Chapter 16. Biological Effects of Radiation

All living species are exposed to a certain amount of natural radiation in the form of particles and rays. In addition to the sunlight, without which life would be impossible to sustain, all beings experience cosmic radiation from space outside the earth and natural background radiation from materials on the earth. Rather large variations occur in the radiation from one place to another, depending on mineral content of the ground and on the elevation above sea level. Man and other species have survived and evolved within such an environment despite the fact that radiation has a damaging effect on biological tissue. The situation has changed somewhat by the discovery of the means to generate high-energy radiation that uses various devices such as X-ray machines, particle accelerators, and nuclear reactors. In the assessment of the potential hazard of the new artificially generated radiation, comparison is often made with levels in naturally occurring background radiation.

We will now describe the biological effect of radiation on cells, tissues, organs, and individuals; identify the units of measurement of radiation and its effect; and review the philosophy and practice of setting limits on exposure. Special attention will be given to regulations related to nuclear power plants.

A brief summary of modern biological information will be useful in understanding radiation effects. As we know, living beings represent a great variety of species of plants and animals; they are all composed of cells, which carry on the processes necessary to survival. The simplest organisms such as algae and protozoa consist of only one cell, whereas complex beings such as man are composed of specialized organs and tissues that contain large numbers of cells, examples of which are nerve, muscle, epithelial, blood, skeletal, and connective. The principal components of a cell are the nucleus as control center, the cytoplasm containing vital substances, and the surrounding membrane as a porous cell wall. Within the nucleus are the chromosomes, which are long threads containing hereditary material. The growth process involves a form of cell multiplication called mitosis in which the chromosomes separate to form two new cells identical to the original one. The reproduction process involves a cell division process called meiosis in which germ cells are produced with only half the necessary complement of chromosomes, such that the union of sperm and egg creates a complete new entity. The laws of heredity are based on this process. The genes are the distinct regions on the chromosomes that are responsible for inheritance of certain body characteristics. They are constructed of a universal molecule called DNA, a very long spiral staircase structure, with the stair steps consisting of paired molecules of four types (see References). Duplication of cells in complete detail involves the splitting of the DNA molecule along its length, followed by the accumulation of the necessary materials from the cell to form two new ones. In the case of man, 46 chromosomes are present, containing approximately 4 billion of the DNA molecule steps in an order that describes each unique person.

16.1. Physiological Effects

The various ways that moving particles and rays interact with matter discussed in earlier chapters can be reexamined in terms of biological effect. Our emphasis previously was on what happened to the radiation. Now, we are interested in the effects on the medium, which are viewed as “damage” in the sense that disruption of the original structure takes place, usually by ionization. We saw that energetic electrons and photons are capable of removing electrons from an atom to create ions; that heavy charged particles slow down in matter by successive ionizing events; that fast neutrons in slowing impart energy to target nuclei, which in turn serve as ionizing agents; and that capture of a slow neutron results in a gamma ray and a new nucleus. In Section 5.2 we defined linear energy transfer (LET). A distinction is made between low LET (electrons and gamma rays) and high LET (alpha particles and neutrons).

As a good rule of thumb, 32 eV of energy is required on average to create an ion pair. This figure is rather independent of the type of ionizing radiation, its energy, and the medium through which it passes. For instance, a single 4-MeV alpha particle would release approximately 10⁵ ion pairs before stopping. Part of the energy goes into molecular excitation and the formation of new chemicals. Water in cells can be converted into free radicals such as H, OH, H²O², and HO². Because the human body is largely water, much of the effect of radiation can be attributed to the chemical reactions of such products. In addition, direct damage can occur, in which the radiation strikes certain molecules of the cells, especially the DNA that controls all growth and reproduction. Turner (see References) displays computer-generated diagrams of ionization effects.

The most important point from the biological standpoint is that the bombarding particles have energy, which can be transferred to atoms and molecules of living cells, with a disruptive effect on their normal function. Because an organism is composed of very many cells, tissues, and organs, a disturbance of one atom is likely to be imperceptible, but exposure to many particles or rays can alter the function of a group of cells and thus affect the whole system. It is usually assumed that damage is cumulative, even though some accommodation and repair take place.

