The ecological and health risks of heavy metal in vegetables irrigated with untreated wastewater under a semi-arid condition

Abstract

The study evaluated the impact of wastewater irrigation (WW) on the severity of pollution and health risk potential of Zn, Cu, Cd, and Pb heavy metals in vegetables irrigated with WW versus those grown with fresh water (FW) across different vegetable kinds. This multifaceted assessment was conducted using the pollution index (PI), ecological risk (ER), bio-concentration factor (BCF), hazard quotient (HQ), overall hazard index (HI), carcinogenic risk (CR), and total carcinogenic risk (TCR). The findings revealed that WW irrigation increased metal concentrations across all soil samples and vegetable varieties in the order of Cd > Zn > Pb > Cu and Zn > Cu > Pb > Cd, respectively. When compared to the FW-irrigated soils, the values of PI and ER indicate a significant increase (an increase of 27%-3.3 times and 2.6-3.1 times, respectively) of the heavy metals in the WW-irrigated soils, falling their class from one to two (PI) and two (ER) grade. The order of heavy metals and BCF values exhibited the following pattern: Zn > Cu > Pb > Cd and Zn > Cu > Cd > Pb >, respectively, in all vegetables under WW irrigation and cabbage has the most potential to take up heavy metals compared with other crops. The mean HQ and HI were in the low category (0.1 ≤ HQ and HI < 1) and the CR and TCR were also within acceptable limits (1.00E-06 to 1.00E-04) by consuming veggies produced with WW, to children and adults implying that there are insignificant health risks to local inhabitants. However, the levels of HQ, HI, CR, and TCR were significantly higher in vegetables grown with WW than in those irrigated with FW, suggesting that wastewater irrigation has a major detrimental impact on human health.