Bioaccumulation of natural radionuclides in molluscs from the Ebro Delta area

²¹⁰Po, ²¹⁰Pb, ²³⁴U, ²³⁸U, ²³²Th and ²³⁰Th were analysed in the edible part of four different species of bivalves typically produced and consumed in the Ebro Delta area. The results show that the main contributor to the radioactive content in these species was ²¹⁰Po, with values ranging between 263.1 ± 26.6 and 813.0 ± 72.9 Bq/kg (d.w.), which are higher than the usual reported activity levels in other geographical areas. This can probably be attributed to the activities of a phosphate industrial plant located upstream on the Ebro River, which may lead to enhanced levels of naturally occurring radioactive isotopes in the aquatic ecosystem. To determine the possible impact on health, the committed effective doses through the consumption of the different species were evaluated and the cumulative total annual effective dose for their consumption was estimated to 187.6 μSv/year, which is in the range of 200-1000 μSv/year given by UNSCEAR.