It has been known for some time that Brazil nuts have a high barium content and their natural radioactivity is the highest among foodstuff grown in areas of normal radiation background.Samples of Brazil nuts of known origin, as well as various parts of their trees, were obtained from different regions of the Amazon valley and analyzed for barium, calcium, 226Ra, 228Ra and total alpha activity.No statistically significant correlation was found between concentrations of calcium and barium in the nuts. In general, however, the samples richer in barium had the highest concentration of radium. In samples of different parts of the same tree a certain parallelism was noticed between barium and radium contents. The high radioactivity of Brazil nuts was explained, in agreement with the opinion of other authors, by its tree capacity of absorbing and concentrating barium, which is the natural carrier of radium.Some observations were made on the possibilities of people who consume a considerable amount of the nuts, during many years, building up elevated radium body burdens.

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Abs tract-Two types of high background regions have been studied in Brazil-the monazite sand region along the Atlantic Coast and the zone of volcanic intrusives in the inland state of Minas Gerais. In both regions there are groups of people living on variable fields of radiation ranging from 0.03 to 1.0 mR/hr.T o evaluate the extent of the radioactive intake and internal contamination of representative populations, an extensive survey was carried out.In villages in the monazite sand region, the local production of food was found to be insignificant and the radioactive contents were practically within normal ranges. In the volcanic intrusive zone, two villages were selected for having extensive agriculture production cultivated, to a large extent, in soils containing thorium and uranium minerals. The radioactivity in local produce is appreciable, mostly due to 228Ra and daughters, which in some types of foodstuff reach two orders of magnitude above average normal values.A dietary inquiry conducted in a representative sample of the population allowed the classification of the inhabitants in groups, according to certain ranges of radioactive intake. In spite of the high levels in some local foods, mostly root vegetables, only 1376 of the inhabitants presented daily intakes of alpha emitters above 5 fold the average in normal regions. The maximum daily intake observed was elevated by a factor of 20. For the high intake group, the estimated 228Ra body-burdens were in the range of 1-3 nCi.