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Did You Know...

...even unborn babies were affected by radiation from the atomic bomb?

...that it would require a wall of concrete over 150 cm thick to completely shield you from the radiation from the atomic bomb?

Hiroshima: Radiation Effects

(International Schools Cyber Fair 1998 Project)

Index

The Effects of Radiation Exposure To Humans
Basics About Radiation
Our Trip To Radiation Effects Research Foundation
Reflection On Our Trip To RERF
Frequently Asked Questions About the Atomic Bomb

The Effects of Radiation Exposure to Humans

by: Sarah Skaer, Grade 8

A-bomb related

Radiation is classified in two main categories: initial radiation and residual radiation. Initial radiation was exposed approximately one minute from the explosion. Residual radiation stayed in the air and soil, even after a long period of time after the explosion. The people who were the closest to the hypocenter (the exact place where the bomb exploded) received the highest amount of radiation. Even if a person entered Hiroshima and came within 1 km of the hypocenter, one hundred hours after the bombing, the person would have been exposed to residual radiation. People who were protected somehow from the bomb blast, by a wall for example, decreased their risk of receiving radiation. Both types of radiation took place when the bomb dropped, and both are deadly.

Radiation is measured in grays. Seven grays are equivalent to seven hundred rads. If someone received more than this dosage of radiation, there would be no chance for the person to stay living.

Effect of Radiation on The Human Body (unit: gray (Gy))
100 Unconsciousness or coma. Death within several hours
10 Destruction of bone marrow, severe radiation sickness and reduced white blood cells and platelets, Death within 30 days
1 Nausea and vomiting. Reduced cell formation in bone marrow, temporary reduction in white blood cells
0.1 Changes appear in lymphocytes produced by bone marrow
0.01 No Apparent symptoms
Effect of Radiation on The Human Body (unit: gray (Gy))
Distance from Hypocenter 100m 500m 1,000m 1.500m 2,000m 2,500m
Gamma Rays (g) 117.0 35.0 3.93 0.487 0.071 0.012
Neutron Rays 33.1 6.04 0.227 0.008 0.000 0.000

Acute radiation syndrome is what the people of Hiroshima received during the months following the bombing. A few hours after the explosion, vomiting was the first sign that acute radiation that occurred. Later, either ones hair would fall out, or it will just become more thin and eventually break off. Vomiting, diarrhea, number of blood cells reduced, bleeding, hair loss, temporary sterility in males, and lens opacity are the most common symptoms that resulted from acute radiation syndrome.

The severity of the symptom, depended upon the dose of radiation received. If the dose of radiation was small, then not all of these symptoms that were described above occurred. If the dose of the radiation was high, one could die of bone marrow disorder in two or more months after the exposure. Obviously, if the radiation dose is extremely high, then the person would die sooner: in ten to twenty days, probably because of intestinal disorder.

Other types of radiation include neutron rays, alpha rays, beta rays, and gamma rays. Descriptions of each type of radiation are as follows: alpha rays are made up of two protons and two neutrons. They are able to travel about l mm in water. An alpha ray is a very weak form of radiation, and can be blocked easily with a piece of paper. Beta rays are able to travel from 1 mm to about 1cm for phosphorus-32 in water. Gamma rays can go deep into a human body and have been mostly observed for cancer radiotherapy. Neutrons are what triggers a nuclear chain reaction to explode an Atomic bomb. Neutrons hardly do any damage to cells, but they do cause various kinds of damage to the human body. Neutrons produce more damage than gamma rays. All of the types of radiation mentioned contrasts with one another, and all developed at some time during or after the A-bomb hit Hiroshima.

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Basics About Radiation

What Is Radiation?

(Taken from Radiation Effects Research Foundation Home Page)

In general, the following kinds of radiation are evaluated for purposes of radiation protection: alpha rays, beta rays, gamma rays, X rays, and neutrons. Brief definitions of these follow:

Alpha rays

A particle ray consisting of two protons and two neutrons (namely, a nucleus of helium). Alpha rays are produced following spontaneous decay of certain radioactive atoms, such as radium, plutonium, uranium, and radon. Because of its large mass and positive charge, an alpha ray can usually pass only a short distance--less than 1 mm--in water. A single piece of paper can stop an alpha ray effectively. Therefore, health effects of alpha-ray exposures appear only when alpha-emitting materials are ingested (i.e., internal exposure).

