The alleged poisoning of Mr Alexander Litvinenko with polonium-210 was an extraordinary event that presented some unique public health challenges.
Environmental polonium-210 contamination was found at a number of locations in London, including parts of 2 hospitals, several hotels, restaurants, and office buildings.
An extensive programme of individual monitoring of potentially exposed persons was rapidly initiated, based on urine sampling. At each location, risk assessments were undertaken to identify persons with significant risk of contamination with polonium-210. These individuals were invited to provide samples, not only to enable a direct assessment to be made of their own exposure, but also to inform decisions on whether others connected with the site should also provide samples or could be reassured.
Urine samples from 753 people were processed: about 500 during the first month, another 250 up to the end of May 2007, and a further 3 up to August 2007. Of these, 139 measurements were above the Reporting Level set by the Health Protection Agency for this incident of 30 mBq d-1, showing the likely presence of polonium-210 from the incident. Committed effective doses were assessed for measurements above the Reporting Level. Most were less than 1 mSv, with 36 in the range ≥ 1 mSv and and <6 mSv, and 17 ≥ 6 mSv, with the highest about 100 mSv.