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.

• FAQs about public health issues related to the Polonium-210 incident
• Advice to relatives, friends, co-workers and those who have been in close contact with people who have received positive test results

If people have concerns then they should contact NHS Direct on 0845 4647 or via the website www.nhsdirect.nhs.uk

Last reviewed: 10 December 2008