Beta ray

A particle ray consisting of a fast electron whose mass is nearly 1/2000 of the mass of a proton or neutron. Beta rays are produced following spontaneous decay of certain radioactive materials, such as tritium (an isotope of hydrogen), carbon-14, phosphorus-32, and strontium-90. Depending on its energy (i.e., speed), a beta ray can traverse different distances in water--less than 1 mm for tritium to nearly 1 cm for phosphorus-32. As with alpha rays, the major concern for health effects is after their ingestion (i.e., internal exposure).

Gamma ray

An electromagnetic wave, a gamma ray is similar to ordinary visible light but differs in energy or wavelength. Sunlight consists of a mixture of electromagnetic rays of various wavelengths, from the longest, infrared, through red, orange, yellow, green, blue, indigo, and violet, to the shortest in wavelength, ultraviolet. A gamma ray's wavelength is far shorter than ultraviolet (i.e., it is far higher in energy). Gamma rays are produced following spontaneous decay of radioactive materials, such as cobalt-60 and cesium-137. A cobalt-60 gamma ray can penetrate deeply into the human body, so it has been widely used for cancer radiotherapy.

X ray

X rays have the same characteristics as gamma rays, although they are produced differently. When high-speed electrons hit metals, electrons are stopped and release energy in the form of an electromagnetic wave. This was first observed by Wilhelm Roentgen in 1895, who considered it a mysterious ray, and thus called it an X ray. X rays consist of a mixture of different wavelengths, whereas gamma-ray energy has a fixed value (or two) characteristic to the radioactive material.

Neutrons

Neutron particles are released following nuclear fission (splitting of an atomic nucleus producing large amounts of energy) of uranium or plutonium. In fact, it is neutrons that trigger the nuclear chain reaction to explode an atomic bomb. Neutrons hardly damage cells because they do not carry any electrical charge. However, the human body contains a large amount of hydrogen (a constituent of water molecules that occupy 70% of the human body), and when neutrons hit the nucleus of hydrogen, i.e., a proton that is positively charged, the proton causes ionizations in the body, leading to various types of damage. At equivalent absorbed doses, neutrons can cause more severe damage to the body than gamma rays.

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Our Trip To Radiation Effects Research Foundation (RERF)

Information on RERF and its History

by: Stephanie Ryan, Blake Wilson, Anna Song, Grade 7/8

The RERF program was started during the November of 1946 when President Harry Truman approved a directive to the national Academy of Sciences (NAS), and the National Research Council (NRC), to study the effects of radiation on people. The NAS and the NRC received finding from the Atomic Energy Commission (now called the Department of Energy). The NRS -NRC began the Atomic Bomb Casualty Commission (ABCC) during March of 1947 and began to conduct research the following year. The Japanese National Institute of Health became a partner in these research committees. In 1975, this same committee developed a new research laboratory an called it the Radiation Effects Research Foundation (RERF). This group reassumed the studies of the ABCC.

RERF scientists conduct research mainly in the categories of cancer and molecular biology. They study people who were directly effected by The radiation of the explosion, and work to help gain the better physical health of people over all. There was some controversy over the medical attention to the survivors of the bomb, and their study of people. They wanted to study the effects of radiation, but did not provide medical attention. They preformed surgeries to further their studies for nothing else.

RERF studies cancer to receive evidence of the dose/cancer risk response patterns. They do this to study the mortality rate of non-cancer sufferers. They also research information on the biological, genetic and environmental effect and also study the impacts of carcinogenic (cancer causing) and non-carcinogenic effects on the younger and more susceptible generation, versus the health of adults tested under the same conditions.

In molecular biology, efforts are being made to monitor the rate of human populations' mutation rates. This is now becoming possible due to a development in the study of DNA, where it is now possible to detect a mutation on the level of nucleotide bases. They are trying to collect a number of cells from both exposed and unexposed parents and their children. These cells are being immortalized using the Epstein-Barr virus until more effective research can be done to them This same technology is being used to research genetic changes leading to cancer and the changes in the human immune system.

Due to their funding problem, they have to confine their research to what they prioritize to be their most important. Basically, there is no room for too much growth right now, or new ideas in research, but new and exciting discoveries are being slowly made piece by piece.

