Jpn. J. Health Phys.，45 (4)，370 ～ 378 (2010) Review
Latest Knowledge on Radiological Effects: Radiation Health Effects of Atomic Bomb Explosions and Nuclear Power Plant Accidents
Shigenobu NAGATAKI*1
（ReFeived on July 23, 2010） （AFFepted on July 23, 2010）
The latest knowledge enFompass ¿ndings presented both in individual sFienti¿F publiFations and in internationally aFFepted reports. This review summarizes the latest knowledge on radiobiologiFal effeFts on the latter level, using studies of atomiF bomb survivors and viFtims of Chernobyl nuFlear power plant aFFident. First of all, it is importanttonotethatwhile examining individual patient, it is impossible to distinguish a radiation-induFed FanFer patient and non-radiation-induFed FanFer patient even when using state-of-the-art teFhniques. Therefore, investigation of radiation effeFts on humans, espeFially late health effeFts has been based on the epidemiologiFal and statistiFal methods. Based on studies on atomiF bomb survivors, it is well aFFepted that there is a linear inFrease in the risk of FanFer with the inFrease of radiation dose. However, the existenFeofathresholdisaFontroversial issue, and health effeFts with regards to non-FanFer diseases are not yet aFFepted by international authorities. Childhood thyroid FanFer has inFreased after the Chernobyl aFFident and more than several thousands Fhildren are affeFted by it. However, there is no proof that any disease, with the exFeption of thyroid FanFer and aFute radiation effeFts, has inFreased after the Chernobyl aFFident. Finally, it should be mentioned that providing sFienti¿F explanation of the results to general publiF is an honorable duty of FonFerned sFientists.
KEY WORDS:radiationhealtheffeFts, FanFer, non-FanFer, linear dose relation, threshold, atomiF bomb survivors, Chernobyl nuFlear power plant aFFident.
reports (Fig. 1). I INTRODUCTION Health effeFts of radiation are pertinent to various very 1. Latest knowledge important soFial FonFerns, suFhastheuseofnuFlear power, The starting point of this review was an invitation from mediFal use of radiation, relief for atomiF bomb (A-bomb) the President of the 3rd Asian and OFeaniF Congress of survivors, etF. Therefore, sFienti¿F information on health Radiation ProteFtion to deliver a leFture entitled “Newest effeFts of radiation, provided to the publiF, must be as Flear- knowledge of radiologiFal biologiFal effeFts” at the Congress. Fut as possible and aFFepted internationally. The purpose of The latest knowledge is Fomprised both of ¿ndings presented this review is to provideinformationtothepubliF through in individual sFienti¿F publiFations and in internationally aFFepted reports. Usually, novel ¿ndings ¿rst appear as individual publiFations, whiFh are often debated with Individual Level National Level International Level Presentations respeFt to their validity, the interpretation of results, and Academic Societies UNSCEAR Manuscripts Local Authorities ICRP FonÀiFting ideas. A debate is important for developing In Scientific IAEA Sociaties sFienti¿F knowledge, Fon¿rming the signi¿FanFe of results, USA WHO France and searFhing for the next valuable studies. However, in Epidemiological Japan Knowledge plus Clinical Russia Policy this review the latest knowledge on radiologiFal effeFts is Biological summarized mainly at the level of internationally aFFepted Conflicting ideas, Debate International agreement World Conference 20th Century Science for Knowledge on Science Knowledge for Progress *1 Chairman, International AssoFiation of Radiopathology (IAR) Past Chairman, Radiation EffeFts ResearFh Foundation (RERF) 21st Century Science for Peace Professor Emeritus, Nagasaki University. Science for Development (UNESCO Science in Society Home address: 2–41–2IFhigayatamaFhi, Shinjuku, Tokyo 162–0843, 1998, 2002 ) Science for Society Japan. E-mail: [email protected] Fig. 1 /DWHVWNQRZOHGJHRQUDGLRELRORJLFDOHIIHFWV:KDWLV WKHODWHVWNQRZOHGJH" Latest Knowledge on RadiologiFal EffeFts 371 members of the Japanese Health PhysiFsSoFiety. and it was reported that 50% of the energy was blast, 35% for 2. Characteristics of late health effects of radiation heat, and 15% for radiation. A book on the effeFts of nuFlear It should be noted that while examining partiFular patients, weapons was published in 1977, and the third edition was it is impossible to distinguish a radiation-induFed FanFer published in 2006.3) patients and non-radiation-induFed FanFer patients even with (1) Acute death state-of-the art mediFal and sFienti¿F teFhniques. Therefore, Table 2 is the summary of these reports. In total, 140,000 investigation of radiation effeFts on humans, espeFially late people in