Email this page

Severe Effects of Internal Exposure by Residual Radiation

Shoji Sawada

Present Situation of Atomic bomb Survivors and Estimation of Radiation Effects

Now, after sixty years of Hiroshima and Nagasaki atomic bombing, many atomic bomb survivors are still suffering aftereffect diseases. The Japanese government has provided special medical and livelihood assistance to survivors whose diseases are verified to be from the effects of the atomic bomb radiation, however, the criteria adopted by the subcommittee of Atomic Bomb Survivors Medical Care of the Ministry of Health, Labor and Welfare are very strict and far removed from the actual situation of many survivors. Fig.1 shows the numbers of legally accepted atomic bomb survivors who hold a health note book and the number of survivors who were certificated their diseases are the atomic bomb radiation effects by the Japanese government. After 1980, the number of certificated survivors rapidly decreased from above 4 thousands to about 2 thousands which were less than 0.8% of the total survivors reflecting only the political and financial grounds of the government. Now a collective lawsuit has been going on from 2003 in 12 local courts by 166 atomic bomb survivors against the Japanese government demanding withdrawal of rejection of application to certify atomic bomb disease. Prior to the collective lawsuit seven successive judgments including those by the Supreme Court and by two high courts had pointed out that the criteria of atomic bomb disease certification by the government is apart from actual conditions of survivors and decided to withdraw of the rejections. However, the Japanese government had introduced more severe criteria by which even the applications of survivors who got victory judicial decisions will be also rejected.

The criteria of atomic bomb disease certification has been based on the Atomic Bomb Radiation Dosimetry System 1986 (DS86) and results of the epidemiological research that has been done at the Radiation Effect Research Foundation (RERF) which is the successor of Atomic Bomb Casualty Commission (ABCC). The epidemiological survey of RERF put emphasis only on the primary radiations (gamma rays and neutrons ) which were emitted within 1 minutes after the explosion and the effects of the residual radiations had not been considered. The primary radiation had caused acute external exposure meaning irradiation from outside of human body. There are two kinds of origin for the atomic bomb residual radiations; one is from radio-activated matter induced by the primary neutron and the other is the radio-active fallout which include the fission products, neutron-induced equipments of the atomic bombs and fissile materials (uranium and /or plutonium) leaving without fission. Beyond external exposure effects, the major effects of residual radiation are chronic internal exposure due to intake of radioactive matter by respiration, ingestion and other form.

The nuclear possessed countries, in which US take a leading role, have hided the severe effects and inhuman character of internal exposure, in order to maintain their arguments that the damages of nuclear explosion can be restricted. The International Commission on Radiological Protection (ICRP), which has set international standards of radiation protection, has been influenced by the policies of governments of US and Soviet Union and especially has based on the epidemiological studies of RERF. Then the international standards of radiation protection set by ICRP have the same problems. Therefore to clarify the severe effects of internal exposure from the scientific standpoint is an important task concerning to the future of human being.

Cover-up Policy of US on Nuclear Damages

Just after the beginning of Japan occupation of the Allied Forces, on 6^th September 1945, a brigadier general T. Farrel, who was a commander of the research commission of the Manhattan Project made a press interview and published a statement that "In Hiroshima and Nagasaki, at present, the beginning of September, anyone for death have already died and no one does suffer from atomic radiation."For opposition by a journalist W. Burchett who had saw the real state of Hiroshima that one hundred survivors died par a day, Farrel made a counterargument that deny the facts. "In order to remove risk by the residual radiation the bomb was exploded considerable attitude, then it is impossible to exist the radioactivity in Hiroshima at present, and if someone died at present it will not owing to residual radiation but by no mean by the effects of damage received at the time of bombing."Farrel was in charge of research on the human effects of radiation including experiments on human body in the Manhattan Project so that he would already well known that if a few fine radioactive accumulate in lung it gives fatal effects.

On the 19th of September 1945, the General Headquarters of the Allied Forces issued the press code that control by sever inspection of press and literature concerning to atomic bomb and by demanding permission before publication of research results on the damage of atomic bombing practically forbid publication. This is the beginning of the US policy that cover-up of radiation damage, especially of the problems of internal exposure by residual radiation.