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Reflection On Our Trip To RERF

by the HIS Middle School

The trip to RERF, for 7-8 graders was not as emotionally moving as the peace park trip, but still informative. First, we asked about the testing of the first atomic bomb and found out that it was held in New Mexico. We asked if there were any effects on the people testing it, and how far the radiation spread. We were then told, that the testing only consisted of the bomb being suspended just above the ground, and exploded. No known radiation effects were shown in the people who tested it, and the radiation did not spread as far as they would have thought.

The next question on our list was why did cancer, caused by radiation, result in specifically Thyroid Cancer? The answer to this was fairly simple. The Thyroid gland collects iodine that is passed through the body, mainly by way of foods, with small amounts of iodine in it. The bomb radiated the iodine found in foods that the Thyroid glands take in, which in turn, radiated the glands, giving them cancer.

We were also told about the effects of the bomb on the 'next generation". Studies so far have shown no biological genetic effects. This means that the effects of the radiation that were experienced by people, is not biologically passed on to their children. We were also told about the way a researcher at RERF used teeth to test for the amount of radiation a person was exposed to.

Another question asked was, "Why were people who suffered from the bomb, always thirsty?" This, again, had a fairly simple answer. The people who suffered from the effects of the bombing usually all suffered from minor or major burns. These burns draw out the body fluids from under the skin of the burn, making the skin puff up. This liquid comes from the body's supply of water. Therefore, people who had suffered from the bomb, and major burns or just many burns, had a lack of water in their systems. This caused their bodies to need a water intake, and so, they became thirsty.

The studies of RERF scientists are now starting to turn to the mortality of the bomb survivors' children. These studies are on going and so the results are unknown at this time. The reason these studies are being undertaken now, is because, the children of bomb survivors are now getting to the age where they are able to be studied for mortality risks.

Our class was shown around the RERF grounds, and were told about what goes on there. People who had experienced the bomb of Hiroshima, still came to RERF to be tested. There were dressing rooms, and rooms that had computers with information of personal X-rays in them, laboratories, and many offices.

The trip seemed to be an overall success in the way of getting enough information. It seemed, though, that we were given so much information to swallow, that we only absorbed the tidbits that stood out in our memories. This was partially due to the long day; we had just gotten back from the trip to the Peace Park, and we were both physically and emotionally tired (those who had never been to the A-bomb museum experienced it more fully than the rest).

In conclusion, the trip to RERF was informative (maybe a little too informative), a new experience, and the end to a long day. We would like to thank all those who volunteered their time to help us understand a little better what the effects of radiation are.

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Frequently Asked Questions About The Atomic Bomb Survivor Research Program at RERF

(Taken from Radiation Effects Research Foundation Home Page)

Question 1. How many persons died in the atomic bombings?

Question 2. How many cancer deaths have occurred among atomic-bomb survivors and how many of these can be attributed to radiation?

Question 3. Are radiation-induced cancers still occurring among atomic-bomb survivors?

Question 4. What health effects have been seen among persons who were exposed while still in their mothers' wombs?

Question 5. What health effects have been seen among the children of atomic-bomb survivors?

Question 6. How many atomic-bomb survivors are included in the group being studied by RERF?

Question 7. RERF research includes the study of deaths and the incidence of cancer occurring among atomic-bomb survivors. Who is included in this study population?

Question 8. What percentage of the original atomic-bomb survivor study population are dead?

Question 9. How is information about the RERF study population obtained?

Question 10. What is meant by "significant" radiation exposure?

Question 11. Are Hiroshima and Nagasaki still radioactive?


Question 1. How many persons died in the atomic bombings?

Deaths caused by the atomic bombings include those that occurred on the days of the bombings resulting from the collapse of houses caused by the blast and from burns due to heat rays and fires as well as deaths that occurred later from burns and radiation exposure. However, the total number of deaths is not precisely known because records of military personnel in each city were destroyed; entire families perished, leaving no one to report the deaths; and forced laborers were present in unknown numbers. Recent estimates of total deaths occurring within two to four months after the bombings are shown in the Table 1.