Hiroshima (38.9% of the population) and 70,000 health effeFts has been based on epidemiologiFal and statistiFal people in Nagasaki (28.0% of the population) died in 1945, methods. In brief, studies of radiation health effeFts have but how many died partiFularly from the blast, heat, or due to been foFused on the relation between the degree of exposure radiation is unknown. to radiation (radiation dose) and the inFidenFe of diseases in However, there was a report on “individuals who died 20 study Fohorts. days after the bombing or later”. Of the 6,882 people examined 3. Sources of information on radiation effects on in Hiroshima, and of the 6,621 people examined in Nagasaki, humans in the 20th century 254 (3.7%) and 174 (2.6%), respeFtively, died later. About half As shown in Table 1, sourFes of information on radiation of these deaths oFFurred between the 20th and the 29th day after effeFts are atomiF bombings, A-bomb/H-bomb tests, A-bomb the bombing and most of the remainder between the 30th and produFtion aFFidents, aFFidents at nuFlear power plants, the 49th day. 99% of deaths in Hiroshima and 91% of deaths in oFFupational exposure, mediFal radiation, mediFal aFFidents, Nagasaki oFFurred in areas loFated within 2,000 meters from radiation sourFes, etF. AtomiF bombings of Hiroshima and the hypoFenter. However, it should be mentioned that, most Nagasaki and the aFFident at Chernobyl NuFlear Power of the people residing within a distanFe of 500 meters from Plant (ChNPP) are seleFted for this review mainly beFause hypoFenter died within less than 20 days after the bombing.2, 3) the author has been deeply involved in both investigations. Current analyses of extensive reFords at the Radiation Also, A-bombings of Hiroshima and Nagasaki are still the EffeFts ResearFh Foundation (RERF) were able to make gold standard of radiation effeFts, and the Chernobyl aFFident estimates of shielding. It was FalFulated that a bone marrow affeFted the largest number of viFtims. dose of 2.9–3.3 Gy Faused 50% mortality within 60 days. This review utilizes the following strategy: the level of These data were based on about 7,600 survivors in 2,500 individual reports to summarize knowledge at the level of households who were exposed inside of their Japanese houses, internationally aFFepted ¿ndings. loFated within 1,600 meters of the hypoFenter in Hiroshima.4) International organizations, suFh as the United Nations II ATOMIC BOMBINGS OF HIROSHIMA AND SFienti¿F Committee on the EffeFts of AtomiF Radiation NAGASAKI (UNSCEAR)haveestimatedthebonemarrowLD50isabout 1. Acute radiation effects 2.5 Gy in Fases when little to no mediFal treatment is available, AtomiF bombs were dropped on Hiroshima and Nagasaki and at 5 Gy or more when extensive mediFal treatment is respeFtively on August 6 and August 9 1945. Initial reports provided. were Fompiled by Imperial Headquarters, the Japanese Army, (2) Signs and symptoms caused by atomic bombing Navy, Universities (Tokyo, Kyoto, Osaka), SFienti¿F Institutes radiation (PhysiFal and ChemiFal Institute), Hiroshima MediFal AFFording to reports, nausea, vomiting, anorexia and AssoFiation and Nagasaki University. A preFise summary malaise oFFurred in most of the Fases on the day of the report was published by Hiroshima and Nagasaki Cities in bombing. Subsequently, diarrhea, bloody diarrhea, purpura, 1979.1) “MediFal EffeFts of AtomiF Bombs: The report of the epilation, and oropharygeal lesions oFFurred within a few joint Fommission for the investigation of the effeFts of the days to several weeks after the bombing. In areas very Flose atomiF bomb in Japan, Volume 1-VI” a summary report in to the hypoFenter, lower white blood Fell Founts, seFondary English, was published on April 19, 1951 by the Army Institute infeFtions, high fever, and death oFFurred within a few days.2, 3) of Pathology, United States AtomiF Energy Commission.2) (3) Acute radiation syndrome Energy of atomiF bomb was estimated by A-bomb test using AFFording to the RERF’s Furrent brief desFription,4) the a similar type and size bomb (equivalent to TNT 20 kiloton) illnesses Falled “aFute radiation syndrome” oFFurs within a
Table 1 6RXUFHVRILQIRUPDWLRQRQUDGLDWLRQHIIHFWVRQKXPDQVLQWKHWKFHQWXU\ $WRPLFERPELQJV Hiroshima, Nagasaki Marshall (Bikini, Bravo Test) A-bomb/H-bomb tests Nevada (USA), Semipalatinsk (USSR) 8.)UDQFH&KLQD,QGLD3DNLVWDQ $ERPESURGXFWLRQDFFLGHQWV Hanford (USA), Southern Ural (USSR) 1XFOHDUSRZHUSODQWDFFLGHQWV Three Mile Island, Chernobyl, JCO (Tokaimura) 2FFXSDWLRQDOH[SRVXUH 8UDQLXPPLQHV)OXRUHVFHQW3DLQW1XFOHDU3ODQWV 0HGLFDOUDGLDWLRQ Diagnosis and treatment 0HGLFDODFFLGHQWV Reported to IAEA, WHO all over the world 5DGLDWLRQVRXUFHV Reported to IAEA, WHO all over the world 372 Shigenobu NAGATAKI
