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| What is polonium 210? Polonium-210 (Po-210) is a radioactive material. It occurs naturally and is present in the environment and in people at very low concentrations. It can also be made by irradiation of other materials. Polonium-210 has a half-life of 138 days. It undergoes decay by emitting alpha particles, accompanied by very low intensity gamma rays. Alpha particles do not travel very far -- no more than a few centimeters in air. They are stopped by a sheet of paper or by the dead layer of outer skin on our bodies. Polonium-210 is used industrially, for example in anti-static devices in factories. Because polonium-210 is a naturally occurring radionuclide, we all have a very small amount in our bodies. This contributes to the natural radiation dose we all get every year. How can polonium-210 harm people? Because it emits alpha particles, Po-210 represents a radiation hazard if it is taken into the body - by inhalation, ingestion or through wound entry. Since Po-210 only emits gamma rays very weakly, it is not a radiological hazard as long as it remains outside the body. If taken into the body, Po-210 is subsequently excreted, mostly through faeces but some is excreted through urine and other pathways. After uptake to blood, Po-210 is widely distributed though soft body tissues including bone marrow. The greatest amounts of polonium-210 are excreted in the first few days after intake. The biological half-time (the time for the level of Po-210 in the body to fall by half) is approximately 50 days. Radiation doses, including those from polonium-210, are assumed to give rise to an increase in lifetime cancer risk. The larger the dose, the larger the risk. Very high radiation doses can cause damage to body tissues and organs and in the extreme can be fatal. If anyone has been internally contaminated by inadvertently ingesting or inhaling polonium-210, it is most unlikely that they would receive a radiation dose high enough to give rise to medical symptoms. |