The physiological effects of radiation may be classified as somatic, which refers to the body and its state of health, and genetic, involving the genes that transmit hereditary characteristics. The somatic effects range from temporary skin reddening when the body surface is irradiated, to a life shortening of an exposed individual because of general impairment of the body functions, to the initiation of cancer in the form of tumors in certain organs or as the blood disease, leukemia. The term “radiation sickness” is loosely applied to the immediate effects of exposure to very large amounts of radiation. The genetic effect consists of mutations, in which progeny are significantly different in some respect from their parents, usually in ways that tend to reduce the chance of survival. The effect may extend over many generations.

Although the amount of ionization produced by radiation of a certain energy is rather constant, the biological effect varies greatly with the type of tissue involved. For radiation of low penetrating power such as α particles, the outside skin can receive some exposure without serious hazard, but for radiation that penetrates tissue readily such as X-rays, gamma rays, and neutrons, the critical parts of the body are bone marrow as blood-forming tissue, the reproductive organs, and the lenses of the eyes. The thyroid gland is important because of its affinity for the fission product iodine, whereas the gastrointestinal tract and lungs are sensitive to radiation from radioactive substances that enter the body through eating or breathing.

If a radioactive substance enters the body, radiation exposure to organs and tissues will occur. However, the foreign substance will not deliver all of its energy to the body because of partial elimination. If there are N atoms present, the physical decay rate is λN and the biological elimination rate is λ^bN. The total rate is λ^eN, where the effective decay constant is

The corresponding relation between half-lives is

For example, iodine-131 has an 8-day physical half-life and a 4-day biological half-life for the thyroid gland. Thus its effective half-life is days.

16.2. Radiation Dose Units

A number of specialized terms need to be defined for discussion of biological effects of radiation. First is the absorbed dose (D). This is the amount of energy in joules imparted to each kilogram of exposed biological tissue, and it appears as excitation or ionization of the molecules or atoms of the tissue. The SI unit of dose is the gray (Gy), which is 1 J/kg. To illustrate, suppose that an adult's gastrointestinal tract weighing 2 kg receives energy of amount 6 × 10⁻⁵ J as the result of ingesting some radioactive material. The dose would be

An older unit of energy absorption is the rad, which is 0.01 J/kg (i.e., 1 Gy = 100 rads). The preceding dose to the GI tract would be 0.003 rad or 3 millirads.

The biological effect of energy deposition may be large or small depending on the type of radiation. For instance a rad dose caused by fast neutrons or alpha particles is much more damaging than a rad dose by X-rays or gamma rays. In general, heavy particles create a more serious effect than do photons because of the greater energy loss with distance and resulting higher concentration of ionization. The dose equivalent (H) as the biologically important quantity takes account of those differences by scaling the energy absorption up by a quality factor (QF), with values as in Table 16.1.

Table 16.1. Quality Factors (NRC 10CFR20, see References)

X-rays, gamma rays, beta particles	1
Thermal neutrons (0.025 eV)	2
Neutrons of unknown energy	10
High-energy protons	10
Heavy ions, including alpha particles	20

Thus

If the D is expressed in Gy, then H is in sieverts (Sv); if the D is in rad, then H is in rems. Suppose that the gastrointestinal tract dose were due to plutonium, an alpha particle emitter. The equivalent dose would then be (20) (3 × 10⁻⁵) = 6 × 10⁻⁴ Sv or 0.6 mSv. Alternately, the H would be (20)(0.003) = 0.06 rem or 60 millirems. In scientific research and the analysis of biological effects of radiation, the SI units gray and sievert are used; in nuclear plant operation, rads and rems are more commonly used. Summarizing, conversion factors commonly needed:

• 1 gray (Gy) = 100 rads
• 0.01 Gy = 1 rad
• 1 sievert (Sv) = 100 rems
• 10 mSv = 1 rem
• 1 mSv = 100 mrems
• 10 μSv = 1 mrem.

