Health risks from radioactive particles on Cumbrian beaches near the Sellafield nuclear site

A monitoring programme, in place since 2006, continues to recover radioactive particles (<2 mm diameter) and larger objects from the beaches of West Cumbria. The potential risks to members of the public using the beaches are mainly related to prolonged skin contact with or the inadvertent ingestion of small particles. Most particles are classified as either ‘beta-rich’ or ‘alpha-rich’ and are detected as a result of their caesium-137 or americium-241 content. Beta-rich particles generally also contain strontium-90, with ⁹⁰Sr:¹³⁷Cs ratios of up to about 1:1, but typically <0.1:1. Alpha-rich particles contain plutonium isotopes, with Pu:²⁴¹Am α ratios usually around 0.5-0.6:1. ‘Beta-rich’ particles have the greatest potential to cause localised skin damage if held in stationary contact with the skin for prolonged periods. However, it is concluded that only particles of >10⁶Bq of ¹³⁷Cs, with high ⁹⁰Sr:¹³⁷Cs ratios, would pose a significant risk of causing acute skin ulceration. No particles of this level of activity have been found. Inadvertent ingestion of a particle will result in the absorption to blood of a small proportion of the radionuclide content of the particle. The subsequent retention of radionuclides in body organs and tissues presents a potential risk of the development of cancer. For ‘beta-rich’ particles with typical activities (mean 2 × 10⁴ Bq ¹³⁷Cs, Sr:Cs ratio of 0.1:1), the estimated committed effective doses are about 30 µSv for adults and about 40 µSv for 1 year old infants, with lower values for ‘alpha-rich’ particles of typical activities. The corresponding estimates of lifetime cancer incidence following ingestion for both particle types are of the order of 10⁻⁶ for adults and up to 10⁻⁵ for infants. These estimates are subject to substantial uncertainties but provide an indication of the low risks to members of the public.