The every obtained results done by Japanese scientists just after the bombing and the results of research done by the Special Committee for Investigation and Research on Damages of Atomic Bomb established by the Japanese Academic Council were brought to America side. Late in September of 1945 the US Army and Naval surgeon group organized the Joint Commission for the Investigation of the Effects of the Atomic Bomb in Japan by making the Medical Faculty of Tokyo Imperial University as collaborator and investigated for about one year, but they carried back to US all collected materials.

ABCC and RERF

The US that adopted a definite world policy to govern the world in terms of nuclear weapon had driven by necessity to study, from both of offensive and defensive sides, effects on human body by use of nuclear weapon especially of the effects of primary radiation. On 26 November in 1946, President Truman ordered to establish Commission on Atomic Bomb Casualty (CAC) and the CAC decided to found Atomic Bomb Casualty Commission (ABCC). After preparatory investigations the ABCC built perpetual institutions at Hiroshima and Nagasaki in 1950 and began investigation of atomic bomb survivors. In the interview investigation of survivor the ABCC made thorough examination concerning to the exposed place (indoors or outdoors, thick or thin sheltered house, etc.) and to the posture of survivor at the instant of bombing in order to estimate exposed dose by the primary radiation of the atomic bomb. On the other hand, the ABCC did not inquire into behaviors of survivors after explosion which are necessary to estimate residual exposure for the survivor.

Due to a occupational closed character of the ABCC and frequent change of American expert staffs as well as bad feeling among citizens of Hiroshima and Nagasaki, the activities of ABCC became stagnant as the whole around 1955. Following to Francis Committees recommendation based on the examination of ABCC activities, the ABCC restarted the Adult Health Study (AHS) on about 20 thousands subject of survivors in 1958 and the Life Span Study (LSS) on about 100 thousands survivors in 1959. At long last in 1975 ABCC was closed and the RERF was started up, but the ABCCs staffs, institutions and projects were left continuously to the RERF as well as involved problems of the ABCC.

Then the epidemiological research in the RERF remains unchanged completely ignoring the effects of residual radiation.

The Bikini-Incident and Studies on Radiation Damage

A hydrogen bomb test Bravo Shot done at Bikini atoll of Marshall Islands on the 1st March 1954 gave Japanese people very big impact and a nationwide movement against nuclear weapon arose and the first World Conference against A & H Bombs was held in the next year August in 1955. On the basis of this movement many scientists and experts in various fields, such as radiation physics and chemistry, radiobiology and fisheries science took part actively in investigation of damages by the Bikini nuclear tests and clarified that the damages by fallout of hydrogen bomb tests had been spread over the wide region of the Pacific Ocean. These investigations and researches by Japanese scientists pointed out that the radiation effects of fallout by these nuclear tests were very severe. Reflecting these findings the Russell-Einstein Manifesto declared in 1955 states as follow pointing out dangerous situation of radioactive fallout:

"... Such a bomb, if exploded near the ground or under water, sends radioactive particles into the upper air. They sink gradually and reach the surface of the earth in the form of a deadly dust or rain. It was this dust which infected the Japanese fishermen and their catch of fish.

No one know how widely such lethal radioactive particles might be diffused, but the best authorities are unanimous in saying that a war with-bombs might quite possibly put an end to the human race. It is feared that if many H-bombs are used there will be universal death--sudden only for a minority, but for the majority a slow torture of disease and disintegration."

This year is also the 50^th anniversary of the Russell-Einstein Manifesto.

Exposure of Marshall Islands People

In the occasion of Bikini incidence not only the crew member of the 5th Lucky Dragon boat and the inhabitants of Rongelap atoll but all the people of Marshall Islands exposed simultaneously to radiation by fallout of the nuclear tests. Although the inhabitants had been received strong exposure by fallout they left unattended for a while. Moreover, in 1967 inhabitants of Rongelap atoll brought back by US army to their atoll because of absence of radioactivity. However due to frequent occurrence of injuries among inhabitants including not exposed to fallout, they departed by themselves again from their atoll in 1985. Recently it is found that the Atomic Energy Commission of US which conducted these nuclear tests had made thorough observation of radiation by fallout during these tests but did not open the observed results to the public.