The great variety of radioactivity and radiation units is confusing and a source of much time and effort to convert between systems. Although it would be desirable to switch completely to the newer units, it is unrealistic to expect it to happen. The United States at least will long be burdened with a dual system of units. We will frequently include the newer units in parentheses. As a memory device, let sieverts be $ and rems be ¢.

Computer Exercise 16.B makes use of the program RADOSE to conveniently translate numbers from a technical article.

The long-term effect of radiation on an organism also depends on the rate at which energy is deposited. Thus the dose rate, expressed in convenient units such as rads per hour or millirems per year, is used. Note that if dose is an energy, the dose rate is a power.

We will describe the methods of calculating dosage in Chapter 21. For perspective, however, we can cite some typical figures. A single sudden exposure that gives the whole body of a person 20 rems (0.2 Sv) will give no perceptible clinical effect, but a dose of 400 rems (4 Sv) will probably be fatal; the typical annual natural radiation exposure, including radon, of the average citizen is 295 millirems; medical and dental applications give another 54, with all other sources 11, giving a total of 360 millirems (3.6 Sv). Figure 16.1 shows the distribution by percentages. Earlier literature on radiation protection cited typical annual dose figures of 100 mrems (0.1 rem), but in recent times the effect of radon amounting to approximately 200 mrems/y has been included. Computer Exercise 16.A addresses the buildup of radon in an enclosed space without ventilation.

Figure 16.1. Annual average radiation exposure to an individual in the United States. The total is 360 millirems (NCRP 93, 1988).

A wide variation of annual dose exists. The radiation level in many parts of the world is larger than the average annual United States figure of 360 mrems (3.6 mSv) and greatly exceeds the Nuclear Regulatory Commission (NRC) regulatory limit of 0.1 mrem/y for members of the public and 5 rems/y for nuclear workers. According to Eisenbud (see References, Chapter 3), in countries such as India the presence of thorium gives exposures of approximately 600 mrems/y. Many waters at health spas give rates that are orders of magnitude higher. Other examples are Brazil with an annual dose of 17,500 mrems (175 mSv) and the city of Ramsar, Iran, where hot springs bring up radium-226, with an annual figure of 26,000 mrems (260 mSv). The frequency of cancer and life span of people in that area is not noticeably different from other populations.

The amounts of energy that result in biological damage are remarkably small. A gamma dose of 400 rems, which is very large in terms of biological hazard, corresponds to 4 J/kg, which would be insufficient to raise the temperature of a kilogram of water as much as 0.001 °C. This fact shows that radiation affects the function of the cells by action on certain molecules, not by a general heating process.

16.3. Basis for Limits of Exposure

A typical bottle of aspirin will specify that no more than two tablets every 4 hours should be administered, implying that a larger or more frequent “dose” would be harmful. Such a limit is based on experience accumulated over the years with many patients. Although radiation has a medical benefit only in certain treatment, the idea of the need for a limit is similar.

As we seek to clean up the environment by controlling emissions of waste products from industrial plants, cities, and farms, it is necessary to specify water or air concentrations of materials such as sulfur or carbon monoxide that are below the level of danger to living beings. Ideally, there would be zero contamination, but it is generally assumed that some releases are inevitable in an industrialized world. Again, limits on the basis of the knowledge of effects on living beings must be set.

For the establishment of limits on radiation exposure, agencies have been in existence for many years. Examples are the International Commission on Radiological Protection (ICRP) and the National Council on Radiation Protection and Measurements (NCRP). Their general procedure is to study data on the effects of radiation and to arrive at practical limits that take account of both risk and benefit of the use of nuclear equipment and processes.

Extensive studies of the survival of colonies of cells exposed to radiation have led to the conclusion that double-strand breaks in DNA are responsible for cell damage. Hall (see References) shows diagrams of various types of breaks. Much of the research was prompted by the need to know the best way to administer radiation for the treatment of cancer. A formula for the number of breaks N as a function of dose D iswhere the first term refers to the effect of a single particle, the second to that of two successive particles. This is the so-called linear-quadratic model. The fraction S of the cells surviving a dose D is deduced to bewhere p is the probability that a break causes cell death. The formula is somewhat analogous to that for radioactive decay or the burn up of an isotope. Cell survival data are fitted to graphs where near zero dose, the curve is linear.

