Occupational Safety and Health Administration OSHA

Common radioactive isotopes

The table below provides information about common radioactive isotopes. Isotopes are forms of an element that have the same number of protons (positively charged particles) but different numbers of neutrons (neutral particles) in their nuclei. The number attached to each isotope is its atomic mass (the sum of its neutrons and protons). The radioactive isotopes in the table have a variety of uses, from industrial measurement equipment to medical therapies to nuclear reactor fuel.

Isotope Type of radiation Half-life Where isotope is commonly found For more information
Americium-241 (Am-241) Alpha particles; weak gamma radiation 432.2 years Medical diagnostic devices; industrial devices that measure density and thickness; household and business smoke detectors CDC Radioisotope Brief
Cesium-137 (Cs-137) Beta particles and gamma radiation 30.17 years Medical radiation therapy devices; calibrating radiation detection equipment; industrial devices that measure density and thickness; as a byproduct of nuclear fission processes in nuclear reactors (e.g., power plants) CDC Radioisotope Brief
Cobalt-60 (Co-60) Beta particles and gamma radiation 5.27 years Medical radiation therapy (implants or external radiation sources); food irradiation CDC Radioisotope Brief
Iodine-131 (I-131) Beta particles and gamma radiation 8.06 days Medical diagnostic and radiation therapy CDC Radioisotope Brief
Iriduim-192 (Ir-192) Beta particles and gamma radiation 73.83 days Industrial gauges for inspecting welding seams; medicines to treat certain cancers CDC Radioisotope Brief
Plutonium-238 (Pu-238) Alpha particles 87.7 years Heat and power source for satellites CDC Radioisotope Brief
Plutonium-239 (Pu-239) 24,110 years Nuclear weapons; byproduct of nuclear reactor operations and nuclear detonations
Plutonium-240 (Pu-240) 6,564 years Byproduct of nuclear reactor operations and nuclear detonations
Polonium-210 (Po-210) Alpha particles 138 days Naturally occurring and found in small amounts in the environment, including in food, water, and the air CDC Clinical Guidance for Polonium Exposure
Strontium-90 (Sr-90) Beta particles 29.1 years Power source for space vehicles, remote weather stations, and navigational beacons; industrial gauges; medical radiation therapy CDC Radioisotope Brief
Uranium-235 (U-235) Alpha particles 700 million years Concentrated (i.e., enriched) for use as nuclear power plant or other reactor fuel; nuclear weapons; as naturally occurring material CDC Radioisotope Brief
Uranium-238 (U-238) 4.47 billion years Radiation shielding (only weakly radioactive, much denser than lead); as naturally occurring material
Back to Top

Thank You for Visiting Our Website

You are exiting the Department of Labor's Web server.

The Department of Labor does not endorse, takes no responsibility for, and exercises no control over the linked organization or its views, or contents, nor does it vouch for the accuracy or accessibility of the information contained on the destination server. The Department of Labor also cannot authorize the use of copyrighted materials contained in linked Web sites. Users must request such authorization from the sponsor of the linked Web site. Thank you for visiting our site. Please click the button below to continue.

Close