Assessment of human health risk of heavy metals for consumption of vegetables irrigated with municipal wastewater

In many regions, due to freshwater scarcity, municipal wastewater (MWW) is used for crop irrigation. However, heavy metals can be transferred to human and pose diseases. Therefore, a greenhouse experiment was conducted in a completely randomized design for cress, radish, spinach and turnip irrigated with MWW to determine heavy metals transfer factor (TF), pollution factor as single (PF) and comprehensive (Pn), daily intake of metals (DIM), health risk index (HRI) and the influence of peeling tuber vegetables on these indices. Five wastewater treatments were applied comprising (1) control, (2) 25% MWW + 75% control, (3) 50% MWW + 50% control, (4) 75% MWW + 25% control, and (5) 100% MWW. PFs were Pb (0.85 – 8.35), Cd (0.76 – 15.32), Zn (0.79 – 10.68) and Cu (0.83 – 9.76) for all vegetable’s soil. Obtained Pn values for Pb, Cd, Zn and Cu in all soils were 1.03-15.46. Among vegetables, turnip showed the highest TF, DIM and HRI for Cd compared to other metals. Peeling significantly declined Pb, Cd, Zn and Cu concentrations by 20.71, 22.22, 21.16 and 19.30% in radish and 20.39, 22.00, 20.46 and 20.93% in turnip compared to unpeeled forms. It decreased HRI of Pb, Cd, Zn and Cu in adults respectively from 0.25-3.11, 0.11-2.20, 0.01-0.14 and 0.09-1.09, to 0.20-2.48, 0.08-1.74, 0.01-0.11 and 0.07-0.87. Regarding children this index was declined from 0.29-3.57, 0.12-2.53, 0.01-0.16 and 0.10-1.25 respectively to 0.23-2.85, 0.09-2.00, 0.01-0.13 and 0.08-1.00. Therefore, peeling is an efficient way to decrease health risk and transfer of heavy metals to human body.