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Naturally-Occurring Radiation: 



TENORM is produced when radionuclides that occur naturally in ores, soils, water, or other natural materials are concentrated or exposed to the environment by activities, such as uranium mining or sewage treatment.

Radioactive materials can be classified under two broad headings:

Man-made radionuclides are produced by splitting atoms in nuclear reactors or by bombarding atoms with subatomic particles in accelerators, nuclear reactors, and other devices. Examples of man-made radionuclides include cobalt-60, strontium-90, and cesium-137. Radionuclides in Naturally-Occurring Radioactive Material (NORM)include primordial radionuclides that are naturally present in the rocks and minerals of the earth's crust and cosmogenic radionuclides produced by interactions of cosmic nucleons with target atoms in the atmosphere and in the earth. Example of cosmogenic radionuclides include carbon-14 and tritium (hydrogen-3). Materials containing cosmogenic radionuclides also fall under the definition of NORM but natural concentrations of nuclides generated by cosmic nucleons are small and present minimal risks.

NORM consists primarily of material containing potassium-40 and isotopes belonging to the primordial series. The principal primordial radionuclides are isotopes of heavy elements belonging to the radioactive series headed by the three long-lived isotopes uranium-238 (uranium series), uranium-235 (actinium series), and thorium-232 (thorium series). All three of these series have numerous radionuclides in their decay chains before reaching a stable end point, lead. At background concentrations, the naturally occurring radionuclides in the uranium, actinium, and thorium series contribute about one-half of the natural background external radiation, and over 80 percent of the background including radon, to which all humans are continuously exposed.

The principal radionuclide of concern in NORM is radium-226, a member of the uranium series, which is present in natural soils in concentrations of about 1 pico Curie per gram (Ci/g). However, NORM radioisotopes may be present in different materials in varying concentrations, and some NORM wastes may have radium-226 concentrations that are much higher than 1 pCi/g, and may be as high as hundreds of thousands of pCi/g.

The ultimate sources of the primordial radionuclides in the environment are the earth's crust and its underlying mantle. Selective movement of some materials from the mantle to the crust, usually resulting from fluid movement driven by temperature differences, has caused a heterogeneous organization of the chemical elements in the crust. Redistribution has also occurred as a result of weathering, sedimentation, and chemical interactions in the crust. As a consequence of these processes, potassium-40 and the uranium and thorium series nuclides have tended to concentrate in certain minerals and certain geologic formations. For example, uranium in significantly elevated concentrations is associated with phosphate ores in three major locations in the U.S.: southeastern Idaho and parts of neighboring states, central Florida, and central Tennessee and northern Alabama. Radionuclides from the uranium and thorium series are also associated in widely varying proportions in the crude oil and brine extracted from underground petroleum reservoirs.

NORM wastes are the radioactive residues from the extraction, treatment, and purification of minerals, petroleum products, or other substances obtained from parent materials that may contain elevated concentrations of primordial radionuclides. They also include any radioactive material made more accessible by the actions of man. Each year, hundreds of millions of metric tons of NORM waste are generated from a wide variety of processes, ranging from uranium and phosphate mining to municipal drinking water treatment. Processes that produce NORM wastes analyzed in this study include uranium mining, phosphate and elemental phosphorus production, phosphate fertilizer production, coal ash generation, oil and gas production, drinking water treatment, metal mining and processing, and geothermal energy production. Primordial radionuclides present in the parent materials can become concentrated in the wastes during mining and beneficiation, mineral processing, oil and gas extraction, or various other processes. This results in radionuclide concentrations in NORM wastes that are often orders of magnitude higher than in the parent materials.

The exposure to individuals from NORM wastes occurs in three main ways. The first is associated with the normal onsite disposal of the waste in piles or stacks. This type of disposal can lead to groundwater contamination and to airborne releases of radioactive particulates and radon. The second is from the improper use and/or disposal of these wastes, such as for soil conditioning or fill dirt around homes. This can lead to build-up of radon gas in homes, direct exposure to individuals located nearby, contamination of soil and the crops growing in that soil, and groundwater contamination. The third way is the reuse of NORM-contaminated materials, such as in concrete aggregate, which could lead to increased radiation risks to members of the public in a variety of ways.

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Why is EPA concerned about TENORM?

Many of the materials that are technically TENORM have only trace amounts of radiation and are part of our everyday landscape. However, some TENORM has very high concentrations of radionuclides that can result in elevated exposures to radiation. 

EPA is concerned about TENORM for three reasons.

EPA is working to coordinate all of its TENORM efforts with other federal agencies, state and tribal governments, industry and public interest organizations. Coordinating our projects in this way will help us see the problem as a whole and will allow us to work together to develop solutions more effectively both within the Agency and with stakeholders outside the Agency.  

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What EPA is Doing about TENORM?

EPA is working to understand the problem and to develop effective ways to protect humans and the environment from harmful exposure to the radiation in these materials. Because TENORM is produced by many industries in varying amounts and occurs in a wide variety of products, it is a particularly challenging problem in the U.S. Although EPA and others working on the problem already have learned a good deal about TENORM, we still do not understand fully all of the potential radiation exposure risks it presents to humans and the environment.

EPA is working on the problem in four ways:

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TENORM-Producing Industries

EPA is studying TENORM-producing industries in the United States to learn which aspects of the problem, including health and environmental risks, are unique to a given industry and which are common across all industries. The results of these studies will appear as a series of reports on individual industries and will be provided on this web site as they become available. Each report will contain the following information:

Information on the following sources of TENORM is now available:

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Existing TENORM Sites

Water-filled open pit uranium mine, northern Arizona

EPA is working cooperatively with several organizations to identify TENORM sites and characterize the contamination:

Navajo Nation

As one of example of cooperative efforts, the EPA, the Navajo EPA, and the Navajo Abandoned Mine Lands Reclamation Department are working together to assess hazards of radioactivity and abandoned uranium mines on the Navajo Reservation. This work includes individual site assessments, hazards mapping, planning for surveys to locate houses built with uranium mine wastes and community education on radiation hazards.

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Education and Guidance

EPA has several activities underway that will help us provide guidance to those who deal with TENORM problems.

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