There have been many studies of the effect of radiation on animals other than human beings, starting with early observations of genetic effects on fruit flies. Small mammals such as mice provide a great deal of data rapidly. Because controlled experiments on humans are unacceptable, most of the available information on somatic effects comes from improper practices or accidents. Data are available, for example, on the incidence of sickness and death from exposure of workers who painted radium on luminous-dial watches or of doctors who used X-rays without proper precautions. The number of serious radiation exposures in the nuclear industry is too small to be of use on a statistical basis. The principal source of information is the comprehensive study of the victims of the atomic bomb explosions in Japan in 1945. Continued studies of effects are being made (see RERF in References). The incidence of fatalities as a function of dose is plotted on a graph similar to Figure 16.2 where the available data are seen to lie only in the high dosage range. In the range below 10 rads, there is no statistical indication of any increase in incidence of fatalities over the number in unexposed populations.

Figure 16.2. Radiation hazard analysis.

The nature of the graph of effect versus dose in the low-dose range is unknown. One can draw various curves starting with one based on the linear-quadratic model. Another would involve a threshold, below which there is no effect. To be conservative (i.e., to overestimate effects in the interest of providing protection) organizations such as NCRP and NRC support a linear extrapolation to zero as sketched in Figure 16.2. This assumption is given the acronym LNT (linear no-threshold). Other organizations such as the American Nuclear Society and BELLE (see References) believe that there is insufficient evidence for the LNT curve. Critics such as Radiation, Science, Health (RSH) (see References) believe that the insistence on conservatism and the adoption by the NRC of the LNT recommendation causes an unwarranted expense for radiation protection. One writer (see References) calls the ethics of the use of the LNT into question.

There is considerable support for the existence of a process called hormesis, in which a small amount of a substance such as aspirin is beneficial, whereas a large amount can cause bleeding and even death. When applied to radiation, the curve of effect versus dose labeled “hormesis” in Figure 16.2 would dip below the horizontal axis near zero. The implication is that a small amount of radiation can be beneficial to health. A definitive physiological explanation for the phenomenon is not available, but it is believed that small doses stimulate the immune system of organisms, a cellular effect. There also may be molecular responses involving DNA repair or free radical detoxification. A book by Luckey (see References) is devoted to the subject of hormesis.

The National Academies sponsored a study designed to settle the matter. In report BEIR VII (see References), the linear no-threshold theory is preserved. The report states that it is unlikely that there is a threshold in the dose-effect relation. The authors of BEIR VII dismiss reports supporting hormesis by saying they are “… based on ecological studies ….” However, research on the subject is recommended. No explanation is given in the report for the low cancer incidence in regions of the United States with much higher radiation dosage than the average.

There are significant economic implications of the distinction among models of radiation effect. The LNT version leads to regulations on the required degree of cleanup of radioactivity-contaminated sites and the limits on doses to workers in nuclear facilities.

There is evidence that the biological effect of a given dose administered almost instantly is greater than if it were given over a long period of time. In other words, the hazard is less for low dose rates, presumably because the organism has the ability to recover or adjust to the radiation effects. If, for example (see Exercise 16.2), the effect actually varied as the square of the dose, the linear curve would overestimate the effect by a factor of 100 in the vicinity of 1 rem. Although the hazard for low dose rates is small, and there is no clinical evidence of permanent injury, it is not assumed that there is a threshold dose (i.e., one below which no biological damage occurs). Instead, it is assumed that there is always some risk. The linear hypothesis is retained despite the likelihood that it is overly conservative. The basic question then faced by standards-setting bodies is “what is the maximum acceptable upper limit for exposure?” One answer is zero, on the grounds that any radiation is deleterious. The view is taken that it is unwarranted to demand zero, as both maximum and minimum, because of the benefit from the use of radiation or from devices that have potential radiation as a byproduct.