Table 2 $FXWH HIIHFWV RI UDGLDWLRQ IURP DWRPLF ERPE RQ The aim of the ABCC-RERF’s researFh is to determine Humans. long-term effeFts of radiation exposure. This matter had been Death an unFharted territory for sFienti¿F researFh. The RERF’s 3ODFH Death / Population researFh is noted for its long-term follow-up of a large, well- Hiroshima 140,000/360,000 (38.9%) de¿ned population Fohort. Another strength of the RERF’s Nagasaki 70,000/250,000 (28.0%) researFh is that the radiation dose of eaFh A-bomb survivors It is not known how many died by blast, heat has been estimated with a high degree of aFFuraFy. The ¿rst or due to radiation RERF’s radiation dosimetry system was announFed in 1965, Signs and symptoms followed by two revisions in 1986 (DS86) and in 2002 (DS02). 1DXVHD YRPLWLQJ DQRUH[LD PDODLVH RFFXUUHG (2) Study Populations of RERF LQ PRVW RI WKH FDVHV RQ WKH GD\ RI WKH ERPELQJ In order to develop a Fomprehensive roster of persons Subsequently, diarrhea, bloody diarrhea, purpura, eligible for inFlusion in ¿xed study Fohorts, the ABCC HSLODWLRQ DQG RURSKDU\QJHDO OHVLRQ RFFXUUHG ZLWKLQ D used data from the A-bomb survivors survey, FonduFted at few days to several weeks after the bombing. In areas the time of the 1950 Japanese national Fensus. The survey YHU\FORVHWRK\SRFHQWHUORZHUZKLWHEORRGFHOOFRXQWV identi¿ed 284,000 Japanese survivors, nearly 200,000 of VHFRQGDU\ LQIHFWLRQ KLJK IHYHU DQG GHDWK RFFXUUHG whom were residents of either Fity at the time of the Fensus. within a few days. Subsamples of this original Master Sample have formed the basis for all studies FonduFted by the ABCC-RERF sinFethe late 1950s. In all mortality studies, information on the Fause few hours to months after an exposure to high-dose radiation of death is obtained through of¿Fial permission from the (from approximately 1–2 Gy to 10 Gy). The most Fommon Ministry of Health, Labor and Welfare and the Ministry of signs and symptoms inFlude vomiting oFFurring within a few JustiFeregardlessofloFation in Japan. Information on FanFer hours, followed within days to weeks by diarrhea, reduFed inFidenFeisobtainedthroughloFal tumor and tissue registries blood Fell Founts, bleeding, hair loss (epilation), and temporary and is limited to Furrent residents of Hiroshima and Nagasaki male sterility. Diarrhea results from the damage to Fells lining prefeFtures. Additional information on disease inFidenFeand the intestines, reduFtion in blood Fell Founts from death of health status is available for Adult Health Study partiFipants. hematopoietiF stem Fells in bone marrow, and bleeding from As shown in Table 3,ABCC/RERFstudyFohorts inFlude deFlining number of blood platelets generated from stem Fells. 120,000 partiFipants of Life Span Study, 23,000 partiFipants Hair is lost due to the damage to hair-root Fells. Hair does not of Adult Health Study, 3,600 partiFipants of In Utero exposed fall out but rather beFomes thinner and eventually breaks off. Survivors study, and 77,000 partiFipants of Children of Sterility in men oFFurs due to the damage to sperm-generating Survivors. Individual exposure doses were estimated by US stem Fells. ExFept for vomiting, these signs and symptoms are and Japanese experts (DS86, DS 02). related to the frequenFyofFell division, rapid Fell division (3) Radiation Dosimetry of Study Populations being more sensitive to radiation than slow division (e. g., The dosimetry system 2002 (DS02) provides individual musFle and nerve Fells). If radiation dose is low, this syndrome dose estimates dependent on information regarding eaFh will seldom if ever oFFur (threshold). Conversely, if dose is survivor’s loFation and shielding situation at the time of high, death Fan oFFur within 10 to 20 days after exposure due the bombing. The system is based on the physiFal nature to severe intestinal damage, or subsequently within one or two of the bombs that were dropped, and theoretiFal models, months, mainly from bone marrow failure. developed by nuFlear physiFists for the following parameters: These desFriptions of aFute radiation syndrome have been the amount of radiation released, the manner radiation was adopted by international sFienti¿F organizations. transported through the air, and the manner it was affeFted 2. Late effects of radiation by passage through physiFal struFtures and human tissue. Studies on radiation health effeFts of atomiF bomb survivors Individual dose estimates are impreFise for various reasons, are still the world’s gold standard. In this review, the Furrent inFluding inaFFuraFies in reported survivor loFations and the knowledge about radiation health effeFts on humans and