Scientists discovered radiation in the late 19th century and have studied it extensively since then, making it one of the best-understood forms of energy. No harmful effects have been detected as a result of exposure to low levels of radiation—in the range of 5,000 to 10,000 millirem (mrem)—depending on whether the exposure occurs in a short period or over a longer time. At high dose levels, radiation can be harmful or lethal. Its many uses—including electricity production—must be controlled carefully through layer upon layer of safety measures.
The nuclear energy industry’s operations include multiple levels of safety. Nuclear energy facilities are massive structures with steel-reinforced concrete walls and layers of backup safety systems. Operators are licensed by the independent U.S. Nuclear Regulatory Commission and spend every sixth week in a continuous training regimen that includes sessions in full-scale reactor control room simulators responding to various scenarios, with the aim of maintaining safe operations.
The NRC, U.S. Environmental Protection Agency and the departments of Energy and Transportation are the principal federal agencies responsible for establishing radiation protection regulations. These agencies work with international organizations to ensure their regulations are based on internationally recognized scientific studies.
Where Does Radiation Come From?
Individuals are exposed to radiation from a variety of sources, both natural and man-made. There are two categories of radiation: ionizing and non-ionizing. The type of radiation we hear about most often is ionizing radiation. It is called “ionizing” because it removes electrons from atoms, causing the atoms to become electrically charged ions. The uses of ionizing radiation include X-rays, CT scans and electricity production. Non-ionizing radiation does not remove electrons from the atoms it encounters. Examples include radio waves and microwaves as well as visible and ultraviolet light. Its uses include radar, lasers and microwave heating.
On average, 50 percent of an individual’s annual exposure to ionizing radiation comes from naturally occurring radiation from the Earth, in the air and water, from outer space, and in our own bodies. The largest contributor is radon, a common, naturally occurring gas.1 Ventilation is the most effective way to manage radon exposure. Medical procedures, such as CT scans, are the other major source of radiation exposure. In 2006, medical procedures accounted for 48 percent of the average American’s exposure to ionizing radiation, according to the National Council on Radiation Protection and Measurements.2 The large contribution of nuclear medicine to the average radiation dose reflects the widespread use of these technologies rather the dose from any individual procedure, which generally is declining as technologies improve. A typical medical X-ray (single exposure) provides a dose of 10 mrem, while a single CT scan typically provides a dose of 1,000 mrem.3 However, the American Association of Physicists in Medicine pointed out that “the vast majority of Americans receive no radiation from medical imaging at all, or they receive imaging exams that do not use ionizing radiation, such as magnetic resonance imaging or ultrasound procedures.”4
The NRC prescribes and enforces limits on the amount of radiation that workers and members of the public can receive from nuclear energy facilities. The annual limit for occupational exposure is 5,000 mrem. The average nuclear energy facility worker receives 115 mrem.5 The average member of the public receives less than 0.5 mrem per year from the entire nuclear energy fuel cycle combined, including uranium mining, fuel fabrication, nuclear power generation and waste disposal.
Who Sets Radiation Standards?
Three international organizations recommend radiation protection levels: the International Commission on Radiological Protection (ICRP), the International Atomic Energy Agency (IAEA) and the International Commission on Radiation Units and Measurements (ICRU).
ICRP. The Second International Congress of Radiology established the ICRP in 1928. Although initially concerned with the safety of medical radiology, it now covers safety for all sources of radiation. Its mission is “to deal with the basic principles of radiation protection and to leave to various national protection committees the responsibility of introducing the detailed technical regulations, recommendations or codes of practice best suited to the needs of their individual countries.” The ICRP is the principal source of recommendations on safe radiation levels. Members come from many countries and include scientists, physicians and engineers.
IAEA. Organized in 1956 to promote the peaceful uses of nuclear energy, the IAEA is a specialized agency of the United Nations. The IAEA publishes both standards and recommendations in addition to books on nuclear science and technology written by consultants or groups of experts invited from member states.
