A field study was conducted in an area of enhanced, natural radioactivity to assess the soil to edible vegetable concentration ratios (CR = concentration in dry vegetable/concentration in dry soil) of 232Th, 230Th, 226Ra, 228Ra, and the light rare earth elements (REE's) La, Ce and Nd. Twenty-nine soil and 42 vegetable samples consisting of relatively equal numbers of seven varieties were obtained from 11 farms on the Pocos de Caldas Plateau in the state of Minas Gerais, Brazil. This region is the site of a major natural analogue study to assess the mobilization and retardation processes affecting Th and the REE's at the Morro do Ferro ore body and U series radionuclides at a nearby open pit U mine. Thorium (IV) serves as a chemical analogue for quadrivalent Pu and the light REE's (III) as chemical analogues for trivalent Am and Cm. The geometric mean CR's (all times 10(-4] decreased as 228Ra (148) greater than 226Ra (76) greater than La (5.4) greater than Nd (3.0) = Ce (2.6) greater than 232Th (0.6), or simply as M (II) greater than M (III) greater than M (IV). These differences may reflect the relative availability of these metals for plant uptake. Significant differences were found in the CR's (for any given analyte) among many of the vegetables sampled. The CR's for the different analytes were also highly correlated. The reasons for the correlations in CR's seen among elements with such diverse chemistries as Ra-REE or Ra-Th are not clear but are apparently related to the essential mineral requirements or mineral status of the different vegetables sampled. This conclusion is based on the significant correlations obtained between the Ca content of the dried vegetables and the CR's for all of the elements studied.

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.

One of the chief problems in industrial radiological health in Brazil concerns 420 people in a plant processing monazite sand, a rare earth mineral containing up to 6 per cent Tho, and 0.3 per cent U,08.Radiation hazards associated with ore concentration and chemical treatment were assessed by sampling and measurement of airborne radioactivity, 210Po bioassay in urine and chromosomal analysis in peripheral blood lymphocytes collected from plant personnel.Results showed that 2lzPb (t1/2 = 10.64 hr) airborne concentrations range from 0.002 up to 3.9 pCi/l. A size distribution analysis showed that in 88 per cent of 212Pb-bearing aerosols the mean count diameter is below 0.4 pm. Calculated values of airborne long-lived activity as 232Th ranged from 6 x lo* up to 1 x IO-*pCi/l.A few workers had a slight increase in the urinary concentration of 210Po, although results did not show a statistically significant difference between these values and those found in control population.Chromosomal analysis revealed a statistically significant difference in the yield of aberrations for the ore mill workers in one of the plant sections, showing the highest airborne 212Pb concentration.

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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.