Public health risk assessment and epidemiology of acute contamination with 210Polonium, London, October-November 2006

Introduction Several hundred persons across multiple locations were assessed for the possibility of acute exposure during the London 210Polonium incident of October-November 2006. This paper describes the public health risk assessment process and the epidemiology of acute exposure to 210Po for persons at risk during this incident. Methods: Locations identified as potentially contaminated with 210Po were assessed for the environmental contamination by monitoring teams of the Health Protection Agency's Radiation Protection Division. Persons associated with sites sufficiently contaminated to warrant risk assessment were interviewed by Agency public health consultants. Urine testing for 210Po was offered to individuals whose assessment indicated potential risk of contamination. Acute exposure to 210Po contamination was defined conservatively as urinary excretion of more than 30mBq/24h. Assessment of committed radiation dose was also carried out. Results: Nine hundred and ninety persons were risk assessed across ten locations, including three hotels, three offices, two hospitals and two restaurants. Family and contacts of the index case were also assessed. Seven hundred and seventy nine persons were offered 210Po urine testing, of which 137 had evidence of acute exposure. Committed dose assessments indicated low level potential health concern for 17 persons; no symptomatic cases were detected. Acute contamination was associated with particular locations, occupations, behavioural and other factors: this epidemiology will be described. Conclusions: A substantial number of persons across several sites and occupations had evidence of acute exposure in the London 210Po incident. Accumulating information on exposure epidemiology facilitated risk minimization, identification and reassurance of people at risk.