Even now inhabitants of Rongelap atolls are forced to leave and pillaged their own birthplace for more than a half century. When the Marshall Islands Republic was independent in 1989, the republic had concluded the Free Alliance Agreement with the US which includes compensation for the use of Kwajaren atoll, the largest atoll of Marshall Islands, as a military test site of missile and compensation for the damage of nuclear tests. Among the 2004 revision of this agreement the part of compensation for nuclear test damages was discontinued by the argument of US who said that there are no effects of residual radiation.

In Fig. 2 an investigation of abnormal bath among Marshallese show that rate of abnormal bath par a woman in each atoll of Marshall Islands decreases for distance from Bikini atoll and clearly indicates that effects of fallout of nuclear tests extend to the whole region of Marshall Islands (The average rate of abnormal bath par a woman among Marshall Islands before nuclear test was 0.04.) Now the people who were inhabitant of the severely contaminated atolls, Enewetok, Rongelap, Utrik and Bikini atolls, set up an organization ERUB on the occasion of the 50th anniversary of the Bravo Shot and began petition for compensation to the Congress of US.

Revision of Dosimetry System of Atomic Bomb Radiation from DS86 to DS02

It is necessary to estimate exposed atomic bomb primary radiation dose of survivors for the epidemiological studies in the ABCC and the RERF. For this purpose US had made estimation of radiation dose, the T57D(Tentative Dose 1957) and the T65D(Tentative Dose 1965) on the basis of nuclear tests. The atomic bomb dosimetry system DS86 is the first computer calculated estimation of the primary radiation dose of the Hiroshima and Nagasaki atomic bombs. The DS86 put emphasis on the primary radiation reached to short distance and makes little concern or neglect of residual radiation from fallout and induced radioactive matter.

At present, the dosimetry system 2002 (DS02), a substitute of the DS86, is in preparation for publication. In the DS02 in order to dissolve an over estimate of primary radiation doses at short distances in the DS86 the height of explosion of Hiroshima bomb is changed from 580m to 600m and the yield of explosion from 15 ktTNT to 16 ktTNT. Leaving the problem of discrepancy between estimated values by the DS86 and experimentally measured values in the distant region without fundamental elucidation, the preparation of DS02 is proceeded pushed by US side argument that measurement values at distance involve background effects other than bomb radiation. The DS02 did not contain a single description concerning to the residual radiations.

Since the estimation of primary radiations (both of gamma rays and neutrons) from measurements systematically exceed the estimation of the DS86 and DS02 in the region more distant than 1.5 km from the hypocenter and the discrepancies increase with distance, the estimation of the DS86 and DS02 can not be applied to the distance beyond 1.5 km from the hypocenter of atomic bombing even confined to the primary radiation.

Physical Consideration of Internal Exposure

Among fallout of the atomic bomb of Hiroshima and Nagasaki (1) 3.6X10²⁴ nuclei of fission products, (2) (2?n5)X10²⁴ nuclei of neutron-induced radioactive matter of bomb equipments and vessel, (3) 1X10²⁶ nuclei of uranium-235 or 2.5X10²⁵ plutonium 239 which did not participate to the chain reaction of fission were included respectively. After explosion of atomic bomb a fire ball of plasma state was formed and all radioactive nuclei listed above were included in this fireball. As are shown in Fig. 3 and Fig. 4, the fireball turned into the mushroom cloud. The central part of clouds rose breaking through the tropopause up to 15 km or more and the other part spread along the tropopause over a region with radius more than 15~20 km. The region where fine particle of the fallout fell can be supposed more spread than region covered by the mushroom. In the fallout a huge number of fine particles were included which had contained in the fireball.

The atomic bomb survivors externally exposed by primary radiation from outside of their bodies. This exposed dose can be estimated roughly if the bombed place of survivor is known. Survivors and people who entered into the regions near the hypocenter are also exposed by radiations emitted by residual radioactive matter induced by the primary neutron beam. The doses irradiated to survivors by the induced radioactive matter can be estimated roughly by use of physical calculations and measurement data if their actions or behaviors were known. It is difficult, however, to estimate the radiation dose of fallout in terms of physical measurement long after explosion because most of fine particles of the fallout were carried out by the wind and the radioactive matter accumulated on the surface of the earth or sank into the earth which had brought by so called black rains or other form of fallout were washed away by heavy rains accompanied typhoons. It is more difficult to estimate the effects of internal exposure by inhalation or ingestion of radioactive matter of the fallout and/or induced matter by physical methods.

