Introduction In recent decades, the impact of chemicals on the environment and human health has been a cause of increasing concern. There continues to be particular concern regarding radioactive substances in the environment. The fact that natural levels of U and its decay products such as 226 Ra and 222 Rn, which are hazardous and present a risk to health, vary widely as a result of geology and, to a lesser extent, historical mining, is poorly understood. In the UK, for example, it has been calculated that the dose of ionising radioactivity from the nuclear industry is less than 0.1%, whereas that from natural radioactivity is approximately 85%. 21 Uranium is key to nuclear energy, which may become increasingly important based on new low cost-technologies and more sustainable practices. 15 In the future, however, the U production cycle will need to minimise environmental impacts and promote best practice in the planning, operation and closure of production facilities. The primary objective of this paper is to provide data on baseline levels of U in soils and stream sediments across Europe. Such data are of crucial importance to the world-wide U production industry, especially if site restoration requires sites to be returned to their ‘original natural condition’ 15 and regulators fail to understand that levels of U can be naturally high. Without data such as those prepared by FOREGS, U production companies could be forced to return sites to unrealistic conditions that do not occur in nature, and which would be unsustain- able. Moreover, public concerns about environmental radioactivity can be more readily addressed by demonstrating the natural variation of radioactivity in the environment as shown by the FOREGS maps. This report presents new data on the baseline values of U over Europe based on the systematic sampling and analysis of U in soil and stream sediment samples by the FOREGS countries. Interpretation is aimed at distinguishing natural levels, including in areas of mineralisation which may have been mined historically, Applied Earth Science (Trans. Inst. Min. Metall. B) December 2003 Vol. 112 B1 DOI 10.1179/037174503225003152 The distribution of uranium over Europe: geological and environmental significance J. A. Plant, S. Reeder, R. Salminen, D. B. Smith, T. Tarvainen, B. De Vivo and M. G. Petterson The variation of baseline levels of uranium in soil and stream sediments over Europe is described, based on new data prepared by the Forum of European Geological Surveys (FOREGS). The samples have been collected and analysed according to the protocols established for the International Union of Geological Sciences/International Association of Geochemistry and Cosmochemistry (IUGS/IAGC) Working Group on Global Geochemical Baselines. The baseline levels of U vary between < 0·2 to 53 mg kg –1 in topsoils, < 0.20 to 30 mg kg –1 in subsoils and < 1 to 59 mg kg –1 in stream sediments. There is generally good agreement between the levels of U in the three sample types, and the median concentration in all three media is approximately 2 mg kg –1 . The most anomalous baseline levels occur over the Variscan orogen, especially areas into which late post- orogenic radiothermal high heat production (HHP) granites were emplaced. Spiderdiagrams based on trace element levels and rare earth element (REE) plots, confirm the association between the highest U anomalies and evolved radiothermal granites. High values are also associated with parts of the Alpine terrain especially in Slovenia, where there are historical U workings, and Southern Italy, where high values of U reflect contemporary volcanism. In contrast, much of the Caledonides of North West Europe and the Precambrian of the Baltic Shield and East European craton and its overlying sedimentary cover have very low values, generally < 4 mg kg –1 . The results suggest that the main concern for the environment and human health from U and the Th and K with which it is generally associated is the naturally occurring total gamma radiation and radon potential, associated with radiothermal granites. This is likely to be especially important where the granites are mineralised and have been worked historically, for example in the North West of the Iberian Peninsula where U and its decay products are likely to be more dispersed in the surface environment. The study also indicates the value of multi- element data in distinguishing between anthropogenic and naturally occurring anomalies. J. A. Plant (also at Imperial College London, UK; for correspond- ence, E-mail japl@bgs.ac.uk), S. Reeder (E-mail sre@bgs.ac.uk) and M. G. Petterson are at British Geological Survey, Keyworth, Nottingham NG12 5GG, UK; R. Salminen and T. Tarvainen are with Geological Survey of Finland, Espoo, Helsinki, Finland; D. B. Smith is with the United States Geological Survey, Denver, Colorado, USA; and B. De Vivo is at the University of Napoli Federico II, Napoli, Italy. © 2003 IoM Communications Ltd. Published by Maney for the Institute of Materials, Minerals and Mining. Keywords: Uranium, Europe, Distribution