Analysis of natural radionuclides and lead in foods and diets

The main purpose of the present study was to determine the lead-210, polonium-210 and lead concentrations in foods and diets. Consumption of food is generally the main route by which radionuclides can enter the human organism. Precision and accuracy of the methods developed were verifies by the analysis of reference materials from the International Atomic Energy Agency (IAEA). The method for polonium-210 analysis consisted of sample dissolution by using a microwave digester (open system) employing concentrated nitric acid and hydrogen peroxide, evaporation almost dryness, addition of hydrochloric acid, polonium deposition onto silver disc for six hours and counting by alpha spectrometry. Lead was analysed by atomic absorption technique. After sample dissolution in a microwave digester (using concentrated nitric acid and hydrogen peroxide) and dilution to 50 ml, 20μl of the sample was injected in a pyrolytic graphite furnace - atomic absorption spectrophotometer equipped with Zeeman background correction. The assessment of the contaminants in foods and diets allowed to estimate the intake of these elements and for the radionuclides were also evaluated the radiation doses that the individuals selected were exposed by the food consumption. The effective dose for lead-210 by diets intake ranged from 1.3 to 4.3 μSv/year, corresponding to 25% of the resulting from polonium-210 intake. The dose due to the both natural radionuclides varied from 6.8 to 23.0 μSv/year. These values are in good agreement with the literature data. The value estimated by the United Nations Scientific Committee on Effects of Atomic Radiation (UNSCEAR, 1993) that is 60 μSv and lower than the dose of 0.02 Sv, limit established by ICRP, 1980. The lead levels found in the majority of the Brazilian foods are in good agreement with the values published by CONAT and FAO/WHO. However, some foods such as bean, potato, papaya, apple and rice present levels above of the recommended values by the Public Health Council. For diets, the total lead intakes varied between 29.1 and 574.7 μg Pb/day and to some of the diets analysed, lead levels exceeded the provisional tolerable weekly intake recommended by the WHO. (author)