Survey of Radioactive Content of Food Grown on Brazilian Areas of High Natural Radioactivity

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Abstract
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/h. The most representative towns and villages in these areas are being intensively studied in order to investigate possible long-term consequences to human beings exposed to continuous levels of radiation. Food produced in the areas has been extensively sampled and assayed for its radioactive content. Total alpha counting, fast alpha pair coincidence counting, radiochemical analysis of 226Ra 228Ra and 228Th as well as gamma and alpha spectrometry have been employed. In villages in the monazite sand areas, only small quantities of food are produced, all for local consumption. Practically every kind of vegetable and fruit grown in this area has been assayed. The total alpha activities found range from 4 to 260 pCi/kg of fresh weight. The per cent of these foods in the local diet is quite small. Therefore, present work centers on the effects of external radiation. The situation is quite different in the volcanic intrusive region around Araxa. The radioactive minerals there are associated with apatite, a natural fertilizer. The local production of beans, vegetables, manioc and fruits is appreciable, and a large fraction of it is locally consumed. In some isolated farms and villages the inhabitants subsist principally on the foods they grow. The levels of total alpha activities found in local foods present wide ranges: beans 71–800; vegetables 3–1990; citrous fruits 2–2000 pCi/kg fresh weight. Ratios of 226Ra/228Ra are quite variable. A systematic sampling is being conducted there to determine the range of levels in the most important crops cultivated in different areas, the differences in values found in various foods grown on the same soils, and the importance of highly contaminated food on the total local crops. Attempts are being made to estimate daily intakes of radium in some of the isolated and highly contaminated farms. Indirect measurements of intake were also made by analysis of urine and feces.

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