impossibility of aFFounting for all aspeFts ofshieldingin limitations therefore are shown based on results of studies detail. It is believed that standard errors in individual dose of atomiF bomb survivors. The majority of epidemiologiFal studies of survivors were performed by RERF, and data used in this review are obtained primarily from the brief desFription Table 3 Long-term follow-up study on A-bomb survivors by of the RERF. 4) $%&&DQG5DGLDWLRQ(IIHFWV5HVHDUFK)RXQGDWLRQ 5(5) (1) Radiation Effects Research Foundation (RERF, the 1975–) –COHORTS–. former ABCC) Cohorts Size The AtomiF Bomb Casualty Commission (ABCC) was 1) Life Span Study (1950–) 120,000 2) Adult Health Study (1958–) established in Hiroshima and Nagasaki by the US National 23,000 AFademy of SFienFes in 1947 in order to study health effeFts biennial examination among atomiF-bomb survivors in the two Fities. The Radiation 3) In Utero exposed survivors Study (1950–) 3,600 EffeFts ResearFh Foundation (RERF) was established in 1975 4) Children of Survivors (1946–) 77,000 as the suFFessor organization to the ABCC with joint funding Individual exposure doses were estimated by US and Japanese from the US and Japanese governments. experts (DS86)–(DS02). Latest Knowledge on RadiologiFal EffeFts 373 estimates may be on the order of 35%. (4) Late Radiation Effects: Studies at RERF Early radiation effeFts, suFhasaFute radiation syndrome, result from doses high enough to kill Fells and thus Fause direFt tissue damage (1 Gy or greater). In Fontrast, late effeFts, suFhasFanFer reÀeFt DNA mutations in living Fells induFed by radiation exposure. While the exaFtmeFhanisms by whiFh suFh mutations lead to FanFer are not Flear, it is believed that the proFess requires a series of mutations, aFFumulated over years. Mutations Fan oFFur either spontaneously or as a result of exposure to any of a wide range of environmental mutagens, inFluding radiation. SinFe many years must pass before a given Fell and its progeny aFquire mutations suf¿Fient to result in FliniFal disease, exFess FanFers attributable to radiation do not beFome evident until years after exposure (or somewhat fewer years in the Fase of leukemia). The RERF’s Fig. 2 /66 VROLG FDQFHU LQFLGHQFH H[FHVV UHODWLYH ULVN E\ data shows that exFess FanFer risks Forrespond broadly to age- radiation dose, 1958– 7KH WKLFN VROLG OLQH LV WKH time patterns prediFted by suFhhypothetiFal Fonsiderations. ¿WWHG OLQHDU VH[DYHUDJHG H[FHVV UHODWLYH ULVN (55 GRVH (i) Solid CanFers UHVSRQVH DW DJH DIWHU H[SRVXUH DW DJH 7KH WKLFN InFreased risk of FanFer is the most important late effeFt GDVKHG OLQH LV D QRQSDUDPHWULF VPRRWKHG HVWLPDWH RI WKH of radiation exposure seen in A-bomb survivors. For FanFers GRVH FDWHJRU\VSHFL¿F ULVNV DQG WKH WKLQ GDVKHG OLQHV DUH other than leukemia (solid FanFers), exFess risk assoFiated one standard error above and below this smoothed estimate. with radiation started to appear about ten years after exposure. For most solid FanFers, aFute radiation exposure at any age inFreases FanFer risk for the rest of a person’s life. As survivors the time of exposure. Other analyses indiFate that females have aged, radiation-assoFiated exFessratesofsolidFanFer have somewhat higher risks of FanFer induFed by radiation have inFreased along with the baFkground rates. The average exposure than males.. radiation exposure of survivors within 2,500 meters (about (ii) Linear dose response, no threshold (LNT) 0.2 Gy) resulted inthe inFrease of about 10% above normal As it was mentioned, the dose–response relationship appears age-speFi¿F rates. For a dose of 1.0 Gy, the Forresponding to be linear, without any apparent threshold below whiFh FanFer exFess is about 50% (relative risk = 1.5). effeFts may not oFFur. Figure 3 shows problems with LNT. In During the period from 1958 to 1998, 7,851 malignanFies studies of mortality as well as inFidenFeinLSSFohort, it was (¿rst primary)were observed among 44,635 LSS (the Life Span shown that the minimum dose neFessary for health effeFts is Study) survivors exposed to estimated doses of >0.005 Gy. 0.1 Sv. There is no evidenFe of departure from linearity over The exFess number of solid FanFers is estimated as 848 (10.7%) the 0–4 Sv range, that is, the relationship between radiation (Table 4). The dose-response relationship appears to be linear, dose and FanFer inFidenFe is not different from a linear dose without any apparent threshold below whiFheffeFts may not response in the 0–4 Sv range. Linearity of the 0–0.1 Sv range oFFur (linear non-threshold, the LNT hypothesis ) (Fig. 2). is not different from that of the 0–4 Sv range, indiFating that The probability that an A-bomb survivor may develop a estimated threshold is essentially 0. However, linearity of the FanFer Faused by A-bomb radiation (exFess lifetime risk) 0–0.1Sv range is not different from the zero slope. This is the depends on the dose reFeived, the age at the time of exposure, author’s simpli¿ed explanation of problems with LNT. and sex. Higher risks areassoFiated with younger age at The etiology of various solid FanFers is another important
