Although the vast majority of the ingestion dose received by the public is caused by naturally occurring radionuclides, we know little about the levels of these radionuclides in food compared to those of anthropogenic origin.
Studies have found seafood to be the food group that causes the largest contribution to the average ingestion dose in several countries, including Norway, due to the relatively high content of natural radionuclides in fish and shellfish. However, concentrations of natural radioactivity have been shown to vary significantly between species. Of the existing data on marine organisms, many originate from studies with a radioecological focus – meaning that the most consumed species are often not represented. In order to make relevant dose assessments, it is therefore important to use data for the fish and shellfish species are consumed in the respective country or region. (See Supplementary description for more details.)
Due to the importance of seafood to the dose from the diet and its relatively high consumption in the Nordic countries, we propose that this NANOD project focuses on the knowledge gap associated with naturally occurring radionuclides in the fish and shellfish species commonly consumed in this region.
In this project, we will produce the data needed to make more appropriate dose estimates for seafood. Statistics on the most commonly consumed species will serve as the basis for the sampling strategy. It is expected that some species will be common for all countries, but that regional dietary differences also exist. We plan to analyse Po-210, Pb-210, Ra-226 and Ra-228.
We will also estimate the reduction in radionuclide concentrations due to food preparation and delay times from harvest to consumption, and perform new dose assessments from seafood for all Nordic countries. Doses are expected to differ based on total seafood intake and composition of species (and possibly also based on food preparation methods). Geographical differences will also be examined – for example between the enclosed, brackish Baltic Sea and the open North/Norwegian Seas.
In summary, the aim of the project is to enable more accurate dose assessments for seafood – and thus the total diet - in the Nordic countries. Other knowledge gaps for natural radioactivity in the diet may be addressed in future NKS projects