Doses from natural radioactivity in wild mushrooms and berries to the Nordic population. Interim Report from the NKS-B BERMUDA activity

Naturally occurring radionuclides (NORs) are the major contributors to the total effective dose of ionizing radiation of the population. Especially hazardous are the decay products of U: Pb, Po and Ra in soils, water and plants. The most important exposure route to Pb and Po is through wild gathered food. Some studies show that Po and also some other NORs accumulate from uranium-rich grounds in mushrooms. In berries the levels are usually lower. In Finland, Sweden and Norway there are sites enriched in NORs. In these areas e.g. the Po levels in certain edible mushroom species may be as high as a few hundred Bq/kg, leading to effective doses of several mSv/year among certain consumer groups. The intake of wild forest products varies greatly among the population, but the public should be informed of the exposure risk and ways to minimize it. In this study, NORs and stable metals are analysed in forest soils and in common edible mushrooms and berries. Transfer factors are calculated and dose estimates from consumption of these products made. Based on the measurement data, it is estimated if highly exposed groups exist, and ways of communication with these groups will be discussed. The practical work started during summer-autumn 2012, when soils, berries and mushrooms were sampled at several sites in Finland, Norway, Denmark and Sweden, and pre-treatments carried out in the local laboratories. All sampling and pre-treatment methods were agreed by all partners and ISO standards were used when applicable, to make all stages of the work harmonized between partners. For the analytical work, samples will be sent to partners with suitable analytical facilities. The analyses will be done during the year 2013 and the results reported in the final report and in scientific publications.