When some radioactive matter are taken into body, if the matter are water or oil soluble then the radioactive matter will spread out to the whole body in the level of atom or molecule and it will occur that some radioactive materials concentrate and/or deposit in special organs depending on the types of chemical elements. Iodine concentrate on thyroid and phosphorus and cobalt do on bone marrow for example. In this case amounts of radioactive materials taken into body can be estimated from excrement such as urine. On the contrary to this soluble case in the case that non-soluble radioactive fine particles were taken into body there are possibilities that the fine particles are deposited in some organ with preserving their size and that radiations emitted from these fine particles irradiate continuously and intensively surrounding cells. In this case it is difficult to identify these radioactive particles from outside of body and presumed from excrements. Effects by such radioactive fine particles largely depend on the size of particles and also on the type of radioactive elements and type of radiation (the average life-time and alpha, beta or gamma ray). It will difficult to represent these effects in terms of simple factor such as the absorbed energy per weight, the unit of absorbed dose, Gy, or by use of the relative biological effectiveness, the unit of equivalent dose, Sv. The difference between external uniform exposure and internal exposure by a radioactive fine particle is illustrated in Fig. 5. Therefore the biological estimation of effective exposure dose which includes both external and internal ones is required on the basis of analyses of the investigation of incidence rates of the acute and clinical radiation diseases and the rate of chromosomal aberration especially appeared among distant survivors and entrant survivors who did not severely exposed by the primary radiation.

Estimation of Residual Radiation in terms of Incident Rate of Acute Radiation Disease

In order to estimate actual effects of both primary and residual radiation it will be useful to analyze examined data of acute radiation disease among survivors of atomic bombed in Hiroshima and Nagasaki. Among many examinations two data of incidence rate of acute radiation disease are analyzed here, because all examinations show common qualitative results that there occurred small but non-negligible incidence rates of the acute radiation diseases. The one article is by Gensaku O-ho, a medical doctor of Hiroshima, titled as "Statistical Observation on Atomic Bomb Residual Radiation Injuries" which was published in "I-ji shinpou ( New Japanese Medical Reports, in Japanese)"in 1957 and will be referred to as O-ho and shown in Fig. 6a. The other is by A. Oughterson and S. Warren "Medical Effects of the Atomic Bomb in Japan--Report of Joint Commission of Investigation of Effects of Atomic Bomb" and will referred to as Joint-Com which is shown in Fig. 7a. In Fig. 6b and Fig. 7b the estimated results of residual radiation obtained from analysis of incidence rates of acute radiation disease are shown. As shown in Fig. 6b and Fig. 7b averaged effects by the residual radiation from fallout (a mountain shape region filled by hatched lines) and neutron induced radioactive matter (a region filled by hatched lines between two horizontal lines) exceeds over those of primary radiation (measured one is shown by a solid curve with closed circles and that of DS86 by dashed curve with open circles) in regions more distant than 1.5km from the hypocenter of Hiroshima. Estimation of fallout radiation of DS86 was made from 1R to 3R at Koi-Takasu region and for people who worked one week in the hypocenter region after the day after tomorrow received about 10R external exposure. Here R is Roentgen and a unit of irradiation of X-ray and gamma ray and nearly corresponds to 0.01Gy of absorbed dose, then 10R is corresponded to 0.1Gy which means that the obtained effects by residual radiation (both of fallout and induced radioactive matter ) from incidence rate of acute radiation disease are several tens or more large than the dose of external exposure estimated by DS86. Estimations of exposure from residual radiation by DS86 are obtained from the measured data of external exposed dose and/or averaged internal exposed dose. This fact suggests that the major effects of residual radiation obtained from the incidence rates of acute radiation disease come from localized sources of radiation which are radioactive fine particles deposited in an organ and are difficult to measure from outside of body.

The present result of fallout effects shows that fallout came down over very wide regions under the mushroom cloud shown in Fig. 3 and Fig. 4.

The epidemiological study in RERF set up as the control cohort (non exposure group) practically among the survivor group who were exposed radiation dose estimated less than 0.005Sv on the basis of the DS86. According to the estimation of DS86, survivors included in the control cohort were bombed in the region distant from the hypocenter more than 2.7 km, and as are seen in Fig. 6b and Fig. 7b these survivors received effects by fallout radiation equivalent to external acute exposure of gamma ray of 0.3 to 0.8 Gy in the average. These effects are 60 times to 160 times of estimation of the primary radiation by the DS86. This will explain the reason how far the government criteria for atomic bomb diseases departs from actual states of survivors who have been suffered after effects of atomic radiation for 60 years.

