Assessment of Minerals, Heavy Metals in Soil and Vegetables Cultivated in Mbezi Luis, Ubungo Municipality: Associated Health Risks to Consumers

Abstract

The present study was intended to determine the levels of minerals and heavy metals in Green Leafy Vegetables (GLV) and soil at Ubungo, Dar es Salaam City, so as to establish the risk associated with consumption of these vegetables. These GLV can absorb heavy metals through contaminated soil and irrigation water sources. The samples were digested by dry-ashing techniques and the minerals and heavy metals were determined using atomic Absorption Spectrophotometry (AAS).The concentration of Pb in all GLV samples ranged between 0.23 and 8.51 mg/kg, where about 78% were higher than TBS acceptable limit (0.3 mg/kg). Zinc concentration ranged from 26.24 mg/kg to 57.34 mg/kg where about 22% of these GLV detected high concentration than joint FAO/WHO allowable limit of 47.4 mg/kg. The heavy metals concentration in the soil was 24.41 mg/kg for Pb and 9.60 mg/kg, both of them lower than WHO/FAO permissible limit of 50 mg/kg and 300 mg/kg respectively. The ratio between sodium and potassium in all samples analysed is < 1. Therefore, consumption of the selected leafy vegetables in this study could probably serve to reduce high blood pressure diseases to consumers. The Target Hazard Quotient (THQ) showed that Pb ranged between 0.001 – 0.026, while Zn ranged between 0.081 – 0.178. These values were far less than 1 in all the vegetables species. Therefore, there is no health risk associated with the current level of exposure to a given substance and the population under study is considered to be safe. Mineral content analyzed in this study showed that the vegetables contained appreciable amounts of macro-minerals like magnesium, calcium and potassium which work synergistically to maintain optimal health by keeping the body and tissue fluids from being too acidic or too alkaline and hence allowing for exchange of nutrients between body cells.