The average concentration of stable cesium in the earth’s crust is low. Naturally-occurring cesium exists as the stable isotope (¹³³Cs) in the earth’s crust at an average concentration of about 1 ppm in granites and 4 ppm in sedimentary rocks.
Cesium is used only in small quantities in electronic and energy production industries, and the risk of significant exposure to stable cesium via inhalation, oral, or dermal routes is expected to be small. Limited information is available on monitoring (or detection) of stable cesium in the environment and on health effects from exposure to stable cesium.
Nonradioactive cesium compounds are only mildly toxic, and nonradioactive cesium is not a significant environmental hazard. Because biochemical processes can confuse and substitute cesium with potassium, excess cesium intake can lead to hypokalemia, arrhythmia, and acute cardiac arrest, but the amounts causing these disorders would not ordinarily be encountered in natural sources. No reports were located regarding adverse effects in humans or animals following acute-, intermediate-, or chronic-duration inhalation or dermal exposure to stable cesium. No reports were located in which cancer in humans or animals could be associated with acute-, intermediate-, or chronic-duration oral exposure to stable cesium.
Continental dust and soil erosion are the main emission sources of naturally occurring cesium present in the environment. Cesium is also released to the environment as a result of human activities. The mining of pollucite ores and the production and use of cesium compounds in the electronic and energy production industries contribute to its direct release to the environment. Cesium has also been detected in the fly ash of hazardous waste incinerators and coal burning power plants.
Radioactive isotopes of cesium are a greater health concern than stable cesium. The most important exposure routes are external exposure to the radiation emitted by the radioisotope and ingestion of radioactive cesium-contaminated food sources. Vascular plants do not accumulate large levels of cesium through root uptake because cesium is strongly adsorbed to soils. However, the deposition of radioactive debris on flora with large surface areas such as lichens or moss is significant. Animals that feed on this vegetation, such as reindeer and caribou, may ingest large quantities of radiocesium (and other radionuclides found in fallout). Human consumption of meat from such animals results in the internalization of these radionuclides. Radioactive cesium particles may be found in the air following the release of nuclear fission products; however.
Adverse health effects resulting from external exposure to beta or gamma emissions from radioisotopes of cesium would be the same as those from other radioactive elements that release beta or gamma radiation, and would not be the result of exposure to cesium per se. Developmental and carcinogenic effects have been reported in Japanese survivors of acute high-dose external radiation from the atomic bombs detonated over Hiroshima and Nagasaki.
Urinary excretion is the major route of elimination of cesium taken into the body in soluble form. In animals, age-related increases in cesium retention rates were observed. Cesium is rapidly absorbed into blood following inhalation or oral exposure to soluble cesium compounds, as demonstrated by the rapid distribution of cesium activity after inhalation or ingestion. Once absorbed, cesium is rapidly distributed throughout the body, becoming incorporated into the intracellular fluid of numerous tissues.
Absorbed cesium behaves in a manner similar to that of potassium. Both potassium and cesium are alkali metals that are distributed throughout the body as cations, becoming incorporated into intracellular fluids. Cesium has been shown to compete with potassium for transport through potassium channels and can also substitute for potassium in activation of the sodium pump and subsequent transport into the cell.
Stable or radioactive isotopes of cesium may be measured in samples of urine, blood, feces, or body tissues incl. hair. Stable cesium is of little toxicological concern. However, overexposure to radioactive isotopes of cesium may pose a significant health risk. Internal exposure may be quantified by direct counting (in vivo measurements) of radioactive emission from the body using whole-body counters capable of distinguishing the gamma emissions that are unique to radioactive isotopes of cesium. Radioactivity can be accurately measured in blood, excrement, and tissue samples using scintillation counting. The biomarkers that may help quantify exposure to stable or radioactive cesium are similar in children and adults.
This is information provided by the US Center of Disease Control (CDC): Toxicological Profile for Cesium CAS#: 7440-46-2, assessed August 7, 2021