Radiation Effects for Entrants after Bombed

In Fig. 8a, the incidence rates of acute radiation disease are shown which were examined by G. O-ho among the people who entered from that day after the bomb exploded to after 34 days into the region within 1km from the hypocenter of Hiroshima. Obtained result of estimated exposure effects from analysis of this incident rate is displayed in Fig. 8b. For the entrant on that day exploded (the 6th August) the accumulated exposed effective dose for onset of acute radiation disease is equivalent to external acute exposure of gamma ray with 1.49}±0.38 Gy. The accumulated exposed effective dose exponentially decreases and almost the half effects for the entrants who entered the central region 9 days to 10 days after the bombed day. In Fig. 8b accumulated exposure dose received from external radiation induced by neutron are shown for staying at the hypocenter, and at 0.5 km and 1 km from the hypocenter. Even at the hypocenter the accumulated exposed dose from external radiation is 0.8 Gy, those at 0.5 km is 0.09 Gy and 0.0017 Gy at 1 km. The large discrepancies between exposure effects estimated from acute radiation disease among the entrants after bombing and measured external accumulated dose suggest that effects of residual radiation come from chronic internal exposure due to inhalation of radioactive matter were very large compared to those of external exposure.

As is shown by the analysis of the incident rate of the acute radiation diseases, however, for the survivors bombed in the distant region than 1.5 km it is shown that the effects of internal exposure of radio-active fallout are more severe than the effects of external exposure by the primary radiation. Therefore application of DS86 or DS02 for the estimation of exposure of distant survivors and the entrant survivors is complete mistake.

Estimation of Fallout Radiation from Chromosomal Aberrations

When one irradiated by radiation there appear abnormalities among chromosome in the irradiated nuclei of cell. Since this frequency of chromosomal aberration closely related to the exposed dose then the frequency of chromosomal aberration in circulating lymphocytes provides estimation of averaged absorbed dose in survivors. M. Sasaki and H. Miyata investigated the frequency of chromosomal aberration in circulating lymphocytes of survivors bombed the Hiroshima atomic bomb and eleven non-irradiated healthy people as a control who were visiting the Japan Red Cross Central Hospital in Tokyo between April 1967 and March 1968 and found that the aberrations occurred even the primary radiation scarcely reached.

Fig. 9 shows internal dose estimated from chromosomal aberration among survivors by Sasaki and Miyata. The obtained dose beyond 2.5 km from the hypocenter of Hiroshima cannot be explained by the primary radiation. In Fig. 9, the open markers correspond to the dose obtained from frequency of chromosomal aberration of stable type and the closed ones to those obtained from unstable type of aberrations. The broken curves are obtained by chi-square fitting to the estimated exposed dose of survivors who had exposed outdoors at distances less than 2.2 km from the hypocenter (denoted by triangles) and at 2.4 km or more away (denoted by circles) . The primary radiation dose given by the T65D and DS86 are denoted by almost straight lines dashed and solid ones, respectively. The solid curves are obtained by subtraction of the contribution of the primary radiation given by DS86 from the broken curves and can be attributed to the effects by fallout contribution. The peak values 0.06 Gy and 0.3 Gy obtained from unstable and stable chromosomal aberrations exceed the primary radiation dose at 2.0 km and 1.6 km, respectively from the hypocenter. In the regions beyond these distances the effects of internal exposure by fallout superior than that of the primary radiation. It should be noted that the estimated dose based on the frequency of chromosomal aberration in circulating lymphocytes represents the effects averaged over whole body and not include local effects by the insoluble radio-active fine particles which are considered in the case of the analysis of the incidence rates of acute diseases.

The chromosomal aberration of a larger sample of survivors had been investigated also by the study group of the RERF after 23 years of bombing and the RERF have denied the existence of chromosomal aberration in the distant region. In the RERF investigation, however, the distant survivors with dose estimation <0.01 Gy and the entrant survivors who were not in the city at the explosion time (NIC) were used as the control group. The frequency of chromosomal aberration of this control is more than 4 fold of the control used world-wide and about ten fold than used by Sasaki and Miyata.

