Heavy metals in edible green vegetables grown along the sites of the Sinza and Msimbazi rivers in Dar es Salaam, Tanzania

Four heavy metals (cadmium, copper, lead and zinc) were determined in some green vegetables cultivated along the sites of the Sinza and Msimbazi rivers. Atomic absorption spectrophotometry was used to estimate and evaluate the levels of these metals in the vegetables. The contributions of the vegetables to the daily intake of the heavy metals from the vegetables were determined. The results showed the following ranges (mg/100 g): 0.01–0.06, 0.25–1.60, 0.19–0.66, and 1.48–4.93 for cadmium, copper, lead and zinc, respectively. Some vegetables contained high levels beyond the permissible levels given by FAO and WHO for human consumption. When the mean levels of cadmium, copper, lead and zinc (0.20, 7.95, 3.95 and 33.75 mg per kg, respectively) were taken into account, the daily intake contribution of these metals was found to be 21.60 μg, 858.60 μg, 426.60 μg and 3.65 mg for cadmium, copper, lead and zinc, respectively.