You can't feel it, smell it or taste it. It can travel in airborne dust particles, and can be present in food and water. Cesium-137 is the major cause of Thyroid Cancer in Belarus, and with a "half-life" of over thirty years will be a silent menace till 2016 and beyond.

Ever since the controversial nuclear weapon tests of the 1950's and 1960's, Cesium-137 has been present in the atmosphere all around the world. Only now has much of it decayed to a more stable form. The Chernobyl Nuclear Disaster, suddenly created a new source of the radioactive, silvery white metal, and 70% of it descended on Belarus.

Cesium-137 was discovered in the late 1930s by Glenn T. Seaborg and his coworker, Margaret Melhase. It is produced when uranium and plutonium absorb neutrons and undergo fission.

Cesium-137 undergoes radioactive decay with the emission of beta particles and relatively strong gamma radiation. Because of the chemical nature of cesium, it moves easily through the environment. This makes the cleanup of cesium-137 difficult.

People may ingest cesium-137 with food and water, or may inhale it as dust. If cesium-137 enters the body, it is distributed fairly uniformly throughout the body's soft tissues, resulting in exposure of those tissues. Slightly higher concentrations of the metal are found in muscle, while slightly lower concentrations are found in bone and fat.

Like all radionuclides, exposure to radiation from cesium-137 results in increased risk of cancer. Everyone is exposed to very small amounts of cesium-137 in soil and water as a result of atmospheric fallout. Exposure to waste materials, from contaminated sites, or from nuclear accidents can result in cancer risks much higher than typical environmental exposures. Great Britain's National Radiological Protection Board predicts that there will be a rise in additional cancers over the next 70 years among the population of Western Europe exposed to fallout from the nuclear accident at Chernobyl, in part due to cesium-137.