Estimated number of deaths in Hiroshima and Nagasaki two to four months after the atomic bombings
City Estimated city population at the time of the bombings Estimated acute deaths
Hiroshima 310,000 persons 90,000-140,000

Five years after the atomic bombings, in the 1950 Japanese national census, approximately 280,000 persons indicated that they "had been exposed" in Hiroshima or Nagasaki. (Although most of them were probably exposed in the former administrative districts of the cities, the census did not require recording the place of exposure.) The census total is a rough estimate of those who were exposed and survived the bombings. However, so-called "early entrants," those who had entered the cities after the bombings, are not included in the census.

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Question 2. How many cancer deaths have occurred among atomic-bomb survivors and how many of these can be attributed to radiation?

Analyses of deaths due to cancer among the atomic-bomb survivors from 1950 through 1990 were recently completed and published in Radiation Research (146:1-27, 1996). Table 2 summarizes the results of the study of survivors exposed to significant radiation doses (See Question 10).

Summary of cancer deaths in atomic-bomb survivors, 1950-1990
Cause of death Total number of deaths Estimated number of deaths due to radiation Percentage of deaths attributable to radiation
Leukemia 176 89 51%
Other types of cancer* 4,687 339 7%
Total 4,863 428 9%
*Solid cancers, such as stomach, lung, breast, and colorectal cancers

The number of cancer deaths among the 36,500 survivors who were exposed beyond 2.5 km is 3,177, including 73 leukemia deaths and 3,104 deaths from cancers other than leukemia.

The proportion of cancer deaths attributable to radiation exposure is higher among those who were exposed closer to the hypocenter, as in the case of deaths due to injuries from the blast, heat, or radiation. Table 3 presents data on the size of the studied population and the number of cancer deaths in relation to distance from the hypocenter for the approximately 50,000 survivors with significant exposures (See Question 10).

Cancer deaths among atomic-bomb survivors, 1950-1990, by distance from hypocenter
    Leukemia Leukemia Other Cancers*
Distance from hypocenter (km) No. of persons No. of deaths Percent attributed to radiation No. of deaths Percent attributed to radiation
<1 810 22 100% 128 42%
1 - 1.5 10,590 79 64% 1156 18%
1.5 - 2.0 17,370 36 29% 1622 4%
2.0-2.5 21,343 39 4% 1781 0.5%
*Solid cancers, such as stomach, lung, breast, and colorectal cancers

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Question 3. Are radiation-induced cancers still occurring among atomic-bomb survivors?

Cancers attributable to radiation are still occurring among atomic-bomb survivors. The excess risk of leukemia, seen especially among those exposed as children, was the highest during the first 10 years after exposure and has continued to decrease throughout the study period. However, the excess risk for cancers other than leukemia continues today, and it seems likely that this excess risk will persist throughout the lifetime of the survivors. About 16% of all cancer deaths and about 25% of the excess cancer deaths for the period from 1950 through 1990 occurred from 1986 to 1990.

Question 4. What health effects have been found among persons who were exposed before birth?

Many health effects are associated with radiation exposure before birth. Among the in utero exposed atomic-bomb survivors, the following have been observed: a reduction in IQ as radiation dose increases, a higher incidence of mental retardation among the heavily exposed, and impairment in the rate of growth and development. Many of these effects seem to be particularly pronounced among those persons who had been exposed between the 8th and 15th weeks of gestation. Death rates and cancer incidence are being monitored for this group. To date, the data suggest a trend of increasing risk as radiation exposure increases, similar in extent to the trend observed among those exposed to atomic-bomb radiation as children.

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Question 5. What health effects have been seen among children of atomic-bomb survivors?

This was one of the earliest concerns in the aftermath of the bombings. Efforts to detect genetic effects were begun in the late 1940s and continue to this day. Thus far, no evidence of genetic effects have been found. Recent advances in molecular biology may make it possible to detect genetic changes at the gene (DNA) level at some time in the future. RERF scientists are working to preserve blood samples that can be used for such studies as suitably powerful techniques are developed. Monitoring of deaths and cancer incidence in the children of survivors also is continuing.

Question 6. How many atomic-bomb survivors are included in the group being studied by RERF?

In the Japanese national census of 1950, approximately 280,000 people indicated that they had been exposed to the atomic bombs. The population studied by RERF probably includes about 50% of the proximally exposed survivors and about 25% of the distally exposed. However, these percentages are not precise because the census did not include recording of the place of exposure.