The limits adopted by the NRC for use starting January 1, 1994, are 5 rems/y (0.05 Sv/y) for total body dose of adult occupational exposure. Alternate limits for worker dose are 50 rems/y (0.5 Sv/y) to any individual organ or tissue other than the eye, 15 rems/y (0.15 Sv/y) for the eye, and 50 rems/y (0.5 Sv/y) to the skin or any extremity. In contrast, the limits for individual members of the public are set at 0.1 rem/y (1 mSv/y) (i.e., 2% of the worker dose). These figures take account of all radiation sources and all affected organs.

For the special case of the site boundary of a low-level radioactive waste disposal facility, NRC specifies a lower figure for the general public, 25 mrems/y (0.25 mSv/y), and for a nuclear power plant, a still lower 3 mrems/y (0.03 mSv/y).

The occupational dose limits are considerably higher than the average United States citizen's background dose of 0.36 rem/y, whereas those for the public are only a fraction of that dose. The National Academy of Sciences Committee on the Biological Effects of Ionizing Radiation analyzes new data and prepares occasional reports, such as BEIR V (see References). In the judgment of that group, the lifetime increase in risk of a radiation-induced cancer fatality for workers when the official dose limits are used is 8 × 10⁻⁴ per rem, and the NRC and other organizations assume half of that figure, 4 × 10⁻⁴ per rem. However, because the practice of maintaining doses as low as reasonably achievable (ALARA) in nuclear facilities keeps doses well below the limit, the increase in chance of cancer is only a few percent. Measured dose figures have decreased considerably over the years, as reported by the Institute of Nuclear Power Operations. Table 16.2 shows the trend.

Table 16.2. Median Radiation Dose in Nuclear Power Plants

Year	Dose (Person-rems Per Unit)
1984	591
1986	344
1988	320
1990	331
1992	251
1994	217
1996	162
1998	119
2000	105
2002	95
2004	88
2006	91

For the general public, the radiation exposure from nuclear power plants is negligible compared with other hazards of existence.

It has been said that knowledge about the origins and effects of radiation is greater than that for any chemical contaminant. The research over decades has led to changes in acceptable limits. In the very early days, soon after radioactivity and X-rays were discovered, no precautions were taken, and indeed radiation was thought to be healthful, hence the popularity of radioactive caves and springs that one might frequent for health purposes. Later, reddening of the skin was a crude indicator of exposure. Limits have decreased a great deal in recent decades, making the older literature outdated. A further complication is the development cycle: research and analysis of effects; discussion, agreement, and publication of conclusions as by ICRP and NCRP; and proposal, review, and adoption of rules by an agency such as the NRC. This cycle requires considerable time. For example, recommendations made in 1977 were not put into effect until 1994, leaving some later suggested modifications in limbo. The time lag can sometimes be different for various applications, leading to apparent inconsistencies.

16.4. Sources of Radiation Dosage

The term “radiation” has come to imply something mysterious and harmful. We will try to provide here a more realistic perspective. The key points are that (a) people are more familiar with radiation than they believe; (b) there are sources of natural radiation that parallel the man-made sources; and (c) radiation can be both beneficial and harmful.

First, solar radiation is the source of heat and light that supports plant and animal life on earth. We use its visible rays for sight; the ultraviolet rays provide vitamin D, cause tanning, and produce sunburn; the infrared rays give us warmth; and finally, solar radiation is the ultimate source of all weather. Man-made devices produce electromagnetic radiation that is identical physically to solar and has the same biological effect. Familiar equipment includes microwave ovens, radio and TV transmitters, infrared heat lamps, ordinary light bulbs and fluorescent lamps, ultraviolet tanning sources, and X-ray machines. The gamma rays from nuclear processes have higher frequencies and thus greater penetrating power than X-rays but are no different in kind from other electromagnetic waves.

In recent years, concern has been expressed about a potential cancer hazard because of electromagnetic fields (EMF) from 60 Hz sources such as power lines or even household circuits or appliances. Biological effects of EMF on lower organisms have been demonstrated, but research on physiological effects on humans is inconclusive and is continuing. More recently, concerns have arisen about the possibility of brain tumors caused by cell phone use.