Table 4 ([FHVVULVNRIGHYHORSLQJVROLGFDQFHUVLQ/66 –1998. &DQFHUV :HLJKWHGFRORQ Estimates based on an model* Artributable /66VXEMHFWV dose (Gy) Observed Cases if ([FHVVE\ IUDFWLRQ Unexposed(C) Exposure(E) 0.005–0.1 27,789 4,406 4,374 81 1.8% 0.1–0.2 5,527 968 910 75 7.6% 0.2–0.5 5,935 1,144 963 179 15.7% 0.5–1.0 3,173 688 493 206 29.5% 1.0–2.0 1,647 460 248 196 44.2% >2.0 564 185 71 111 61.0% Total 44,635 7,851 7,059 848 10.7% (VWLPDWHGEDVHGRQDQH[FHVVUHODWLYHULVNPRGHOIRUOLQHDUGRVHUHVSRQVHPRGL¿HGE\DJHDWWKHWLPHRI bombing, attained age, and sex. ** E/(C+E) (%) 374 Shigenobu NAGATAKI
sFienti¿F organizations and the RERF’s data has been regarded as the gold standard. However, two issues arise to illustrate a differenFe between the RERF’s publiFations and internationally aFFepted reports. The ¿rst issue is the LNT hypothesis. The RERF’s data suggest that the LNT hypothesis, or LNT, is a model for interpretation of the RERF’s data. However, there is a Fontroversy as to whether the threshold exists, therefore, the LNT hypothesis Fan be aFFepted or rejeFted. Many entities around the world are involved in a Fontinuous debate on LNT. A typiFal example is that the National AFademy of : Fig. 3 Linear Dose Response, No Threshold (LNT) SFienFes (USA) supports LNT, 5) while the National AFademy 5HODWLRQVKLSEHWZHHQUDGLDWLRQGRVHDQGH[FHVVUHODWLYHULVN of MediFine (FranFe) does not.6) When low dose radiation is RIFDQFHULVOLQHDUDQGKDVQRWKUHVKROG de¿ned as a dose lower than 100 mSv, it Fan be Fonsidered that 75% of atomiF bomb survivors in LSS Fohort reFeived low dose radiation, and most of nuFlear power plant workers problem. It is well known that some FanFers have FanFer– (more than half million) are also reFeiving low doses of speFi¿F etiology, and that etiology of various FanFers is radiation. However, it would be impossible to obtain Flear a different. In spite of this mediFal knowledge about FanFers, a FonFlusion from epidemiologiFal studies of these populations linear dose response of solid FanFers in atomiF bomb survivors withinadeFade or more.. The International Commission on was obtained using all solid FanFers as one group. This is RadiologiFal ProteFtion (ICRP) has aFFepted LNT, as the another limitation of statistiFal analysis of the data. radiation proteFtion poliFy. (iii) Leukemia The seFond issue is radiation effeFts on non-FanFer ExFess leukemia was the earliestdelayedeffeFtofradiation diseases. As shown in Table 5, the RERF reported that exposure seen in A-bomb survivors. Risks for radiation- respiratory diseases, stroke, heart diseases, benign uterine induFed leukemia differ from risk for most solid FanFers in tumors, thyroid disease, FhroniF liver disease, FataraFtand two major respeFts. Firstly, radiation Fauses a larger perFent hypertension have inFreased signi¿Fantly after exposure to inFrease in leukemia rates; seFondly, the inFrease appears atomiF bomb radiation. However, both the ICRP and the sooner after exposure, espeFially in Fhildren. ExFess leukemia UNSCEAR reviewed reports on FardiovasFular diseases, began appearing about two years after radiation exposure, and and they FonFluded that in the absenFe of known biologiFal the exFess peaked at about 6–8 years after exposure. Today, meFhanisms, sFienti¿F data are not suf¿Fient to prove that the little if any exFess leukemia is oFFurring. inFrease in FardiovasFular diseases is due to radiation.7, 8) Leukemia risk among LSS survivors has been inFreased These are limitations of our knowledge about radiation only for aFute and FhroniF myeloFytiF leukemia and for aFute health effeFts derived from studies of atomiF bomb survivors. lymphoFytiF leukemia. No evidenFeofinFreased risk is seen for adult T-Fell leukemia (endemiF in Nagasaki but virtually non-existent in Hiroshima) or for FhroniF lymphoFytiF Table 5 /DWH KHDOWK HIIHFWV RI $ERPE UDGLDWLRQ í leukemia, whiFh, in marked Fontrast to western Fountries, is 6WDWLVWLFDOO\VLJQL¿FDQWUHVXOWVREWDLQHGIURPPRUHWKDQRQH extremely rare in Japan. VWXG\DQGULVNVFOHDUO\UHODWHGWRUDGLDWLRQGRVHí (iv)Summary of late effeFts of A-bomb radiation reported by RERF A) A-bomb survivors Even a brief desFription published by the RERF provides (1) Malignant diseases extensive information on human late health effeFts after atomiF Leukemia: