Agent Name

Cesium, radioactive



Major Category



Caesium; The most important radionuclides are Cesium-134 (13967-70-9) and Cesium-137 (10045-97-3); For the stable isotope, see "Cesium" and "Cesium hydroxide."




Silver metal with a melting point of 28.5 degrees C. Reacts explosively with water to form cesium hydroxide; [Merck Index] The mineral, pollucite, is 13% stable cesium oxide;


Naturally occurring is Cs-133 (7440-46-2). "Radioactive cesium-137 is produced when uranium and plutonium absorb neutrons and undergo fission." [ATSDR] Of the 11 major radionuclides, only three have long enough half-lives to persist in the environment: Cs-134, Cs-135, and Cs-137. The decay product of Cs-137 is Ba-137m with a T1/2 of 2.6 minutes. Ba-137m emits a gamma ray with an energy of 0.6 MeV, and this is what makes Cs-137 an external radiation hazard. Cs-137 is used in cancer radiation therapy. [Argonne]


Most Important Radionuclide: Cs-137 Source: Fission of uranium and plutonium; Half-Life: 30 years Effective Half-Life: 70 days Specific Activity: 88 Ci/g Decay Mode: Beta GI Absorption: "essentially all" Lung Clearance Half-Time: Days (all compounds) Critical Organ: Total body; Internal Toxicity: High Annual Limit on Intake: 0.1 mCi Tenth-Value Layer: 18.9 mm Pb Gamma Ray Constant: 3.5 R/h @1 cm per mCi Radiation Energy (MeV): Beta 0.514 (95%); Ba-137m Daughter Radiation Accidents: Goiania, Brazil accident in 1987 with 50 people contaminated and 4 deaths from a Cs-137 source (1375 Ci) taken from an abandoned teletherapy machine; 6 other accidents and 25 reports of "Meltings of Radioactive Materials"; [See Glossary for references.] See "Radiation, ionizing."

Reference Link

Cesium | Radiation Protection | US EPA

Exposure Assessment
Vapor Pressure

4.24E-9 mm Hg

Links to Other NLM Databases
Health Studies

Human Health Effects from Hazardous Substances Data Bank:

Toxicity Information


Biomedical References

Search PubMed

Related Information in HazMap
Other Information

No other related information on this agent was found.