Human beings are continually exposed to gamma rays, beta particles, and α particles from radon and its daughters. Radon gas is present in homes and other buildings as a decay product of natural uranium, a mineral occurring in many types of soil. Neutrons as a part of cosmic radiation bombard all living things.

If is often said that all nuclear radiation is harmful to biological organisms. There is evidence, however, that the statement is not quite true. First, there seems to be no increase in cancer incidence in the geographic areas where natural radiation background is high. Second, in the application of radiation for the treatment of disease such as cancer, advantage is taken of differences in response of normal and abnormal tissue. The net effect in many cases is of benefit to the patient. Third, it is possible that the phenomenon of hormesis occurs with small doses of radiation, as discussed in Section 16.3.

In Chapter 21 we will discuss radiation protective measures and the application of regulatory limits on exposure.

16.5. Radiation and Terrorism

One of the weapons that terrorists could use is the “dirty bomb” or technically “radiological dispersal device (RDD).” It would consist of a radioactive substance that is a gamma emitter such as cobalt-60 (5.26 y) or cesium-137 (30.2 y), combined with an explosive such as dynamite. An explosion would kill or maim those nearby but the dispersed radioactivity would harm relatively few people.

The resulting damage would be very small compared with that of a nuclear bomb. The main effects would be to create fear and panic, to cause serious property damage, and to require extensive decontamination over an area such as a city block. It can be called a “weapon of mass disruption.” The effect would be psychological because of public fear of radiation. Also, as noted by Mark M. Hart (see References) “… effectiveness [of an RDD] can be unintentionally enhanced by professionals and public officials.” The news media could also contribute to terror. With the public in panic, the intent of terrorists would be achieved.

To reduce the chance of terrorist action, tight control must be maintained over radiation sources used in research, processing, and medical treatment. The NRC addresses the main features of dirty bombs (see References), and the Centers for Disease Control and Prevention (CDC) has a Web site containing answers to questions (see References).

16.6. Summary

When radiation interacts with biological tissue, energy is deposited and ionization takes place that causes damage to cells. The effect on organisms is somatic, related to body health, and genetic, related to inherited characteristics. Radiation dose equivalent as a biologically effective energy deposition per gram is usually expressed in rems, with natural background giving approximately 0.36 rem/y in the United States. Exposure limits are set by use of data on radiation effects at high dosages with a conservative linear hypothesis applied to predict effects at low dose rates. Such assumptions have been questioned. The terrorist use of a radiological dispersal device (dirty bomb) is of concern.

16.7. Exercises

1. A beam of 2-MeV alpha particles with current density 10⁶ cm⁻²−s⁻¹ is stopped in a distance of 1 cm in air, number density 2.7 × 10¹⁹ cm⁻³. How many ion pairs per cm³ are formed? What fraction of the targets experience ionization?
2. If the chance of fatality from radiation dose is taken as 0.5 for 400 rems, by what factor would the chance at 2 rems be overestimated if the effect varied as the square of the dose rather than linearly?
3. A worker in a nuclear laboratory receives a whole-body exposure for 5 minutes by a thermal neutron beam at a rate 20 millirads per hour. What dose (in mrads) and dose equivalent (in mrems) does he receive? What fraction of the yearly dose limit of 5000 mrems/y for an individual is this?
4. A person receives the following exposures in millirems in a year: 1 medical X-ray, 100; drinking water, 50; cosmic rays, 30; radon in house, 150; K-40 and other isotopes, 25; airplane flights, 10. Find the percentage increase in exposure that would be experienced if he also lived at a reactor site boundary, assuming that the maximum NRC radiation level existed there.
5. A plant worker accidentally breathes some stored gaseous tritium, a beta emitter with maximum particle energy 0.0186 MeV. The energy absorbed by the lungs, of total weight l kg, is 4 × 10⁻³ J. How many millirems dose equivalent was received? How many millisieverts? (Note: The average beta energy is one third of the maximum).
6. If a radioisotope has a physical half-life t^H and a biological half-life t^b, what fraction of the substance decays within the body? Calculate that fraction for 8-days I-131, biological half-life 4 days.