ICRU. Created in 1925, the ICRU develops international recommendations regarding quantities and units of radiation and radioactivity, procedures for their measurement and application in clinical radiology and radiobiology, and physical data needed to ensure uniformity in reporting on their applications.
U.S. groups involved with recommending radiation standards include the National Council on Radiation Protection and Measurements (NCRP) and federal and state agencies.
NCRP. The NCRP began its work in 1929 as the Advisory Committee on X-Ray and Radium Protection. Congress chartered the organization in 1964 as the NCRP to address the scientific and technical aspects of radiation protection. The nonprofit corporation is not a federal agency, although its recommendations are part of the basis of federal, state and local regulations dealing with radiation hazards. The organization draws its members from public and private universities, medical centers, national and private laboratories, the government, and industry solely on the basis of their scientific expertise.
EPA. The U.S. Environmental Protection Agency is responsible for recommending federal guidance on radiation protection for use by federal agencies in their regulatory processes and for establishing standards to protect the general environment from radioactive material under a variety of authorities, including the Clean Air Act, Safe Drinking Water Act, Superfund and Atomic Energy Act.
NRC. The independent NRC is the federal agency responsible for regulating commercial nuclear technologies. The NRC prescribes and enforces separate limits on the amount of radiation that workers and members of the public can receive from all pathways, such as air and water. These regulations apply to operators of nuclear power plants, as well as industrial and medical facilities licensed to use man-made radioactive materials. The NRC bases its regulations on recommendations made by the NCRP and the ICRP and on the EPA’s federal guidance and standards.
Sources of Data Used to Set Radiation Standards
Two series of reports provide much of the data used in setting radiation standards. The reports are produced by National Academy of Sciences (NAS) and United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR).
National Academy of Sciences. NAS has published seven reports on the biological effects of ionizing radiation (BEIR) since 1956. The BEIR reports focus on the probability of health effects associated with a given dose of radiation and provide a quantitative basis for limiting the radiation exposure of the entire population. The most recent reports to examine the health risks from exposure to low levels of ionizing radiation are the BEIR V and BEIR VII reports. The BEIR VI report, issued in 1990, reviewed the health effects of exposure to radon.
The BEIR VII report, “Health Risks From Exposure to Low Levels of Ionizing Radiation,” is the current scientific basis for radiation safety standards in the United States. The 2006 report concluded that scientific studies and radiation data accumulated since publication of the BEIR V report support previous estimates of health risks associated with low doses of radiation, defined as ranging from zero to 10,000 mrem. To put this in perspective, the average American is exposed to approximately 600 mrem of radiation annually from all sources. The report concluded that one percent of individuals receiving a dose of 10,000 mrem would be expected to develop cancer, compared with the 42 percent likely to develop cancer from other causes. The committee that prepared the report said it is difficult to estimate cancer risk from radiation doses below that level. However, the committee concluded that the study continues to support the “linear-no-threshold model” for radiation exposure. The model holds that risk declines commensurate with lower radiation exposures; very low exposures present a very low risk to an individual but cannot be assumed to be zero.
United Nations Committee. UNSCEAR produces reports on the sources of radiation exposure around the world and estimates of radiation risk. Its most recent, "Sources and Effects of Ionizing Radiation," was published in 2010.
1 NCRP Report No. 160, Section 3 Pie Chart, National Council on Radiation Protection & Measurements, March 2009.
2 “Ionizing Radiation Exposure of the Population of the United States,” Report No. 160, National Council on Radiation Protection and Measurements, March 2009.
3 Health Physics Society.
4 “Average radiation exposure of the US population requires perspective and caution,” American Association of Physicists in Medicine, press release, March 3, 2009.
5 “Occupational Radiation Exposure at Commercial Nuclear Power Reactors,” NUREG 0713, Vol. 32, Table 4-3, U.S. Nuclear Regulatory Commission, March 2012.