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Question 7. RERF research includes the study of deaths and the incidence of cancer occurring among atomic-bomb survivors. Who is included in this study population?

Current studies of deaths and cancer incidence are based on a sample of 86,500 atomic-bomb survivors who were alive and living in either Hiroshima or Nagasaki at the time of the national census in October 1950 and for whom radiation dose estimates can be computed. About 50,000 of these persons were exposed to significant radiation doses (See Question 10) within a distance of 2.5 km from the hypocenter. The other 36,500 members of the study population were exposed beyond 2.5 km and received very low doses.

Question 8. What percentage of the original atomic-bomb survivor study population are dead?

In 1995, the average age of the surviving atomic-bomb victims was about 66 years. In 1990, about 46% of the RERF study population was dead, and as of 1995, slightly fewer than 50% were dead. Looking at vital status in terms of age at exposure, we find that at the end of 1990, fewer than 10% of the survivors exposed under the age of 20 were dead.

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Question 9. How is information about the RERF study population obtained?

To make monitoring easier in long-term follow-up of mortality and cancer incidence due to radiation exposure, approximately 90,000 people who were resident in Hiroshima or Nagasaki at the time of the national census on October 1, 1950 were selected from about 280,000 survivors who were directly exposed in Hiroshima City or Nagasaki City. The cohort includes another group of 27,000 people whose family registry was in one of the cities and who lived in Hiroshima or Nagasaki at the time of the national census but were not exposed to the atomic bomb. However, this latter group is not usually included in analyses because of data suggesting that there are socioeconomic differences from the survivor population. These two groups together are formally known as the Life Span Study (LSS) cohort.

In addition to the LSS, RERF scientists are involved in studies of several other populations. These include the Adult Heath Study (AHS), In Utero Exposed, and F1 Cohorts. The AHS population comprises 20,000 members of the LSS, who, since 1958, have been asked to participate in biennial clinic examinations carried out at RERF. About 3,000 people who were exposed to the bombings while in utero make up a second group. Finally, a group of about 80,000 constitute the F1 cohort and include children born to parents with and without exposure to the bombs.

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Question 10. What is meant by "significant" exposure?

In the discussion of cancer risks presented here, attention is focused on survivors with estimated doses greater than 5 millisieverts (mSv; 0.005 Sv). While no excess risks of cancer or other diseases are detectable among survivors with doses at the low end of this range, a dose of 5 mSv is several times higher than the typical annual background radiation level to which people are exposed in daily life (1-2 mSv), or about one-fourth of the currently accepted maximum annual dose allowed for radiation workers (20 mSv). Survivors with doses of 5 mSv or more were typically within about 2.4 km of the hypocenter in Hiroshima and within 2.6 km of the hypocenter in Nagasaki. The average dose received by the group of survivors considered here is about 200 mSv. The radiation dose decreases by half for every 200-meter increase in distance from the hypocenter.

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Question 11. Are Hiroshima and Nagasaki still radioactive?

No. There are two ways radioactivity is produced from an atomic blast. The first is due to fallout of the fission products or the nuclear material itself, i.e., uranium or plutonium that contaminate the ground. (The same ground contamination occurred as a consequence of the Chernobyl accident.) The Hiroshima and Nagasaki bombs exploded at 500 to 600 m of altitude, then formed huge fireballs that rose with ascending air currents. Subsequently, the material cooled down and started to fall with rain. Because of the wind, the rain did not fall directly on the hypocenter but rather in the northwest region (Koi, Takasu area) of Hiroshima and the eastern region (Nishiyama area) of Nagasaki. Nowadays, the radioactivity is so miniscule that it is difficult to distinguish from trace amounts of radioactivity caused by atmospheric atomic-bomb tests.

Another way radioactivity is produced is by neutron irradiation of soil or buildings. (Neutrons comprise 10% or less of A-bomb radiation; nonradioactive materials become radioactive after absorbing neutrons. In contrast, gamma rays--which comprise the majority of A-bomb radiation--do not cause ground materials to become radioactive.) However, most of the radioactivity decayed very quickly so that it now takes months to measure the radioactivity using highly sensitive equipment. Despite miniscule levels, these measurements are currently utilized to estimate neutron doses released from the bombs.

In both cases, the residual radioactivity is far less than the dose received from background radiation; hence, there are no detectable effects on human health.

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