Heavy metals concentration in vegetables irrigated with municipal wastewater and their human daily intake in Erbil city

Assessment of heavy metals accumulation in vegetables and their levels in human is vital in countries where wastewater is used for irrigation. In this study, The aim of this research was to investigate the concentrations of highly toxic metals such as Nickel (Ni), chrome (Cr), lead (Pb), zinc (Zn), cadmium (Cd), and copper (Cu) in wastewater, farmlands soils and vegetables (chard, celery, cress and leek), and also their possible human health risk in the area of Erbil city. The heavy metals concentration in the vegetable, soil and water samples were analyzed by using an atomic absorption spectrophotometer. Bio-concentration factor (BCF), daily intake (DI) and health risk index (HRI) were calculated in order to estimate the human health risk. Overall, results indicated that the water, soil and vegetable samples were contaminated with Ni, Cd, Cr, Cu, Pb, and Zn. The trends of these metals concentrations were as follows: 0.613 > 0.316 > 0.162 > 0.065 > 0.041 > 0.028 mL/L for Ni, Cd, Pb, Cr, Cu, and Zn, respectively in the wastewater and 189.09 > 125 > 104.92 > 41.85 > 28.58 > 21.72 for Zn, Cr, Ni, Pb, Cu and Cd mgkg⁻¹ in the soil. The mean concentrations (mg kg⁻¹) in the vegetable samples ranged from 22.74 to 30.30, 5.18–9.19, 29.50–33.87, 39.42–64.78, 7.87–11.83 and 77.68–117.98 for Ni, Cd, Pb, Cr, Cu and Zn, respectively. In addition, the calculated BCFs value ranged from 0.21 to 71.295, with Pb having the highest BCF. The calculated DI for Ni, Cd and Pb exceeded WHO/FAW safe limits for adult and children. Furthermore, the HRI values of Cd and Pb exceeded the safe limit (1) for both adults and children, but the values for Ni (> 1) exceeded the safe limit only for children. These findings clearly indicate that the practice of irrigating the vegetables with untreated wastewater by local farmers have caused high accumulation of heavy metals in the soils and vegetables which are posing health risk to the population in the vicinity. Therefore, regular monitoring of these metals in the wastewater-irrigated vegetables is necessary.