Chapter 1. Public Health Statement

This chapter of the profile is a health effects summary written in non-technical language. Its intended audience is the general public, especially people living in the vicinity of a hazardous waste site or chemical release. If the Public Health Statement were separate from the rest of the document, it would still communicate to the lay public essential information about the chemical.

The major headings in the Public Health Statement are useful for finding specific topics of concern. The topics are written in a question and answer format. The answer to each question includes a sentence that direct the reader to chapters in the profile that provide more information on the given topic.

Chapter 2. Principles of Ionizing Radiation

This chapter is an introductory discussion of the principles of ionizing radiation. It addresses what ionizing radiation is and provides a brief overview of the history of ionizing radiation as it pertains to health effects and uses, both peaceful and military. The chapter goes on to discuss the concept of radioactive transformation and the concept of half-life, characteristics of nuclear radiation, how radiation interacts with matter, ionizing radiation and DNA interactions, energy deposition in biological tissues, radiation dosimetry, and internal vs. external exposure. Chapter 2 also introduces the concept of dose-response and the concept of acute and chronic (delayed) health effects, in addition to briefly summarizing the major health effects caused by exposure to ionizing radiation. This chapter concludes with a thorough discussion of how ionizing radiationis measured, internally, externally, and in media using a variety of instruments.

Chapter 3. Summary of Health Effects of Ionizing Radiation

This chapter provides an overview of the health effects related to ionizing radiation exposure in humans and laboratory animals. The top 25 radionuclides present currently or in the past at Department of Energy (DOE) waste sites are identified and some information on their physical half-life and retention characteristics in the body are summarized. The health effects associated with exposure to ionizing radiation are summarized and divided into non-carcinogenic and carcinogenic responses for discussion purposes. A discussion of the non-carcinogenic health effects by major organ system iss presented, followed by a discussion of the carcinogenic responses using data from laboratory animals and the limited amount of human data available. The effects of ionizing radiation on teratogenesis, reproduction, genotoxicity, and ocular toxicities, including the available information on human risk assessments, are also addressed. Readers are encouraged to use Chapter 8 as a supplement to the discussion of the health effects presented in Chapter 3 of this profile.

Chapter 4. Radiation Accidents

This chapter discusses the major radiation accidents of this century, including health effects data, if such data were reported.

Chapter 5. Mechanisms of Biological Effects

This chapter discusses the major mechanisms by which ionizing radiation exerts it toxic effects on cellular activities and organ systems. This discussion addresses the major target molecules of ionizing radiation, with emphasis on how ionizing radiation interacts with DNA. The concept of direct vs. indirect damage to DNA and other macromolecules is also introduced, followed by a discussion of how these mechanisms induce specific types of damage to macromolecules, cells, tissues, and organs to elicit a toxic or adverse event. A brief discussion of the mechanisms by which ionizing radiation induces cancer in laboratory animals and humans is presented, along with a number of models that reflect possible mechanisms of cancer induction and a brief discussion of the three steps of cancer formation.

Chapter 6. Sources of Population Exposure to Ionizing Radiation

There are many ways humans and animals can be exposed to ionizing radiation. This chapter addresses the potential for exposure to sources of ionizing radiation to the human population. Exposure to ionizing radiation is divided into natural external (cosmic rays, terrestrial, coal production, crude oil and natural gas, hot springs and caves, etc.), anthropogenic external (nuclear weapons, fallout, nuclear fuel cycle, medical, dental, and occupational) and internal exposure (inhalation, oral and dermal routes). Discussion of the human health hazards associated with each type of exposure is also presented in this chapter.

Chapter 7. Regulations

This chapter provides summarizes the regulations pertaining to radionuclides.

Chapter 8. Levels of Significant Exposure to Radiation and Radioactive Material

Tables 8-1 (inhalation exposure), 8-2 (oral exposure), 8-3 (dermal exposure), and 8-4 (external exposure) are used to summarize health effects associated with exposure to ionizing radiation. These tables cover the health effects observed at increasing radiation doses and durations, the specific isotope and activity used, and the differences in response by species. These tables provide a quick review of the health effects and a convenient way to locate data for a specific exposure scenario. The tables should be used in conjunction with the text in chapters 2, 3 and 4. All entries in these tables represent studies that provide reliable, quantitative estimates of no-observed-adverse-effect levels (NOAELs), lowest-observed-adverse-effect levels (LOAELs), or cancer effect levels (CELs).

Chapter 9. Glossary

This chapter contains of definitions and terminology pertaining to ionizing radiation and should be consulted when reviewing and interpreting the data present in chapters 2 through 8 of this toxicological profile.

Chapter 10. References

This chapter lists the references used to construct this profile and references that the reader may use to obtain more information on many of the topics discussed in this profile.