Abstract
Samples of two staple foods (rice and maize flour) which were locally cultivated in different regions and are consumed by children in Tanzania were analysed to determine the levels of essential and toxic elements as a possible criterion to identify food varieties with more bioavailable nutrients. Short irradiation Instrumental Neutron Activation Analysis (INAA) was applied to food samples and Particle Induced X-ray Emission (PIXE) analysis was used as a complementary technique for the determination of P, Cr, Ni, Fe, Zn, and Cd that could not be determined by short irradiation INAA. The concentrations of .Na, Mg, Al, P, Cl, K, Ca, V, Cr, Mn, Fe, Cu, Zn, Br, and I were determined in food samples using a combination of both techniques. The concentrations of elements in both foods were in the range of the elemental levels reported in the literature. However, concentrations of P, which is an indicator of the anti-nutrition compound phytic acid, were found to be high. Methods of reducing phytic acid in a meal are reviewed and suggested. Rice from two regions reported to be the major cultivators of rice in Tanzania (Mbeya and Morogoro) showed similar elemental mean concentration levels. However, rice cultivated in Mbeya was found to have more bioavailable Fe than rice from Morogoro. Hair samples from children living in three regions in Tanzania were analysed as a bio-indicator of their nutrition and health. The samples were analysed by short and long irradiation INAA. Ag, Al, As, Au, Ba, Br, Ca, Cd, Ce, Cl, Co, Cr, Cu, Dy, Eu, Fe, Hf, I, K, La, Mg, Mn, Na, S, Sb, Sc, Se, Sm, Sr, Ta, Th, U, V, Zn were determined in varying concentrations depending on geographic location, environmental exposures and food consumption habits. The mean hair concentrations of the elements in this study were comparable to the published elemental levels of healthy children of the same age group. However, the mean concentrations of Zn in samples from the mainland part of Tanzania (Dar es Salaam and Moshi) were lower than the values reported in the literature. Mean concentration of Al, which needed further follow up, was found to be considerably higher in hair samples from children in Moshi compared to the values reported in literature. Radioactivity measurements were carried out in samples of rice and maize flour from Tanzania using low-level gamma spectrometry. The specific activities of 238U, 226Ra, 232Th and 40K were in the same range as the values in foods from uncontaminated soils reported in the literature. The specific activities of the radionuclides were found to be higher in maize flour than rice cultivated in the same region. The calculated total committed effective dose due to the consumption of rice and maize to children of age 7 -12 years in Tanzania was found to be less than the annual dose guideline of 1 mSv recommended by ICRP.