelopmentin the future. For this purpose,it is imrtant to measure and analyzethe quantityof radioactivityin the urine. The study is now being proceededfrom this viewpoint. In order to dischargethe fissionproductsdepositedin the bones,EDTA(Ethylenediamine tetra aceticacid) can be used which howeveris not very efficient. It is reportedthat in an animal. experimentabout 20% of the substmces were dischargedwhen EDTA-Na and EBTA-Gawere appliedalternativelyin an early stage of deposit. In our case, too, it may be possible,using EDTA, to dischargethe fissionproductsseveral times faster than otherwise. Since EBTA-Na,being poisonous,cannotbe used to the human body, we are nom b. About the Hygienicsof the Environmentand the Foodt (i) The Boat as the Living Place - As is discussedin the section of the physicalpropertiesof the ashes,the half-lifeof the fission productson the IslkuryuMaru was changingfrom time to time. It was about 8 days at March 17 and 20 days at April 22. By this time, the intensityalso decreasedto about 20% of that of March 17. On April 22, the intensityof radiationin the boat ranged from 2 mr/hr to 20 mr/hr. It may not be verg long before the intensitybecomesless than the permissibledose 1.8 mr/hr. As is seen from Table 5, the measuredintensityfort- ray alone and the * total intensityof both ?- andr- rays are not very different. This may be understood s the result of the distancebetweenthe measuringinstmments and thet - ray sources,the absorptionof considerableamount of rays by the wooden parts of the boat into which the radioactivesubstance soaked,and the penetrationof extraf- rays from remote sourcesthrough the ceilingsand the walls. The radiationhas an effecton the human body so that the amountof injury shouldbe measuredby It is not appropriateto use the GM -counter. The from one to the other is not simple either. There are many boats besidesthe IUuryu Maru on which the ash fell through the ionization when they were making voage severalhundredmiles off Bikini. The count of radioactivityon these boats varies from hundredsto ten-thousands by the G&counter. But the intensityis at Illost3 mr/hr when measuredat a distanceof 5 cm w the miliroentgenmeter.Since the intensityat 50 cm is only one-hundredthof the amount at 5 cm, it may have hardly any effect on the human body. The amount of radioactivityon these boats is there fore very small and trivialcomparedto the case of the FukuryuMaru. Honever, if the radioactivityis presentat all, it may have a chance of getting into the body throughthe mouth, skin or lung. Of course,it is better not to be exposed to the radiation,howevera bit it is. It is

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thereforenecessaryto wash and removethe radioactivityfrom the boat, letterswrittenby the oil which was on the deck of the Ko'eiMarn and the glovesof the crew are shown in Figure 5. ii. About the Tuna. Since differentpeople have differentinterests it involvesmany intricateproblems. I will simplyrefer aspectof this problem. The questionis then how much of ash can be eaten togetherwith the tuna without violating in this subject, to the medical the human body. This is againnot a simpleproblem. F&t of all, the ash itself consistsof variouselementsand they are absorbedin the human bow at variousrates. Even the same elementwill be absorbed differentlyaccordingto the form of compoundsthey constitute.-FurthermOre, they depositin variousorgans such as the bone, kidney,liver logical. To simplifythe argument,we shall assumefor the moment that the ash consistsof only the most dangerouselementSr9O. In the usual form of compounds,about 60% of Srw is absorbedby the body through digestiveorgans and about4s depositsin the bones. Its physicalhalflife is abou 20 years,while the biologicaland effectivehalf-lives days (about10 years) and 2.7 x 103 days (about7.4 years), It is thereforevery difficultto dischargeonce it depositsin the bones. The permissibledose of deposit in the body is curie.Since bO% of the absorbedstrontiumdepositsin the bones, it is dangerousto eat more than 2.5 microcuries. It is not unambiguoushow much count the radioactivityof 2.5 microcurieswill give to the G.M. counter at 10 cm, since it dependson the geometry,measuringinstrument,the thicknessof the mica window of the G.M. counter,etc. But, roughly speaking,it may be about 5000 ct/min. Since the safetylimit adopted today is 100 ct/minat the distance10 cm, it may be concludedthat it is not dangerousat sll to eat …