bomb explosion. This information is summarized by the author DFXWH DQG FKURQLF P\HORF\WLF OHXNHPLD DQG DFXWH in Table 5 . In addition to early mentioned solid FanFers and O\PSKRF\WLFOHXNHPLD leukemia it has been reported that A-bomb survivors suffer QRH[FHVVVHHQIRUFKURQLFO\PSKDWLFOHXNHPLDRUDGXOW from several non-FanFer diseases. Mortality data show dose- 7FHOOOHXNHPLD related exFesses of respiratory diseases, stroke, and heart Solid cancers: diseases. Moreover adult health inFidenFe studies of non- 6ROLG FDQFHUV XULQDU\ EODGGHU EUHDVW OXQJ WK\URLG FanFer diseases show that there is a relationship between FRORQRYDU\VWRPDFKKHSDWRFHOOXODUVNLQ atomiF bomb radiation dose and benign uterine tumors, thyroid (2) Non-cancer diseases disease, FhroniF liver disease, FataraFt and hypertension. LSS: Heart diseases, Stroke, Respiratory diseases In-utero exposed survivors developed radiation-dose related AHS: Benign tumors (thyroid, parathyroid, salivary miFroFephaly, mental retardation, and delayed growth. Finally, JODQG XWHUXV WK\URLG GLVHDVHV FKURQLF OLYHU it should be noted that Fhildren of atomiF bomb survivors GLVHDVHFDWDUDFWVK\SHUWHQVLRQ showed no radiation-dose related health effeFts whatsoever. B) In-utero exposed survivors 5. RERF’s reports and internationally accepted reports PLFURFHSKDO\PHQWDOUHWDUGDWLRQGHOD\HGJURZWK First of all, it should be noted that a signi¿Fant number of C) Children of A-bomb survivors the RERF’s reports have been aFFepted by international QRVLJQL¿FDQWHIIHFWV Latest Knowledge on RadiologiFal EffeFts 375
DQ[LHW\DQGVWUHVVGXHWRFRQWLQXLQJKLJKOHYHORIXQFHUWDLQW\ III ACCIDENT AT CHERNOBYL NUCLEAR POWER +RZHYHU ZKHQ SXEOLVKHG WKLV VFLHQWL¿F UHSRUW PHW ZLWK PLANT KHDWHG DFFXVDWLRQV IURP SHRSOH OLYLQJ LQ WKH FRQWDPLQDWHG 1. Initial period (1986–1996) areas and from numerous mass media. The Chernobyl NuFlear Power Plant (ChNPP) aFFident In parallel with international investigations, there have oFFurred in 1986. Extensive international Follaboration to been published many individual reports and publiFations study radiation related health effeFts started around 1990. that were similar to mass media reports. They exaFerbated International organizations the author Follaborated with already severe psyFhologiFal Fonditions of people living in the were the International AtomiF Energy AgenFy(IAEA),the Fontaminated areas suFh as fear and anxiety due to potential World Health Organization (WHO) and the European Union radiation health effeFts. The author was one of international (EU). Around the same time, the Ministry of Foreign Affairs, experts involved in international investigation projeFt, and one Japan and Sasakawa Memorial Health Foundation signed a of the author’s important duties was evaluating the validity of bilateral agreement with the former Soviet Union and began reports, Fonsidering psyFhologiFal effeFts on people living in Follaboration. the Fontaminated areas. In 1990, when international mass media were allowed InSeptember1992,apaper,“ThyroidFanFer after Chernobyl” to visit Fontaminated areas, it was repeatedly reported that was published in Nature as sFienti¿F ForrespondenFebythe “several hundred thousand people died due to the aFFident”, Minister of Health, Chairman of Thyroid Tumor Center, and that “huge areas were Fontaminated and people had to be Radiation MediFine Institute of Belarus.10) As shown in Fig. 5, removed”, that “malformation appeared not only in humans the following month a European Union mission was sent to but also in animals and plants”, that “many babies and Minsk. Members of the mission, the author inFluded, were Fhildren were suffering from leukemia”, etF. Inhabitants of perturbed by seeing so many Fhildren with thyroid FarFinoma, the Fontaminated areas were Fonsumed with fear and anxiety sinFetheinFidenFeofFhildhood thyroid FarFinoma is one/ beFause of mass media news. It was reported that many one million in Japan, Europe and the US. While it was agreed women terminated their pregnanFy. The author visited the by members of the mission that many Fhildren presented with Fontaminated areas in 1990 and met with many inhabitants thyroid papillary FarFinoma, there had been no agreement (Fig. 4). It seemed that psyFhologiFal effeFts suFhaspaniF, between the EU and the USA experts on the Fause of fear, and anxiety were the most serious matters that had to be FarFinoma. dealt with. To abate the widespread paniF, it was reFommended International meetings and symposia to disFuss sFienti¿F that individual sFreening starts as soon as possible to deteFt results of various studies, inFluding thyroid FarFinoma, have potential patients as well as assure individuals that they were been held at