Problems of Epidemiological Studies in the RERF

There are serious problems in epidemiological studies of the RERF when the results of the studies are applied to survivors. One is neglect of contribution from the residual radiation for the estimation of exposed dose of survivors. This has originated in the initial investigation of survivors interview done by the ABCC. The other serious problems is selection of non-irradiated control. The epidemiological studies in the ABCC-RERF have been adopted survivors themselves as the non-exposed control of the studies. In the recent RERF investigations the survivors who had exposed less than 0.005 Sv of the DS86 and the NIC group in which the early entered survivors are included are used as the control group. As is shown in the preceding sections these distant and entrant survivors were affected by the residual radiations estimated more than 0.1?s0.5 Gy in the average which is several tens or one hundred of 0.005 Sv. Then it is evident that the ABCC-RERF studies can not be applied to the estimation of exposure for distant and entrant survivors.

The analysis of chronic diseases among the RERF control cohort by use of all Japanese as the control was made by Inge Schmitz-Feuerhake, a physics professor of Bremen University, Germany and deduced the effects of exposure of fallout and the induced radioactive matter. Her result of the analysis is given in Fig. 10. The high relative risk of both mortality and incidence of leukemia, thyroid, female breast cancer and respiratory system cancers of the control of epidemiological study of RERF (both distant and after entrant survivor) had affected by fallout and residual radiation. If the early entrants (4500 of 26,500 people entered the cities within three days after explosion ) among the NIC group of the RERF investigation are extracted then the relative risk becomes about twice the normal rate as shown by point EE in Fig. 10. Hirose found 45 cases of leukemia among 25,798 early entrants of Hiroshima which corresponds to about 3.7 times the Japanese normal rate.

These facts conclude that the epidemiological studies of the RERF have severe basic problems concerning to the adoption of the control cohorts. The results of the ABCC-RERF should not be applied to the criteria of atomic diseases at the very least for distant and entrant survivors even though they may used to the estimation of external irradiation effects by the strong primary radiation.

Danger of Usable Nuclear Weapon and Earth-Penetrating Nuclear Weapon

Recently the government of US decide to research and development of usable nuclear weapon and the earth-penetrating nuclear weapons. This pro-nuclear-weapon policy of US will be largely based on the ignorance or little concern on the damage of atomic bombing especially negligence of the effects of residual radiation and severe effects of internal exposure. If an earth-penetrating nuclear weapon were used, a huge disaster of residual radiation which did not seen in the bombing of Hiroshima and Nagasaki, where the bombs were exploded at the height 600 and 500 m above the ground then the fallout fell after radioactivity somewhat weakened and the neutron beam largely decreased before reach to the ground and to induce the residual radiation. On the other hand, in the case of earth penetrating nuclear weapon it can penetrate only a few tens meters under ground and the fire ball produced by nuclear explosion will cause a stream of heated rocks and ash which contains various strong radioactive matter in the fire ball and induced by neutrons as illustrated in Fig. 11. This may cause another the '21sts hell on the earth' instead of the 20th hell on the earth, Hiroshima and Nagasaki.

The 1993 UNSCEAR published calculated estimation of total death by cancer caused by fallout or down wind of nuclear tests and accidents of power stations and nuclear factories between 1945 and 1989 as 1,116,000 on the basis of ICPR model which had been constructed mainly by use of the results of the RERF studies and where the effects of internal exposure are paid little attention. If the effects by the internal exposure of residual radiation cause cancer death is more severe than that of ICRP model by fifty times, then total death by cancer caused by fallout becomes more than 50 millions which is about 1% of total population of the world. Thinking of responsibility as a scientist and as a survivor of the Hiroshima atomic bombing, if cover-up policy of US did not enforce and scientists had clarified the severe effects of internal exposure by the residual radiation of atomic bombing before frequent large scale nuclear tests then the nuclear weapon tests will be forbidden without producing great loss of human life comparable or more than wars.

To win for the collective lawsuit of survivors, who are taking their lives, will contribute for promotion of the movement towards elimination of nuclear weapon in the 60 anniversary of atomic bombing by pointing out that nuclear weapon should never be used by indicating the severe and inhuman characters of internal exposure.

^ Top of page