What is uranium?

Uranium is a naturally occurring element that is mined from the earth. Uranium is weakly radioactive and is the heaviest naturally occurring element. Uranium is a silver-white lustrous solid that is almost as hard as steel and much denser than lead. The chemical symbol for uranium is U.

Uranium is commonly found in rocks, soil, water, plants, and animals. It can be released into the environment through wind and water erosion, and volcanic eruptions.

Uranium ore is mined from underground and open-pit mines. Uranium mining produces large amounts of radioactive waste. This waste includes soil and rocks that covered the uranium ore, excavated topsoil, and bits of solid waste material from drilling.

Uranium is extracted from the ore by a process called milling, which crushes the uranium ore, treats it with chemicals, and extracts the uranium. Uranium tailings are the radioactive, sand-like materials left over from uranium milling. From the ore, uranium mills produce yellowcake, a solid form of uranium that is used to produce nuclear fuel.

Natural uranium is a mixture of three isotopes, or species:  U^234_, U²³⁵ and U²³⁸. The most common isotope is U²³⁸, which makes up 99 percent of all natural uranium. All uranium isotopes are radioactive. The radioactive decay of uranium in rocks and soil forms radon, an invisible and odorless radioactive gas.

The main use of uranium is to fuel nuclear power plants. Uranium can be separated, or enriched, to increase the concentration of one isotope relative to another. The enriched fraction has increased U²³⁵. Enriched uranium is a fissionable material, which can release nuclear energy by splitting into smaller fragments. Enriched uranium is used in nuclear power plants and nuclear weapons because it can start this nuclear reaction and keep it going to produce energy.

The enrichment process produces uranium that is almost pure U²³⁸, called depleted uranium. Depleted uranium is about half as radioactive as natural uranium.  

Depleted uranium is used as a shield to protect people from radiation that may occur in medicine, research, and transportation. Depleted uranium is used in counterweights for helicopters, airplanes, boats, yachts, and satellites.

Because of its high density, depleted uranium is used by the military as tank armor and armor-piercing bullets and missiles. The military also uses enriched uranium in nuclear weapons and to fuel nuclear-propelled ships and submarines.

Uranium is used in small nuclear reactors to produce isotopes for medical and industrial uses. It has been used in ceramic glazes to add color. Some lighting fixtures and photographic chemicals contain uranium. Phosphate fertilizers may contain natural uranium.

Concentrated deposits of uranium exist in only a few places. In the United States, there are an estimated 15,000 uranium mines in 14 states in the West and Southwest. Seventy-five percent of the mines are on federal and tribal lands.

You can be exposed to uranium in drinking water or in uranium dust in the air. In most areas of the United States, drinking water contains very low levels of uranium. Higher levels may be found in areas with naturally occurring uranium in rocks and soil. You may also be exposed through root vegetables such as potatoes, parsnips, turnips, and sweet potatoes that are grown in soil having uranium..

At home, you may be exposed to uranium if you collect rocks and minerals that contain uranium. You may be exposed to uranium if you live near facilities that make or test nuclear weapons, mine or process uranium ore, or enrich uranium for reactor fuel. You may be exposed if you live near an abandoned uranium mine or an area where depleted uranium weapons are used. You may be exposed if you own old ceramic dishes that have a uranium glaze or if you collect rocks and minerals that contain uranium.

You can be exposed to the breakdown product of uranium, through radon, if you live in an area where the amount of uranium and radium in rocks is high.

At work, you can be exposed to uranium if you work at a facility that mines, mills, processes, or produces uranium. You can be exposed if you work at a nuclear power plant, shipyard, or medical facility. You may be exposed if you work with phosphate fertilizers or some photographic chemicals.

Military personnel may be exposed to uranium if they work on a ship or submarine, or handle ammunition or nuclear weapons. They can be exposed through shrapnel that contains depleted uranium or dust from ammunition. Personnel may be exposed if their armored vehicle is penetrated by uranium munitions, or if they salvage vehicles that have been in contact with uranium munitions. When a depleted uranium projectile hits a vehicle, the projectile forms particles of varying sizes. Personnel in or near such vehicles may breathe or swallow depleted uranium, or have tiny uranium fragments in their bodies.

The health effects of natural and depleted uranium are caused by its chemical properties as a heavy metal and not by radiation.

Eating or breathing very high levels of uranium can cause acute kidney failure and death. Exposure to high levels of uranium may lead to increased cancer risk, liver damage, and internal irradiation. Exposure to uranium can damage the kidneys and respiratory tract, and cause dermatitis and blood changes.

The National Institute for Occupational Safety and Health considers uranium compounds to be potential occupational carcinogens. Uranium is not listed as a known or anticipated carcinogen in the Twelfth Report on Carcinogens published by the National Toxicology Program.

Radon is listed as a human carcinogen in the Twelfth Report on Carcinogens because it causes lung cancer. Exposure to high levels of radon can cause other lung diseases such as emphysema and thickening of lung tissues. Simultaneous exposure to radon and cigarette smoking can increase the incidence of lung cancer and lung disease.

Abandoned uranium mines pose a threat of exposure to radiation. They may contain radioactive waste, arsenic, lead, and naturally occurring radioactive materials, including radon. They may contain fuels, solvents, degreasers, and other chemicals used with heavy equipment and rock blasting operations.

Abandoned uranium mines may contain uranium tailings. Uranium tailings contain radium, which stays radioactive for thousands of years. Radium decays to produce radon. Tailings can also contain selenium and thorium.

If you think your health has been affected by exposure to uranium, contact your health care professional.

For poisoning emergencies or questions about possible poisons, contact your local poison control center at 1-800-222-1222.

This description is based on the information found in the Web links listed with this topic.

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Last Updated: February 12, 2013