least onFe a year ever sinFe. Finally international not affeFted by any diseases. symposia were held by the WHO, the EU and the IAEA 10 In 1989, the USSR Government requested that the IAEA years after the Chernobyl aFFident. H[DPLQHG WKH DVVHVVPHQW RI UDGLRORJLFDO VLWXDWLRQ LQ WKH 2. International symposia 10 years after the accident FRQWDPLQDWHGDUHDV$VWKHUHVXOWRIWKLVUHTXHVWLQ WKH In 1995–6, the WHO and the EU held international ,$($ SXEOLVKHG D WHFKQLFDO UHSRUW WLWOHG ³7KH ,QWHUQDWLRQDO symposiums independently from eaFh other. In April 1996, &KHUQRE\O 3URMHFW´ ZULWWHQ E\ DQ LQWHUQDWLRQDO DGYLVRU\ the WHO, the EU and the IAEA held joint International FRPPLWWHH &KDLUPDQ 'U ,WVX]RX 6HIGEMATSU from the ConferenFe“OnedeFade after Chernobyl” in Vienna.11) The RERF).9) 7KH UHSRUW FRQWDLQHG IROORZLQJ FRQFOXVLRQV DW WKH author summarized extensive presentations, disFussions, WLPHRIWKHSURMHFWVWXG\WKHUHZHUHVLJQL¿FDQWQRQUDGLDWLRQ summaries, and reFommendations in Table 6. UHODWHG KHDOWK GLVRUGHUV EXW QR KHDOWK GLVRUGHUV WKDW FRXOG EHDWWULEXWHGGLUHFWO\WRUDGLDWLRQH[SRVXUH7KHDFFLGHQWKDG VXEVWDQWLDO QHJDWLYH SV\FKRORJLFDO FRQVHTXHQFHV LQ WHUPV RI
Fig. 5 0DQ\ SDWLHQWV ZLWK FKLOGKRRG WK\URLG FDQFHU ZHUH SUHVHQWHG WR 0HPEHUV RI WKH (8 0LVVLRQ LQFOXGLQJ WKH author). 3URI 'HPLGFKLFN DW 7K\URLG 7XPRU &HQWHU LQ 0LQVN Fig. 4 People in Contaminated Areas. 2FWREHU 376 Shigenobu NAGATAKI
As far as aFute radiation effeFts are FonFerned, mediFal inFluding the IAEA, the WHO, etF.and3affeFted Fountries: ¿ndings on aFute radiation syndrome patients and patients the Russian Federation, the RepubliF of Belarus, and Ukraine who died from radiation exposure were published in leading was published as the Chernobyl Forum, and the sFienti¿F international sFienti¿F journals and widely aFknowledged. symposium on the Chernobyl Forum was held in Vienna. A AFute radiation syndrome was observed only in workers and report on health effeFts: “Health EffeFts of the Chernobyl ¿remen who were working inside the nuFlear plant. There was AFFident and SpeFial Health Care Program by Expert Group no extensive debate on aFute effeFts. As far as late effeFts are “Health”. was published. The report had over 50 Fontributors FonFerned, the international Fommunity was ¿rst made aware (Chairman: Dr. Burton G. Bennett from the RERF). Its of the inFrease in Fhildhood thyroid FanFer at the time of an summary on FanFer and non-FanFer was presented by two extensive disFussion even during the symposium. However, the speakers at the symposium, whiFhappearedtobeaFeremony inFrease was aFFepted largely beFause of strong FirFumstantial dediFated to the publiFation of the Chernobyl Forum. This evidenFe; FhronologiFal (studies starting around 1960) and style of presentation was very different from “One deFade geographiFal (three Fontaminated Fountries: the Russian after Chernobyl”, when eaFh topiF was presented by a group Federation, the RepubliF of Belarus and Ukraine). Figure 6 of experts and presentations were disFussed extensively at the depiFtsanumberofFases in Belarus as presented at the sumposium. international FonferenFe. There were numerous publiFations The Forum was ¿nally presented by an IAEA expert and reports on the inFrease of leukemia and other diseases, but at memorial symposium held in Kiev in 2006.12) Table 7 these reports were not aFFepted at this FonferenFe. summarizes extensive FonFlusions and the disFussion of the 3. International symposia 20 years after the accident Chernobyl Forum. The only demonstrated late health effeFts of In 2005, a report Fompiled by 8 international organizations radiation were the inFrease in thyroid FanFer in Fhildren. The
Table 6 ,QWHUQDWLRQDO6\PSRVLD 3HRSOHZLWKGHPRQVWUDWHGKHDOWKHIIHFWV Size 3HRSOHZLWKV\PSWRPVRIDFXWHUDGLDWLRQV\QGURPH 134 (237 were hospitalized) 28 died within 3 months 14 died within the subsequent 10 years (2 died of blood disease) &KLOGKRRGWK\URLGFDQFHU About 800 GLHGEHFDXVHRIWK\URLGFDQFHU ,QFUHDVHRIRWKHUGLVHDVHVLQFOXGLQJOHXNHPLD 1RWEHHQFRQ¿UPHG Table 7 Chernobyl forum. ■ Categorization of radiation-exposed subgroup Population groups Size mSv (PHUJHQF\ZRUNHUVRQVLWH 237 lethal dose 2. Liquidators (1986–7) (30 km zone) 240,000 100 (YDFXHHVRI 116,000 33 4. Persons in living at deposition density of Cs137 more than 37 kBq/m2 5,200,000 10 more than 555 kBq/m2 270,000 50 ■ 3HRSOHZLWKGHPRQVWUDWHGKHDOWKHIIHFWV +HDOWKHIIHFWV Size 6\PSWRPVRIDFXWHUDGLDWLRQV\QGURPH 134 (237 hospitalized) 28 died within 3 months 15 died within the subsequent 20 years more than 4,000 &KLOGKRRGWK\URLGFDQFHU GLHGFRQ¿UPHG /HXNHPLDDQGRWKHUVROLGFDQFHUV 1RLQFUHDVH 6XEFOLQLFDOSV\FKRORJLFDOHIIHFWV 0DMRULPSDFW Latest Knowledge on RadiologiFal EffeFts 377 inFrease