On This Page ToxFAQs™ for Cesium This fact sheet answers the
most frequently asked health questions about cesium. For more
information, you may call the ATSDR Information Center at
1-888-422-8737. This fact sheet is one in a series of summaries
about hazardous substances and their health effects. It is
important you understand this information because this substance
may harm you. The effects of exposure to any hazardous substance
depend on the dose, the duration, how you are exposed, personal
traits and habits, and whether other chemicals are present. What
is cesium? 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 i