Cesium

CAS ID#: 7440-46-2

Affected Organ Systems: Developmental (effects during periods when organs are developing), Gastrointestinal (Stomach and Intestines, part of the digestive system), Neurological (Nervous System)

Cancer Classification:  Please contact NTP, IARC, or EPA with questions on cancer and cancer classification.

Chemical Classification: Radionuclides (radioactive materials)

Summary: Cesium is a naturally occurring element found combined with other elements in rocks, soil, and dust in low amounts. Naturally occurring cesium is not radioactive and is referred to as stable cesium. There is only one stable form of cesium naturally present in the environment, ¹³³Cs (read as cesium one-thirty-three). Nuclear explosions or the breakdown of uranium in fuel elements can produce two radioactive forms of cesium, ¹³⁴Cs and ¹³⁷Cs. Both isotopes decay into non-radioactive elements. ¹³⁴Cs and ¹³⁷Cs generate beta particles as they decay. It takes about 2 years for half of ¹³⁴Cs to give off its radiation and about 30 years for ¹³⁷Cs; this is called the halflife.