Computer Exercises

1. A room with concrete walls is constructed with sand with a small uranium content, such that the concentration of radium-226 (1599 y) is 10⁶ atoms per cm³. Normally, the room is well ventilated so the gaseous radon-222 (3.82 d) is continually removed, but during a holiday the room is closed up. With the parent-daughter computer program RADIOGEN (Chapter 3), calculate the trend in air activity caused by Rn-222 over a week's period, assuming that half of the radon enters the room. Data on the room: 10 ft × 10 ft × 10 ft, walls 3 in. thick.
2. A mixture of radiation and radioactivity units are used in an article on high natural doses (IAEA Bulletin, Vol. 33, No. 2, 1991, p. 36), as follows:
   • Average radiation exposure in the world, 2.4 mSv/y.
   • Average radiation exposure in S.W. India, 10 mGy/y.
   • High outdoor dose in Iran, 9 mrems/h.
   • Radon concentration at high altitudes in Iran, 37 kBq/m³.
   • Radon concentration in Czech houses, 10 kBq/m³.
   • High outdoor dose in Poland, 190 nGy/h.
   With the computer program RADOSE, which converts numbers between units, find what the numbers mean in the familiar United States units mrems/y or pCi/1.

16.8 References

DNA Structure DNA Structure

http://www.accessexcellence.org/AE/AEC/CC http://www.accessexcellence.org/AE/AEC/CC

Explains the role of radioactive labeling and displays the structure of DNA Explains the role of radioactive labeling and displays the structure of DNA. From National Health Museum.

Alberts et al., 1997 Bruce Alberts, Dennis Bray, Alexander Johnson, Julian Lewis, Martin Raff, Keith Roberts, Peter Walter, Essential Cell Biology: An Introduction to the Molecular Biology of the Cell 1997 Garland Publishing New York Highly recommended. Stunning diagrams and readable text

Shapiro, 2002 Jacob Shapiro, Radiation Protection 4th Ed. 2002 Harvard University Press Cambridge Subtitle: A Guide for Scientists and Physicians. A very readable textbook

Cember, 1996 Herman Cember, Introduction to Health Physics 1996 McGraw-Hill New York Thorough and up-to-date information and instruction. Contains many illustrative calculations and tables of data. Also see Herman Cember and Thomas E. Johnson, The Health Physics Solutions Manual, PS&E Publications, 1999

Hall, 2005 Eric J. Hall, Radiobiology for the Radiologist 5th Ed. 2005 J. B. Lippincott Co Philadelphia An authoritative work that explains DNA damage, cell survival curves, and radiotherapy techniques.

Turner, 2007 James E. Turner, Atoms, Radiation, and Radiation Protection 2007 John Wiley & Sons New York Shows Monte Carlo electron tracks in water to illustrate radiation effects

Pochin, 1985 Edward Pochin, Nuclear Radiation: Risks and Benefits 1985 Clarendon Press, Oxford University Press Oxford, UK, New York Sources of radiation and biological effects, including cancer and damage to cells and genes

Hall, 1984 Eric J. Hall, Radiation and Life 2th Ed. 1984 Pergamon Press New York Discusses natural background, beneficial uses of radiation, and nuclear power. The author urges greater control of medical and dental X-rays

Mettler et al., 1995 Fred A. Mettler, Arthur C. Upton, Robert D. Moseley, Medical Effects of Ionizing Radiation 1995 Elsevier Netherlands

Schleien et al., 1998 Bernard Schleien, Lester A. Slayback Jr., Brian Kent Birky, Handbook of Health Physics and Radiological Health 3rd Ed. 1998 Williams & Wilkins Baltimore A greatly expanded version of a classical document of 1970.

Health Risks from Exposure to Low Levels of Ionizing Radiation (BEIR VII), 2005 Health Risks from Exposure to Low Levels of Ionizing Radiation (BEIR VII) Committee to Assess Health Risks … of National Research Council 2005 National Academy Press Washington DC

Radiation and Health Physics Radiation and Health Physics

http://www.umich.edu/~radinfo http://www.umich.edu/~radinfo

Many links Many links. By University of Michigan Student Chapter of the Health Physics Society.