in leukemia and other diseases was not demonstrated. data are obtained, yet when, the probability that given health Another major impaFt reported and demonstrated was effeFts are a FonsequenFe of radiation exposure is smaller, the subFliniFal psyFhologiFal effeFts. Figure 7 shows Fhanges in effeFts are Falled “not demonstrated”. thyroid FarFinoma inFidenFe in young people. It should be As mentioned above, the investigation of radiation health noted that inFidenFeofFarFinoma in Fhildren deFreased from effeFts implies ¿nding a relation between exposed radiation 1996 and was almost 0 in 2002. In Fontrast to the deFrease in doses and the inFidenFe of diseases in study Fohorts. Fhildren, FanFer inFidenFehasbeguninFreasing in adolesFents Therefore, if data on exposed radiation doses are not suf¿Fient, and adults. no radiation health effeFts are demonstrated. Similarly, if data There is no signi¿Fant differenFe between reports produFed on the inFidenFeofdiseasesinstudyFohorts are insuf¿Fient, at 10 and 20 years after the aFFident, with the exFeption of no radiation health effeFts are demonstrated. It should be reporting the average radiation dose reFeived by eaFh group.. noted that the inFrease in Fhildhood thyroid FanFer was When radiation dose and the LNT hypothesis were taken reFognized largely beFause of strong FirFumstantial evidenFe; into aFFount, it was shown that there were 4,000 deaths from FhronologiFal (starting around 1960) and geographiFal (three FanFer preFipitated by radiation. Most of mass media reports Fontaminated Fountries, the Russian Federation, the RepubliF quoted numbers only; no explanation of the baFkground was of Belarus, and Ukraine). provided.However, the above-referenFed estimation was not IV EXPLAINING SCIENTIFIC RESULTS TO THE aFFepted after disFussions within international organizations. PUBLIC IS THE DUTY OF CONCERNED SCIENTISTS 4. The report compiled by international organizations hastobeexplainedtothepublic The dissoFiation between sFienti¿F results and general One of the FonFepts to be explained to the publiF is publiF understanding has often been found in many ¿elds. “demonstrated health effeFts”. The word “demonstrated” or The dissoFiation between the Chernobyl Forum and the publiF proved means that some health effeFtsaredemonstratedor understanding of the Chernobyl aFFident is a typiFal example. proved by epidemiologiFal studies and statistiFal methods While providing explanation to the publiF, it is important to be a FonsequenFe of radiation exposure. However, “not to rely on information that is aFFepted by all experts on demonstrated” does not mean that there are no effeFts. “Not international and national levels. LoFal governments are of key demonstrated” may Fhangeto“demonstrated”whensuf¿Fient importanFeinpromotingpubliF understanding. However, as sFientists we have a duty to generate a new knowledge, whiFh starts with individual investigations. Before new knowledge is established internationally, it needs to be puri¿ed and solidi¿ed in the proFess of disagreement and debates among individual sFientists, and, for the purpose of obtaining funding for further researFh, it is neFessary that the publiF be made aware of the unknowns, unFertainty, and disagreement about results. SFientists must inform the publiF that there are areas of sFienti¿F Fertainty and unFertainty. In regards to areas of sFienti¿F Fertainty,weshouldaskthepubliF to aFFept sFienti¿F knowledge as muFh as feasible. Speaking of areas of sFienti¿F unFertainty, sFientists must strive to Fhange unFertainty into Fertainty. SFientists have a duty to present and publish results of all sFienti¿F investigations and disFuss them Fig. 6 $QQXDOQXPEHURIFKLOGKRRGFDUFLQRPDV DJHXQGHU with the sFienti¿F Fommunity to assess their validity. 15 years at the time of operation) in Belarus, 1986–1995. Also it is imperative to reFognize that there are many ¿elds that Fall for further sFienti¿F knowledge, suFhas: (1) Health and well-being of, and Fompensation of atomiF bomb survivors and other surviving viFtims of radiation (HIBAKUSHA) in the world, (2) Preparedness for radiation emergenFies,, (3) Safety and seFurity of the utilization of atomiF energy, (4) Safety and seFurity of the utilization of radiation, (5) Radiation proteFtion, (6) Utilization of radiation in mediFine, (7) ProteFting of the environment, etF. In regards to areas of sFienti¿F unFertainty, sFientists must request that responsible individuals stakeholders, and deFision makers in relevant ¿elds explain to the publiF the Fig. 7 ,QFUHDVHLQWK\URLGFDQFHULQFLGHQFHLQ\RXQJSHRSOH reasons behind their deFision making not in terms of unFertain ,QFLGHQFH SHU LQ %HODUXV a&RXUWHV\ RI