Radiation Dose and Biological Effects Radiation Dose and Biological Effects

http://www.hps.org http://www.hps.org

Select Radiation Terms and Position Statements Select Radiation Terms and Position Statements. From Health Physics Society.

Health Effects of Low-Level Radiation Health Effects of Low-Level Radiation

http://www.ans.org/pi/ps http://www.ans.org/pi/ps

American Nuclear Society Position Statement American Nuclear Society Position Statement No. 41 (2001).

Radiation Effects Research Foundation (RERF) Radiation Effects Research Foundation (RERF)

http://www.rerf.or.jp/index_e.html http://www.rerf.or.jp/index_e.html

Studies of health effects of atomic bomb radiation Studies of health effects of atomic bomb radiation.

Biological Effects of Low-Level Exposure (BELLE) Biological Effects of Low-Level Exposure (BELLE)

http://www.belleonline.com http://www.belleonline.com

Select Newsletters for commentary on hormesis Select Newsletters for commentary on hormesis.

Radiation, Science, and Health (RSH) Radiation, Science, and Health (RSH)

http://www.radscihealth.org/rsh http://www.radscihealth.org/rsh

Advocates use of scientific information on radiation matters Advocates use of scientific information on radiation matters.

Jaworowski, September 1999 Zbigniew Jaworowski, Radiation Risk and Ethics Physics Today September 199924- The article prompted a number of Letters in the April 2000 issue, p. 11

Luckey, 1991 T.D. Luckey, Radiation Hormesis 1991 CRC Press Boca Raton

National Council on Radiation Protection and Measurements (NCRP) National Council on Radiation Protection and Measurements (NCRP)

http://www.ncrp.com http://www.ncrp.com

Provides summaries of reports Provides summaries of reports.

Fact Sheet on Biological Effects of Radiation Fact Sheet on Biological Effects of Radiation

http://www.nrc.gov/reading-rm/doc-collections/fact-sheets/bio-effects-radiation.html http://www.nrc.gov/reading-rm/doc-collections/fact-sheets/bio-effects-radiation.html

Extensive discussion Extensive discussion. Information from NRC.

Standards for Protection Against Radiation Standards for Protection Against Radiation

http://www.nrc.gov/reading-rm/doc-collections/cfr/part020 http://www.nrc.gov/reading-rm/doc-collections/cfr/part020

Part 20 of the Code of Federal Regulations—Energy Part 20 of the Code of Federal Regulations—Energy.

Health Effects of Radiation Health Effects of Radiation

http://www.epa.gov/rpdweb00/understand/health_effects.html http://www.epa.gov/rpdweb00/understand/health_effects.html

Questions and answers from Environmental Protection Agency Questions and answers from Environmental Protection Agency.

Wilson, 1999 Richard Wilson, Resource Letter EIRLD-1: Effects of Ionizing Radiation at Low Doses tfmAmerican Journal of Physics 67 1999372-377 Puts radiation risks into perspective

Wilson and Crouch, 2001 Richard Wilson, Edmund A.C. Crouch, Risk-Benefit Analysis 2001 Harvard University Press Cambridge, MA

Mark M. Hart Mark M. Hart, “Disabling Radiological Dispersal Terror”

http://eed.llnl.gov/ans/2002/hart/hart_ans_2002.pdf http://eed.llnl.gov/ans/2002/hart/hart_ans_2002.pdf

Select Conferences/…Terrorism…/…2002… Select Conferences/…Terrorism…/…2002…

Fact Sheet on Dirty Bombs (NRC) Fact Sheet on Dirty Bombs (NRC)

http://www.nrc.gov/reading-rm/doc-collections/fact-sheets http://www.nrc.gov/reading-rm/doc-collections/fact-sheets

Select Dirty Bombs Select Dirty Bombs.

Frequently Asked Questions (FAQs) about Dirty Bombs Frequently Asked Questions (FAQs) about Dirty Bombs

http://www.bt.cdc.gov/radiation/dirtybombs.asp http://www.bt.cdc.gov/radiation/dirtybombs.asp

Centers for Disease Control and Prevention (CDC) Centers for Disease Control and Prevention (CDC).